import { generateId } from './_helpers';
import { CustomObjectFieldSection } from './custom-object-field-section';
import type {
  CustomObject,
  CustomObjectFieldInput,
  CustomObjectStandardFieldIdentifier,
} from './custom-object';
import { getExistingManifestContext, type ExistingManifestContextOptions } from './existing-manifest-context';
import type { Field } from './field';
import type { ManifestComponentDeletion } from './manifest-builder';
import { requireStringComponentField } from './_existing-component-fields';

export interface PageLayoutDeletionIdentifier {
  layoutId: string;
  objectRqlName: string;
}

export type ObjectRqlName = string;
export type BlueprintKey = string;
export type LayoutApiName = string;
export type TabKey = string;
export type SectionKey = string;
export type HeaderFieldKey = string;
export type FieldRqlName = string;
export type RelatedObjectRqlName = string;
export type CanvasCompositionId = string;
export type HeaderButtonKey = string;

export type JsonPrimitive = string | number | boolean | null;
export type JsonValue = JsonPrimitive | JsonObject | JsonValue[];
export interface JsonObject {
  [key: string]: JsonValue;
}

// ---------------------------------------------------------------------------
// header_edits — HeaderEditsDTO
// ---------------------------------------------------------------------------

/** Edit to a built-in (system) header field. */
export interface SystemHeaderFieldEdit {
  /** Replace the system field's RQL field reference. Optional. */
  newRqlField?: FieldRqlName;
  /** Remove this system field from the header. Optional. */
  deleted?: boolean;
}

/**
 * Custom header field added via `newFields`.
 *
 * `key` is required and must be non-empty — it is used as the stable identity
 * for this field in visibility conditions.
 */
export interface NewHeaderField {
  /** RQL field name to display. Required. */
  rqlName: FieldRqlName;
  /** Stable key for this field. Required. */
  key: HeaderFieldKey;
  /** Whether the user can remove this field. Optional. */
  canBeDeleted?: boolean;
  /** Whether the user can swap this field for another. Optional. */
  canBeChanged?: boolean;
  /** Whether the user can reorder this field. Optional. */
  canBeMoved?: boolean;
}

/**
 * Header configuration for a page layout (`header_edits`).
 *
 * Only the keys listed here are accepted — anything else is silently dropped
 * on the wire. Pass `{}` for an unchanged header.
 *
 * > **Caution:** key names are camelCase on the wire. Snake_case keys are
 * > silently dropped and produce an empty header on deploy.
 */
export interface HeaderEdits {
  /** Replace the record title field (pass the field's api_name). Optional. */
  newTitleField?: FieldRqlName;
  /** Remove the title field from the header. Optional. */
  titleFieldDeleted?: boolean;
  /** Replace the record description field. Optional. */
  newDescriptionField?: FieldRqlName;
  /** Remove the description field from the header. Optional. */
  descriptionFieldDeleted?: boolean;
  /** Edits to built-in system header fields, keyed by system field key. Optional. */
  systemFieldEdits?: Record<HeaderFieldKey, SystemHeaderFieldEdit>;
  /** Additional custom fields to add to the header. Optional. */
  newFields?: NewHeaderField[];
  /** Ordered list of header field RQL names. Custom header keys are accepted and converted. Optional. */
  headerFieldsOrder?: FieldRqlName[];
  /** Action button keys to show in the header. Optional. */
  buttons?: HeaderButtonKey[];
}

interface SerializedSystemHeaderFieldEdit extends Omit<SystemHeaderFieldEdit, 'newRqlField'> {
  newRqlField?: FieldRqlName | null;
}

interface SerializedHeaderEdits
  extends Omit<HeaderEdits, 'newTitleField' | 'newDescriptionField' | 'systemFieldEdits'> {
  newTitleField?: FieldRqlName | null;
  newDescriptionField?: FieldRqlName | null;
  systemFieldEdits?: Record<HeaderFieldKey, SerializedSystemHeaderFieldEdit>;
}

// ---------------------------------------------------------------------------
// tab_edits — TabEditsDTO + section/tab DTOs
// ---------------------------------------------------------------------------

export type SectionFieldsLayout = 'one_column' | 'two_column' | 'three_column' | 'responsive';
export type TabLayout = 'vertical' | 'horizontal';
export type SectionMovementOption = 'static' | 'tab' | 'free';
export type FieldMovementOption = 'tab' | 'free';
export type CustomObjectCustomSectionComponentKey = 'attachments' | 'comments';

/** Default value wrapper used by `SectionField.defaultValue`. */
export interface SectionFieldDefaultValue {
  value: JsonValue;
}

/** Options for one field entry inside a `fields_section`. */
export interface SectionFieldOptions {
  /** Hide this field from view. Optional. */
  hidden?: boolean;
  /** Allow inline editing of this field. Optional. */
  editable?: boolean;
  /** Render this field read-only. Optional. */
  readOnly?: boolean;
  /** Default value metadata for the field. Optional. */
  defaultValue?: SectionFieldDefaultValue;
  /** Rich-text field height. Optional. */
  height?: number;
  /** Whether the layout manager can remove this field. Optional. */
  canBeDeleted?: boolean;
  /** Controls how the field can be moved in the UI. Optional. */
  movementOption?: FieldMovementOption;
}

/** A typed field entry inside a `fields_section`. */
export interface SectionField extends SectionFieldOptions {
  /** Field to display. Required. */
  field: CustomObjectFieldInput;
}

/** @deprecated Use `SectionField` for object entries or `SectionFieldInput` for field arrays. */
export type SectionFieldRef = SectionField;

/** One field entry inside a `fields_section`. */
export type SectionFieldInput = CustomObjectFieldInput | SectionField;

/** Common edit controls for sections. */
export interface PageLayoutSectionOptions {
  /** Whether the layout manager can delete this section. Optional. */
  canBeDeleted?: boolean;
  /** Whether the layout manager can rename this section. Optional. */
  canBeRenamed?: boolean;
  /** Controls how the section can be moved. Optional. */
  movementOption?: SectionMovementOption;
  /** Hide the section title. Optional. */
  hideName?: boolean;
}

/** A standard field-grid section inside a tab. */
export interface FieldsSection extends PageLayoutSectionOptions {
  type: 'fields_section';
  /** Field section metadata for the fields displayed in this layout section. Required. */
  section: CustomObjectFieldSection;
  /** Stable layout section key. Optional. Defaults to `section.getSectionId()`. */
  key?: SectionKey;
  /** Display name of the layout section. Optional. Defaults to the field section name. */
  name?: string;
  /** Fields to display in this section. Required. */
  fields: SectionFieldInput[];
  /** Column layout for the fields. Optional. @default `'responsive'` (backend default). */
  layout?: SectionFieldsLayout;
}

export interface RelatedObjectSection extends PageLayoutSectionOptions {
  type: 'related_object_section';
  /** Stable layout section key. Required. */
  key: SectionKey;
  /** Display name of the layout section. Required. */
  name: string;
  /** Related object whose records point back to this custom object. Required. */
  relatedObjectRqlName: RelatedObjectRqlName;
  /** Field on the related object that points back to this custom object. Required. */
  relatedFieldRqlName: FieldRqlName;
  /** Field RQL names to display for related records. Required. */
  fields: FieldRqlName[];
}

export interface RelatedFieldSection extends PageLayoutSectionOptions {
  type: 'related_field_section';
  /** Stable layout section key. Required. */
  key: SectionKey;
  /** Display name of the layout section. Required. */
  name: string;
  /** Related object reached from this custom object. Required. */
  relatedObjectRqlName: RelatedObjectRqlName;
  /** Field on this custom object that points to the related object. Required. */
  relatedFieldRqlName: FieldRqlName;
  /** Field RQL names to display from the related object. Required. */
  fields: FieldRqlName[];
  /** Column layout for the fields. Optional. @default `'responsive'` (backend default). */
  layout?: SectionFieldsLayout;
}

export interface CustomSection extends PageLayoutSectionOptions {
  type: 'custom_section';
  /** Stable layout section key. Required. */
  key: SectionKey;
  /** Display name of the layout section. Required. */
  name: string;
  /** Custom object section component key. Required. */
  componentKey: CustomObjectCustomSectionComponentKey;
}

export interface ResizableLayoutPosition {
  identifier: string;
  width: number;
  height: number;
  minWidth?: number;
  minHeight?: number;
  maxWidth?: number;
  maxHeight?: number;
}

export interface ReportsSectionItem {
  key: string;
  reportId: string;
  position: ResizableLayoutPosition;
  contextualFieldAttrName?: FieldRqlName;
  visualizationType?: string;
}

export interface ReportsSection extends PageLayoutSectionOptions {
  type: 'reports_section';
  /** Stable layout section key. Required. */
  key: SectionKey;
  /** Display name of the layout section. Required. */
  name: string;
  /** Reports to display in this section. Required. */
  reports: ReportsSectionItem[];
}

export interface CanvasSection extends PageLayoutSectionOptions {
  type: 'canvas_section';
  /** Stable layout section key. Required. */
  key: SectionKey;
  /** Display name of the layout section. Required. */
  name: string;
  /** Canvas composition to render. Required. */
  canvasCompositionId: CanvasCompositionId;
  /** Composition input name to field or state path mapping. Optional. */
  inputMapping?: Record<string, string>;
}

/** A section inside a page layout tab. */
export type PageLayoutSection =
  | FieldsSection
  | RelatedObjectSection
  | RelatedFieldSection
  | CustomSection
  | ReportsSection
  | CanvasSection;

/** A tab that contains one or more field-grid sections. */
export interface TabWithSections {
  type: 'tab_with_sections';
  /** Stable key for this tab. Required. */
  key: TabKey;
  /** Display name of the tab. Required. */
  name: string;
  /** Sections inside this tab. Required. */
  sections: PageLayoutSection[];
}

/** A tab that hosts a custom UI component. */
export interface CustomTab {
  type: 'custom_tab';
  /** Stable key for this tab. Required. */
  key: TabKey;
  /** Display name of the tab. Required. */
  name: string;
  /** Key of the custom component to render. Required. */
  componentKey: string;
}

/** A tab entry in a page layout — either a sections-based tab or a custom component tab. */
export type PageLayoutTab = TabWithSections | CustomTab;

/** Column layout for a `fields_section`. */
/** Edits to a built-in section inside a system tab. */
export interface SystemSectionEdit {
  /** Rename this section. Optional. */
  newName?: string;
  /** Remove this section. Optional. */
  deleted?: boolean;
  /** Change the column layout. Optional. */
  newLayout?: SectionFieldsLayout;
  /** Add fields to this section. Optional. */
  newFields?: SectionFieldInput[];
  /** Hide the section name header. Optional. */
  newHideName?: boolean;
}

/** Edits to a built-in (system) tab. */
export interface SystemTabEdit {
  /** Rename this tab. Optional. */
  newName?: string;
  /** Remove this tab. Optional. */
  deleted?: boolean;
  /** Add new sections to this tab. Optional. */
  newSections?: PageLayoutSection[];
  /** Edits to built-in sections inside this tab, keyed by section key. Optional. */
  systemSectionEdits?: Record<SectionKey, SystemSectionEdit>;
  /** Reorder sections by key. Optional. */
  sectionsOrder?: SectionKey[];
}

/**
 * Tab structure configuration for a page layout (`tab_edits`).
 *
 * All fields are optional. An omitted `tabEdits` defaults to `{}`.
 *
 * > **Caution:** key names are camelCase on the wire. Snake_case keys are
 * > silently dropped and produce an empty layout on deploy.
 */
export interface TabEdits {
  /** New tabs to add to this layout. Each must include a `type` discriminator. Optional. */
  newTabs?: PageLayoutTab[];
  /** Edits to existing system tabs, keyed by tab key. Optional. */
  systemTabEdits?: Record<TabKey, SystemTabEdit>;
  /** Ordered list of tab `key` values (new + system). Optional. */
  tabsOrder?: TabKey[];
  /** Tab strip orientation. Optional. */
  newTabLayout?: TabLayout;
}

// ---------------------------------------------------------------------------
// visibility_conditions — VisibilityConditionsDTO
// ---------------------------------------------------------------------------

/**
 * A single visibility condition applied to a section or tab.
 *
 * Both fields are required by the backend — pass an empty string / empty object
 * if you have no formula or condition tree.
 */
export interface VisibilityCondition {
  /** RQL formula that controls visibility. Required. */
  rqlFormula: string;
  /** Layered conditions tree (AST). Required. */
  layeredConditionsTree: JsonObject;
}

/**
 * Visibility conditions for sections and tabs on a page layout.
 *
 * Pass `{}` for no conditions.
 */
export interface VisibilityConditions {
  /** Per-section visibility conditions, keyed by section key. Optional. */
  sections?: Record<SectionKey, VisibilityCondition>;
  /** Per-tab visibility conditions, keyed by tab key. Optional. */
  tabs?: Record<TabKey, VisibilityCondition>;
}

// ---------------------------------------------------------------------------
// Mutation helpers
// ---------------------------------------------------------------------------

/** Where to insert a new layout item. Defaults to `'end'`. */
export type PageLayoutMutationPosition = 'start' | 'end' | number;

interface AddPageLayoutFieldOptionsBase extends SectionFieldOptions {
  /** Insert position inside the section field list. Optional. @default `'end'` */
  position?: PageLayoutMutationPosition;
  /** Allow the same field to appear twice in the same section. Optional. @default false */
  allowDuplicate?: boolean;
}

/** Options for adding a field to a typed custom-object field section. */
export interface AddCustomPageLayoutFieldOptions extends AddPageLayoutFieldOptionsBase {
  /**
   * Tab key containing the target section. Optional when `section` is unique
   * across the layout.
   */
  tabKey?: string;
  /** Field-section metadata used to find typed custom layout sections and assign field metadata. */
  section?: CustomObjectFieldSection;
  /** Layout section key. Optional escape hatch for ambiguous custom sections. */
  sectionKey?: SectionKey;
  /** Deprecated. Use `section`. */
  fieldSection?: never;
  /** Custom layout sections are selected by `section`; `sectionKey` can disambiguate. */
  systemSection?: false;
}

/** Options for adding a field to a built-in system section. */
export interface AddSystemPageLayoutFieldOptions extends AddPageLayoutFieldOptionsBase {
  /**
   * Add to a built-in system section via `systemTabEdits`.
   *
   * When true, `tabKey` and `sectionKey` are required and the edit is created
   * if it does not already exist.
   */
  systemSection: true;
  /** System tab key containing the target section. Required. */
  tabKey: string;
  /** Built-in system section key. Required. */
  sectionKey: string;
  /** Custom field-section objects are only accepted for custom layout sections. */
  section?: never;
  /** Deprecated. Use `section` for custom sections, or `sectionKey` for system sections. */
  fieldSection?: never;
}

/** Options for adding a field to an existing layout section. */
export type AddPageLayoutFieldOptions = AddCustomPageLayoutFieldOptions | AddSystemPageLayoutFieldOptions;

/** Options for adding multiple fields to an existing layout section. */
export type AddPageLayoutFieldsOptions = AddPageLayoutFieldOptions;

/** Options for removing fields from a layout. */
interface RemovePageLayoutFieldOptionsBase {
  /**
   * Remove all matching occurrences. When false, removing a field that appears
   * more than once throws. Optional. @default true
   */
  removeAll?: boolean;
}

/** Options for removing fields from typed custom-object field sections. */
export interface RemoveCustomPageLayoutFieldOptions extends RemovePageLayoutFieldOptionsBase {
  /** Limit removal to one tab. Optional. */
  tabKey?: string;
  /** Limit removal to one field section. Optional. */
  section?: CustomObjectFieldSection;
  /** Limit removal to one layout section key. Optional. */
  sectionKey?: SectionKey;
  /** Custom layout sections are selected by `section`; `sectionKey` can disambiguate. */
  systemSection?: false;
}

/** Options for removing fields from built-in system section edits. */
export interface RemoveSystemPageLayoutFieldOptions extends RemovePageLayoutFieldOptionsBase {
  /** Remove from a built-in system section edit. Required. */
  systemSection: true;
  /** System tab key containing the target section. Required. */
  tabKey: string;
  /** Built-in system section key. Required. */
  sectionKey: string;
  /** Custom field-section objects are only accepted for custom layout sections. */
  section?: never;
}

/** Options for removing fields from a layout. */
export type RemovePageLayoutFieldOptions =
  | RemoveCustomPageLayoutFieldOptions
  | RemoveSystemPageLayoutFieldOptions;

/** Options for adding a section to an existing tab. */
export interface AddPageLayoutSectionOptions {
  /** Tab key to add the section to. Required. */
  tabKey: string;
  /** Insert position inside the tab. Optional. @default `'end'` */
  position?: PageLayoutMutationPosition;
  /** Allow another section with the same key in the same tab. Optional. @default false */
  allowDuplicate?: boolean;
  /**
   * Add to a built-in system tab via `systemTabEdits.newSections`.
   *
   * When false, the tab must already be present in `newTabs`.
   */
  systemTab?: boolean;
}

/** Options for removing sections from a layout. */
export interface RemovePageLayoutSectionOptions {
  /** Limit removal to one tab. Optional. */
  tabKey?: string;
  /**
   * Remove all matching occurrences. When false, removing a section that appears
   * more than once throws. Optional. @default true
   */
  removeAll?: boolean;
  /** Custom layout sections are selected by layout section key or `CustomObjectFieldSection`. */
  systemSection?: false;
}

/** Options for removing a built-in system section from a layout. */
export interface RemoveSystemPageLayoutSectionOptions {
  /** System tab key containing the target section. Required. */
  tabKey: string;
  /** Delete a built-in system section via `systemSectionEdits`. Required. */
  systemSection: true;
}

/** Options for adding a tab to a layout. */
export interface AddPageLayoutTabOptions {
  /** Insert position inside `newTabs` and `tabsOrder`. Optional. @default `'end'` */
  position?: PageLayoutMutationPosition;
  /** Allow another tab with the same key. Optional. @default false */
  allowDuplicate?: boolean;
}

/** Options for removing a tab from a layout. */
export interface RemovePageLayoutTabOptions {
  /**
   * Remove all matching occurrences. When false, removing a tab that appears
   * more than once throws. Optional. @default true
   */
  removeAll?: boolean;
  /** Delete a built-in system tab via `systemTabEdits`. */
  systemTab?: boolean;
}

/** Options for adding a custom header field. */
export interface AddHeaderFieldOptions extends Omit<NewHeaderField, 'rqlName' | 'key'> {
  /**
   * Stable header key. Defaults to the field api_name when adding a `Field`.
   * Required when adding a raw `NewHeaderField`.
   */
  key?: string;
  /** Insert position inside `newFields` and `headerFieldsOrder`. Optional. @default `'end'` */
  position?: PageLayoutMutationPosition;
  /** Allow another custom header field with the same key. Optional. @default false */
  allowDuplicate?: boolean;
}

/** Options for removing custom header fields. */
export interface RemoveHeaderFieldOptions {
  /**
   * Remove all matching occurrences. When false, removing a header field that
   * appears more than once throws. Optional. @default true
   */
  removeAll?: boolean;
}

// ---------------------------------------------------------------------------
// Public props
// ---------------------------------------------------------------------------

/**
 * Initialization properties for {@link CustomObjectPageLayout}.
 */
export interface CustomObjectPageLayoutProps {
  /**
   * Stable identifier for this layout (e.g. `'default'`).
   *
   * Required. Use `'default'` for the layout that drives the **Add** form and
   * the default record detail view. Each custom object supports one `'default'`
   * layout.
   */
  apiName: string;
  /**
   * Display name of this layout shown in the layout selector.
   *
   * Required.
   */
  name: string;
  /**
   * Tab structure — which tabs and sections to show on the detail page.
   *
   * Optional. @default `{}`
   */
  tabEdits?: TabEdits;
  /**
   * Header configuration — title field, description field, and action buttons.
   *
   * Optional. @default `{}`
   */
  headerEdits?: HeaderEdits;
  /**
   * Visibility conditions for individual tabs and sections.
   *
   * Optional. @default `{}`
   */
  visibilityConditions?: VisibilityConditions;
  /**
   * Stable identifier for this layout record. Pass a human-readable slug
   * to keep it stable across regenerations.
   *
   * Optional. Auto-generated when omitted. @default generateId('layout')
   */
  layoutId?: string;
  /**
   * Blueprint key used during install. Defaults to the parent object's api_name.
   *
   * Optional.
   */
  blueprintKey?: string;
}

export interface CustomObjectPageLayoutLoadFromExistingOptions extends ExistingManifestContextOptions {
  customObjectApiName?: string;
}

type ResolveFieldSectionId = (fieldRqlName: string) => string | undefined;

interface SerializedSectionField extends SectionFieldOptions {
  fieldRqlName: string;
}

interface SerializedFieldsSection extends PageLayoutSectionOptions {
  key?: string;
  type: 'fields_section';
  name: string;
  fields: SerializedSectionField[];
  layout?: SectionFieldsLayout;
}

type SerializedPageLayoutSection =
  | SerializedFieldsSection
  | RelatedObjectSection
  | RelatedFieldSection
  | CustomSection
  | ReportsSection
  | CanvasSection;

interface SerializedTabWithSections {
  type: 'tab_with_sections';
  key: string;
  name: string;
  sections: SerializedPageLayoutSection[];
}

type SerializedPageLayoutTab = SerializedTabWithSections | CustomTab;

interface SerializedSystemSectionEdit extends Omit<SystemSectionEdit, 'newFields'> {
  newFields?: SerializedSectionField[];
}

interface SerializedSystemTabEdit extends Omit<SystemTabEdit, 'newSections' | 'systemSectionEdits'> {
  newSections?: SerializedPageLayoutSection[];
  systemSectionEdits?: Record<string, SerializedSystemSectionEdit>;
}

interface SerializedTabEdits extends Omit<TabEdits, 'newTabs' | 'systemTabEdits'> {
  newTabs?: SerializedPageLayoutTab[];
  systemTabEdits?: Record<string, SerializedSystemTabEdit>;
}

function isField(value: unknown): value is Field {
  const candidate = value as {
    getApiName?: unknown;
    getCustomObjectApiName?: unknown;
    getSectionId?: unknown;
    _assignSection?: unknown;
  } | null;
  return (
    candidate != null &&
    typeof candidate.getApiName === 'function' &&
    typeof candidate.getCustomObjectApiName === 'function' &&
    typeof candidate.getSectionId === 'function' &&
    typeof candidate._assignSection === 'function'
  );
}

function isFieldRef(value: SectionFieldInput): value is SectionField {
  const candidate = value as { field?: unknown } | null;
  return (
    candidate != null &&
    typeof candidate === 'object' &&
    (isField(candidate.field) || typeof candidate.field === 'string')
  );
}

const LAYOUT_SECTION_KEY = Symbol('CustomObjectPageLayout.layoutSectionKey');

function isCustomObjectFieldSection(value: unknown): value is CustomObjectFieldSection {
  return value instanceof CustomObjectFieldSection;
}

function explicitLayoutSectionKey(section: { key?: string }): string | undefined {
  const record = section as unknown as Record<string, unknown>;
  const key = section.key ?? record['layout_section_key'] ?? record['layoutSectionKey'];
  return typeof key === 'string' ? key : undefined;
}

function attachLayoutSectionKey(
  section: SerializedFieldsSection,
  sectionKey: string,
): SerializedFieldsSection {
  if (explicitLayoutSectionKey(section) == null) section.key = sectionKey;
  Object.defineProperty(section, LAYOUT_SECTION_KEY, {
    value: sectionKey,
    enumerable: false,
    configurable: true,
  });
  return section;
}

function layoutSectionKey(section: { key?: string }): string | undefined {
  return (
    explicitLayoutSectionKey(section) ??
    (section as unknown as Record<typeof LAYOUT_SECTION_KEY, string | undefined>)[LAYOUT_SECTION_KEY]
  );
}

function layoutSectionMatches(section: { key?: string }, sectionKey: string): boolean {
  return layoutSectionKey(section) === sectionKey;
}

function isSerializedFieldsSection(section: SerializedPageLayoutSection): section is SerializedFieldsSection {
  return section.type === 'fields_section';
}

function assertSameObject(customObject: CustomObject, field: Field, sectionKey: string): void {
  if (field.getCustomObjectApiName() !== customObject.getApiName()) {
    throw new Error(
      `CustomObjectPageLayout fields_section "${sectionKey}" references field "${field.getApiName()}" ` +
        `from "${field.getCustomObjectApiName()}", but the layout belongs to "${customObject.getApiName()}".`,
    );
  }
}

function assignSectionForLayout(field: Field, section: CustomObjectFieldSection | string): void {
  if (!field.isStandard()) field._assignSection(section);
}

function assertSectionBelongsTo(customObject: CustomObject, section: CustomObjectFieldSection): void {
  if (section.getModelApiName() !== customObject.getApiName()) {
    throw new Error(
      `CustomObjectPageLayout section "${section.getSectionId()}" belongs to "${section.getModelApiName()}", ` +
        `but the layout belongs to "${customObject.getApiName()}".`,
    );
  }
}

function requireFieldSectionOption(value: unknown, label: string): CustomObjectFieldSection {
  if (isCustomObjectFieldSection(value)) return value;
  if (typeof value === 'string') {
    throw new TypeError(
      `${label} must be a CustomObjectFieldSection object; received raw section id "${value}". ` +
        'Load/include the existing field section first.',
    );
  }
  throw new TypeError(`${label} must be a CustomObjectFieldSection object.`);
}

function assertOptionAbsent(options: unknown, key: string, message: string): void {
  if (options == null || typeof options !== 'object') return;
  if (Object.prototype.hasOwnProperty.call(options, key)) throw new TypeError(message);
}

function toSerializedSectionField(
  fieldRqlName: string,
  options: SectionFieldOptions = {},
): SerializedSectionField {
  const normalized: SerializedSectionField = { fieldRqlName };
  if (options.hidden != null) normalized.hidden = options.hidden;
  if (options.editable != null) normalized.editable = options.editable;
  if (options.readOnly != null) normalized.readOnly = options.readOnly;
  if (options.defaultValue != null) normalized.defaultValue = options.defaultValue;
  if (options.height != null) normalized.height = options.height;
  if (options.canBeDeleted != null) normalized.canBeDeleted = options.canBeDeleted;
  if (options.movementOption != null) normalized.movementOption = options.movementOption;
  return normalized;
}

function copySectionOptions<T extends PageLayoutSectionOptions>(
  target: T,
  input: PageLayoutSectionOptions,
): T {
  if (input.canBeDeleted != null) target.canBeDeleted = input.canBeDeleted;
  if (input.canBeRenamed != null) target.canBeRenamed = input.canBeRenamed;
  if (input.movementOption != null) target.movementOption = input.movementOption;
  if (input.hideName != null) target.hideName = input.hideName;
  return target;
}

function normalizeSectionField(
  customObject: CustomObject,
  section: CustomObjectFieldSection | string,
  sectionKey: string,
  entry: SectionFieldInput,
): SerializedSectionField {
  if (isField(entry) || typeof entry === 'string') {
    const field = customObject._resolveField(entry);
    assertSameObject(customObject, field, sectionKey);
    assignSectionForLayout(field, section);
    return toSerializedSectionField(field.getApiName());
  }

  if (isFieldRef(entry)) {
    const field = customObject._resolveField(entry.field);
    assertSameObject(customObject, field, sectionKey);
    assignSectionForLayout(field, section);
    return toSerializedSectionField(field.getApiName(), entry);
  }

  throw new Error(
    `CustomObjectPageLayout fields_section "${sectionKey}" has an invalid field entry; ` +
      'pass a Field instance or { field }.',
  );
}

function normalizeFieldsSection(customObject: CustomObject, input: FieldsSection): SerializedFieldsSection {
  assertSectionBelongsTo(customObject, input.section);
  const sectionKey = input.key ?? input.section.getSectionId();
  const name = input.name ?? input.section.getName();
  const normalized = copySectionOptions<SerializedFieldsSection>(
    {
      name,
      type: 'fields_section',
      fields: input.fields.map((field) =>
        normalizeSectionField(customObject, input.section, sectionKey, field),
      ),
    },
    input,
  );
  if (input.layout != null) normalized.layout = input.layout;
  return attachLayoutSectionKey(normalized, sectionKey);
}

function normalizeSection(
  customObject: CustomObject,
  section: PageLayoutSection,
): SerializedPageLayoutSection {
  if (section.type === 'fields_section') return normalizeFieldsSection(customObject, section);
  return { ...section };
}

function normalizeTab(customObject: CustomObject, tab: PageLayoutTab): SerializedPageLayoutTab {
  if (tab.type === 'custom_tab') return tab;
  return {
    ...tab,
    sections: tab.sections.map((section) => normalizeSection(customObject, section)),
  };
}

function normalizeSystemSectionEdit(
  customObject: CustomObject,
  tabKey: string,
  sectionKey: string,
  edit: SystemSectionEdit,
): SerializedSystemSectionEdit {
  const { newFields: _newFields, ...rest } = edit;
  const normalized: SerializedSystemSectionEdit = { ...rest };
  if (edit.newFields != null) {
    normalized.newFields = edit.newFields.map((field) =>
      normalizeSectionField(customObject, sectionKey, `${tabKey}.${sectionKey}`, field),
    );
  }
  return normalized;
}

function normalizeSystemTabEdit(
  customObject: CustomObject,
  tabKey: string,
  edit: SystemTabEdit,
): SerializedSystemTabEdit {
  const { newSections: _newSections, systemSectionEdits: _systemSectionEdits, ...rest } = edit;
  const normalized: SerializedSystemTabEdit = { ...rest };
  if (edit.newSections != null) {
    normalized.newSections = edit.newSections.map((section) => normalizeSection(customObject, section));
  }
  if (edit.systemSectionEdits != null) {
    const systemSectionEdits: Record<string, SerializedSystemSectionEdit> = {};
    for (const [sectionKey, sectionEdit] of Object.entries(edit.systemSectionEdits)) {
      systemSectionEdits[sectionKey] = normalizeSystemSectionEdit(
        customObject,
        tabKey,
        sectionKey,
        sectionEdit,
      );
    }
    normalized.systemSectionEdits = systemSectionEdits;
  }
  return normalized;
}

function normalizeTabEdits(customObject: CustomObject, tabEdits: TabEdits): SerializedTabEdits {
  const { newTabs: _newTabs, systemTabEdits: _systemTabEdits, ...rest } = tabEdits;
  const normalized: SerializedTabEdits = { ...rest };
  if (tabEdits.newTabs != null) {
    normalized.newTabs = tabEdits.newTabs.map((tab) => normalizeTab(customObject, tab));
  }
  if (tabEdits.systemTabEdits != null) {
    const systemTabEdits: Record<string, SerializedSystemTabEdit> = {};
    for (const [tabKey, tabEdit] of Object.entries(tabEdits.systemTabEdits)) {
      systemTabEdits[tabKey] = normalizeSystemTabEdit(customObject, tabKey, tabEdit);
    }
    normalized.systemTabEdits = systemTabEdits;
  }
  return normalized;
}

function cloneJson<T>(value: T): T {
  if (value == null) return value;
  return JSON.parse(JSON.stringify(value)) as T;
}

const HEADER_EDIT_KEYS = new Set([
  'newTitleField',
  'titleFieldDeleted',
  'newDescriptionField',
  'descriptionFieldDeleted',
  'systemFieldEdits',
  'newFields',
  'headerFieldsOrder',
  'buttons',
]);

const SYSTEM_HEADER_FIELD_EDIT_KEYS = new Set(['newRqlField', 'deleted']);

const NEW_HEADER_FIELD_KEYS = new Set(['rqlName', 'key', 'canBeDeleted', 'canBeChanged', 'canBeMoved']);

function assertKnownKeys(
  record: Record<string, unknown>,
  allowedKeys: ReadonlySet<string>,
  label: string,
  hint: string,
): void {
  for (const key of Object.keys(record)) {
    if (!allowedKeys.has(key)) {
      throw new Error(`${label} contains unsupported key "${key}". ${hint}`);
    }
  }
}

function normalizeHeaderEdits(headerEdits: HeaderEdits): SerializedHeaderEdits {
  assertKnownKeys(
    headerEdits as unknown as Record<string, unknown>,
    HEADER_EDIT_KEYS,
    'CustomObjectPageLayout headerEdits',
    'Use addHeaderField(), setTitleField(), setDescriptionField(), or the HeaderEdits keys documented by the SDK.',
  );

  for (const [key, edit] of Object.entries(headerEdits.systemFieldEdits ?? {})) {
    assertKnownKeys(
      edit as Record<string, unknown>,
      SYSTEM_HEADER_FIELD_EDIT_KEYS,
      `CustomObjectPageLayout headerEdits.systemFieldEdits.${key}`,
      'Use newRqlField and deleted for system header field edits.',
    );
  }

  for (const [index, field] of (headerEdits.newFields ?? []).entries()) {
    assertKnownKeys(
      field as unknown as Record<string, unknown>,
      NEW_HEADER_FIELD_KEYS,
      `CustomObjectPageLayout headerEdits.newFields[${index}]`,
      'Use { rqlName, key } entries, or call addHeaderField(field).',
    );
  }

  if (headerEdits.newTitleField === '') {
    throw new Error(
      'CustomObjectPageLayout headerEdits.newTitleField cannot be empty. Use titleFieldDeleted.',
    );
  }
  if (headerEdits.newDescriptionField === '') {
    throw new Error(
      'CustomObjectPageLayout headerEdits.newDescriptionField cannot be empty. Use descriptionFieldDeleted.',
    );
  }
  if (headerEdits.newTitleField != null && headerEdits.titleFieldDeleted === true) {
    throw new Error(
      'CustomObjectPageLayout headerEdits cannot both set newTitleField and titleFieldDeleted.',
    );
  }
  if (headerEdits.newDescriptionField != null && headerEdits.descriptionFieldDeleted === true) {
    throw new Error(
      'CustomObjectPageLayout headerEdits cannot both set newDescriptionField and descriptionFieldDeleted.',
    );
  }

  if (headerEdits.headerFieldsOrder == null) return headerEdits;
  return {
    ...headerEdits,
    headerFieldsOrder: normalizeHeaderFieldsOrder(headerEdits),
  };
}

function addUniqueHeaderOrderField(order: string[], field: unknown): void {
  if (typeof field !== 'string' || field.length === 0) return;
  if (!order.includes(field)) order.push(field);
}

function normalizeHeaderFieldsOrder(headerEdits: SerializedHeaderEdits): string[] {
  const customFieldRqlByKey = new Map(
    (headerEdits.newFields ?? []).map((field) => [field.key, field.rqlName]),
  );
  const systemFieldRqlByKey = new Map(
    Object.entries(headerEdits.systemFieldEdits ?? {})
      .filter((entry): entry is [string, SerializedSystemHeaderFieldEdit & { newRqlField: string }] => {
        const [, edit] = entry;
        return typeof edit.newRqlField === 'string' && edit.newRqlField.length > 0;
      })
      .map(([key, edit]) => [key, edit.newRqlField]),
  );
  const order: string[] = [];

  for (const entry of headerEdits.headerFieldsOrder ?? []) {
    addUniqueHeaderOrderField(
      order,
      customFieldRqlByKey.get(entry) ?? systemFieldRqlByKey.get(entry) ?? entry,
    );
  }

  addUniqueHeaderOrderField(order, headerEdits.newTitleField);
  addUniqueHeaderOrderField(order, headerEdits.newDescriptionField);
  for (const field of headerEdits.newFields ?? []) {
    addUniqueHeaderOrderField(order, field.rqlName);
  }
  for (const systemEdit of Object.values(headerEdits.systemFieldEdits ?? {})) {
    addUniqueHeaderOrderField(order, systemEdit.newRqlField);
  }

  return order;
}

type MutableSectionField = SerializedSectionField | Record<string, any> | string;

interface MutableFieldContainer {
  tabKey: string;
  sectionKey: string | undefined;
  section?: SerializedFieldsSection;
  fields: MutableSectionField[];
  label: string;
}

interface FieldSectionLayoutSection {
  tabKey: string;
  sectionKey: string;
}

function isTabWithSections(tab: SerializedPageLayoutTab): tab is SerializedTabWithSections {
  return tab.type === 'tab_with_sections';
}

function insertionIndex(length: number, position: PageLayoutMutationPosition | undefined): number {
  if (position == null || position === 'end') return length;
  if (position === 'start') return 0;
  if (!Number.isInteger(position) || position < 0 || position > length) {
    throw new Error(`Invalid insertion position ${position}; expected 'start', 'end', or 0-${length}.`);
  }
  return position;
}

function insertAt<T>(items: T[], item: T, position: PageLayoutMutationPosition | undefined): void {
  items.splice(insertionIndex(items.length, position), 0, item);
}

function insertUniqueAt(
  items: string[],
  item: string | null | undefined,
  position: PageLayoutMutationPosition | undefined,
): void {
  if (item == null || item.length === 0 || items.includes(item)) return;
  insertAt(items, item, position);
}

function fieldRqlNameOf(entry: unknown): string | undefined {
  if (typeof entry === 'string') return entry;
  if (entry == null || typeof entry !== 'object') return undefined;
  const record = entry as Record<string, any>;
  const fieldRqlName =
    record['fieldRqlName'] ?? record['field_rql_name'] ?? record['apiName'] ?? record['api_name'];
  return typeof fieldRqlName === 'string' ? fieldRqlName : undefined;
}

function addFieldSectionLayoutSection(
  index: Map<string, FieldSectionLayoutSection[]>,
  fieldSectionId: string,
  entry: FieldSectionLayoutSection,
): void {
  const entries = index.get(fieldSectionId) ?? [];
  if (
    !entries.some((existing) => existing.tabKey === entry.tabKey && existing.sectionKey === entry.sectionKey)
  ) {
    entries.push(entry);
  }
  index.set(fieldSectionId, entries);
}

function indexFieldsSectionInput(
  index: Map<string, FieldSectionLayoutSection[]>,
  tabKey: string,
  section: FieldsSection,
): void {
  addFieldSectionLayoutSection(index, section.section.getSectionId(), {
    tabKey,
    sectionKey: section.key ?? section.section.getSectionId(),
  });
}

function indexPageLayoutSectionInput(
  index: Map<string, FieldSectionLayoutSection[]>,
  tabKey: string,
  section: PageLayoutSection,
): void {
  if (section.type === 'fields_section') indexFieldsSectionInput(index, tabKey, section);
}

function buildFieldSectionLayoutIndexFromProps(
  tabEdits: TabEdits | undefined,
): Map<string, FieldSectionLayoutSection[]> {
  const index = new Map<string, FieldSectionLayoutSection[]>();
  if (tabEdits == null) return index;

  for (const tab of tabEdits.newTabs ?? []) {
    if (tab.type !== 'tab_with_sections') continue;
    for (const section of tab.sections) indexPageLayoutSectionInput(index, tab.key, section);
  }

  for (const [tabKey, tabEdit] of Object.entries(tabEdits.systemTabEdits ?? {})) {
    for (const section of tabEdit.newSections ?? []) {
      indexPageLayoutSectionInput(index, tabKey, section);
    }
  }

  return index;
}

function indexLoadedFieldsSection(
  index: Map<string, FieldSectionLayoutSection[]>,
  tabKey: string,
  section: SerializedFieldsSection,
  resolveFieldSectionId: ResolveFieldSectionId | undefined,
): void {
  const sectionKey = layoutSectionKey(section);
  if (sectionKey == null || resolveFieldSectionId == null) return;

  for (const field of section.fields ?? []) {
    const fieldRqlName = fieldRqlNameOf(field);
    if (fieldRqlName == null) continue;
    const fieldSectionId = resolveFieldSectionId(fieldRqlName);
    if (fieldSectionId != null) {
      addFieldSectionLayoutSection(index, fieldSectionId, { tabKey, sectionKey });
    }
  }
}

function buildFieldSectionLayoutIndexFromLoadedTabEdits(
  tabEdits: SerializedTabEdits,
  resolveFieldSectionId: ResolveFieldSectionId | undefined,
): Map<string, FieldSectionLayoutSection[]> {
  const index = new Map<string, FieldSectionLayoutSection[]>();

  for (const tab of tabEdits.newTabs ?? []) {
    if (!isTabWithSections(tab)) continue;
    for (const section of tab.sections) {
      if (isSerializedFieldsSection(section)) {
        indexLoadedFieldsSection(index, tab.key, section, resolveFieldSectionId);
      }
    }
  }

  for (const [tabKey, tabEdit] of Object.entries(tabEdits.systemTabEdits ?? {})) {
    for (const section of tabEdit.newSections ?? []) {
      if (isSerializedFieldsSection(section)) {
        indexLoadedFieldsSection(index, tabKey, section, resolveFieldSectionId);
      }
    }
  }

  return index;
}

function annotateLoadedFieldsSection(section: SerializedFieldsSection): SerializedFieldsSection {
  const sectionKey = layoutSectionKey(section);
  return sectionKey == null ? section : attachLayoutSectionKey(section, sectionKey);
}

function annotateLoadedTabEdits(tabEdits: SerializedTabEdits): SerializedTabEdits {
  for (const tab of tabEdits.newTabs ?? []) {
    if (!isTabWithSections(tab)) continue;
    tab.sections = tab.sections.map((section) =>
      isSerializedFieldsSection(section) ? annotateLoadedFieldsSection(section) : section,
    );
  }

  for (const tabEdit of Object.values(tabEdits.systemTabEdits ?? {})) {
    if (tabEdit.newSections != null) {
      tabEdit.newSections = tabEdit.newSections.map((section) =>
        isSerializedFieldsSection(section) ? annotateLoadedFieldsSection(section) : section,
      );
    }
  }
  return tabEdits;
}

function removeIndexes<T>(items: T[], indexes: number[]): void {
  for (const index of [...indexes].sort((a, b) => b - a)) {
    items.splice(index, 1);
  }
}

function removeFromArray<T>(
  items: T[],
  predicate: (item: T) => boolean,
  label: string,
  removeAll = true,
): number {
  const indexes: number[] = [];
  items.forEach((item, index) => {
    if (predicate(item)) indexes.push(index);
  });
  if (indexes.length > 1 && !removeAll) {
    throw new Error(`${label} matched ${indexes.length} entries; pass removeAll: true to remove them all.`);
  }
  removeIndexes(items, removeAll ? indexes : indexes.slice(0, 1));
  return removeAll ? indexes.length : Math.min(indexes.length, 1);
}

function removeKeyFromOrder(order: string[] | undefined, key: string): void {
  if (order == null) return;
  removeFromArray(order, (entry) => entry === key, `order key "${key}"`);
}

function ensureRecordProperty(record: Record<string, any>, key: string, label: string): Record<string, any> {
  const existing = record[key];
  if (existing == null) {
    const next: Record<string, any> = {};
    record[key] = next;
    return next;
  }
  if (typeof existing !== 'object' || Array.isArray(existing)) {
    throw new Error(`${label} must be an object.`);
  }
  return existing as Record<string, any>;
}

function ensureArrayProperty<T>(record: Record<string, any>, key: string, label: string): T[] {
  const existing = record[key];
  if (existing == null) {
    const next: T[] = [];
    record[key] = next;
    return next;
  }
  if (!Array.isArray(existing)) {
    throw new Error(`${label} must be an array.`);
  }
  return existing as T[];
}

// ---------------------------------------------------------------------------
// Class
// ---------------------------------------------------------------------------

/**
 * Defines a page layout and registers it with the manifest.
 *
 * A page layout controls the tab structure, section groupings, header fields,
 * and visibility conditions on a custom object's record detail page. You would
 * normally define one layout per custom object using `apiName: 'default'`.
 *
 * For simple single-tab layouts, use the {@link CustomObjectPageLayout.basic}
 * factory instead of constructing the full props manually.
 *
 * > **Caution:** all keys inside `tabEdits` and `headerEdits` must be camelCase.
 * > Snake_case keys are silently dropped on the wire and produce an empty layout.
 *
 * @example
 * ```ts
 * new CustomObjectPageLayout(memberObj, {
 *   apiName: 'default',
 *   name: 'Member',
 *   layoutId: 'layout_gym_member',
 *   tabEdits: {
 *     newTabs: [{
 *       key: 'member', name: 'Member', type: 'tab_with_sections',
 *       sections: [{
 *         name: 'Profile',
 *         type: 'fields_section',
 *         section: profileSection,
 *         fields: [{ field: 'name', editable: true }, memberEmail],
 *       }],
 *     }],
 *     systemTabEdits: {},
 *     tabsOrder: ['member'],
 *   },
 *   visibilityConditions: {},
 * });
 * ```
 *
 * @see {@link CustomObjectPageLayout.basic} — factory for simple single-tab layouts.
 */
export class CustomObjectPageLayout {
  static readonly componentType = 'CUSTOM_OBJECT_PAGE_LAYOUT' as const;

  static toDeletionIdentifier(identifier: PageLayoutDeletionIdentifier): ManifestComponentDeletion {
    return {
      type: CustomObjectPageLayout.componentType,
      layout_id: identifier.layoutId,
      object_rql_name: identifier.objectRqlName,
    };
  }

  private readonly _layoutId: string;
  private readonly _apiName: string;
  private readonly _customObjectApiName: string;
  private readonly _name: string;
  private readonly _tabEdits: SerializedTabEdits;
  private readonly _headerEdits: SerializedHeaderEdits;
  private readonly _visibilityConditions: VisibilityConditions;
  private readonly _blueprintKey: string | undefined;
  private readonly _fieldSectionLayoutSections: Map<string, FieldSectionLayoutSection[]>;
  private readonly _customObject: CustomObject;

  /**
   * @param customObject - The custom object this layout belongs to.
   * @param props - Initialization properties.
   * @throws {Error} If `apiName` or `name` is empty.
   */
  constructor(customObject: CustomObject, props: CustomObjectPageLayoutProps) {
    if (!props.apiName) throw new Error('CustomObjectPageLayout: apiName cannot be empty');
    if (!props.name) throw new Error('CustomObjectPageLayout: name cannot be empty');
    this._layoutId = props.layoutId ?? generateId('layout');
    this._apiName = props.apiName;
    this._customObjectApiName = customObject.getApiName();
    this._customObject = customObject;
    this._name = props.name;
    this._tabEdits = normalizeTabEdits(customObject, props.tabEdits ?? {});
    this._fieldSectionLayoutSections = buildFieldSectionLayoutIndexFromProps(props.tabEdits);
    this._headerEdits = normalizeHeaderEdits(props.headerEdits ?? {});
    this._visibilityConditions = props.visibilityConditions ?? {};
    this._blueprintKey = props.blueprintKey;
    customObject._register(this);
  }

  /**
   * Loads this page layout from the active existing-manifest JSON context.
   *
   * `id` resolves against `layout_id` first, then `api_name`. When loading by
   * api_name such as `'default'`, pass `customObjectApiName` if multiple objects
   * have a layout with the same api_name.
   */
  static loadFromExisting(
    layoutIdOrApiName: string,
    options: CustomObjectPageLayoutLoadFromExistingOptions = {},
  ): CustomObjectPageLayout {
    return getExistingManifestContext(options).loadPageLayout(layoutIdOrApiName, options);
  }

  /** @internal Hydrates a page layout from existing manifest wire JSON. */
  static _fromExistingComponent(
    customObject: CustomObject,
    component: Record<string, any>,
    resolveFieldSectionId?: ResolveFieldSectionId,
  ): CustomObjectPageLayout {
    const layout = Object.create(CustomObjectPageLayout.prototype) as CustomObjectPageLayout;
    const tabEdits = annotateLoadedTabEdits(cloneJson(component['tab_edits'] ?? {}));
    Object.assign(layout as Record<string, any>, {
      _layoutId: requireStringComponentField(component, 'layout_id', CustomObjectPageLayout.componentType),
      _apiName: requireStringComponentField(component, 'api_name', CustomObjectPageLayout.componentType),
      _customObjectApiName: requireStringComponentField(
        component,
        'object_rql_name',
        CustomObjectPageLayout.componentType,
      ),
      _customObject: customObject,
      _name: requireStringComponentField(component, 'name', CustomObjectPageLayout.componentType),
      _tabEdits: tabEdits,
      _headerEdits: cloneJson(component['header_edits'] ?? {}),
      _visibilityConditions: cloneJson(component['visibility_conditions'] ?? {}),
      _blueprintKey: component['blueprint_key'],
      _fieldSectionLayoutSections: buildFieldSectionLayoutIndexFromLoadedTabEdits(
        tabEdits,
        resolveFieldSectionId,
      ),
    });
    customObject._register(layout);
    return layout;
  }

  /**
   * Returns the stable identifier for this layout record (e.g. `'layout_gym_member'`).
   */
  getLayoutId(): string {
    return this._layoutId;
  }

  /**
   * Returns the api_name of this layout (e.g. `'default'`).
   */
  getApiName(): string {
    return this._apiName;
  }

  /**
   * Returns the api_name of the custom object this layout belongs to.
   */
  getCustomObjectApiName(): string {
    return this._customObjectApiName;
  }

  /**
   * Adds one field to an existing layout section.
   *
   * For loaded layouts, this mutates the preserved `tab_edits` JSON in place
   * and normalizes only the inserted field entry.
   */
  addField(field: CustomObjectFieldInput, options: AddPageLayoutFieldOptions): this {
    return this.addFields([field], options);
  }

  /**
   * Adds multiple fields to an existing layout section.
   *
   * Fields are inserted in the order provided. For custom layout sections,
   * pass `section` to choose the typed field section. Use `sectionKey` only
   * when a field section maps to multiple layout sections.
   */
  addFields(fields: CustomObjectFieldInput[], options: AddPageLayoutFieldsOptions): this {
    if (fields.length === 0) return this;

    let fieldSectionForMutation: CustomObjectFieldSection | undefined;
    const container =
      options.systemSection === true ?
        (() => {
          assertOptionAbsent(
            options,
            'section',
            'CustomObjectPageLayout addField section is only supported for custom layout sections.',
          );
          assertOptionAbsent(
            options,
            'fieldSection',
            'CustomObjectPageLayout addField fieldSection is no longer supported. ' +
              'Use sectionKey only for systemSection: true.',
          );
          return this.ensureSystemSectionFieldContainer(options.tabKey, options.sectionKey);
        })()
      : (() => {
          assertOptionAbsent(
            options,
            'fieldSection',
            'CustomObjectPageLayout addField fieldSection is no longer supported. ' +
              'Pass section: CustomObjectFieldSection instead.',
          );
          const section =
            options.section == null ?
              undefined
            : requireFieldSectionOption(options.section, 'CustomObjectPageLayout addField section');
          if (section != null) {
            this.assertFieldSectionBelongsToLayout(section);
            fieldSectionForMutation = section;
          }
          const sectionKey =
            options.sectionKey ??
            (section == null ? undefined : this.layoutSectionKeyForFieldSection(options.tabKey, section)) ??
            section?.getSectionId();
          return this.requireOneFieldContainer(options.tabKey, sectionKey, section);
        })();
    const entries = fields.map((field) =>
      this.serializeFieldForMutation(
        field,
        container.sectionKey ?? container.label,
        options,
        fieldSectionForMutation,
      ),
    );

    if (options.allowDuplicate !== true) {
      const existing = new Set(container.fields.map((entry) => fieldRqlNameOf(entry)).filter(Boolean));
      const seen = new Set<string>();
      for (const entry of entries) {
        const fieldRqlName = entry.fieldRqlName;
        if (existing.has(fieldRqlName) || seen.has(fieldRqlName)) {
          throw new Error(
            `CustomObjectPageLayout section "${container.label}" already contains field "${fieldRqlName}".`,
          );
        }
        seen.add(fieldRqlName);
      }
    }

    const index = insertionIndex(container.fields.length, options.position);
    container.fields.splice(index, 0, ...entries);
    return this;
  }

  /**
   * Removes a field from the layout's field sections.
   *
   * This only removes the field from the page layout. It does not delete the
   * `CUSTOM_OBJECT_FIELD` component from the manifest.
   */
  removeField(field: Field | string, options: RemovePageLayoutFieldOptions = {}): this {
    const fieldApiName = this.fieldApiName(field);
    if (isField(field)) this.assertFieldBelongsToLayout(field);

    let sectionKey: string | undefined;
    if (options.systemSection === true) {
      assertOptionAbsent(
        options,
        'section',
        'CustomObjectPageLayout removeField section is only supported for custom layout sections.',
      );
      sectionKey = options.sectionKey;
    } else {
      sectionKey = options.sectionKey;
      if (options.section != null) {
        const section = requireFieldSectionOption(
          options.section,
          'CustomObjectPageLayout removeField section',
        );
        this.assertFieldSectionBelongsToLayout(section);
        sectionKey ??= this.layoutSectionKeyForFieldSection(options.tabKey, section);
        sectionKey ??= section.getSectionId();
      }
    }

    const containers = this.findFieldContainers({
      tabKey: options.tabKey,
      sectionKey,
      systemSectionOnly: options.systemSection === true,
    });
    const matches: Array<{ container: MutableFieldContainer; index: number }> = [];
    for (const container of containers) {
      container.fields.forEach((entry, index) => {
        if (fieldRqlNameOf(entry) === fieldApiName) {
          matches.push({ container, index });
        }
      });
    }

    if (matches.length === 0) {
      throw new Error(`CustomObjectPageLayout does not contain field "${fieldApiName}".`);
    }
    const removeAll = options.removeAll !== false;
    if (matches.length > 1 && !removeAll) {
      throw new Error(
        `CustomObjectPageLayout field "${fieldApiName}" matched ${matches.length} entries; ` +
          'pass removeAll: true to remove them all.',
      );
    }

    const removals = removeAll ? matches : matches.slice(0, 1);
    const byContainer = new Map<MutableFieldContainer, number[]>();
    for (const match of removals) {
      const indexes = byContainer.get(match.container) ?? [];
      indexes.push(match.index);
      byContainer.set(match.container, indexes);
    }
    for (const [container, indexes] of byContainer.entries()) {
      removeIndexes(container.fields, indexes);
    }
    return this;
  }

  /** Removes multiple fields from the layout's field sections. */
  removeFields(fields: Array<Field | string>, options: RemovePageLayoutFieldOptions = {}): this {
    for (const field of fields) {
      this.removeField(field, options);
    }
    return this;
  }

  /**
   * Adds a section to an existing tab.
   *
   * Pass `systemTab: true` to add a new section to a built-in tab via
   * `systemTabEdits.newSections`.
   */
  addSection(section: PageLayoutSection, options: AddPageLayoutSectionOptions): this {
    const normalized = this.normalizeSectionForMutation(section);
    if (options.systemTab === true) {
      const tabEdit = this.ensureSystemTabEdit(options.tabKey);
      const sections = ensureArrayProperty<SerializedPageLayoutSection>(
        tabEdit as Record<string, any>,
        'newSections',
        `systemTabEdits.${options.tabKey}.newSections`,
      );
      this.assertSectionKeyAvailable(
        sections,
        layoutSectionKey(normalized),
        options.tabKey,
        options.allowDuplicate,
      );
      const sectionsOrder = this.ensureSystemSectionsOrder(tabEdit);
      insertAt(sections, normalized, options.position);
      insertUniqueAt(sectionsOrder, layoutSectionKey(normalized), options.position);
      if (section.type === 'fields_section') {
        this.rememberFieldSectionLayoutSection(section.section, options.tabKey, layoutSectionKey(normalized));
      }
      return this;
    }

    const tab = this.findNewTabWithSections(options.tabKey);
    if (tab == null) {
      throw new Error(
        `CustomObjectPageLayout could not find new tab "${options.tabKey}". ` +
          'Pass systemTab: true to add a section to a built-in system tab.',
      );
    }
    this.assertSectionKeyAvailable(
      tab.sections,
      layoutSectionKey(normalized),
      options.tabKey,
      options.allowDuplicate,
    );
    insertAt(tab.sections, normalized, options.position);
    if (section.type === 'fields_section') {
      this.rememberFieldSectionLayoutSection(section.section, tab.key, layoutSectionKey(normalized));
    }
    return this;
  }

  /**
   * Removes a section from `newTabs` / `systemTabEdits.newSections`.
   *
   * Pass `systemSection: true` with `tabKey` to delete a built-in section via
   * `systemSectionEdits[sectionKey].deleted`.
   */
  removeSection(section: CustomObjectFieldSection, options?: RemovePageLayoutSectionOptions): this;
  removeSection(sectionKey: string, options?: RemovePageLayoutSectionOptions): this;
  removeSection(sectionKey: string, options: RemoveSystemPageLayoutSectionOptions): this;
  removeSection(
    sectionOrKey: CustomObjectFieldSection | string,
    options: RemovePageLayoutSectionOptions | RemoveSystemPageLayoutSectionOptions = {},
  ): this {
    if (options.systemSection === true) {
      if (typeof sectionOrKey !== 'string') {
        throw new TypeError(
          'CustomObjectPageLayout removeSection with systemSection: true requires a system section key.',
        );
      }
      if (options.tabKey == null) {
        throw new Error('CustomObjectPageLayout removeSection with systemSection: true requires tabKey.');
      }
      const sectionEdit = this.ensureSystemSectionEdit(options.tabKey, sectionOrKey);
      sectionEdit.deleted = true;
      removeKeyFromOrder(this._tabEdits.systemTabEdits?.[options.tabKey]?.sectionsOrder, sectionOrKey);
      this.removeSectionVisibility(sectionOrKey);
      return this;
    }

    let sectionKey: string;
    if (typeof sectionOrKey === 'string') {
      sectionKey = sectionOrKey;
    } else {
      const section = requireFieldSectionOption(sectionOrKey, 'CustomObjectPageLayout removeSection section');
      this.assertFieldSectionBelongsToLayout(section);
      sectionKey = this.layoutSectionKeyForFieldSection(options.tabKey, section) ?? section.getSectionId();
    }
    const matches: Array<{
      sections: SerializedPageLayoutSection[];
      section: SerializedFieldsSection;
      index: number;
      tabEdit?: SerializedSystemTabEdit;
      tabKey: string;
    }> = [];
    for (const tab of this._tabEdits.newTabs ?? []) {
      if (!isTabWithSections(tab)) continue;
      if (options.tabKey != null && tab.key !== options.tabKey) continue;
      tab.sections.forEach((section, index) => {
        if (isSerializedFieldsSection(section) && layoutSectionMatches(section, sectionKey))
          matches.push({ sections: tab.sections, section, index, tabKey: tab.key });
      });
    }
    for (const [tabKey, tabEdit] of Object.entries(this._tabEdits.systemTabEdits ?? {})) {
      if (options.tabKey != null && tabKey !== options.tabKey) continue;
      (tabEdit.newSections ?? []).forEach((section, index) => {
        if (isSerializedFieldsSection(section) && layoutSectionMatches(section, sectionKey))
          matches.push({ sections: tabEdit.newSections!, section, index, tabEdit, tabKey });
      });
    }

    if (matches.length === 0) {
      throw new Error(`CustomObjectPageLayout does not contain section "${sectionKey}".`);
    }
    const removeAll = options.removeAll !== false;
    if (matches.length > 1 && !removeAll) {
      throw new Error(
        `CustomObjectPageLayout section "${sectionKey}" matched ${matches.length} entries; ` +
          'pass removeAll: true to remove them all.',
      );
    }

    const removals = removeAll ? matches : matches.slice(0, 1);
    const byArray = new Map<SerializedPageLayoutSection[], number[]>();
    for (const match of removals) {
      const indexes = byArray.get(match.sections) ?? [];
      indexes.push(match.index);
      byArray.set(match.sections, indexes);
      if (match.tabEdit != null) removeKeyFromOrder(match.tabEdit.sectionsOrder, sectionKey);
      this.removeSectionVisibility(sectionKey);
    }
    for (const [sections, indexes] of byArray.entries()) {
      removeIndexes(sections, indexes);
    }
    return this;
  }

  /** Adds a new tab to `tab_edits.newTabs`. */
  addTab(tab: PageLayoutTab, options: AddPageLayoutTabOptions = {}): this {
    const normalized = this.normalizeTabForMutation(tab);
    const newTabs = (this._tabEdits.newTabs ??= []);
    if (options.allowDuplicate !== true && newTabs.some((existing) => existing.key === normalized.key)) {
      throw new Error(`CustomObjectPageLayout already contains tab "${normalized.key}".`);
    }
    const tabsOrder = this.ensureTabsOrder();
    insertAt(newTabs, normalized, options.position);
    insertUniqueAt(tabsOrder, normalized.key, options.position);
    if (tab.type === 'tab_with_sections') {
      for (const section of tab.sections)
        indexPageLayoutSectionInput(this._fieldSectionLayoutSections, tab.key, section);
    }
    return this;
  }

  /**
   * Removes a tab from `newTabs`.
   *
   * Pass `systemTab: true` to delete a built-in tab via `systemTabEdits[tabKey].deleted`.
   */
  removeTab(tabKey: string, options: RemovePageLayoutTabOptions = {}): this {
    if (options.systemTab === true) {
      const tabEdit = this.ensureSystemTabEdit(tabKey);
      tabEdit.deleted = true;
      removeKeyFromOrder(this._tabEdits.tabsOrder, tabKey);
      this.removeTabVisibility(tabKey);
      return this;
    }

    const newTabs = this._tabEdits.newTabs ?? [];
    const removed = removeFromArray(
      newTabs,
      (tab) => tab.key === tabKey,
      `CustomObjectPageLayout tab "${tabKey}"`,
      options.removeAll !== false,
    );
    if (removed === 0) {
      throw new Error(`CustomObjectPageLayout does not contain tab "${tabKey}".`);
    }
    removeKeyFromOrder(this._tabEdits.tabsOrder, tabKey);
    this.removeTabVisibility(tabKey);
    return this;
  }

  /** Adds a custom header field to `header_edits.newFields`. */
  addHeaderField(field: Field | NewHeaderField, options: AddHeaderFieldOptions = {}): this {
    const headerField = this.normalizeHeaderFieldForMutation(field, options);
    const newFields = (this._headerEdits.newFields ??= []);
    if (options.allowDuplicate !== true && newFields.some((existing) => existing.key === headerField.key)) {
      throw new Error(`CustomObjectPageLayout header already contains field key "${headerField.key}".`);
    }
    const headerFieldsOrder = this.ensureHeaderFieldsOrder();
    insertAt(newFields, headerField, options.position);
    insertUniqueAt(headerFieldsOrder, headerField.rqlName, options.position);
    return this;
  }

  /** Removes custom header fields from `header_edits.newFields`. */
  removeHeaderField(fieldOrKey: Field | string, options: RemoveHeaderFieldOptions = {}): this {
    const fieldApiName = typeof fieldOrKey === 'string' ? undefined : fieldOrKey.getApiName();
    if (isField(fieldOrKey)) this.assertFieldBelongsToLayout(fieldOrKey);
    const key = typeof fieldOrKey === 'string' ? fieldOrKey : fieldApiName;
    const newFields = this._headerEdits.newFields ?? [];
    const removedFields: NewHeaderField[] = [];
    const removed = removeFromArray(
      newFields,
      (field) => {
        const matched = field.key === key || (fieldApiName != null && field.rqlName === fieldApiName);
        if (matched) removedFields.push(field);
        return matched;
      },
      `CustomObjectPageLayout header field "${key}"`,
      options.removeAll !== false,
    );
    if (removed === 0) {
      throw new Error(`CustomObjectPageLayout header does not contain field "${key}".`);
    }
    for (const removedField of removedFields) this.removeHeaderOrderFieldIfUnused(removedField);
    return this;
  }

  /** Sets the record title field in `header_edits`. */
  setTitleField(field: Field): this;
  setTitleField(fieldApiName: FieldRqlName): this;
  setTitleField(field: Field | FieldRqlName): this {
    const previousTitleField = this._headerEdits.newTitleField;
    const nextTitleField = this.headerFieldApiName(field);
    this._headerEdits.newTitleField = nextTitleField;
    this._headerEdits.titleFieldDeleted = false;
    insertUniqueAt(this.ensureHeaderFieldsOrder(), nextTitleField, 'end');
    this.removeHeaderOrderFieldIfUnused(previousTitleField);
    return this;
  }

  /** Removes the record title field from the header. */
  removeTitleField(): this {
    const previousTitleField = this._headerEdits.newTitleField;
    this._headerEdits.newTitleField = null;
    this._headerEdits.titleFieldDeleted = true;
    this.removeHeaderOrderFieldIfUnused(previousTitleField);
    return this;
  }

  /** Sets the record description field in `header_edits`. */
  setDescriptionField(field: Field): this;
  setDescriptionField(fieldApiName: FieldRqlName): this;
  setDescriptionField(field: Field | FieldRqlName): this {
    const previousDescriptionField = this._headerEdits.newDescriptionField;
    const nextDescriptionField = this.headerFieldApiName(field);
    this._headerEdits.newDescriptionField = nextDescriptionField;
    this._headerEdits.descriptionFieldDeleted = false;
    insertUniqueAt(this.ensureHeaderFieldsOrder(), nextDescriptionField, 'end');
    this.removeHeaderOrderFieldIfUnused(previousDescriptionField);
    return this;
  }

  /** Removes the record description field from the header. */
  removeDescriptionField(): this {
    const previousDescriptionField = this._headerEdits.newDescriptionField;
    this._headerEdits.newDescriptionField = null;
    this._headerEdits.descriptionFieldDeleted = true;
    this.removeHeaderOrderFieldIfUnused(previousDescriptionField);
    return this;
  }

  private ensureTabsOrder(): string[] {
    const order = (this._tabEdits.tabsOrder ??= []);
    for (const tab of this._tabEdits.newTabs ?? []) insertUniqueAt(order, tab.key, 'end');
    for (const [tabKey, tabEdit] of Object.entries(this._tabEdits.systemTabEdits ?? {})) {
      if (tabEdit.deleted !== true) insertUniqueAt(order, tabKey, 'end');
    }
    return order;
  }

  private ensureSystemSectionsOrder(tabEdit: SerializedSystemTabEdit): string[] {
    const order = (tabEdit.sectionsOrder ??= []);
    for (const section of tabEdit.newSections ?? []) insertUniqueAt(order, layoutSectionKey(section), 'end');
    for (const [sectionKey, sectionEdit] of Object.entries(tabEdit.systemSectionEdits ?? {})) {
      if (sectionEdit.deleted !== true) insertUniqueAt(order, sectionKey, 'end');
    }
    return order;
  }

  private ensureHeaderFieldsOrder(): string[] {
    this._headerEdits.headerFieldsOrder = normalizeHeaderFieldsOrder({
      ...this._headerEdits,
      headerFieldsOrder: this._headerEdits.headerFieldsOrder ?? [],
    });
    return this._headerEdits.headerFieldsOrder;
  }

  private headerOrderFieldIsUsed(rqlName: string): boolean {
    return (
      this._headerEdits.newTitleField === rqlName ||
      this._headerEdits.newDescriptionField === rqlName ||
      (this._headerEdits.newFields ?? []).some((field) => field.rqlName === rqlName) ||
      Object.values(this._headerEdits.systemFieldEdits ?? {}).some((edit) => edit.newRqlField === rqlName)
    );
  }

  private removeHeaderOrderFieldIfUnused(field: NewHeaderField | string | null | undefined): void {
    const rqlName = typeof field === 'string' ? field : field?.rqlName;
    if (field != null && typeof field !== 'string' && field.key !== rqlName) {
      removeKeyFromOrder(this._headerEdits.headerFieldsOrder, field.key);
    }
    if (rqlName == null || this.headerOrderFieldIsUsed(rqlName)) return;
    removeKeyFromOrder(this._headerEdits.headerFieldsOrder, rqlName);
  }

  private serializeFieldForMutation(
    field: CustomObjectFieldInput,
    fallbackSectionKey: string,
    options: AddPageLayoutFieldOptions,
    fieldSection: CustomObjectFieldSection | undefined,
  ): SerializedSectionField {
    const resolved = this._resolveField(field);
    this.assertFieldBelongsToLayout(resolved);
    this.assignFieldSectionForMutation(resolved, fallbackSectionKey, fieldSection);
    return toSerializedSectionField(resolved.getApiName(), options);
  }

  private normalizeSectionFieldForMutation(
    section: CustomObjectFieldSection | string,
    sectionKey: string,
    entry: SectionFieldInput,
  ): SerializedSectionField {
    if (isField(entry) || typeof entry === 'string') {
      const field = this._resolveField(entry);
      this.assertFieldBelongsToLayout(field);
      assignSectionForLayout(field, section);
      return toSerializedSectionField(field.getApiName());
    }

    if (isFieldRef(entry)) {
      const field = this._resolveField(entry.field);
      this.assertFieldBelongsToLayout(field);
      assignSectionForLayout(field, section);
      return toSerializedSectionField(field.getApiName(), entry);
    }

    throw new Error(
      `CustomObjectPageLayout fields_section "${sectionKey}" has an invalid field entry; ` +
        'pass a Field instance or { field }.',
    );
  }

  private normalizeSectionForMutation(input: PageLayoutSection): SerializedPageLayoutSection {
    if (input.type !== 'fields_section') return { ...input };

    this.assertFieldSectionBelongsToLayout(input.section);

    const sectionKey = input.key ?? input.section.getSectionId();
    const name = input.name ?? input.section.getName();
    const normalized = copySectionOptions<SerializedFieldsSection>(
      {
        name,
        type: 'fields_section',
        fields: input.fields.map((field) =>
          this.normalizeSectionFieldForMutation(input.section, sectionKey, field),
        ),
      },
      input,
    );
    if (input.layout != null) normalized.layout = input.layout;
    return attachLayoutSectionKey(normalized, sectionKey);
  }

  private normalizeTabForMutation(tab: PageLayoutTab): SerializedPageLayoutTab {
    if (tab.type === 'custom_tab') return { ...tab };
    return {
      ...tab,
      sections: tab.sections.map((section) => this.normalizeSectionForMutation(section)),
    };
  }

  private assignFieldSectionForMutation(
    field: Field,
    fallbackSectionKey: string,
    fieldSection: CustomObjectFieldSection | undefined,
  ): void {
    if (field.isStandard()) return;
    const rawFieldSection = fieldSection as CustomObjectFieldSection | string | undefined;
    if (rawFieldSection != null) {
      if (typeof rawFieldSection === 'string') {
        throw new TypeError(
          `CustomObjectPageLayout section must be a CustomObjectFieldSection object; ` +
            `received raw section id "${rawFieldSection}". Load/include the existing field section first.`,
        );
      }
      if (rawFieldSection.getModelApiName() !== this._customObjectApiName) {
        throw new Error(
          `CustomObjectPageLayout field section "${rawFieldSection.getSectionId()}" belongs to ` +
            `"${rawFieldSection.getModelApiName()}", but the layout belongs to "${
              this._customObjectApiName
            }".`,
        );
      }
      field._assignSection(rawFieldSection);
      return;
    }

    if (field.getSectionId() == null) {
      throw new Error(
        `CustomObjectPageLayout field "${field.getApiName()}" is missing field-section metadata. ` +
          `Construct the field with a CustomObjectFieldSection or pass section when adding it to ` +
          `section "${fallbackSectionKey}".`,
      );
    }
  }

  private assertFieldBelongsToLayout(field: Field): void {
    if (field.getCustomObjectApiName() !== this._customObjectApiName) {
      throw new Error(
        `CustomObjectPageLayout references field "${field.getApiName()}" from ` +
          `"${field.getCustomObjectApiName()}", but the layout belongs to "${this._customObjectApiName}".`,
      );
    }
  }

  private _resolveField(field: CustomObjectFieldInput): Field {
    return this._customObject._resolveField(field);
  }

  private fieldApiName(field: Field | string): FieldRqlName {
    if (typeof field !== 'string') return field.getApiName();
    if (field.endsWith('__c')) return field;
    return this._customObject.standardField(field as CustomObjectStandardFieldIdentifier).getApiName();
  }

  private assertFieldSectionBelongsToLayout(section: CustomObjectFieldSection): void {
    if (section.getModelApiName() !== this._customObjectApiName) {
      throw new Error(
        `CustomObjectPageLayout field section "${section.getSectionId()}" belongs to ` +
          `"${section.getModelApiName()}", but the layout belongs to "${this._customObjectApiName}".`,
      );
    }
  }

  private rememberFieldSectionLayoutSection(
    section: CustomObjectFieldSection,
    tabKey: string,
    sectionKey: string | undefined,
  ): void {
    if (sectionKey == null) return;
    addFieldSectionLayoutSection(this._fieldSectionLayoutSections, section.getSectionId(), {
      tabKey,
      sectionKey,
    });
  }

  private layoutSectionKeyForFieldSection(
    tabKey: string | undefined,
    section: CustomObjectFieldSection,
  ): string | undefined {
    const entries = this._fieldSectionLayoutSections.get(section.getSectionId()) ?? [];
    const matches = tabKey == null ? entries : entries.filter((entry) => entry.tabKey === tabKey);
    const sectionKeys = [...new Set(matches.map((entry) => entry.sectionKey))];
    if (sectionKeys.length === 0) return undefined;
    if (sectionKeys.length === 1) return sectionKeys[0];

    const scope = tabKey == null ? '' : ` in tab "${tabKey}"`;
    throw new Error(
      `CustomObjectPageLayout field section "${section.getSectionId()}" maps to multiple layout sections${scope}: ` +
        `${sectionKeys.join(', ')}. Pass sectionKey to choose one.`,
    );
  }

  private requireOneFieldContainer(
    tabKey: string | undefined,
    sectionKey: string | undefined,
    fallbackFieldSection?: CustomObjectFieldSection,
  ): MutableFieldContainer {
    const containers = this.findFieldContainers({
      tabKey,
      sectionKey,
      systemSectionOnly: false,
    });
    if (containers.length === 0) {
      if (sectionKey != null && fallbackFieldSection != null) {
        const unkeyedContainers = this.findFieldContainers({
          tabKey,
          sectionKey: undefined,
          systemSectionOnly: false,
        }).filter((container) => container.section != null && container.sectionKey == null);
        if (unkeyedContainers.length === 1) {
          if (fallbackFieldSection.getModelApiName() !== this._customObjectApiName) {
            throw new Error(
              `CustomObjectPageLayout field section "${fallbackFieldSection.getSectionId()}" belongs to ` +
                `"${fallbackFieldSection.getModelApiName()}", but the layout belongs to "${
                  this._customObjectApiName
                }".`,
            );
          }
          const container = unkeyedContainers[0] as MutableFieldContainer & {
            section: SerializedFieldsSection;
          };
          attachLayoutSectionKey(container.section, sectionKey);
          container.sectionKey = sectionKey;
          container.label = `${container.tabKey}.${container.sectionKey}`;
          return container;
        }
      }
      const scope =
        sectionKey == null ? 'a field section' : (
          `section "${tabKey != null ? `${tabKey}.` : ''}${sectionKey}"`
        );
      throw new Error(`CustomObjectPageLayout could not find ${scope}.`);
    }
    if (containers.length > 1) {
      if (sectionKey == null) {
        throw new Error(
          `CustomObjectPageLayout matched multiple sections: ` +
            `${containers.map((container) => container.label).join(', ')}. Pass section to choose one.`,
        );
      }
      throw new Error(
        `CustomObjectPageLayout section "${sectionKey}" matched multiple sections: ` +
          `${containers.map((container) => container.label).join(', ')}. Pass tabKey to choose one.`,
      );
    }
    return containers[0] as MutableFieldContainer;
  }

  private findFieldContainers(filter: {
    tabKey: string | undefined;
    sectionKey: string | undefined;
    systemSectionOnly: boolean;
  }): MutableFieldContainer[] {
    const containers: MutableFieldContainer[] = [];

    if (!filter.systemSectionOnly) {
      for (const tab of this._tabEdits.newTabs ?? []) {
        if (!isTabWithSections(tab)) continue;
        if (filter.tabKey != null && tab.key !== filter.tabKey) continue;
        for (const [index, section] of tab.sections.entries()) {
          if (!isSerializedFieldsSection(section)) continue;
          const sectionKey = layoutSectionKey(section);
          if (filter.sectionKey != null && !layoutSectionMatches(section, filter.sectionKey)) continue;
          const label = sectionKey == null ? `${tab.key}.sections[${index}]` : `${tab.key}.${sectionKey}`;
          containers.push({
            tabKey: tab.key,
            sectionKey,
            section,
            fields: ensureArrayProperty<MutableSectionField>(
              section as unknown as Record<string, any>,
              'fields',
              `newTabs.${label}.fields`,
            ),
            label,
          });
        }
      }

      for (const [tabKey, tabEdit] of Object.entries(this._tabEdits.systemTabEdits ?? {})) {
        if (filter.tabKey != null && tabKey !== filter.tabKey) continue;
        for (const [index, section] of (tabEdit.newSections ?? []).entries()) {
          if (!isSerializedFieldsSection(section)) continue;
          const sectionKey = layoutSectionKey(section);
          if (filter.sectionKey != null && !layoutSectionMatches(section, filter.sectionKey)) continue;
          const label = sectionKey == null ? `${tabKey}.newSections[${index}]` : `${tabKey}.${sectionKey}`;
          containers.push({
            tabKey,
            sectionKey,
            section,
            fields: ensureArrayProperty<MutableSectionField>(
              section as unknown as Record<string, any>,
              'fields',
              `systemTabEdits.${label}.fields`,
            ),
            label,
          });
        }
      }
    }

    for (const [tabKey, tabEdit] of Object.entries(this._tabEdits.systemTabEdits ?? {})) {
      if (filter.tabKey != null && tabKey !== filter.tabKey) continue;
      for (const [sectionKey, sectionEdit] of Object.entries(tabEdit.systemSectionEdits ?? {})) {
        if (filter.sectionKey != null && sectionKey !== filter.sectionKey) continue;
        const fields = (sectionEdit as Record<string, any>)['newFields'];
        if (fields == null) continue;
        if (!Array.isArray(fields)) {
          throw new Error(
            `systemTabEdits.${tabKey}.systemSectionEdits.${sectionKey}.newFields must be an array.`,
          );
        }
        containers.push({
          tabKey,
          sectionKey,
          fields: fields as MutableSectionField[],
          label: `${tabKey}.${sectionKey}`,
        });
      }
    }

    return containers;
  }

  private ensureSystemSectionFieldContainer(
    tabKey: string | undefined,
    sectionKey: string | undefined,
  ): MutableFieldContainer {
    if (tabKey == null) {
      throw new Error('CustomObjectPageLayout addField with systemSection: true requires tabKey.');
    }
    if (sectionKey == null) {
      throw new Error('CustomObjectPageLayout addField with systemSection: true requires sectionKey.');
    }
    const sectionEdit = this.ensureSystemSectionEdit(tabKey, sectionKey);
    if (sectionEdit.deleted === true) {
      throw new Error(`CustomObjectPageLayout system section "${tabKey}.${sectionKey}" is marked deleted.`);
    }
    return {
      tabKey,
      sectionKey,
      fields: ensureArrayProperty<MutableSectionField>(
        sectionEdit as Record<string, any>,
        'newFields',
        `systemTabEdits.${tabKey}.systemSectionEdits.${sectionKey}.newFields`,
      ),
      label: `${tabKey}.${sectionKey}`,
    };
  }

  private ensureSystemTabEdit(tabKey: string): SerializedSystemTabEdit {
    const systemTabEdits = ensureRecordProperty(
      this._tabEdits as unknown as Record<string, any>,
      'systemTabEdits',
      'tab_edits.systemTabEdits',
    );
    return ensureRecordProperty(
      systemTabEdits,
      tabKey,
      `systemTabEdits.${tabKey}`,
    ) as SerializedSystemTabEdit;
  }

  private ensureSystemSectionEdit(tabKey: string, sectionKey: string): SerializedSystemSectionEdit {
    const tabEdit = this.ensureSystemTabEdit(tabKey);
    const systemSectionEdits = ensureRecordProperty(
      tabEdit as Record<string, any>,
      'systemSectionEdits',
      `systemTabEdits.${tabKey}.systemSectionEdits`,
    );
    return ensureRecordProperty(
      systemSectionEdits,
      sectionKey,
      `systemTabEdits.${tabKey}.systemSectionEdits.${sectionKey}`,
    ) as SerializedSystemSectionEdit;
  }

  private findNewTabWithSections(tabKey: string): SerializedTabWithSections | undefined {
    let found: SerializedTabWithSections | undefined;
    for (const tab of this._tabEdits.newTabs ?? []) {
      if (tab.key !== tabKey) continue;
      if (!isTabWithSections(tab)) {
        throw new Error(
          `CustomObjectPageLayout tab "${tabKey}" is a custom_tab and cannot contain sections.`,
        );
      }
      if (found != null) {
        throw new Error(`CustomObjectPageLayout contains multiple new tabs with key "${tabKey}".`);
      }
      found = tab;
    }
    return found;
  }

  private assertSectionKeyAvailable(
    sections: SerializedPageLayoutSection[],
    sectionKey: string | undefined,
    tabKey: string,
    allowDuplicate: boolean | undefined,
  ): void {
    if (allowDuplicate === true) return;
    if (sectionKey != null && sections.some((section) => layoutSectionMatches(section, sectionKey))) {
      throw new Error(`CustomObjectPageLayout tab "${tabKey}" already contains section "${sectionKey}".`);
    }
  }

  private normalizeHeaderFieldForMutation(
    field: Field | NewHeaderField,
    options: AddHeaderFieldOptions,
  ): NewHeaderField {
    const source = isField(field) ? undefined : field;
    const rqlName = isField(field) ? field.getApiName() : field.rqlName;
    if (isField(field)) this.assertFieldBelongsToLayout(field);
    if (!rqlName) throw new Error('CustomObjectPageLayout header field rqlName cannot be empty.');

    const key = options.key ?? source?.key ?? (isField(field) ? field.getApiName() : undefined);
    if (!key) throw new Error('CustomObjectPageLayout header field key cannot be empty.');

    const normalized: NewHeaderField = { rqlName, key };
    const canBeDeleted = options.canBeDeleted ?? source?.canBeDeleted;
    const canBeChanged = options.canBeChanged ?? source?.canBeChanged;
    const canBeMoved = options.canBeMoved ?? source?.canBeMoved;
    if (canBeDeleted != null) normalized.canBeDeleted = canBeDeleted;
    if (canBeChanged != null) normalized.canBeChanged = canBeChanged;
    if (canBeMoved != null) normalized.canBeMoved = canBeMoved;
    return normalized;
  }

  private headerFieldApiName(field: Field | FieldRqlName): FieldRqlName {
    if (typeof field === 'string') return this.fieldApiName(field);
    this.assertFieldBelongsToLayout(field);
    return field.getApiName();
  }

  private removeSectionVisibility(sectionKey: string): void {
    if (this._visibilityConditions.sections != null) {
      delete this._visibilityConditions.sections[sectionKey];
    }
  }

  private removeTabVisibility(tabKey: string): void {
    if (this._visibilityConditions.tabs != null) {
      delete this._visibilityConditions.tabs[tabKey];
    }
  }

  /**
   * Serializes this layout to the wire format consumed by the manifest install endpoint.
   *
   * @returns A plain object with `type: 'CUSTOM_OBJECT_PAGE_LAYOUT'`.
   */
  toDict(): Record<string, any> {
    const d: Record<string, any> = {
      type: CustomObjectPageLayout.componentType,
      layout_id: this._layoutId,
      api_name: this._apiName,
      object_rql_name: this._customObjectApiName,
      name: this._name,
      // Packaged layouts are never system-created (backend invariant).
      system_created: false,
      tab_edits: this._tabEdits,
      header_edits: this._headerEdits,
      visibility_conditions: this._visibilityConditions,
      blueprint_key: this._blueprintKey ?? this._customObjectApiName,
    };
    return d;
  }

  /**
   * Creates a simple single-tab "Details" layout with a single "General" section.
   *
   * Use this factory when you want a straightforward layout without customizing
   * tabs or sections. Always uses `apiName: 'default'`.
   *
   * @param customObject - The custom object to create the layout for.
   * @param props - Optional. Pass `section` and `fields` to populate the General section.
   * @returns A new `CustomObjectPageLayout` registered with the manifest.
   *
   * @example
   * ```ts
   * CustomObjectPageLayout.basic(memberObj, {
   *   section: profileSection,
   *   fields: [memberFirstName, memberEmail, memberStatusField],
   * });
   * ```
   */
  static basic(
    customObject: CustomObject,
    props: {
      section?: CustomObjectFieldSection;
      fields?: CustomObjectFieldInput[];
    } = {},
  ): CustomObjectPageLayout {
    const coApiName = customObject.getApiName();
    const coName = customObject.getName();
    const fields = (props.fields ?? []).map((field) => customObject._resolveField(field));
    const generalSection =
      props.section ??
      (() => {
        const alreadySectionedField = fields.find((field) => field.getSectionId() != null);
        if (alreadySectionedField != null) {
          throw new Error(
            `CustomObjectPageLayout.basic field "${alreadySectionedField.getApiName()}" already belongs to ` +
              `field section "${alreadySectionedField.getSectionId()}". Pass that CustomObjectFieldSection ` +
              'as section so basic() does not reassign the field.',
          );
        }
        const sectionPrefix = coApiName.replace(/__c$/, '').replace(/[^a-zA-Z0-9]+/g, '_');
        return new CustomObjectFieldSection(customObject, {
          sectionId: `sec_${sectionPrefix}_general`,
          name: 'General',
        });
      })();
    assertSectionBelongsTo(customObject, generalSection);
    for (const field of fields) {
      const fieldSectionId = field.getSectionId();
      if (fieldSectionId != null && fieldSectionId !== generalSection.getSectionId()) {
        throw new Error(
          `CustomObjectPageLayout.basic field "${field.getApiName()}" belongs to field section ` +
            `"${fieldSectionId}", but basic() was given section "${generalSection.getSectionId()}".`,
        );
      }
    }
    return new CustomObjectPageLayout(customObject, {
      apiName: 'default',
      name: `${coName} Layout`,
      tabEdits: {
        newTabs: [
          {
            key: 'details',
            name: 'Details',
            type: 'tab_with_sections',
            sections: [
              {
                name: 'General',
                type: 'fields_section',
                section: generalSection,
                fields,
              },
            ],
          },
        ],
        systemTabEdits: {},
        tabsOrder: ['details'],
      },
      headerEdits: {},
      visibilityConditions: {},
    });
  }
}