import type {
  SduiActionWire,
  SduiBlockWire,
  SduiHeaderWire,
  SduiScreenMetaWire,
  SduiScreenWire,
  StyleWire,
} from '@proulr/sdui-contract';
import type { BdcElement } from './jsx-runtime';

function camelToSnake(key: string): string {
  return key.replace(/[A-Z]/g, (letter) => `_${letter.toLowerCase()}`);
}

function mapPropsToWire(props: Record<string, unknown>): Record<string, unknown> {
  const wire: Record<string, unknown> = {};
  for (const [key, value] of Object.entries(props)) {
    if (key === 'children') continue;
    if (key === 'actionId') {
      wire.action_id = value;
      continue;
    }
    if (key === 'style' && value && typeof value === 'object') {
      const styleWire: Record<string, unknown> = {};
      for (const [sk, sv] of Object.entries(value as StyleWire)) {
        styleWire[camelToSnake(sk)] = sv;
      }
      wire.style = styleWire;
      continue;
    }
    wire[camelToSnake(key)] = value;
  }
  return wire;
}

function textFromChildren(children: BdcElement[]): string {
  return children
    .map((child) => {
      if (child.type === '_text_node') return String(child.props.value ?? '');
      if (child.type === 'text' && typeof child.props.text === 'string') return child.props.text;
      return '';
    })
    .join('')
    .trim();
}

function mapHeaderToWire(header: Record<string, unknown>): SduiHeaderWire {
  const wire: Record<string, unknown> = {};
  for (const [key, value] of Object.entries(header)) {
    if (key === 'slotBlocks' || key === 'slot_blocks' || key === 'headerSlot') continue;
    if (key === 'headerSearch') {
      wire.header_search = value;
      continue;
    }
    wire[camelToSnake(key)] = value;
  }
  return wire as SduiHeaderWire;
}

export function compileBdcBlock(element: BdcElement, path = '0'): SduiBlockWire {
  return mapBlock(element, path);
}

function flattenBlockChildren(children: BdcElement[]): BdcElement[] {
  const out: BdcElement[] = [];
  for (const child of children) {
    if (child.type === '_text_node') continue;
    if (child.type === '_fragment') {
      out.push(...flattenBlockChildren(child.children));
      continue;
    }
    out.push(child);
  }
  return out;
}

function mapBlock(element: BdcElement, path: string): SduiBlockWire {
  if (element.type === '_text_node') {
    return { id: path, type: 'text', props: { text: String(element.props.value ?? '') } };
  }

  const props = mapPropsToWire(element.props);

  if (element.type === 'button' && !props.label) {
    props.label = textFromChildren(element.children);
  }

  if (element.type === 'text' && !props.text) {
    props.text = textFromChildren(element.children);
  }

  const blockChildren = flattenBlockChildren(element.children);

  return {
    id: typeof element.props.id === 'string' ? element.props.id : path,
    type: element.type,
    props,
    children: blockChildren.map((child, index) => mapBlock(child, `${path}.${index}`)),
  };
}

export function compileBdcToWire(root: BdcElement): SduiScreenWire {
  if (root.type !== 'screen') {
    throw new Error('bdc_root_must_be_screen');
  }

  const {
    id,
    header,
    headerSlot,
    actions,
    meta,
    data,
    children: _ignored,
    ...rest
  } = root.props as {
    id: string;
    header?: SduiHeaderWire;
    headerSlot?: BdcElement | BdcElement[];
    actions?: Record<string, SduiActionWire>;
    meta?: SduiScreenMetaWire;
    data?: Record<string, unknown>;
    children?: unknown;
  };

  void rest;

  const blocks = flattenBlockChildren(root.children).map((child, index) =>
    mapBlock(child, String(index)),
  );

  const compiledHeader = header ? mapHeaderToWire(header as Record<string, unknown>) : undefined;
  if (compiledHeader && headerSlot) {
    const slotRoots = Array.isArray(headerSlot) ? headerSlot : [headerSlot];
    compiledHeader.slot_blocks = slotRoots.map((slot, index) => mapBlock(slot, `header.${index}`));
  }

  return {
    schema_version: 1,
    screen_id: id,
    header: compiledHeader,
    blocks,
    data: data ?? {},
    actions: actions ?? {},
    meta: meta ?? { bff: undefined, cache_ttl_ms: 30_000, offline_policy: 'cache_only' },
  };
}