import { XRegularIcon } from "alouette-icons/phosphor-icons/X";
import { type ReactNode, useId } from "react";
import {
  Platform,
  Pressable,
  Modal as RNModal,
  useWindowDimensions,
} from "react-native";
import type { VariantProps } from "tailwind-variants";
import type { Accent } from "../../core/AlouetteConfig";
import { useReducedMotion } from "../../core/ReducedMotionContext";
import { tv } from "../../core/tv";
import { useScrollEndState } from "../../core/useScrollEndState";
import { IconButton } from "../actions/IconButton";
import { Icon, type SVGIconElement } from "../primitives/Icon";
import { ScrollView } from "../primitives/ScrollView";
import { Text } from "../primitives/Text";
import { View } from "../primitives/View";
import { PortalAccentScope } from "./PortalAccentScope";

// Yoga only knows `relative` and `absolute` — `position: sticky` is a web-only
// feature and the class compiles away on native. A component that pins an
// element to the edge of a scroll box has to lay it out differently there.
const supportsStickyPosition = Platform.OS === "web";

// The panel padding is split in half so the web scrollbar sits in a balanced
// gutter: one half stays on the panel (outside the scroll box, between the panel
// edge and the bar), the other moves into the scroll content container (inside
// it, between the bar and the content). The header is outside the scroll box, so
// it carries the inner half itself to stay aligned with the scrolling content;
// the footer carries the bottom half, which the scroll content drops (pb-0).
const modalVariants = tv({
  slots: {
    // w-full so the panel shrinks on small screens (the backdrop padding keeps a
    // margin); max-w caps it on wide viewports.
    panel: "w-full max-h-full",
    inset: "bg-highlight shadow-l",
    header: "flex-row items-center gap-xs",
    scrollContent: "",
    // `sticky` pins it to the bottom of the scroll box on web. The border is
    // transparent at rest so toggling it can't shift the layout.
    footer:
      "flex-row items-center justify-end gap-m sticky bottom-0 bg-highlight border-t border-transparent",
  },
  variants: {
    size: {
      sm: {
        panel: "max-w-[360px]",
        inset: "rounded-sm p-sm",
        // As tall as the close button, shown or not, so the title never moves.
        header: "pl-xs min-h-control-sm",
        scrollContent: "p-xs",
        footer: "py-xs",
      },
      md: {
        panel: "max-w-[520px]",
        inset: "rounded-sm p-m",
        header: "pl-m min-h-control-md",
        scrollContent: "p-m",
        footer: "py-sm",
      },
      lg: {
        panel: "max-w-[720px]",
        inset: "rounded-md p-l",
        header: "pl-l min-h-control-md",
        scrollContent: "p-l",
        footer: "py-m",
      },
    },
    withFooter: {
      true: { scrollContent: "pb-0" },
    },
    // Native has no sticky positioning, so the footer sits below the scroll box
    // instead of inside it — outside the scroll content container it has to
    // carry that container's horizontal padding itself to stay aligned with the
    // body.
    detachedFooter: {
      true: {},
    },
    // Only while the footer overlaps scrolled-past content does it need a rule
    // separating it from the body; at the end of the scroll it sits in flow.
    stuck: {
      true: { footer: "border-border-muted" },
    },
  },
  compoundVariants: [
    { size: "sm", detachedFooter: true, class: { footer: "px-xs" } },
    { size: "md", detachedFooter: true, class: { footer: "px-m" } },
    { size: "lg", detachedFooter: true, class: { footer: "px-l" } },
  ],
  defaultVariants: { size: "md" },
});

type ModalVariantProps = VariantProps<typeof modalVariants>;

export interface ModalProps {
  visible: boolean;
  /**
   * Called when the user dismisses the modal — backdrop press, close button, the
   * Android back button, or the Escape key (web).
   */
  onClose: () => void;
  children: ReactNode;
  /**
   * Heading rendered in the fixed header; also labels the dialog for assistive
   * tech.
   */
  title: string;
  /** Accent-tinted icon rendered before the title in the header. */
  icon?: SVGIconElement;
  /** Actions row rendered below the body (e.g. Cancel/Confirm buttons). */
  footer?: ReactNode;
  accent?: Accent;
  size?: ModalVariantProps["size"];
  /** Hide the header close button (the modal stays dismissible otherwise). */
  hideCloseButton?: boolean;
  /** Accessible label for the close button. */
  closeButtonAriaLabel?: string;
  /**
   * `alertdialog` for interruptions that require an explicit response
   * (destructive confirmation, errors). Defaults to `dialog`.
   */
  role?: "alertdialog" | "dialog";
  /** ID of the element describing the dialog (announced by assistive tech). */
  "aria-describedby"?: string;
  testID?: string;
}

export interface ModalPanelProps extends Omit<
  ModalProps,
  "accent" | "visible"
> {
  /** `true` under `Modal`; a panel rendered in flow is a non-modal dialog. */
  "aria-modal"?: boolean;
}

/**
 * The dialog panel of `Modal` without its overlay, so a story can render it in
 * flow: a snapshot never captures the portal an open `Modal` renders into.
 */
export function ModalPanel({
  onClose,
  children,
  icon,
  footer,
  size = "md",
  title,
  hideCloseButton = false,
  closeButtonAriaLabel = "Close",
  role = "dialog",
  "aria-modal": ariaModal,
  "aria-describedby": ariaDescribedby,
  testID,
}: ModalPanelProps): ReactNode {
  const { height: windowHeight } = useWindowDimensions();
  const titleId = useId();
  const iconSize = size === "lg" ? "md" : size;
  const { isScrolledToEnd, scrollViewProps } = useScrollEndState();
  const styles = modalVariants({
    size,
    withFooter: footer !== undefined,
    stuck: footer !== undefined && !isScrolledToEnd,
    detachedFooter: !supportsStickyPosition,
  });
  const footerElement =
    footer === undefined ? null : (
      <View className={styles.footer()}>{footer}</View>
    );

  return (
    <View
      aria-modal={ariaModal}
      role={role}
      aria-labelledby={titleId}
      aria-describedby={ariaDescribedby}
      testID={testID}
      className={styles.panel()}
    >
      <View className={styles.inset()}>
        {/* Header sits outside the scroll box: the title and the close
            button stay put while the body scrolls under them. */}
        <View className={styles.header()}>
          {icon === undefined ? null : (
            <Icon icon={icon} size={24} className="text-accent" />
          )}
          <Text
            nativeID={titleId}
            className="shrink grow font-heading-bold text-xl leading-tight text-sharp"
          >
            {title}
          </Text>
          {hideCloseButton ? null : (
            <IconButton
              icon={<XRegularIcon />}
              accent="neutral"
              variant="soft"
              size={iconSize}
              aria-label={closeButtonAriaLabel}
              onPress={onClose}
            />
          )}
        </View>

        {/* Pixel maxHeight (not a %) so the ScrollView sizes to its
            content and only scrolls once it exceeds ~70% of the screen;
            `shrink` lets it give way to the header and the detached
            footer when the panel hits the screen height. */}
        <ScrollView
          className="shrink"
          style={{ maxHeight: windowHeight * 0.7 }}
          contentContainerClassName={styles.scrollContent()}
          {...scrollViewProps}
        >
          {children}

          {/* Web keeps the footer in the scroll content, where `sticky`
              pins it to the bottom edge and the body scrolls under it. */}
          {supportsStickyPosition ? footerElement : null}
        </ScrollView>

        {/* Native has no sticky positioning: the footer sits after the
            scroll box instead. Same result — the ScrollView grows with
            its content up to its maxHeight, so the footer is right below
            short content and pinned under a full-height body. */}
        {supportsStickyPosition ? null : footerElement}
      </View>
    </View>
  );
}

export function Modal({
  visible,
  onClose,
  accent,
  ...panelProps
}: ModalProps): ReactNode {
  const reducedMotion = useReducedMotion();
  return (
    <RNModal
      transparent
      visible={visible}
      animationType={reducedMotion ? "none" : "fade"}
      onRequestClose={onClose}
    >
      <PortalAccentScope accent={accent}>
        <View className="flex-1 flex-center p-l">
          {/* Backdrop is an absolutely-filled sibling behind the panel, so it
              catches outside clicks without wrapping the panel — clicks inside
              the panel never reach it. aria-hidden + focusable={false} keep this
              dismiss target out of the accessibility tree and the tab order. */}
          <Pressable
            aria-hidden
            focusable={false}
            className="absolute inset-0 bg-translucent"
            onPress={onClose}
          />
          <ModalPanel aria-modal {...panelProps} onClose={onClose} />
        </View>
      </PortalAccentScope>
    </RNModal>
  );
}