import React, { forwardRef, useEffect, useMemo, useRef } from "react";
import { StyleSheet, View } from "react-native";

import {
  KEYBOARD_BORDER_RADIUS,
  KEYBOARD_HAS_ROUNDED_CORNERS,
} from "../../constants";
import { KeyboardController } from "../../module";
import KeyboardStickyView from "../KeyboardStickyView";

import type { KeyboardStickyViewProps } from "../KeyboardStickyView";

type TranslucentStackEntry = { translucent: boolean };

const translucentStack: TranslucentStackEntry[] = [];
let currentTranslucent = false;

const applyTranslucent = () => {
  const next =
    translucentStack.length > 0
      ? translucentStack[translucentStack.length - 1].translucent
      : false;

  if (next !== currentTranslucent) {
    currentTranslucent = next;
    KeyboardController.setTranslucent(next);
  }
};

const pushTranslucentEntry = (entry: TranslucentStackEntry) => {
  translucentStack.push(entry);
  applyTranslucent();
};

const removeTranslucentEntry = (entry: TranslucentStackEntry) => {
  const index = translucentStack.indexOf(entry);

  if (index !== -1) {
    translucentStack.splice(index, 1);
  }

  applyTranslucent();
};

export type KeyboardEffectsProps = {
  /**
   * Whether the keyboard backdrop should be translucent.
   *
   * @default false
   */
  translucent?: boolean;
  /**
   * Whether the effect view should match the keyboard's rounded top corners.
   *
   * Set to `false` when the effect should fully cover the keyboard bounds.
   *
   * @default true
   */
  rounded?: boolean;
} & KeyboardStickyViewProps;

/**
 * A component that renders content behind the keyboard. Since the keyboard
 * is translucent, the content (colors, gradients, animations) will blend
 * through and create visual effects on the keyboard.
 *
 * On iOS 26+ the keyboard has rounded corners, and the effect view
 * automatically matches that shape.
 *
 * @returns A view component positioned behind the keyboard.
 * @example
 * ```tsx
 * <KeyboardEffects>
 *   <View style={{ flex: 1, backgroundColor: "purple" }} />
 * </KeyboardEffects>
 * ```
 */
const KeyboardEffects = forwardRef<
  View,
  React.PropsWithChildren<KeyboardEffectsProps>
>(({ translucent, rounded = true, children, ...props }, ref) => {
  const stackEntry = useRef<TranslucentStackEntry>({
    translucent: Boolean(translucent),
  }).current;
  const containerStyle = useMemo(
    () => [
      styles.container,
      KEYBOARD_HAS_ROUNDED_CORNERS && rounded && styles.rounded,
    ],
    [rounded],
  );

  useEffect(() => {
    pushTranslucentEntry(stackEntry);

    return () => {
      removeTranslucentEntry(stackEntry);
    };
  }, [stackEntry]);

  useEffect(() => {
    stackEntry.translucent = Boolean(translucent);
    applyTranslucent();
  }, [stackEntry, translucent]);

  return (
    <KeyboardStickyView ref={ref} {...props}>
      <View style={containerStyle}>{children}</View>
    </KeyboardStickyView>
  );
});

const styles = StyleSheet.create({
  container: {
    position: "absolute",
    bottom: 0,
    top: 0,
    left: 0,
    right: 0,
    height: 999,
  },
  rounded: {
    borderTopLeftRadius: KEYBOARD_BORDER_RADIUS,
    borderTopRightRadius: KEYBOARD_BORDER_RADIUS,
    overflow: "hidden",
  },
});

export default KeyboardEffects;