/**
 * Skia-based image decoder for getting RGBA pixel data.
 * Uses react-native-skia to decode images and extract pixel buffers.
 */

import {
  Skia,
  useImage,
  SkImage,
} from "@shopify/react-native-skia";

/**
 * Decode a base64 PNG/JPEG image and return RGBA pixel data.
 *
 * @param base64 - Base64 encoded image data (without data URI prefix)
 * @returns RGBA pixel data with dimensions
 */
export function decodeImageBase64(base64: string): {
  pixels: Uint8Array;
  width: number;
  height: number;
} | null {
  try {
    // Decode base64 to data
    const data = Skia.Data.fromBase64(base64);
    if (!data) return null;

    // Create image from data
    const image = Skia.Image.MakeImageFromEncoded(data);
    if (!image) return null;

    const width = image.width();
    const height = image.height();

    // Read pixels from the image
    // Note: Skia images are in RGBA format
    const pixels = image.readPixels(0, 0, {
      width,
      height,
      colorType: 4, // RGBA_8888
      alphaType: 1, // Unpremultiplied
    });

    if (!pixels) return null;

    return {
      pixels: new Uint8Array(pixels),
      width,
      height,
    };
  } catch (error) {
    console.error("[SkiaDecoder] Failed to decode image:", error);
    return null;
  }
}

/**
 * Decode an image from a file URI and return RGBA pixel data.
 *
 * @param uri - File URI (e.g., file:///path/to/image.png)
 * @returns Promise with RGBA pixel data
 */
export async function decodeImageFromUri(uri: string): Promise<{
  pixels: Uint8Array;
  width: number;
  height: number;
} | null> {
  try {
    // Fetch the image data
    const response = await fetch(uri);
    const arrayBuffer = await response.arrayBuffer();
    const base64 = arrayBufferToBase64(arrayBuffer);

    return decodeImageBase64(base64);
  } catch (error) {
    console.error("[SkiaDecoder] Failed to load image from URI:", error);
    return null;
  }
}

/**
 * Convert ArrayBuffer to base64 string.
 */
function arrayBufferToBase64(buffer: ArrayBuffer): string {
  let binary = "";
  const bytes = new Uint8Array(buffer);
  const len = bytes.byteLength;
  for (let i = 0; i < len; i++) {
    binary += String.fromCharCode(bytes[i]);
  }
  return btoa(binary);
}

/**
 * React hook to decode an image from URI.
 * Uses Skia's useImage hook for caching.
 */
export function useDecodedImage(uri: string | null) {
  const skiaImage = useImage(uri);

  if (!skiaImage) {
    return { loading: true, pixels: null, width: 0, height: 0 };
  }

  const width = skiaImage.width();
  const height = skiaImage.height();

  const pixels = skiaImage.readPixels(0, 0, {
    width,
    height,
    colorType: 4, // RGBA_8888
    alphaType: 1, // Unpremultiplied
  });

  return {
    loading: false,
    pixels: pixels ? new Uint8Array(pixels) : null,
    width,
    height,
  };
}