import { readAssetBytes } from './assetReadUrlService';

export type Match3DSpritesheetRegion = {
  label: string;
  x: number;
  y: number;
  width: number;
  height: number;
};

export type Match3DItemSpritesheetViewRegion = Match3DSpritesheetRegion & {
  itemIndex: number;
  itemName: string;
  viewIndex: number;
};

export type DetectMatch3DSpritesheetRegionsInput = {
  alpha: ArrayLike<number>;
  width: number;
  height: number;
  labels?: readonly string[];
  minArea?: number;
  alphaThreshold?: number;
};

export type Match3DDecodedSpritesheetRegion = Match3DSpritesheetRegion & {
  imageSrc: string;
  sheetWidth: number;
  sheetHeight: number;
};

export type LoadMatch3DSpritesheetAssetRegionsInput = {
  source: string;
  labels?: readonly string[];
  minArea?: number;
  alphaThreshold?: number;
  maxRegions?: number;
  signal?: AbortSignal;
};

type Match3DDetectedComponent = Omit<Match3DSpritesheetRegion, 'label'> & {
  area: number;
};

/**
 * 中文注释：AI spritesheet 只保证透明背景，不保证固定坐标；运行态和编辑器统一按 alpha 连通域识别独立素材矩形。
 */
export function detectMatch3DSpritesheetRegions({
  alpha,
  width,
  height,
  labels = [],
  minArea = 1,
  alphaThreshold = 0,
}: DetectMatch3DSpritesheetRegionsInput): Match3DSpritesheetRegion[] {
  const pixelCount = width * height;
  if (width <= 0 || height <= 0 || alpha.length < pixelCount) {
    return [];
  }

  const visited = new Uint8Array(pixelCount);
  const components: Match3DDetectedComponent[] = [];

  for (let start = 0; start < pixelCount; start += 1) {
    if (visited[start] || (alpha[start] ?? 0) <= alphaThreshold) {
      continue;
    }

    const component = floodFillMatch3DSpritesheetComponent({
      alpha,
      visited,
      width,
      height,
      start,
      alphaThreshold,
    });
    if (component.area >= minArea) {
      components.push(component);
    }
  }

  return components
    .sort((left, right) => left.y - right.y || left.x - right.x)
    .map((component, index) => ({
      label: labels[index] ?? `素材${index + 1}`,
      x: component.x,
      y: component.y,
      width: component.width,
      height: component.height,
    }));
}

export function buildMatch3DItemSpritesheetViewRegions<
  Region extends Match3DSpritesheetRegion,
>(
  regions: readonly Region[],
  itemNames: readonly string[],
): Array<{
  itemIndex: number;
  itemName: string;
  regions: Region[];
}> {
  if (regions.length <= 0 || itemNames.length <= 0) {
    return [];
  }

  const itemCount = Math.min(20, Math.floor(regions.length / 5));
  return Array.from({ length: itemCount }, (_, itemIndex) => {
    const itemName = itemNames[itemIndex]?.trim() || `物品${itemIndex + 1}`;
    return {
      itemIndex,
      itemName,
      regions: regions.slice(itemIndex * 5, itemIndex * 5 + 5).map(
        (region, viewIndex): Region => ({
          ...region,
          label: `${itemName}-形态${viewIndex + 1}`,
        }) as Region,
      ),
    };
  });
}

export async function loadMatch3DSpritesheetAssetRegions({
  source,
  labels = [],
  minArea = 16,
  alphaThreshold = 8,
  maxRegions,
  signal,
}: LoadMatch3DSpritesheetAssetRegionsInput): Promise<
  Match3DDecodedSpritesheetRegion[]
> {
  const decoded = await decodeMatch3DSpritesheetImage(source, signal);
  if (signal?.aborted) {
    throw new DOMException('spritesheet 读取已取消', 'AbortError');
  }

  const regions = detectMatch3DSpritesheetRegions({
    alpha: decoded.alpha,
    width: decoded.width,
    height: decoded.height,
    labels,
    minArea,
    alphaThreshold,
  }).slice(0, maxRegions ?? Number.POSITIVE_INFINITY);

  return regions.map((region) => ({
    ...region,
    imageSrc: cropMatch3DSpritesheetRegionToDataUrl(decoded.image, region),
    sheetWidth: decoded.width,
    sheetHeight: decoded.height,
  }));
}

function loadMatch3DSpritesheetImage(source: string) {
  return new Promise<HTMLImageElement>((resolve, reject) => {
    const image = new Image();
    image.onload = () => resolve(image);
    image.onerror = () => reject(new Error('读取抓大鹅 spritesheet 失败'));
    image.src = source;
  });
}

async function readMatch3DSpritesheetImageSource(
  source: string,
  signal?: AbortSignal,
) {
  const response = await readAssetBytes(source, {
    signal,
    expireSeconds: 300,
  });
  const blob = await response.blob();
  const canCreateObjectUrl =
    typeof URL.createObjectURL === 'function' &&
    typeof URL.revokeObjectURL === 'function';
  if (canCreateObjectUrl) {
    return {
      imageSource: URL.createObjectURL(blob),
      revoke: (imageSource: string) => URL.revokeObjectURL(imageSource),
    };
  }

  return {
    imageSource: await new Promise<string>((resolve, reject) => {
      const reader = new FileReader();
      reader.onload = () => resolve(String(reader.result ?? ''));
      reader.onerror = () => reject(new Error('读取抓大鹅 spritesheet 失败'));
      reader.readAsDataURL(blob);
    }),
    revoke: () => {},
  };
}

async function decodeMatch3DSpritesheetImage(
  source: string,
  signal?: AbortSignal,
) {
  const { imageSource, revoke } = await readMatch3DSpritesheetImageSource(
    source,
    signal,
  );
  try {
    const image = await loadMatch3DSpritesheetImage(imageSource);
    if (signal?.aborted) {
      throw new DOMException('spritesheet 读取已取消', 'AbortError');
    }
    const width = Math.max(1, image.naturalWidth || image.width || 1);
    const height = Math.max(1, image.naturalHeight || image.height || 1);
    const canvas = document.createElement('canvas');
    canvas.width = width;
    canvas.height = height;
    const context = canvas.getContext('2d', {
      willReadFrequently: true,
    });
    if (!context) {
      throw new Error('浏览器不支持解析抓大鹅 spritesheet');
    }
    context.clearRect(0, 0, width, height);
    context.drawImage(image, 0, 0, width, height);
    const pixels = context.getImageData(0, 0, width, height).data;
    const alpha = new Uint8ClampedArray(width * height);
    for (let index = 0; index < alpha.length; index += 1) {
      alpha[index] = pixels[index * 4 + 3] ?? 0;
    }
    return {
      alpha,
      height,
      image,
      width,
    };
  } finally {
    revoke(imageSource);
  }
}

function cropMatch3DSpritesheetRegionToDataUrl(
  image: HTMLImageElement,
  region: Match3DSpritesheetRegion,
) {
  const canvas = document.createElement('canvas');
  canvas.width = Math.max(1, Math.round(region.width));
  canvas.height = Math.max(1, Math.round(region.height));
  const context = canvas.getContext('2d');
  if (!context) {
    throw new Error('浏览器不支持裁切抓大鹅 spritesheet');
  }
  context.clearRect(0, 0, canvas.width, canvas.height);
  context.drawImage(
    image,
    region.x,
    region.y,
    region.width,
    region.height,
    0,
    0,
    canvas.width,
    canvas.height,
  );
  return canvas.toDataURL('image/png');
}

function floodFillMatch3DSpritesheetComponent({
  alpha,
  visited,
  width,
  height,
  start,
  alphaThreshold,
}: {
  alpha: ArrayLike<number>;
  visited: Uint8Array;
  width: number;
  height: number;
  start: number;
  alphaThreshold: number;
}): Match3DDetectedComponent {
  const stack = [start];
  visited[start] = 1;

  let minX = start % width;
  let maxX = minX;
  let minY = Math.floor(start / width);
  let maxY = minY;
  let area = 0;

  while (stack.length > 0) {
    const index = stack.pop()!;
    const x = index % width;
    const y = Math.floor(index / width);
    area += 1;
    minX = Math.min(minX, x);
    maxX = Math.max(maxX, x);
    minY = Math.min(minY, y);
    maxY = Math.max(maxY, y);

    visitMatch3DSpritesheetNeighbor(
      index - 1,
      x > 0,
      alpha,
      visited,
      stack,
      alphaThreshold,
    );
    visitMatch3DSpritesheetNeighbor(
      index + 1,
      x + 1 < width,
      alpha,
      visited,
      stack,
      alphaThreshold,
    );
    visitMatch3DSpritesheetNeighbor(
      index - width,
      y > 0,
      alpha,
      visited,
      stack,
      alphaThreshold,
    );
    visitMatch3DSpritesheetNeighbor(
      index + width,
      y + 1 < height,
      alpha,
      visited,
      stack,
      alphaThreshold,
    );
  }

  return {
    area,
    x: minX,
    y: minY,
    width: maxX - minX + 1,
    height: maxY - minY + 1,
  };
}

function visitMatch3DSpritesheetNeighbor(
  index: number,
  inBounds: boolean,
  alpha: ArrayLike<number>,
  visited: Uint8Array,
  stack: number[],
  alphaThreshold: number,
) {
  if (!inBounds || visited[index] || (alpha[index] ?? 0) <= alphaThreshold) {
    return;
  }
  visited[index] = 1;
  stack.push(index);
}