import {
  removeEditorImageBackground,
  type EditorBackgroundRemovalInput,
  type EditorBackgroundRemovalResult,
} from '../../services/image-editor/editorProjectClient';

export type CropExpandInsets = {
  left: number;
  top: number;
  right: number;
  bottom: number;
};

export type CropExpandGeometry = {
  outputWidth: number;
  outputHeight: number;
  sourceX: number;
  sourceY: number;
  sourceWidth: number;
  sourceHeight: number;
  targetX: number;
  targetY: number;
};

export type CropExpandFrame = {
  x: number;
  y: number;
  width: number;
  height: number;
};

export type RasterEditResult = {
  imageSrc: string;
  objectKey?: string | null;
  assetObjectId?: string | null;
  width: number;
  height: number;
  taskId?: string | null;
  elapsedMs?: number;
  provider?: string;
};

function assertCanvasSupport() {
  if (typeof document === 'undefined') {
    throw new Error('当前环境不支持图片编辑');
  }
}

function loadImageElement(source: string) {
  return new Promise<HTMLImageElement>((resolve, reject) => {
    const image = new Image();
    image.crossOrigin = 'anonymous';
    image.onload = () => resolve(image);
    image.onerror = () => reject(new Error('图片读取失败'));
    image.src = source;
  });
}

function createRasterCanvas(width: number, height: number) {
  assertCanvasSupport();
  const canvas = document.createElement('canvas');
  canvas.width = width;
  canvas.height = height;
  const context = canvas.getContext('2d', { willReadFrequently: true });
  if (!context) {
    throw new Error('当前浏览器不支持图片编辑');
  }
  return { canvas, context };
}

function resolveImageSize(image: HTMLImageElement) {
  return {
    width: Math.max(1, image.naturalWidth || image.width || 1),
    height: Math.max(1, image.naturalHeight || image.height || 1),
  };
}

export function parseCropExpandInsetValue(value: string) {
  const trimmedValue = value.trim();
  if (!trimmedValue) {
    return 0;
  }
  const parsedValue = Number.parseInt(trimmedValue, 10);
  if (!Number.isFinite(parsedValue)) {
    throw new Error('裁扩数值必须是整数');
  }
  return parsedValue;
}

export function buildCropExpandInsetsFromFrame({
  layer,
  frame,
}: {
  layer: {
    x: number;
    y: number;
    width: number;
    height: number;
    originalWidth: number;
    originalHeight: number;
  };
  frame: CropExpandFrame;
}): CropExpandInsets {
  const scaleX =
    layer.width > 0 ? Math.max(1, layer.originalWidth) / layer.width : 1;
  const scaleY =
    layer.height > 0 ? Math.max(1, layer.originalHeight) / layer.height : 1;
  const sourceRight = layer.x + layer.width;
  const sourceBottom = layer.y + layer.height;
  const frameRight = frame.x + frame.width;
  const frameBottom = frame.y + frame.height;

  return {
    left: Math.round((layer.x - frame.x) * scaleX),
    top: Math.round((layer.y - frame.y) * scaleY),
    right: Math.round((frameRight - sourceRight) * scaleX),
    bottom: Math.round((frameBottom - sourceBottom) * scaleY),
  };
}

export function buildCropExpandGeometry({
  width,
  height,
  insets,
}: {
  width: number;
  height: number;
  insets: CropExpandInsets;
}): CropExpandGeometry {
  const sourceWidth = Math.max(1, Math.round(width || 1));
  const sourceHeight = Math.max(1, Math.round(height || 1));
  const cropLeft = Math.max(0, -insets.left);
  const cropTop = Math.max(0, -insets.top);
  const cropRight = Math.max(0, -insets.right);
  const cropBottom = Math.max(0, -insets.bottom);
  const targetX = Math.max(0, insets.left);
  const targetY = Math.max(0, insets.top);
  const drawableWidth = sourceWidth - cropLeft - cropRight;
  const drawableHeight = sourceHeight - cropTop - cropBottom;
  if (drawableWidth <= 0 || drawableHeight <= 0) {
    throw new Error('裁剪范围不能小于 1 像素');
  }

  return {
    outputWidth: targetX + drawableWidth + Math.max(0, insets.right),
    outputHeight: targetY + drawableHeight + Math.max(0, insets.bottom),
    sourceX: cropLeft,
    sourceY: cropTop,
    sourceWidth: drawableWidth,
    sourceHeight: drawableHeight,
    targetX,
    targetY,
  };
}

export function buildCropExpandLayerPatch({
  layerX,
  layerY,
  insets,
  outputWidth,
  outputHeight,
}: {
  layerX: number;
  layerY: number;
  insets: CropExpandInsets;
  outputWidth: number;
  outputHeight: number;
}) {
  return {
    x: layerX - insets.left,
    y: layerY - insets.top,
    width: outputWidth,
    height: outputHeight,
    originalWidth: outputWidth,
    originalHeight: outputHeight,
  };
}

export async function renderCropExpandImage({
  source,
  insets,
}: {
  source: string;
  insets: CropExpandInsets;
}): Promise<RasterEditResult> {
  const image = await loadImageElement(source);
  const imageSize = resolveImageSize(image);
  const geometry = buildCropExpandGeometry({
    width: imageSize.width,
    height: imageSize.height,
    insets,
  });
  const { canvas, context } = createRasterCanvas(
    geometry.outputWidth,
    geometry.outputHeight,
  );
  // 中文注释：画布默认透明，扩大出来的新区域不填色，直接保留 alpha=0。
  context.clearRect(0, 0, geometry.outputWidth, geometry.outputHeight);
  context.drawImage(
    image,
    geometry.sourceX,
    geometry.sourceY,
    geometry.sourceWidth,
    geometry.sourceHeight,
    geometry.targetX,
    geometry.targetY,
    geometry.sourceWidth,
    geometry.sourceHeight,
  );

  return {
    imageSrc: canvas.toDataURL('image/png'),
    width: geometry.outputWidth,
    height: geometry.outputHeight,
  };
}

export async function removeImageBackground(
  input: string | EditorBackgroundRemovalInput,
): Promise<EditorBackgroundRemovalResult> {
  return removeEditorImageBackground(
    typeof input === 'string' ? { sourceImageSrc: input } : input,
  );
}