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

function loadImage(src: string): Promise<HTMLImageElement> {
  return new Promise((resolve, reject) => {
    const image = new Image();
    image.addEventListener("load", () => resolve(image));
    image.addEventListener("error", (error) => reject(error));
    image.crossOrigin = "anonymous";
    image.src = src;
  });
}

/**
 * Crop that may extend outside the source image.
 * Outside pixels stay transparent (PNG) or fillColor (JPEG).
 */
export async function getCroppedImageFile(
  imageSrc: string,
  pixelCrop: Area,
  fileName: string,
  mimeType = "image/jpeg",
  quality = 0.92,
  fillColor = "#ffffff",
): Promise<File> {
  const image = await loadImage(imageSrc);
  const canvas = document.createElement("canvas");
  const ctx = canvas.getContext("2d");
  if (!ctx) throw new Error("Could not crop image.");

  const outputWidth = Math.max(1, Math.round(pixelCrop.width));
  const outputHeight = Math.max(1, Math.round(pixelCrop.height));
  canvas.width = outputWidth;
  canvas.height = outputHeight;

  if (mimeType !== "image/png") {
    ctx.fillStyle = fillColor;
    ctx.fillRect(0, 0, outputWidth, outputHeight);
  } else {
    ctx.clearRect(0, 0, outputWidth, outputHeight);
  }

  const srcX = Math.max(0, pixelCrop.x);
  const srcY = Math.max(0, pixelCrop.y);
  const srcRight = Math.min(image.naturalWidth, pixelCrop.x + pixelCrop.width);
  const srcBottom = Math.min(
    image.naturalHeight,
    pixelCrop.y + pixelCrop.height,
  );
  const srcWidth = srcRight - srcX;
  const srcHeight = srcBottom - srcY;

  if (srcWidth > 0 && srcHeight > 0) {
    const destX = Math.round(srcX - pixelCrop.x);
    const destY = Math.round(srcY - pixelCrop.y);
    ctx.drawImage(
      image,
      srcX,
      srcY,
      srcWidth,
      srcHeight,
      destX,
      destY,
      srcWidth,
      srcHeight,
    );
  }

  const blob = await new Promise<Blob>((resolve, reject) => {
    canvas.toBlob(
      (result) => {
        if (result) resolve(result);
        else reject(new Error("Could not export cropped image."));
      },
      mimeType,
      quality,
    );
  });

  const base = fileName.replace(/\.[^.]+$/, "") || "image";
  const extension = mimeType === "image/png" ? "png" : "jpg";
  return new File([blob], `${base}-cropped.${extension}`, { type: mimeType });
}