export const MAX_IMAGE_SIDE = 1000;

/**
 * Re-encodes a picked image to WebP (JPEG where WebP encoding is unsupported), at most
 * MAX_IMAGE_SIDE px on the longer side. Re-encoding drops EXIF; orientation is applied first.
 */
export async function compressImage(file: Blob): Promise<Blob> {
  const bitmap = await createImageBitmap(file, { imageOrientation: 'from-image' });
  try {
    const scale = Math.min(1, MAX_IMAGE_SIDE / Math.max(bitmap.width, bitmap.height));
    const width = Math.max(1, Math.round(bitmap.width * scale));
    const height = Math.max(1, Math.round(bitmap.height * scale));
    const canvas = document.createElement('canvas');
    canvas.width = width;
    canvas.height = height;
    const ctx = canvas.getContext('2d');
    if (!ctx) throw new Error('Canvas is not available');
    ctx.drawImage(bitmap, 0, 0, width, height);
    const encode = (type: string) => new Promise<Blob | null>((resolve) => canvas.toBlob(resolve, type, 0.85));
    const webp = await encode('image/webp');
    if (webp?.type === 'image/webp') return webp;
    const jpeg = await encode('image/jpeg');
    if (!jpeg) throw new Error('Could not encode the image');
    return jpeg;
  } finally {
    bitmap.close();
  }
}

export function fileNameFor(blob: Blob, base: string): string {
  return `${base}.${blob.type === 'image/webp' ? 'webp' : 'jpg'}`;
}