import { supabase } from './supabase';

const BUCKET = 'profile-avatars';
const MAX_DIM = 512;
const QUALITY = 0.85;

// Resizes the source image to a centred-cropped square ≤ MAX_DIM and
// re-encodes as WebP. Falls back to JPEG if WebP isn't supported (rare).
async function resizeToSquare(file: File): Promise<Blob> {
  const url = URL.createObjectURL(file);
  try {
    const img = await new Promise<HTMLImageElement>((resolve, reject) => {
      const i = new Image();
      i.onload = () => resolve(i);
      i.onerror = () => reject(new Error('image load failed'));
      i.src = url;
    });

    const minSide = Math.min(img.naturalWidth, img.naturalHeight);
    const sx = (img.naturalWidth - minSide) / 2;
    const sy = (img.naturalHeight - minSide) / 2;
    const target = Math.min(MAX_DIM, minSide);

    const canvas = document.createElement('canvas');
    canvas.width = target;
    canvas.height = target;
    const ctx = canvas.getContext('2d');
    if (!ctx) throw new Error('canvas context unavailable');
    ctx.drawImage(img, sx, sy, minSide, minSide, 0, 0, target, target);

    const blob = await new Promise<Blob | null>((resolve) =>
      canvas.toBlob(resolve, 'image/webp', QUALITY),
    );
    if (blob) return blob;

    const jpeg = await new Promise<Blob | null>((resolve) =>
      canvas.toBlob(resolve, 'image/jpeg', QUALITY),
    );
    if (!jpeg) throw new Error('canvas toBlob returned null');
    return jpeg;
  } finally {
    URL.revokeObjectURL(url);
  }
}

const MAX_ANIMATED_BYTES = 2 * 1024 * 1024; // 2 MB hard cap on animated uploads
const ANIMATED_MIMES = new Set(['image/gif', 'image/apng', 'image/webp', 'image/png']);

export async function uploadAvatar(userId: string, file: File): Promise<string> {
  if (!file.type.startsWith('image/')) {
    throw new Error('only image files are accepted');
  }
  // Animated formats bypass the canvas re-encode (which would strip
  // animation by sampling the first frame). We still validate dimensions
  // and size so a 40-MB animated WebP can't slip through.
  if (ANIMATED_MIMES.has(file.type) && (await isAnimated(file))) {
    if (file.size > MAX_ANIMATED_BYTES) {
      throw new Error('animated avatar too large (max 2 MB)');
    }
    const dims = await readDimensions(file);
    if (dims.width > MAX_DIM || dims.height > MAX_DIM) {
      throw new Error('animated avatar exceeds ' + MAX_DIM + 'px (got ' + dims.width + 'x' + dims.height + ')');
    }
    return uploadAvatarBlob(userId, file);
  }
  const blob = await resizeToSquare(file);
  return uploadAvatarBlob(userId, blob);
}

async function readDimensions(file: File): Promise<{ width: number; height: number }> {
  const url = URL.createObjectURL(file);
  try {
    const img = await new Promise<HTMLImageElement>((resolve, reject) => {
      const i = new Image();
      i.onload = () => resolve(i);
      i.onerror = () => reject(new Error('image load failed'));
      i.src = url;
    });
    return { width: img.naturalWidth, height: img.naturalHeight };
  } finally {
    URL.revokeObjectURL(url);
  }
}

async function isAnimated(file: File): Promise<boolean> {
  // GIF: any GIF89a/GIF87a header is treated as potentially animated. The
  // static-GIF case (one image-descriptor block) is rare enough that
  // re-encoding wouldn't save much, so we accept the false-positives.
  if (file.type === 'image/gif') return true;
  // APNG: presence of an 'acTL' chunk inside the PNG stream. Scan the
  // first 64 KB — APNGs put acTL near the front, before IDAT.
  if (file.type === 'image/apng' || file.type === 'image/png') {
    const head = await file.slice(0, 65536).arrayBuffer();
    return containsBytes(head, [0x61, 0x63, 0x54, 0x4c]); // 'acTL'
  }
  // Animated WebP: 'ANIM' chunk in the RIFF container.
  if (file.type === 'image/webp') {
    const head = await file.slice(0, 65536).arrayBuffer();
    return containsBytes(head, [0x41, 0x4e, 0x49, 0x4d]); // 'ANIM'
  }
  return false;
}

function containsBytes(buf: ArrayBuffer, needle: number[]): boolean {
  const view = new Uint8Array(buf);
  const len = view.length;
  const nlen = needle.length;
  outer: for (let i = 0; i + nlen <= len; i++) {
    for (let j = 0; j < nlen; j++) {
      if (view[i + j] !== needle[j]) continue outer;
    }
    return true;
  }
  return false;
}

// Upload an already-cropped Blob (e.g. from ImageCropDialog) without going
// through the legacy center-crop. Caller is responsible for sizing — the
// dialog already clamps to MAX_DIM via its outputWidth.
export async function uploadAvatarBlob(userId: string, blob: Blob): Promise<string> {
  const ext =
    blob.type === 'image/webp' ? 'webp' :
    blob.type === 'image/gif' ? 'gif' :
    blob.type === 'image/apng' || blob.type === 'image/png' ? 'png' :
    'jpg';
  // Random filename so old uploads don't get overwritten before we update
  // the profile row — Supabase Storage CDN caches by URL, so a fresh path
  // also forces clients to fetch the new image.
  const name =
    userId + '/' + Date.now().toString(36) + '-' + Math.random().toString(36).slice(2, 8) + '.' + ext;
  const { error: upErr } = await supabase.storage.from(BUCKET).upload(name, blob, {
    contentType: blob.type,
    cacheControl: '604800',
    upsert: false,
  });
  if (upErr) throw upErr;
  const { data: pub } = supabase.storage.from(BUCKET).getPublicUrl(name);
  return pub.publicUrl;
}

export const AVATAR_TARGET_DIM = MAX_DIM;

export async function deleteAvatarObject(publicUrl: string): Promise<void> {
  // Public URLs look like
  //   https://<host>/storage/v1/object/public/profile-avatars/<path>
  // Extract <path> and remove.
  const marker = '/object/public/' + BUCKET + '/';
  const idx = publicUrl.indexOf(marker);
  if (idx === -1) return;
  const path = publicUrl.slice(idx + marker.length);
  const { error } = await supabase.storage.from(BUCKET).remove([path]);
  if (error) throw error;
}