import { accounts } from "$lib/stores/accounts.svelte";
import { auth } from "$lib/stores/auth.svelte";

const BASE = import.meta.env.VITE_API_BASE ?? "/api";
const FILENAME_STAR = /filename\*=UTF-8''([^;]+)/i;
const FILENAME_PLAIN = /filename="?([^";]+)"?/i;

function nameFromHeader(header: string | null, fallback: string): string {
  if (!header) {
    return fallback;
  }
  const encoded = FILENAME_STAR.exec(header);
  if (encoded) {
    return decodeURIComponent(encoded[1]);
  }
  const plain = FILENAME_PLAIN.exec(header);
  return plain ? plain[1] : fallback;
}

function saveBlob(blob: Blob, fileName: string) {
  const url = URL.createObjectURL(blob);
  const link = document.createElement("a");
  link.href = url;
  link.download = fileName;
  document.body.append(link);
  link.click();
  link.remove();
  setTimeout(() => URL.revokeObjectURL(url), 1000);
}

async function save(path: string, fallback: string): Promise<void> {
  const response = await fetch(`${BASE}${path}`, {
    headers: auth.token ? { Authorization: `Bearer ${auth.token}` } : {},
  });
  if (!response.ok) {
    throw new Error(`download failed: ${response.status}`);
  }
  const fileName = nameFromHeader(
    response.headers.get("content-disposition"),
    fallback
  );
  saveBlob(await response.blob(), fileName);
}

export function downloadMedia(mediaId: number): Promise<void> {
  return save(`/media/${mediaId}?download=true`, `media_${mediaId}`);
}

export function downloadMediaVersion(versionId: number): Promise<void> {
  return save(
    `/media/version/${versionId}?download=true`,
    `media_${versionId}`
  );
}

export function downloadStory(peerId: number, storyId: number): Promise<void> {
  return save(
    `/stories/${peerId}/${storyId}/media?download=true&account_id=${accounts.selectedId}`,
    `story_${peerId}_${storyId}`
  );
}