// Google Drive AppData helpers. Files written to the appDataFolder space are
// invisible to the user in the regular Drive UI and only readable by the
// OAuth client (i.e. *this* app's client_id) that created them.
//
// Docs: https://developers.google.com/drive/api/guides/appdata

const DRIVE = "https://www.googleapis.com/drive/v3";
const UPLOAD = "https://www.googleapis.com/upload/drive/v3";

async function driveFetch(token, url, init = {}) {
  const res = await fetch(url, {
    ...init,
    headers: {
      Authorization: `Bearer ${token}`,
      ...(init.headers || {}),
    },
  });
  if (!res.ok) {
    const text = await res.text();
    throw new Error(`Drive API ${res.status}: ${text.slice(0, 300)}`);
  }
  return res;
}

// Find a file by exact name inside the appDataFolder. Returns the file id, or
// null if not found.
export async function findAppDataFile(token, name) {
  const url =
    `${DRIVE}/files?spaces=appDataFolder` +
    `&q=${encodeURIComponent(`name = '${name.replace(/'/g, "\\'")}'`)}` +
    `&fields=files(id,name,modifiedTime)`;
  const res = await driveFetch(token, url);
  const { files } = await res.json();
  if (!files || files.length === 0) return null;
  // If somehow multiple, prefer the most recent.
  files.sort((a, b) => (b.modifiedTime || "").localeCompare(a.modifiedTime || ""));
  return files[0].id;
}

export async function downloadFile(token, fileId) {
  const res = await driveFetch(token, `${DRIVE}/files/${fileId}?alt=media`);
  return res.text();
}

// Multipart upload of a small JSON blob to appDataFolder. If fileId is given,
// updates that file (preserving parents); otherwise creates a new file.
export async function uploadAppDataJson(token, name, content, fileId = null) {
  const boundary = "goostr-" + Math.random().toString(36).slice(2);
  const metadata = fileId
    ? { name }
    : { name, parents: ["appDataFolder"] };

  const body =
    `--${boundary}\r\n` +
    `Content-Type: application/json; charset=UTF-8\r\n\r\n` +
    `${JSON.stringify(metadata)}\r\n` +
    `--${boundary}\r\n` +
    `Content-Type: application/json\r\n\r\n` +
    `${content}\r\n` +
    `--${boundary}--`;

  const url = fileId
    ? `${UPLOAD}/files/${fileId}?uploadType=multipart`
    : `${UPLOAD}/files?uploadType=multipart`;

  const res = await driveFetch(token, url, {
    method: fileId ? "PATCH" : "POST",
    headers: { "Content-Type": `multipart/related; boundary=${boundary}` },
    body,
  });
  return res.json();
}

export async function fetchUserInfo(token) {
  const res = await driveFetch(token, "https://www.googleapis.com/oauth2/v3/userinfo");
  return res.json(); // { sub, name, picture, email, ... }
}