// @ts-check
/**
 * Files outside the notebooks: image files to put on a page, and the place
 * a picture of a page is exported to.  A web page cannot look through the
 * user's directories or write where the user chooses, so it asks the local
 * program (kokkoja.py), as it does for the notebooks.
 */

import { askLocalProgram } from './notebook.js';

/**
 * @typedef {object} DirectoryListing
 * @property {string} directory          Its full path.
 * @property {string | null} parent      Null at the top of the file system.
 * @property {{name: string, path: string}[]} directories
 * @property {{name: string, path: string, size: number}[]} files  Image files only.
 */

/**
 * @param {Response} response
 * @returns {Promise<string>}  What the local program says went wrong.
 */
async function reason(response) {
  try {
    return String((await response.json()).error);
  } catch {
    return `error ${response.status}`;
  }
}

/**
 * @param {string} [directory]  A full path; without one, where the notebooks are.
 * @returns {Promise<DirectoryListing>}
 */
export async function listFiles(directory = '') {
  const response = await askLocalProgram(`api/files?directory=${encodeURIComponent(directory)}`);
  if (!response.ok) throw new Error(`${directory}: ${await reason(response)}`);
  return response.json();
}

/**
 * @param {string} path  The full path of an image file, from a listing.
 * @returns {Promise<Blob>}
 */
export async function readFile(path) {
  const response = await askLocalProgram(`api/file?path=${encodeURIComponent(path)}`);
  if (!response.ok) throw new Error(`${path}: ${await reason(response)}`);
  return response.blob();
}

/**
 * Write a PNG picture into a directory.
 * @param {string} directory  Its full path.
 * @param {string} name       Ending in .png.
 * @param {Blob} picture
 * @param {boolean} replace   Whether a file of that name may be replaced.
 * @returns {Promise<string | null>}  The full path written, or null if a
 *     file of that name exists and may not be replaced.
 */
export async function writePicture(directory, name, picture, replace) {
  const query = `directory=${encodeURIComponent(directory)}&name=${encodeURIComponent(name)}` +
    (replace ? '&replace=1' : '');
  const response = await askLocalProgram(`api/file?${query}`, 'PUT', picture);
  if (response.status === 409) return null;
  if (!response.ok) throw new Error(await reason(response));
  return (await response.json()).saved;
}