import { readFile, writeFile } from 'fs/promises';

import { getArg } from './lib/args.js';
import { getMany } from './lib/dl.js';
import { error, log } from './lib/log.js';
import { createDb, userSchema } from './lib/schema.js';

const ctx = 'downloadDb.js';

/**
 * Downloads all media possible for the users stored in db.json at the specified `--path`.
 * Useful for first run or for augmenting existing media
 * if it may be only partially archived in an uncertain state.
 *
 * If the db.json is missing, it will be automatically created,
 * as this depends on users being defined in the db.json and not the folders present
 * (as there could be some users whose accounts no longer exist
 * or otherwise may not be maintained by the db.json anymore)
 */
const downloadDb = async () => {
  log(ctx, 'Grabbing db');
  let directory = '', threadMax = 1, db, usersPerBatch, waitTime;
  try {
    directory = getArg('path');
  } catch (err) {
    error(ctx, err);
    return;
  }
  try {
    threadMax = getArg('threads');
    log(ctx, `Using ${threadMax} threads`);
  } catch (err) {
    log(ctx, 'Using 1 thread');
  }
  try {
    usersPerBatch = getArg('usersPerBatch');
    let waitTimeSec = getArg('waitTime');
    waitTime = waitTimeSec * 1000;
    log(ctx, `Splitting into batches with ${usersPerBatch} per batch with ${waitTimeSec} seconds pausing between each batch.`);
  } catch (err) {
    log(ctx, `Not using batches${!!usersPerBatch ? ' (usersPerBatch provided without waitTime)' : ''}`);
    usersPerBatch = null;
  }
  const tryReadDb = async () => {
    let file = await readFile(`${directory}/db.json`, { encoding: 'utf8' });
    db = JSON.parse(file);
  }
  try {
    await tryReadDb();
  } catch (err) {
    if (err.toString().includes('ENOENT')) {
      try {
        log(ctx, 'Database was not yet present. Creating it now.');
        await createDb(directory);
        await tryReadDb();
      } catch (err2) {
        error(ctx, err2);
        return;
      }
    } else {
      error(ctx, err);
      return;
    }
  }

  let processes = [];
  Object.keys(db.userList).forEach(user => {
    processes.push({
      ...db.userList[user],
      user,
      lastUpdated: Date.now(),
      lastError: undefined,
      logs: [],
    })
  });

  const errorReadout = [];
  const executeDl = async (arr) => {
    log(ctx, `Downloading media using /<user>/media for ${arr.length} users`);
    await getMany(arr, threadMax, directory, 'media');
  
    arr.forEach(entry => {
      entry.logs.forEach(log => {
        if (log.includes('NotFoundError')) {
          const strOut = `${entry.user} wasn't found: "${log.replace('\n', '')}". You may want to remove them from the db.json file or update their username.`;
          errorReadout.push(strOut);
          entry.lastError = strOut;
        } else if (log.includes('AuthorizationError')) {
          const strOut = `There was an authorization error for user ${entry.user}: "${log.replace('\n', '')}"`;
          errorReadout.push(strOut);
          entry.lastError = strOut;
        }
      });
    });
  
    log(ctx, 'Downloading media using /search');
    await getMany(arr, threadMax, directory, 'search');
  }

  if (!!usersPerBatch) {
    const batches = processes.reduce((arr, item, i) => {
      const chunkIndex = Math.floor(i / usersPerBatch);
      if (!arr[chunkIndex]) {
        arr[chunkIndex] = [];
      }
      arr[chunkIndex].push(item);
      return arr;
    }, []);

    const delay = ms => new Promise(res => setTimeout(res, ms));
    log(ctx, JSON.stringify(batches, null, 2));

    for (let i = 0; i < batches.length; i++) {
      const batch = batches[i];
      log(ctx, `Executing batch ${batch[0]?.user}-${batch[batch.length - 1]?.user}`);
      await executeDl(batch);
      log(ctx, `Waiting ${waitTime / 1000} seconds before next batch.`);
      await delay(waitTime);
    }

    processes = batches.flat(1);
  } else {
    await executeDl(processes);
  }

  log(ctx, 'Updating the db');
  try {
    let updated = {
      ...db,
      userList: {
        ...db.userList,
        ...Object.fromEntries(processes.map(e => [e.user, userSchema(e)])),
      },
    }
    await writeFile(`${directory}/db.json`, JSON.stringify(updated, null, 2));
  } catch (err) {
    error(ctx, err);
    return;
  }

  log(ctx, 'Collecting errors');
  errorReadout.forEach(err => error(ctx, err));
  log(ctx, 'Done');
}

downloadDb();