#!/usr/bin/env node
'use strict';

/**
 * Migration: backfill App.avgSpraySpeed for all existing applications.
 *
 * Uses a cursor over App documents to avoid loading everything into memory.
 * Safe to run on production — read-only on AppDetail, bulkWrite on App.
 * Re-entrant: apps that already have avgSpraySpeed are skipped.
 *
 * Usage:
 *   node scripts/migrate_avg_spray_speed.js
 *   node scripts/migrate_avg_spray_speed.js --dry-run
 */

'use strict';
const debug = require('debug')('agm:migrate-avg-spray-speed');
const { DBConnection } = require('../helpers/db/connect.js');
const { App, AppFile, AppDetail } = require('../model/index.js');
const utils = require('../helpers/utils.js');

const DRY_RUN = process.argv.includes('--dry-run');
const BATCH_SIZE = 50;   // Apps per bulkWrite batch
const PROGRESS_EVERY = 100;  // Log every N apps

async function computeAvgSpraySpeed(appId) {
  const files = await AppFile.find({ appId, markedDelete: { $ne: true } }, '_id').lean();
  if (!files.length) return null;

  const fileIds = files.map(f => f._id);
  let speedAcc = 0, count = 0;

  const cursor = AppDetail.find(
    { fileId: { $in: fileIds }, sprayStat: { $in: [1, 2] } },
    { grSpeed: 1 },
    { lean: true }
  ).cursor();

  for await (const record of cursor) {
    if (utils.isNumber(record.grSpeed)) {
      speedAcc += record.grSpeed;
      count++;
    }
  }

  return count > 0 ? speedAcc / count : null;
}

async function migrate() {
  debug(`Starting${DRY_RUN ? ' (DRY RUN)' : ''}...`);

  const total = await App.countDocuments({ avgSpraySpeed: { $exists: false }, status: 3 });
  debug(`Apps to process: ${total}`);

  if (!total) {
    debug('Nothing to do.');
    return;
  }

  let processed = 0, updated = 0, skipped = 0, errors = 0;
  let bulk = [];

  const appCursor = App.find(
    { avgSpraySpeed: { $exists: false }, status: 3 },
    '_id'
  ).sort({ _id: 1 }).lean().cursor();

  for await (const app of appCursor) {
    try {
      const avgSpeed = await computeAvgSpraySpeed(app._id);
      if (avgSpeed !== null) {
        bulk.push({
          updateOne: {
            filter: { _id: app._id },
            update: { $set: { avgSpraySpeed: avgSpeed } }
          }
        });
        updated++;
      } else {
        skipped++;
      }
    } catch (err) {
      errors++;
      debug(`Error on App ${app._id}: ${err.message}`);
    }

    processed++;
    if (processed % PROGRESS_EVERY === 0) {
      debug(`Progress: ${processed}/${total} (updated=${updated}, skipped=${skipped}, errors=${errors})`);
    }

    if (bulk.length >= BATCH_SIZE) {
      if (!DRY_RUN) await App.bulkWrite(bulk, { ordered: false });
      bulk = [];
    }
  }

  if (bulk.length && !DRY_RUN) {
    await App.bulkWrite(bulk, { ordered: false });
  }

  debug(`Done. processed=${processed}, updated=${updated}, skipped=${skipped}, errors=${errors}${DRY_RUN ? ' (DRY RUN — no writes)' : ''}`);
}

const workerDB = new DBConnection('Migrate avgSpraySpeed');
workerDB.initialize({
  setupExitHandlers: false,
  onReady: async () => {
    try {
      await migrate();
      process.exit(0);
    } catch (err) {
      debug('Migration failed:', err);
      process.exit(1);
    }
  }
});