#!/usr/bin/env node
// One-time migration: copy SourceText and Slide from source cluster to target (APG5604)

const mongoose = require('mongoose');
const SourceText = require('./models/SourceText');
const Slide = require('./models/Slide');

const SOURCE_URI = process.env.SOURCE_MONGODB_URI || 'mongodb+srv://nothingyu:wSg3lbO1PkHiRMq9@sandbox.ecysggv.mongodb.net/test?retryWrites=true&w=majority&appName=sandbox';
const TARGET_URI = process.env.MONGODB_URI || process.env.TARGET_MONGODB_URI || 'mongodb+srv://nothingyu_db_user:zjxVXtaIfUVBesdt@apg5604.tdavbvz.mongodb.net/?retryWrites=true&w=majority&appName=APG5604';

async function fetchAll(conn, modelName) {
  const docs = await conn.connection.db.collection(modelName.toLowerCase() + 's').find({}).toArray();
  return docs;
}

async function upsertAll(conn, collectionName, docs) {
  if (!Array.isArray(docs) || docs.length === 0) return { inserted: 0, updated: 0 };
  const col = conn.connection.db.collection(collectionName);
  let inserted = 0; let updated = 0;
  for (const doc of docs) {
    const _id = doc._id;
    // Remove _id to allow upsert by _id
    await col.updateOne({ _id }, { $set: { ...doc } }, { upsert: true });
  }
  // Rough counts
  inserted = docs.length;
  return { inserted, updated };
}

async function main() {
  console.log('Starting migration...');
  console.log('Source:', SOURCE_URI.replace(/:[^@]+@/, ':***@'));
  console.log('Target:', TARGET_URI.replace(/:[^@]+@/, ':***@'));

  const source = await mongoose.createConnection(SOURCE_URI, { maxPoolSize: 5 }).asPromise();
  const target = await mongoose.createConnection(TARGET_URI, { maxPoolSize: 5 }).asPromise();
  try {
    // Slides
    const slideDocs = await source.db.collection('slides').find({}).toArray();
    console.log('Slides to migrate:', slideDocs.length);
    const slideResult = await upsertAll({ connection: { db: target.db } }, 'slides', slideDocs);
    console.log('Slides migrated:', slideResult.inserted);

    // SourceText (tutorial + weekly-practice)
    const stDocs = await source.db.collection('sourcetexts').find({ category: { $in: ['tutorial', 'weekly-practice'] } }).toArray();
    console.log('SourceTexts to migrate:', stDocs.length);
    const stResult = await upsertAll({ connection: { db: target.db } }, 'sourcetexts', stDocs);
    console.log('SourceTexts migrated:', stResult.inserted);

    // Optional: Week briefs if used
    const briefsExists = await source.db.listCollections({ name: 'weekbriefs' }).hasNext();
    if (briefsExists) {
      const wbDocs = await source.db.collection('weekbriefs').find({}).toArray();
      console.log('WeekBriefs to migrate:', wbDocs.length);
      await upsertAll({ connection: { db: target.db } }, 'weekbriefs', wbDocs);
    }

    console.log('Migration completed successfully.');
  } catch (e) {
    console.error('Migration failed:', e);
    process.exitCode = 1;
  } finally {
    await source.close();
    await target.close();
  }
}

main();