feat: New watchlist migration from users MongoDB collection

migrations/20240529104825-create-user-collection.js

@@ -1,30 +1,43 @@
 /**
  * User collection migration.
- * @module migrations/create-users
+ * @module migrations/createUsers
  * @description This module contains a migration function that creates a 'users' collection in the database.
  */
 module.exports = {
   /**
    * Migrates the database schema by creating a 'users' collection.
-   *
    * @param {import('mongodb').Db} db - The MongoDB database instance.
    * @param {import('mongodb').MongoClient} client - The MongoDB client instance.
-   *
    * @returns {Promise<void>} A Promise that resolves when the migration is complete.
+   * @see https://github.com/seppevs/migrate-mongo/#creating-a-new-migration-script
+   * @example await db.collection('albums').updateOne({artist: 'The Beatles'}, {$set: {blacklisted: true}});
    */
   async up(db, client) {
-    await db.createCollection('users');
+    const session = client.startSession();
+    try {
+      await session.withTransaction(async () => {
+        await db.createCollection('users');
+      });
+    } finally {
+      await session.endSession();
+    }
   },
 
   /**
    * Migrates the database schema by dropping the 'users' collection.
-   *
    * @param {import('mongodb').Db} db - The MongoDB database instance.
    * @param {import('mongodb').MongoClient} client - The MongoDB client instance.
-   *
    * @returns {Promise<void>} A Promise that resolves when the migration is complete.
+   * @example await db.collection('albums').updateOne({artist: 'The Beatles'}, {$set: {blacklisted: false}});
    */
   async down(db, client) {
-    await db.collection('users').drop();
+    const session = client.startSession();
+    try {
+      await session.withTransaction(async () => {
+        await db.collection('users').drop();
+      });
+    } finally {
+      await session.endSession();
+    }
   }
 };

migrations/20240604090347-migrate-watchlist-to-new-collection.js

@@ -0,0 +1,67 @@
+const mongoose = require('mongoose');
+
+/**
+ * Watchlist collection migration.
+ * @module migrations/migrateWatchlists
+ * @description This module contains a migration function that creates a 'watchlist' collection in the database.
+ */
+module.exports = {
+  /**
+   * This function migrates the 'watchlist' field from 'users' collection to a new 'watchlists' collection.
+   * @param {Object} db - The MongoDB database instance.
+   * @param {Object} client - The MongoDB client instance.
+   * @returns {Promise<void>}
+   */
+  async up(db, client) {
+    const session = client.startSession();
+    const users = await db.collection('users').find({ watchlist: { $exists: true, $ne: [] } }).toArray();
+    const watchlists = users.map(user => ({
+      userId: user._id,
+      items: user.watchlist.map(item => ({
+        _id: new mongoose.Types.ObjectId(),
+        type: item.type,
+        imdbId: item.imdbID,
+        title: item.title,
+        poster: item.poster,
+      })),
+    }));
+
+    try {
+      await session.withTransaction(async () => {
+        if (watchlists.length > 0) await db.collection('watchlists').insertMany(watchlists);
+        await db.collection('users').updateMany({}, { $unset: { watchlist: 1 } });
+      });
+    } finally {
+      await session.endSession();
+    }
+  },
+
+  /**
+   * This function reverts the migration by moving the 'watchlist' items back to the 'users' collection.
+   * @param {Object} db - The MongoDB database instance.
+   * @param {Object} client - The MongoDB client instance.
+   * @returns {Promise<void>}
+   */
+  async down(db, client) {
+    const session = client.startSession();
+    const watchlists = await db.collection('watchlists').find().toArray();
+
+    try {
+      await session.withTransaction(async () => {
+        for (const watchlist of watchlists) {
+          await db.collection('users').updateOne(
+            { _id: watchlist.userId },
+            {
+              $set: {
+                watchlist: watchlist.items,
+              },
+            }
+          );
+        }
+        await db.collection('watchlists').deleteMany({});
+      });
+    } finally {
+      await session.endSession();
+    }
+  },
+};