// graphql/loaders.js
const DataLoader = require('dataloader');
const { User, Follow, Post } = require('../server');
const {mongoose } = require('mongoose');

const createLoaders = () => ({
  // ✅ User Loader
  userLoader: new DataLoader(async (userIds) => {
    const users = await User.find({ _id: { $in: userIds } });
    return userIds.map(id => users.find(u => u._id.toString() === id.toString()));
  }),
  
  // ✅ Followers Count Loader
  followersCountLoader: new DataLoader(async (userIds) => {
    const counts = await Follow.aggregate([
      { $match: { followingId: { $in: userIds.map(id => new mongoose.Types.ObjectId(id)) }, status: 'accepted' } },
      { $group: { _id: '$followingId', count: { $sum: 1 } } }
    ]);
    return userIds.map(id => counts.find(c => c._id.toString() === id.toString())?.count || 0);
  }),
  
  // ✅ Following Count Loader
  followingCountLoader: new DataLoader(async (userIds) => {
    const counts = await Follow.aggregate([
      { $match: { followerId: { $in: userIds.map(id => new mongoose.Types.ObjectId(id)) }, status: 'accepted' } },
      { $group: { _id: '$followerId', count: { $sum: 1 } } }
    ]);
    return userIds.map(id => counts.find(c => c._id.toString() === id.toString())?.count || 0);
  }),
  
  // ✅ Posts Count Loader
  postsCountLoader: new DataLoader(async (userIds) => {
    const counts = await Post.aggregate([
      { $match: { userId: { $in: userIds.map(id => new mongoose.Types.ObjectId(id)) } } },
      { $group: { _id: '$userId', count: { $sum: 1 } } }
    ]);
    return userIds.map(id => counts.find(c => c._id.toString() === id.toString())?.count || 0);
  }),
});

module.exports = { createLoaders };