MongoDB Aggregation

const Order = require('../models/Order');

exports.getTopCategories = async (req, res) => {
    const pipeline = [
        // 1. Filter completed orders from the last 30 days
        { $match: { 
            status: 'completed',
            createdAt: { $gte: new Date(Date.now() - 30 * 24 * 60 * 60 * 1000) } 
        }},
        // 2. Group by category and calculate total revenue & units sold
        { $group: { 
            _id: '$category', 
            totalRevenue: { $sum: '$price' },
            unitsSold: { $sum: 1 }
        }},
        // 3. Sort by total revenue (Descending)
        { $sort: { totalRevenue: -1 } },
        // 4. Limit to top 5 categories
        { $limit: 5 }
    ];

    const report = await Order.aggregate(pipeline);
    res.json(report);
};