const express = require('express');
const router = express.Router();
const { getDb } = require('../db');

router.get('/', (req, res) => {
  try {
    const db = getDb();
    const { start, end } = req.query;

    const endWithTime = end ? end + ' 23:59:59' : null;

    // Build date filter fragments and positional params for order-based queries
    let dateFilter = '';
    const orderParams = [];
    if (start) { dateFilter += ' AND o.created_at >= ?'; orderParams.push(start); }
    if (end) { dateFilter += ' AND o.created_at <= ?'; orderParams.push(endWithTime); }

    // For stock adjustments
    let dateFilterSA = '';
    const saParams = [];
    if (start) { dateFilterSA += ' AND sa.created_at >= ?'; saParams.push(start); }
    if (end) { dateFilterSA += ' AND sa.created_at <= ?'; saParams.push(endWithTime); }

    // For inventory summary, the SA params repeat 3 times (3 subqueries)
    const invParams = [...saParams, ...saParams, ...saParams];

    const salesByProduct = db.prepare(`
      SELECT p.name as product_name,
             COALESCE(SUM(oi.quantity), 0) as units_sold,
             COALESCE(SUM(oi.quantity * oi.price_at_sale), 0) as revenue
      FROM products p
      LEFT JOIN (
        SELECT oi.product_id, oi.quantity, oi.price_at_sale
        FROM order_items oi
        JOIN orders o ON o.id = oi.order_id
        WHERE 1=1 ${dateFilter}
      ) oi ON oi.product_id = p.id
      GROUP BY p.id, p.name
      ORDER BY revenue DESC
    `).all(...orderParams);

    const topCustomers = db.prepare(`
      SELECT c.name as customer_name,
             COUNT(DISTINCT o.id) as order_count,
             COALESCE(SUM(oi.quantity * oi.price_at_sale), 0) as total_spent
      FROM customers c
      JOIN orders o ON o.customer_id = c.id ${dateFilter ? 'AND 1=1' + dateFilter : ''}
      JOIN order_items oi ON oi.order_id = o.id
      GROUP BY c.id, c.name
      ORDER BY total_spent DESC
    `).all(...orderParams);

    const revenueOverTime = db.prepare(`
      SELECT date(o.created_at) as date,
             COALESCE(SUM(oi.quantity * oi.price_at_sale), 0) as revenue,
             COUNT(DISTINCT o.id) as order_count
      FROM orders o
      JOIN order_items oi ON oi.order_id = o.id
      WHERE 1=1 ${dateFilter}
      GROUP BY date(o.created_at)
      ORDER BY date
    `).all(...orderParams);

    const orderStatusBreakdown = db.prepare(`
      SELECT o.status, COUNT(*) as count
      FROM orders o
      WHERE 1=1 ${dateFilter}
      GROUP BY o.status
      ORDER BY count DESC
    `).all(...orderParams);

    const inventorySummary = db.prepare(`
      SELECT p.name as product_name,
             p.quantity_on_hand as current_stock,
             p.low_stock_threshold,
             COALESCE((SELECT SUM(sa.adjustment) FROM stock_adjustments sa WHERE sa.product_id = p.id AND sa.reason = 'restock' ${dateFilterSA}), 0) as total_restocked,
             COALESCE((SELECT ABS(SUM(sa.adjustment)) FROM stock_adjustments sa WHERE sa.product_id = p.id AND sa.adjustment < 0 ${dateFilterSA}), 0) as total_sold,
             COALESCE((SELECT COUNT(*) FROM stock_adjustments sa WHERE sa.product_id = p.id AND sa.reason = 'restock' ${dateFilterSA}), 0) as restock_count
      FROM products p
      ORDER BY p.name
    `).all(...invParams);

    res.json({
      salesByProduct,
      topCustomers,
      revenueOverTime,
      orderStatusBreakdown,
      inventorySummary,
    });
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

module.exports = router;