const express = require('express');
const router = express.Router();

// Status code constants
const STATUS = {
  CANCELED: 0,
  CREATED: 1,
  ELECTRONICALLY_READY_SEND: 10,
  ORDERED: 11,
  PREORDERED: 12,
  ELECTRONICALLY_SENT: 13,
  RECEIVING_STARTED: 15,
  DONE: 50
};

const RECEIVING_STATUS = {
  CANCELED: 0,
  CREATED: 1,
  PARTIAL_RECEIVED: 30,
  FULL_RECEIVED: 40,
  PAID: 50
};

// Get all purchase orders with summary metrics
router.get('/', async (req, res) => {
  try {
    const pool = req.app.locals.pool;
    const { search, status, vendor, startDate, endDate, page = 1, limit = 100, sortColumn = 'date', sortDirection = 'desc' } = req.query;
    
    let whereClause = '1=1';
    const params = [];
    
    if (search) {
      whereClause += ' AND (po.po_id LIKE ? OR po.vendor LIKE ?)';
      params.push(`%${search}%`, `%${search}%`);
    }
    
    if (status && status !== 'all') {
      whereClause += ' AND po.status = ?';
      params.push(Number(status));
    }
    
    if (vendor && vendor !== 'all') {
      whereClause += ' AND po.vendor = ?';
      params.push(vendor);
    }
    
    if (startDate) {
      whereClause += ' AND po.date >= ?';
      params.push(startDate);
    }
    
    if (endDate) {
      whereClause += ' AND po.date <= ?';
      params.push(endDate);
    }

    // Get filtered summary metrics
    const [summary] = await pool.query(`
      WITH po_totals AS (
        SELECT 
          po_id,
          SUM(ordered) as total_ordered,
          SUM(received) as total_received,
          CAST(SUM(ordered * cost_price) AS DECIMAL(15,3)) as total_cost
        FROM purchase_orders po
        WHERE ${whereClause}
        GROUP BY po_id
      )
      SELECT 
        COUNT(DISTINCT po_id) as order_count,
        SUM(total_ordered) as total_ordered,
        SUM(total_received) as total_received,
        ROUND(
          SUM(total_received) / NULLIF(SUM(total_ordered), 0), 3
        ) as fulfillment_rate,
        CAST(SUM(total_cost) AS DECIMAL(15,3)) as total_value,
        CAST(AVG(total_cost) AS DECIMAL(15,3)) as avg_cost
      FROM po_totals
    `, params);

    // Get total count for pagination
    const [countResult] = await pool.query(`
      SELECT COUNT(DISTINCT po_id) as total
      FROM purchase_orders po
      WHERE ${whereClause}
    `, params);

    const total = countResult[0].total;
    const offset = (page - 1) * limit;
    const pages = Math.ceil(total / limit);

    // Get recent purchase orders
    const [orders] = await pool.query(`
      WITH po_totals AS (
        SELECT 
          po_id,
          vendor,
          date,
          status,
          receiving_status,
          COUNT(DISTINCT pid) as total_items,
          SUM(ordered) as total_quantity,
          CAST(SUM(ordered * cost_price) AS DECIMAL(15,3)) as total_cost,
          SUM(received) as total_received,
          ROUND(
            SUM(received) / NULLIF(SUM(ordered), 0), 3
          ) as fulfillment_rate
        FROM purchase_orders po
        WHERE ${whereClause}
        GROUP BY po_id, vendor, date, status, receiving_status
      )
      SELECT 
        po_id as id,
        vendor as vendor_name,
        DATE_FORMAT(date, '%Y-%m-%d') as order_date,
        status,
        receiving_status,
        total_items,
        total_quantity,
        total_cost,
        total_received,
        fulfillment_rate
      FROM po_totals
      ORDER BY 
        CASE 
          WHEN ? = 'order_date' THEN date
          WHEN ? = 'vendor_name' THEN vendor
          WHEN ? = 'total_cost' THEN CAST(total_cost AS DECIMAL(15,3))
          WHEN ? = 'total_received' THEN CAST(total_received AS DECIMAL(15,3))
          WHEN ? = 'total_items' THEN CAST(total_items AS SIGNED)
          WHEN ? = 'total_quantity' THEN CAST(total_quantity AS SIGNED)
          WHEN ? = 'fulfillment_rate' THEN CAST(fulfillment_rate AS DECIMAL(5,3))
          WHEN ? = 'status' THEN status
          ELSE date
        END ${sortDirection === 'desc' ? 'DESC' : 'ASC'}
      LIMIT ? OFFSET ?
    `, [...params, sortColumn, sortColumn, sortColumn, sortColumn, sortColumn, sortColumn, sortColumn, sortColumn, Number(limit), offset]);

    // Get unique vendors for filter options
    const [vendors] = await pool.query(`
      SELECT DISTINCT vendor 
      FROM purchase_orders 
      WHERE vendor IS NOT NULL AND vendor != ''
      ORDER BY vendor
    `);

    // Get unique statuses for filter options
    const [statuses] = await pool.query(`
      SELECT DISTINCT status 
      FROM purchase_orders 
      WHERE status IS NOT NULL
      ORDER BY status
    `);

    // Parse numeric values
    const parsedOrders = orders.map(order => ({
      id: order.id,
      vendor_name: order.vendor_name,
      order_date: order.order_date,
      status: Number(order.status),
      receiving_status: Number(order.receiving_status),
      total_items: Number(order.total_items) || 0,
      total_quantity: Number(order.total_quantity) || 0,
      total_cost: Number(order.total_cost) || 0,
      total_received: Number(order.total_received) || 0,
      fulfillment_rate: Number(order.fulfillment_rate) || 0
    }));

    // Parse summary metrics
    const parsedSummary = {
      order_count: Number(summary[0].order_count) || 0,
      total_ordered: Number(summary[0].total_ordered) || 0,
      total_received: Number(summary[0].total_received) || 0,
      fulfillment_rate: Number(summary[0].fulfillment_rate) || 0,
      total_value: Number(summary[0].total_value) || 0,
      avg_cost: Number(summary[0].avg_cost) || 0
    };

    res.json({
      orders: parsedOrders,
      summary: parsedSummary,
      pagination: {
        total,
        pages,
        page: Number(page),
        limit: Number(limit)
      },
      filters: {
        vendors: vendors.map(v => v.vendor),
        statuses: statuses.map(s => Number(s.status))
      }
    });
  } catch (error) {
    console.error('Error fetching purchase orders:', error);
    res.status(500).json({ error: 'Failed to fetch purchase orders' });
  }
});

// Get vendor performance metrics
router.get('/vendor-metrics', async (req, res) => {
  try {
    const pool = req.app.locals.pool;
    
    const [metrics] = await pool.query(`
      WITH delivery_metrics AS (
        SELECT 
          vendor,
          po_id,
          ordered,
          received,
          cost_price,
          CASE 
            WHEN status >= ${STATUS.RECEIVING_STARTED} AND receiving_status >= ${RECEIVING_STATUS.PARTIAL_RECEIVED}
            AND received_date IS NOT NULL AND date IS NOT NULL
            THEN DATEDIFF(received_date, date)
            ELSE NULL
          END as delivery_days
        FROM purchase_orders
        WHERE vendor IS NOT NULL AND vendor != ''
          AND status != ${STATUS.CANCELED}  -- Exclude canceled orders
      )
      SELECT 
        vendor as vendor_name,
        COUNT(DISTINCT po_id) as total_orders,
        SUM(ordered) as total_ordered,
        SUM(received) as total_received,
        ROUND(
          SUM(received) / NULLIF(SUM(ordered), 0), 3
        ) as fulfillment_rate,
        CAST(ROUND(
          SUM(ordered * cost_price) / NULLIF(SUM(ordered), 0), 2
        ) AS DECIMAL(15,3)) as avg_unit_cost,
        CAST(SUM(ordered * cost_price) AS DECIMAL(15,3)) as total_spend,
        ROUND(
          AVG(NULLIF(delivery_days, 0)), 1
        ) as avg_delivery_days
      FROM delivery_metrics
      GROUP BY vendor
      HAVING total_orders > 0
      ORDER BY total_spend DESC
    `);

    // Parse numeric values
    const parsedMetrics = metrics.map(vendor => ({
      id: vendor.vendor_name,
      vendor_name: vendor.vendor_name,
      total_orders: Number(vendor.total_orders) || 0,
      total_ordered: Number(vendor.total_ordered) || 0,
      total_received: Number(vendor.total_received) || 0,
      fulfillment_rate: Number(vendor.fulfillment_rate) || 0,
      avg_unit_cost: Number(vendor.avg_unit_cost) || 0,
      total_spend: Number(vendor.total_spend) || 0,
      avg_delivery_days: vendor.avg_delivery_days === null ? null : Number(vendor.avg_delivery_days)
    }));

    res.json(parsedMetrics);
  } catch (error) {
    console.error('Error fetching vendor metrics:', error);
    res.status(500).json({ error: 'Failed to fetch vendor metrics' });
  }
});

// Get cost analysis
router.get('/cost-analysis', async (req, res) => {
  try {
    const pool = req.app.locals.pool;
    
    const [analysis] = await pool.query(`
      WITH category_costs AS (
        SELECT 
          c.name as category,
          po.pid,
          po.cost_price,
          po.ordered,
          po.received,
          po.status,
          po.receiving_status
        FROM purchase_orders po
        JOIN product_categories pc ON po.pid = pc.pid
        JOIN categories c ON pc.cat_id = c.cat_id
        WHERE po.status != ${STATUS.CANCELED}  -- Exclude canceled orders
      )
      SELECT 
        category,
        COUNT(DISTINCT pid) as unique_products,
        CAST(AVG(cost_price) AS DECIMAL(15,3)) as avg_cost,
        CAST(MIN(cost_price) AS DECIMAL(15,3)) as min_cost,
        CAST(MAX(cost_price) AS DECIMAL(15,3)) as max_cost,
        CAST(STDDEV(cost_price) AS DECIMAL(15,3)) as cost_variance,
        CAST(SUM(ordered * cost_price) AS DECIMAL(15,3)) as total_spend
      FROM category_costs
      GROUP BY category
      ORDER BY total_spend DESC
    `);

    // Parse numeric values
    const parsedAnalysis = {
      categories: analysis.map(cat => ({
        category: cat.category,
        unique_products: Number(cat.unique_products) || 0,
        avg_cost: Number(cat.avg_cost) || 0,
        min_cost: Number(cat.min_cost) || 0,
        max_cost: Number(cat.max_cost) || 0,
        cost_variance: Number(cat.cost_variance) || 0,
        total_spend: Number(cat.total_spend) || 0
      }))
    };

    res.json(parsedAnalysis);
  } catch (error) {
    console.error('Error fetching cost analysis:', error);
    res.status(500).json({ error: 'Failed to fetch cost analysis' });
  }
});

// Get receiving status metrics
router.get('/receiving-status', async (req, res) => {
  try {
    const pool = req.app.locals.pool;
    
    const [status] = await pool.query(`
      WITH po_totals AS (
        SELECT 
          po_id,
          status,
          receiving_status,
          SUM(ordered) as total_ordered,
          SUM(received) as total_received,
          CAST(SUM(ordered * cost_price) AS DECIMAL(15,3)) as total_cost
        FROM purchase_orders
        WHERE status != ${STATUS.CANCELED}
        GROUP BY po_id, status, receiving_status
      )
      SELECT 
        COUNT(DISTINCT po_id) as order_count,
        SUM(total_ordered) as total_ordered,
        SUM(total_received) as total_received,
        ROUND(
          SUM(total_received) / NULLIF(SUM(total_ordered), 0), 3
        ) as fulfillment_rate,
        CAST(SUM(total_cost) AS DECIMAL(15,3)) as total_value,
        CAST(AVG(total_cost) AS DECIMAL(15,3)) as avg_cost,
        COUNT(DISTINCT CASE 
          WHEN receiving_status = ${RECEIVING_STATUS.CREATED} THEN po_id 
          END) as pending_count,
        COUNT(DISTINCT CASE 
          WHEN receiving_status = ${RECEIVING_STATUS.PARTIAL_RECEIVED} THEN po_id 
          END) as partial_count,
        COUNT(DISTINCT CASE 
          WHEN receiving_status >= ${RECEIVING_STATUS.FULL_RECEIVED} THEN po_id 
          END) as completed_count,
        COUNT(DISTINCT CASE 
          WHEN receiving_status = ${RECEIVING_STATUS.CANCELED} THEN po_id 
          END) as canceled_count
      FROM po_totals
    `);

    // Parse numeric values
    const parsedStatus = {
      order_count: Number(status[0].order_count) || 0,
      total_ordered: Number(status[0].total_ordered) || 0,
      total_received: Number(status[0].total_received) || 0,
      fulfillment_rate: Number(status[0].fulfillment_rate) || 0,
      total_value: Number(status[0].total_value) || 0,
      avg_cost: Number(status[0].avg_cost) || 0,
      status_breakdown: {
        pending: Number(status[0].pending_count) || 0,
        partial: Number(status[0].partial_count) || 0,
        completed: Number(status[0].completed_count) || 0,
        canceled: Number(status[0].canceled_count) || 0
      }
    };

    res.json(parsedStatus);
  } catch (error) {
    console.error('Error fetching receiving status:', error);
    res.status(500).json({ error: 'Failed to fetch receiving status' });
  }
});

// Get order vs received quantities by product
router.get('/order-vs-received', async (req, res) => {
  try {
    const pool = req.app.locals.pool;
    
    const [quantities] = await pool.query(`
      SELECT 
        p.product_id,
        p.title as product,
        p.SKU as sku,
        SUM(po.ordered) as ordered_quantity,
        SUM(po.received) as received_quantity,
        ROUND(
          SUM(po.received) / NULLIF(SUM(po.ordered), 0) * 100, 1
        ) as fulfillment_rate,
        COUNT(DISTINCT po.po_id) as order_count
      FROM products p
      JOIN purchase_orders po ON p.product_id = po.product_id
      WHERE po.date >= DATE_SUB(CURDATE(), INTERVAL 90 DAY)
      GROUP BY p.product_id, p.title, p.SKU
      HAVING order_count > 0
      ORDER BY ordered_quantity DESC
      LIMIT 20
    `);

    // Parse numeric values and add id for React keys
    const parsedQuantities = quantities.map(q => ({
      id: q.product_id,
      ...q,
      ordered_quantity: Number(q.ordered_quantity),
      received_quantity: Number(q.received_quantity),
      fulfillment_rate: Number(q.fulfillment_rate),
      order_count: Number(q.order_count)
    }));

    res.json(parsedQuantities);
  } catch (error) {
    console.error('Error fetching order vs received quantities:', error);
    res.status(500).json({ error: 'Failed to fetch order vs received quantities' });
  }
});

module.exports = router;