const { query } = require('../config/database')
const { COST_RATIO, PROFIT_RATIO } = require('../config/constants')

async function getSalesTrend(ctx) {
  const days = parseInt(ctx.query.days) || 30
  const group = ctx.query.group || 'day'

  let dateFormat
  if (group === 'week') {
    dateFormat = 'DATE_FORMAT(created_at, \'%x-W%v\')'
  } else if (group === 'month') {
    dateFormat = 'DATE_FORMAT(created_at, \'%Y-%m\')'
  } else {
    dateFormat = 'DATE(created_at)'
  }

  const rows = await query(
    `SELECT ${dateFormat} as period,
            COUNT(*) as order_count,
            COALESCE(SUM(total_price), 0) as total_sales
     FROM orders
     WHERE status IN ('paid', 'completed')
       AND created_at >= DATE_SUB(NOW(), INTERVAL ? DAY)
     GROUP BY period
     ORDER BY period ASC`,
    [days]
  )

  ctx.body = { code: 200, data: rows }
}

async function getHotProducts(ctx) {
  const limit = parseInt(ctx.query.limit) || 10

  const rows = await query(
    `SELECT goods.id, goods.name, goods.price, goods.sales, goods.stock,
            COALESCE(s.quantity, 0) as stock_qty
     FROM goods
     LEFT JOIN stock s ON goods.id = s.goods_id
     ORDER BY goods.sales DESC
     LIMIT ?`,
    [limit]
  )

  ctx.body = { code: 200, data: rows }
}

async function getProfitAnalysis(ctx) {
  const days = parseInt(ctx.query.days) || 30

  const revenueRows = await query(
    `SELECT DATE(created_at) as date,
            COUNT(*) as order_count,
            COALESCE(SUM(total_price), 0) as revenue
     FROM orders
     WHERE status IN ('paid', 'completed')
       AND created_at >= DATE_SUB(NOW(), INTERVAL ? DAY)
     GROUP BY DATE(created_at)
     ORDER BY date ASC`,
    [days]
  )

  const avgCost = await query(
    `SELECT COALESCE(AVG(purchase_price), 0) as avg_cost
     FROM purchase_items`
  )

  const costPerUnit = parseFloat(avgCost[0]?.avg_cost || 0)

  const enriched = revenueRows.map(row => ({
    ...row,
    revenue: parseFloat(row.revenue),
      estimated_cost: parseFloat(row.revenue) * COST_RATIO,
      estimated_profit: parseFloat(row.revenue) * PROFIT_RATIO
  }))

  const totalRevenue = enriched.reduce((s, r) => s + r.revenue, 0)
  const totalCost = enriched.reduce((s, r) => s + r.estimated_cost, 0)
  const totalProfit = enriched.reduce((s, r) => s + r.estimated_profit, 0)

  ctx.body = {
    code: 200,
    data: {
      days,
      summary: {
        total_revenue: totalRevenue,
        total_cost: totalCost,
        total_profit: totalProfit,
        profit_margin: totalRevenue > 0 ? ((totalProfit / totalRevenue) * 100).toFixed(1) : '0.0',
        avg_purchase_cost: costPerUnit
      },
      details: enriched
    }
  }
}

async function getInventoryTurnover(ctx) {
  const rows = await query(
    `SELECT g.id, g.name, g.price, g.sales,
            COALESCE(s.quantity, 0) as stock_qty,
            CASE
              WHEN COALESCE(s.quantity, 0) <= 0 THEN g.sales
              ELSE ROUND(g.sales / s.quantity, 2)
            END as turnover_ratio
     FROM goods g
     LEFT JOIN stock s ON g.id = s.goods_id
     ORDER BY turnover_ratio DESC`
  )

  const lowStock = rows.filter(r => r.stock_qty <= 5)
  const outOfStock = rows.filter(r => r.stock_qty <= 0)
  const slowMoving = rows.filter(r => r.turnover_ratio < 0.1 && r.sales > 0)

  ctx.body = {
    code: 200,
    data: {
      total_items: rows.length,
      low_stock_count: lowStock.length,
      out_of_stock_count: outOfStock.length,
      slow_moving_count: slowMoving.length,
      items: rows
    }
  }
}

module.exports = {
  getSalesTrend,
  getHotProducts,
  getProfitAnalysis,
  getInventoryTurnover
}