package main

import (
	"encoding/json"
	"fmt"
	"net/http"
	"time"
)

// Симулирует агрегацию данных за день (в реальности — запрос к БД)

type DailyStat struct {
	Date        string  `json:"date"`
	Orders      int     `json:"orders"`
	Revenue     float64 `json:"revenue"`
	AvgOrder    float64 `json:"avg_order_value"`
	NewUsers    int     `json:"new_users"`
	TopCategory string  `json:"top_category"`
}

func generateDailyStats(days int) []DailyStat {
	stats := make([]DailyStat, days)
	base := time.Now().UTC()
	revenues := []float64{4821.50, 3920.00, 6100.75, 5200.10, 7330.40, 4100.00, 8950.30}
	orders := []int{38, 31, 49, 42, 58, 33, 72}
	categories := []string{"electronics", "furniture", "electronics", "stationery", "electronics", "furniture", "electronics"}

	for i := 0; i < days; i++ {
		day := base.AddDate(0, 0, -(days - 1 - i))
		rev := revenues[i%len(revenues)]
		ord := orders[i%len(orders)]
		stats[i] = DailyStat{
			Date:        day.Format("2006-01-02"),
			Orders:      ord,
			Revenue:     rev,
			AvgOrder:    float64(int(rev/float64(ord)*100)) / 100,
			NewUsers:    5 + i*2,
			TopCategory: categories[i%len(categories)],
		}
	}
	return stats
}

func Handler(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")

	days := 7
	stats := generateDailyStats(days)

	totalRevenue := 0.0
	totalOrders := 0
	for _, s := range stats {
		totalRevenue += s.Revenue
		totalOrders += s.Orders
	}

	report := map[string]interface{}{
		"status":          "ok",
		"generated_at":    time.Now().UTC().Format(time.RFC3339),
		"period_days":     days,
		"total_revenue":   fmt.Sprintf("%.2f", totalRevenue),
		"total_orders":    totalOrders,
		"avg_daily_rev":   fmt.Sprintf("%.2f", totalRevenue/float64(days)),
		"daily_breakdown": stats,
	}

	json.NewEncoder(w).Encode(report)
}