package main

import (
	"context"
	"html/template"
	"io/fs"
	"log"
	"net/http"
	"os"
	"os/signal"
	"syscall"
	"time"

	"shop/internal/config"
	"shop/internal/database"
	"shop/internal/handlers"
	"shop/internal/repository"
	"shop/internal/web"
)

func main() {
	cfg, err := config.Load()
	if err != nil {
		log.Fatalf("config: %v", err)
	}

	ctx := context.Background()
	pool, err := database.Connect(ctx, cfg.DatabaseURL)
	if err != nil {
		log.Fatalf("database: %v", err)
	}
	defer pool.Close()

	tmpl, err := loadTemplates()
	if err != nil {
		log.Fatalf("templates: %v", err)
	}

	products := repository.NewProductRepository(pool)
	home := handlers.NewHomeHandler(products, tmpl)

	staticSub, err := fs.Sub(web.StaticFS, "static")
	if err != nil {
		log.Fatalf("static fs: %v", err)
	}

	mux := http.NewServeMux()
	mux.Handle("GET /static/", http.StripPrefix("/static/", http.FileServer(http.FS(staticSub))))
	mux.Handle("GET /health", http.HandlerFunc(handlers.Health))
	mux.Handle("GET /", home)

	srv := &http.Server{
		Addr:         cfg.HTTPAddr,
		Handler:      mux,
		ReadTimeout:  cfg.ReadTimeout,
		WriteTimeout: cfg.WriteTimeout,
	}

	go func() {
		log.Printf("server listening on %s", cfg.HTTPAddr)
		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
			log.Fatalf("listen: %v", err)
		}
	}()

	quit := make(chan os.Signal, 1)
	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
	<-quit

	shutdownCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	if err := srv.Shutdown(shutdownCtx); err != nil {
		log.Printf("shutdown: %v", err)
	}
}

func loadTemplates() (*template.Template, error) {
	funcMap := template.FuncMap{
		"formatPrice": func(v float64) string {
			return formatRub(v)
		},
	}
	return template.New("").Funcs(funcMap).ParseFS(web.TemplatesFS, "templates/*.html")
}

func formatRub(v float64) string {
	intPart := int64(v)
	frac := int64((v - float64(intPart)) * 100)
	if frac < 0 {
		frac = -frac
	}
	return formatThousands(intPart) + "," + pad2(frac) + " ₽"
}

func formatThousands(n int64) string {
	if n < 0 {
		n = -n
	}
	s := ""
	for n >= 1000 {
		s = "," + pad3(n%1000) + s
		n /= 1000
	}
	return itoa(n) + s
}

func pad3(n int64) string {
	if n < 10 {
		return "00" + itoa(n)
	}
	if n < 100 {
		return "0" + itoa(n)
	}
	return itoa(n)
}

func pad2(n int64) string {
	if n < 10 {
		return "0" + itoa(n)
	}
	return itoa(n)
}

func itoa(n int64) string {
	if n == 0 {
		return "0"
	}
	var b [20]byte
	i := len(b)
	for n > 0 {
		i--
		b[i] = byte('0' + n%10)
		n /= 10
	}
	return string(b[i:])
}