// Command server 是 FuelLog API 入口。
//
// 启动流程:
//  1. 加载 .env
//  2. 解析配置
//  3. 打开 SQLite + 运行迁移
//  4. 装配路由
//  5. 监听并优雅退出
package main

import (
	"context"
	"log/slog"
	"net/http"
	"os"
	"os/signal"
	"syscall"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/joho/godotenv"
	"gorm.io/gorm"

	"github.com/kennethcheng/fuellog-api/internal/config"
	"github.com/kennethcheng/fuellog-api/internal/db"
	"github.com/kennethcheng/fuellog-api/internal/middleware"
	"github.com/kennethcheng/fuellog-api/pkg/apperror"
)

func main() {
	// .env 加载失败不致命(可能是生产环境用环境变量注入)
	if err := godotenv.Load(); err != nil && !os.IsNotExist(err) {
		slog.Warn(".env load failed", "err", err)
	}

	cfg, err := config.Load()
	if err != nil {
		slog.Error("config load failed", "err", err)
		os.Exit(1)
	}
	gin.SetMode(cfg.GinMode)
	slog.SetDefault(slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
		Level: parseLogLevel(cfg.LogLevel),
	})))

	gormDB, err := db.Open(cfg.DBPath)
	if err != nil {
		slog.Error("db open failed", "err", err)
		os.Exit(1)
	}
	if err := db.Migrate(gormDB); err != nil {
		slog.Error("db migrate failed", "err", err)
		os.Exit(1)
	}
	slog.Info("db ready", "path", cfg.DBPath)

	app := &application{cfg: cfg, db: gormDB}

	srv := &http.Server{
		Addr:              cfg.ServerAddr,
		Handler:           app.router(),
		ReadHeaderTimeout: 10 * time.Second,
	}

	// 启动 + 优雅退出
	go func() {
		slog.Info("server starting", "addr", cfg.ServerAddr, "mode", cfg.GinMode)
		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
			slog.Error("server error", "err", err)
			os.Exit(1)
		}
	}()

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

	slog.Info("server shutting down")
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	if err := srv.Shutdown(ctx); err != nil {
		slog.Error("graceful shutdown failed", "err", err)
		os.Exit(1)
	}
	slog.Info("server stopped")
}

// application 持有所有依赖,避免散落全局变量。
type application struct {
	cfg *config.Config
	db  *gorm.DB
	// Phase 1.3 起注入:vehicleRepo / refuelRepo / vehicleSvc / refuelSvc
}

// router 构建并返回 Gin 引擎。
// 当前阶段只暴露 /health;Phase 1.3 起逐步接 /api/vehicles、/api/refuels。
func (a *application) router() *gin.Engine {
	r := gin.New()
	r.Use(
		middleware.Recover(),
		middleware.Logger(),
		middleware.CORS(a.cfg.CORSOrigins),
	)

	r.NoRoute(func(c *gin.Context) {
		c.JSON(http.StatusNotFound, gin.H{
			"code":    apperror.CodeNotFound,
			"message": "路径不存在: " + c.Request.URL.Path,
		})
	})

	r.GET("/health", func(c *gin.Context) {
		c.JSON(http.StatusOK, gin.H{
			"status": "ok",
			"time":   a.cfg.Now().In(a.cfg.Location()).Format(time.RFC3339),
		})
	})

	// /api 路由组(Phase 1.3 起在此挂载业务路由)
	api := r.Group("/api")
	_ = api // 占位,避免未使用告警

	return r
}

func parseLogLevel(s string) slog.Level {
	switch s {
	case "debug":
		return slog.LevelDebug
	case "warn":
		return slog.LevelWarn
	case "error":
		return slog.LevelError
	default:
		return slog.LevelInfo
	}
}