package main

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

	"git.lzcwy.cn/zhengchiliu/zt-closet-manage-backend/global"
	"git.lzcwy.cn/zhengchiliu/zt-closet-manage-backend/internal/mysqlmodel"
	"git.lzcwy.cn/zhengchiliu/zt-closet-manage-backend/internal/redismodel"
	"git.lzcwy.cn/zhengchiliu/zt-closet-manage-backend/internal/routers"
	"git.lzcwy.cn/zhengchiliu/zt-closet-manage-backend/internal/service"
	"git.lzcwy.cn/zhengchiliu/zt-closet-manage-backend/pkg/setting"
	"git.lzcwy.cn/zhengchiliu/zt-closet-manage-backend/pkg/tracing"

	"github.com/gin-gonic/gin"
	"go.opentelemetry.io/contrib/bridges/otelslog"
	"go.opentelemetry.io/otel"
	"gopkg.in/natefinch/lumberjack.v2"
)

func init() {
	if err := setupSetting(); err != nil {
		panic(err)
	}

	// OTel 需在 logger 之前初始化，使 LoggerProvider 就绪后 slog 可桥接到 OTel Logs。
	setupOTel()

	if err := setupSlogLogger(); err != nil {
		panic(err)
	}

	if err := setupMysqlEngine(); err != nil {
		panic(err)
	}

	if err := setupRedisEngine(); err != nil {
		panic(err)
	}
}

func main() {
	gin.SetMode(global.ServerSetting.RunMode)

	// 建管理员表并幂等创建初始超级管理员（依赖 MySQL 已就绪，故在 main 中执行）。
	migrateAdminTables()
	service.EnsureInitialSuperAdmin(context.Background())

	router := routers.NewRouter()

	s := &http.Server{
		Addr:         ":" + global.ServerSetting.HttpPort,
		Handler:      router,
		ReadTimeout:  time.Duration(global.ServerSetting.ReadTimeout) * time.Second,
		WriteTimeout: time.Duration(global.ServerSetting.WriteTimeout) * time.Second,

		// 限制http请求头的大小为1MB
		MaxHeaderBytes: 1 << 20,
	}

	// 后台启动 HTTP 服务；启动失败（如端口占用）通过 channel 反馈主流程，避免进程「假存活」。
	serverErr := make(chan error, 1)
	go func() {
		if err := s.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
			serverErr <- err
		}
	}()
	slog.Info("server started", "port", global.ServerSetting.HttpPort)

	// 等待退出信号或服务启动错误。
	quit := make(chan os.Signal, 1)
	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)

	select {
	case <-quit:
		slog.Info("shutting down server...")
	case err := <-serverErr:
		slog.Error("http server start failed", "error", err)
	}

	// 优雅关闭：HTTP 与 OTel 使用独立 context，避免 HTTP 等待耗尽 OTel flush 的超时。
	shutdownCtx, shutdownCancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer shutdownCancel()
	if err := s.Shutdown(shutdownCtx); err != nil {
		slog.Error("http server shutdown error", "error", err)
	}

	if global.OTelShutdown != nil {
		otelCtx, otelCancel := context.WithTimeout(context.Background(), 5*time.Second)
		defer otelCancel()
		if err := global.OTelShutdown(otelCtx); err != nil {
			slog.Error("otel shutdown error", "error", err)
		}
	}
	slog.Info("server exited")
}

// migrateAdminTables 仅迁移管理后台自建表（admin_users）。
func migrateAdminTables() {
	if err := mysqlmodel.AutoMigrateAdminTables(global.MysqlEngine); err != nil {
		slog.Error("auto migrate admin tables failed", "error", err)
		panic(err)
	}
}

func setupSetting() error {
	setting, err := setting.NewSetting()
	if err != nil {
		return err
	}

	err = setting.ReadSection("Server", &global.ServerSetting)
	if err != nil {
		return err
	}

	err = setting.ReadSection("Log", &global.LogSetting)
	if err != nil {
		return err
	}

	err = setting.ReadSection("Mysql", &global.MysqlSetting)
	if err != nil {
		return err
	}

	err = setting.ReadSection("Redis", &global.RedisSetting)
	if err != nil {
		return err
	}

	err = setting.ReadSection("Otel", &global.OtelSetting)
	if err != nil {
		return err
	}

	err = setting.ReadSection("JWT", &global.JWTSetting)
	if err != nil {
		return err
	}
	// 校验 JWT 关键配置，防止密钥缺失导致可用空密钥伪造 token。
	if global.JWTSetting == nil || global.JWTSetting.SecretKey == "" {
		return fmt.Errorf("JWT secret key must not be empty")
	}

	err = setting.ReadSection("Admin", &global.AdminSetting)
	if err != nil {
		return err
	}

	err = setting.ReadSection("Quota", &global.QuotaSetting)
	if err != nil {
		return err
	}

	err = setting.ReadSection("Cos", &global.CosSetting)
	if err != nil {
		return err
	}

	// 校验 Server 配置（时间字段已按秒解析，此处仅做存在性校验）。
	if global.ServerSetting == nil {
		return fmt.Errorf("Server config section is missing")
	}

	return nil
}

func setupSlogLogger() error {
	// 确保日志目录存在（lumberjack 不会自动创建父目录，目录缺失时文件日志会静默失效）。
	if err := os.MkdirAll(global.LogSetting.LogSavePath, 0o755); err != nil {
		return fmt.Errorf("create log dir: %w", err)
	}

	writer := &lumberjack.Logger{
		Filename:   global.LogSetting.LogSavePath + "/" + global.LogSetting.LogFileName + global.LogSetting.LogFileExt,
		MaxSize:    global.LogSetting.MaxSize,
		MaxBackups: global.LogSetting.MaxBackups,
		MaxAge:     global.LogSetting.MaxAge,
		Compress:   true,
	}

	multiWriter := io.MultiWriter(writer, os.Stdout)

	level := slog.LevelInfo
	switch global.LogSetting.LogLevel {
	case "Debug":
		level = slog.LevelDebug
	case "Warn":
		level = slog.LevelWarn
	case "Error":
		level = slog.LevelError
	default:
		level = slog.LevelInfo
	}

	// 本地 JSON 日志（文件 + stdout），并注入 trace_id/span_id。
	localHandler := tracing.OtelContextHandler{
		Handler: slog.NewJSONHandler(multiWriter, &slog.HandlerOptions{
			AddSource: true,
			Level:     level,
		}),
	}

	// OTel 日志桥接：将 slog 记录导出到 OTel Logs（LoggerProvider 已在 setupOTel 就绪；
	// 未启用 OTel 时为 no-op，不产生开销）。
	otelHandler := otelslog.NewHandler("zt-closet-manage-backend")

	// 扇出：本地日志 + OTel 日志同时输出。
	slog.SetDefault(slog.New(tracing.NewFanoutHandler(localHandler, otelHandler)))

	return nil
}

// setupMysqlEngine 初始化 MySQL 数据库连接。
func setupMysqlEngine() error {
	var err error
	global.MysqlEngine, err = mysqlmodel.NewMysqlEngine(global.MysqlSetting)
	if err != nil {
		return err
	}
	return nil
}

// setupRedisEngine 初始化 Redis 连接。
func setupRedisEngine() error {
	var err error
	global.RedisEngine, err = redismodel.NewRedisEngine(global.RedisSetting)
	if err != nil {
		return err
	}
	return nil
}

func setupOTel() {
	tracer, shutdown, err := tracing.NewOTelProvider(global.OtelSetting)
	// NewOTelProvider 在任何错误路径都会返回可用的 no-op tracer 与安全 shutdown。
	global.Tracer = tracer
	global.OTelShutdown = shutdown
	if err != nil {
		// 此时 logger 尚未就绪，用标准输出告警；已降级为 no-op。
		fmt.Printf("[WARN] init otel failed, downgraded to no-op: %v\n", err)
	}

	name := "zt-closet-manage-backend"
	if global.OtelSetting != nil && global.OtelSetting.ServiceName != "" {
		name = global.OtelSetting.ServiceName
	}
	global.Meter = otel.Meter(name)
}