package database

import (
	"fmt"
	"os"
	"path/filepath"
	"runtime"

	"github.com/pressly/goose/v3"
	"go.uber.org/zap"
	"gorm.io/driver/mysql"
	"gorm.io/driver/sqlite"
	"gorm.io/gorm"

	"nex/backend/internal/config"
	pkglogger "nex/backend/pkg/logger"
)

func Init(cfg *config.DatabaseConfig, zapLogger *zap.Logger) (*gorm.DB, error) {
	moduleLogger := pkglogger.WithModule(zapLogger, "database")
	
	db, err := initDB(cfg, moduleLogger)
	if err != nil {
		return nil, fmt.Errorf("初始化数据库失败: %w", err)
	}

	if err := runMigrations(db, cfg.Driver, moduleLogger); err != nil {
		return nil, fmt.Errorf("数据库迁移失败: %w", err)
	}

	configurePool(db, cfg, moduleLogger)

	return db, nil
}

func Close(db *gorm.DB) {
	sqlDB, err := db.DB()
	if err != nil {
		return
	}
	sqlDB.Close()
}

func initDB(cfg *config.DatabaseConfig, zapLogger *zap.Logger) (*gorm.DB, error) {
	gormLogger := pkglogger.NewGormLogger(zapLogger)

	gormConfig := &gorm.Config{
		Logger: gormLogger,
	}

	switch cfg.Driver {
	case "mysql":
		dsn := fmt.Sprintf("%s:%s@tcp(%s:%d)/%s?charset=utf8mb4&parseTime=true&loc=Local",
			cfg.User, cfg.Password, cfg.Host, cfg.Port, cfg.DBName)
		if zapLogger != nil {
			zapLogger.Info("连接 MySQL 数据库",
				zap.String("host", cfg.Host),
				zap.Int("port", cfg.Port),
				zap.String("database", cfg.DBName))
		}
		return gorm.Open(mysql.Open(dsn), gormConfig)
	default:
		dbDir := filepath.Dir(cfg.Path)
		if err := os.MkdirAll(dbDir, 0755); err != nil {
			return nil, fmt.Errorf("创建数据库目录失败: %w", err)
		}
		if zapLogger != nil {
			zapLogger.Info("连接 SQLite 数据库", zap.String("path", cfg.Path))
		}
		return gorm.Open(sqlite.Open(cfg.Path), gormConfig)
	}
}

func runMigrations(db *gorm.DB, driver string, zapLogger *zap.Logger) error {
	sqlDB, err := db.DB()
	if err != nil {
		return err
	}

	gooseDialect := "sqlite3"
	migrationsSubDir := "sqlite"
	if driver == "mysql" {
		gooseDialect = "mysql"
		migrationsSubDir = "mysql"
	}

	migrationsDir := getMigrationsDir(driver)
	if _, err := os.Stat(migrationsDir); os.IsNotExist(err) {
		return fmt.Errorf("迁移目录不存在: %s", migrationsDir)
	}

	if zapLogger != nil {
		zapLogger.Info("执行数据库迁移",
			zap.String("dialect", gooseDialect),
			zap.String("dir", migrationsSubDir))
	}

	goose.SetDialect(gooseDialect)
	if err := goose.Up(sqlDB, migrationsDir); err != nil {
		return err
	}

	return nil
}

func configurePool(db *gorm.DB, cfg *config.DatabaseConfig, zapLogger *zap.Logger) {
	if cfg.Driver == "sqlite" {
		if err := db.Exec("PRAGMA journal_mode=WAL").Error; err != nil {
			if zapLogger != nil {
				zapLogger.Warn("启用 WAL 模式失败", zap.Error(err))
			}
		}
	}

	sqlDB, err := db.DB()
	if err != nil {
		return
	}
	sqlDB.SetMaxIdleConns(cfg.MaxIdleConns)
	sqlDB.SetMaxOpenConns(cfg.MaxOpenConns)
	sqlDB.SetConnMaxLifetime(cfg.ConnMaxLifetime)

	if zapLogger != nil {
		zapLogger.Info("数据库连接池配置",
			zap.Int("max_idle_conns", cfg.MaxIdleConns),
			zap.Int("max_open_conns", cfg.MaxOpenConns),
			zap.Duration("conn_max_lifetime", cfg.ConnMaxLifetime))
	}
}

func getMigrationsDir(driver string) string {
	_, filename, _, ok := runtime.Caller(0)
	if ok {
		subDir := "sqlite"
		if driver == "mysql" {
			subDir = "mysql"
		}
		dir := filepath.Join(filepath.Dir(filename), "..", "..", "migrations", subDir)
		if abs, err := filepath.Abs(dir); err == nil {
			return abs
		}
	}
	return "./migrations"
}

func BuildDSN(cfg *config.DatabaseConfig) string {
	return fmt.Sprintf("%s:%s@tcp(%s:%d)/%s?charset=utf8mb4&parseTime=true&loc=Local",
		cfg.User, cfg.Password, cfg.Host, cfg.Port, cfg.DBName)
}