package db

import (
	"database/sql"
	"fmt"
	"os"
	"path/filepath"
	"sync"

	_ "github.com/go-sql-driver/mysql"
	_ "github.com/mattn/go-sqlite3"

	"sunhpc/internal/config"
	"sunhpc/internal/log"
)

// DB wraps the sql.DB connection pool.
type DB struct {
	engine *sql.DB
}

// Engine returns the underlying *sql.DB.
func (d *DB) Engine() *sql.DB {
	return d.engine
}

// InitSchema initializes the database schema.
// If force is true, drops existing tables before recreating them.
func (d *DB) InitSchema(force bool) error {
	db := d.engine

	if force {
		if err := dropTables(db); err != nil {
			return fmt.Errorf("failed to drop tables: %w", err)
		}
	}

	// ✅ 调用 schema.go 中的函数
	for _, ddl := range CreateTableStatements() {
		if _, err := db.Exec(ddl); err != nil {
			return fmt.Errorf("failed to create table: %w", err)
		}
	}

	return nil
}

func dropTables(db *sql.DB) error {
	// ✅ 调用 schema.go 中的函数
	for _, table := range DropTableOrder() {
		if _, err := db.Exec(fmt.Sprintf("DROP TABLE IF EXISTS `%s`", table)); err != nil {
			return err
		}
	}
	return nil
}

// --- Singleton DB Instance ---
var (
	globalDB *DB
	initOnce sync.Once
	initErr  error
)

func GetDB() (*DB, error) {
	initOnce.Do(func() {
		cfg, err := config.LoadConfig()
		if err != nil {
			initErr = fmt.Errorf("数据库配置文件加载失败: %w", err)
			return
		}

		if _, err := os.Stat(cfg.DB.Path); err != nil {
			// 创建数据库目录
			if err := os.MkdirAll(cfg.DB.Path, 0755); err != nil {
				log.Fatalf("创建数据库目录失败: %v", err)
			}
			log.Infof("数据库目录创建成功: %s", cfg.DB.Path)
		}

		var dsn string
		var driver string

		switch cfg.DB.Type {
		case "sqlite":
			driver = "sqlite3"
			fullPath := filepath.Join(cfg.DB.Path, cfg.DB.Name)
			dsn = fmt.Sprintf("%s?_foreign_keys=on&_journal_mode=WAL&_timeout=5000", fullPath)
		case "mysql":
			driver = "mysql"
			if cfg.DB.Socket != "" {
				dsn = fmt.Sprintf("%s:%s@unix(%s)/%s?parseTime=true&loc=Local",
					cfg.DB.User, cfg.DB.Password, cfg.DB.Socket, cfg.DB.Name)
			} else {
				dsn = fmt.Sprintf("%s:%s@tcp(%s)/%s?parseTime=true&loc=Local",
					cfg.DB.User, cfg.DB.Password, cfg.DB.Host, cfg.DB.Name)
			}
		default:
			initErr = fmt.Errorf("unsupported database type: %s", cfg.DB.Type)
			return
		}

		engine, err := sql.Open(driver, dsn)
		if err != nil {
			initErr = fmt.Errorf("failed to open database: %w", err)
			return
		}

		if err := engine.Ping(); err != nil {
			engine.Close()
			initErr = fmt.Errorf("failed to ping database: %w", err)
			return
		}

		globalDB = &DB{engine: engine}
	})

	return globalDB, initErr
}

// MustGetDB is a helper that panics on error (use in main/init only).
func MustGetDB() *DB {
	db, err := GetDB()
	if err != nil {
		log.Fatalf("数据库初始化失败: %v", err)
	}
	return db
}