package main

import (
	"context"
	"database/sql"
	"fmt"
	"strings"
	"time"

	_ "github.com/go-sql-driver/mysql"
)

// TestMySQLConnection 测试MySQL连接字符串的各种格式
func TestMySQLConnection() {
	// 测试参数
	host := "127.0.0.1"
	port := 3306
	username := "root"
	password := "123456"
	timeoutDuration := 3 * time.Second
	timeoutStr := timeoutDuration.String() // "3s"

	fmt.Println("=== MySQL连接字符串测试 ===")
	fmt.Printf("目标: %s:%d\n", host, port)
	fmt.Printf("用户: %s\n", username)
	fmt.Printf("超时: %s\n", timeoutStr)
	fmt.Println()

	// 测试不同的连接字符串格式
	testConfigs := []struct {
		name   string
		dsn    string
		desc   string
	}{
		{
			name: "当前fscan格式",
			dsn:  fmt.Sprintf("%s:%s@tcp(%s:%d)/mysql?charset=utf8&timeout=%s", username, password, host, port, timeoutStr),
			desc: "fscan当前使用的格式，包含数据库名mysql",
		},
		{
			name: "不指定数据库",
			dsn:  fmt.Sprintf("%s:%s@tcp(%s:%d)/?charset=utf8&timeout=%s", username, password, host, port, timeoutStr),
			desc: "不指定具体数据库，连接到默认数据库",
		},
		{
			name: "无数据库名",
			dsn:  fmt.Sprintf("%s:%s@tcp(%s:%d)?charset=utf8&timeout=%s", username, password, host, port, timeoutStr),
			desc: "完全不指定数据库名",
		},
		{
			name: "标准格式+readTimeout",
			dsn:  fmt.Sprintf("%s:%s@tcp(%s:%d)/mysql?charset=utf8&timeout=%s&readTimeout=%s&writeTimeout=%s", username, password, host, port, timeoutStr, timeoutStr, timeoutStr),
			desc: "添加读写超时参数",
		},
		{
			name: "使用parseTime",
			dsn:  fmt.Sprintf("%s:%s@tcp(%s:%d)/mysql?charset=utf8&timeout=%s&parseTime=true", username, password, host, port, timeoutStr),
			desc: "添加parseTime参数处理时间类型",
		},
		{
			name: "最小参数",
			dsn:  fmt.Sprintf("%s:%s@tcp(%s:%d)/", username, password, host, port),
			desc: "最简单的连接字符串",
		},
	}

	for i, config := range testConfigs {
		fmt.Printf("[%d] %s\n", i+1, config.name)
		fmt.Printf("描述: %s\n", config.desc)
		fmt.Printf("DSN: %s\n", config.dsn)
		
		// 测试连接
		success := testConnection(config.dsn, timeoutDuration)
		
		if success {
			fmt.Printf("结果: ✅ 连接成功\n")
		} else {
			fmt.Printf("结果: ❌ 连接失败\n")
		}
		fmt.Println(strings.Repeat("-", 80))
	}

	// 测试context超时的影响
	fmt.Println("\n=== Context超时测试 ===")
	testContextTimeout()
}

// testConnection 测试指定DSN的连接
func testConnection(dsn string, timeout time.Duration) bool {
	// 创建context，设置超时时间
	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()

	// 尝试连接
	db, err := sql.Open("mysql", dsn)
	if err != nil {
		fmt.Printf("  Open失败: %v\n", err)
		return false
	}
	defer db.Close()

	// 设置连接池参数
	db.SetMaxOpenConns(1)
	db.SetMaxIdleConns(1)
	db.SetConnMaxLifetime(timeout)

	// 测试ping - 这是实际建立连接的地方
	err = db.PingContext(ctx)
	if err != nil {
		fmt.Printf("  Ping失败: %v\n", err)
		return false
	}

	// 执行简单查询测试
	var version string
	err = db.QueryRowContext(ctx, "SELECT VERSION()").Scan(&version)
	if err != nil {
		fmt.Printf("  查询失败: %v\n", err)
		return false
	}

	fmt.Printf("  MySQL版本: %s\n", version)
	return true
}

// testContextTimeout 测试context超时对连接的影响
func testContextTimeout() {
	host := "127.0.0.1"
	port := 3306
	username := "root"
	password := "123456"

	// 基础连接字符串（不设置timeout参数）
	baseDSN := fmt.Sprintf("%s:%s@tcp(%s:%d)/mysql?charset=utf8", username, password, host, port)

	timeoutTests := []struct {
		name           string
		dsn            string
		contextTimeout time.Duration
		desc           string
	}{
		{
			name:           "仅Context超时3s",
			dsn:            baseDSN,
			contextTimeout: 3 * time.Second,
			desc:           "只使用context超时，不在DSN中设置timeout",
		},
		{
			name:           "DSN超时3s + Context超时3s",
			dsn:            baseDSN + "&timeout=3s",
			contextTimeout: 3 * time.Second,
			desc:           "同时设置DSN和context超时",
		},
		{
			name:           "DSN超时10s + Context超时3s",
			dsn:            baseDSN + "&timeout=10s",
			contextTimeout: 3 * time.Second,
			desc:           "DSN超时更长，context超时更短",
		},
		{
			name:           "DSN超时3s + Context超时10s",
			dsn:            baseDSN + "&timeout=3s",
			contextTimeout: 10 * time.Second,
			desc:           "DSN超时更短，context超时更长",
		},
	}

	for i, test := range timeoutTests {
		fmt.Printf("[%d] %s\n", i+1, test.name)
		fmt.Printf("描述: %s\n", test.desc)
		fmt.Printf("DSN: %s\n", test.dsn)
		fmt.Printf("Context超时: %v\n", test.contextTimeout)

		start := time.Now()
		success := testConnectionWithTiming(test.dsn, test.contextTimeout)
		elapsed := time.Since(start)

		if success {
			fmt.Printf("结果: ✅ 连接成功，耗时: %v\n", elapsed)
		} else {
			fmt.Printf("结果: ❌ 连接失败，耗时: %v\n", elapsed)
		}
		fmt.Println(strings.Repeat("-", 80))
	}
}

// testConnectionWithTiming 带时间统计的连接测试
func testConnectionWithTiming(dsn string, contextTimeout time.Duration) bool {
	ctx, cancel := context.WithTimeout(context.Background(), contextTimeout)
	defer cancel()

	db, err := sql.Open("mysql", dsn)
	if err != nil {
		fmt.Printf("  Open失败: %v\n", err)
		return false
	}
	defer db.Close()

	db.SetMaxOpenConns(1)
	db.SetMaxIdleConns(1)

	err = db.PingContext(ctx)
	if err != nil {
		fmt.Printf("  Ping失败: %v\n", err)
		return false
	}

	return true
}

// 优化建议和分析
func printOptimizationSuggestions() {
	fmt.Println("\n=== MySQL连接字符串优化建议 ===")
	
	suggestions := []string{
		"1. 连接字符串格式建议：",
		"   推荐: user:pass@tcp(host:port)/dbname?charset=utf8mb4&parseTime=true&timeout=3s",
		"",
		"2. 超时参数优化：",
		"   - 使用charset=utf8mb4而不是utf8，支持完整的UTF-8字符集",
		"   - 添加parseTime=true自动解析时间类型",
		"   - 分别设置timeout、readTimeout、writeTimeout更精细控制",
		"",
		"3. Context vs DSN超时：",
		"   - Context超时控制整个操作的最大时间",
		"   - DSN timeout参数控制连接建立的超时",
		"   - 建议Context超时 >= DSN timeout + 额外处理时间",
		"",
		"4. 连接池优化：",
		"   - SetMaxOpenConns(1) 对于扫描场景是合适的",
		"   - SetConnMaxLifetime应该设置适当的值避免连接泄露",
		"   - 使用defer db.Close()确保连接被释放",
		"",
		"5. 错误处理：",
		"   - 'context deadline exceeded' 通常表示网络问题或超时设置过短",
		"   - 检查防火墙设置和网络连接",
		"   - 确认MySQL服务器配置允许远程连接",
	}

	for _, suggestion := range suggestions {
		fmt.Println(suggestion)
	}
}

func main() {
	fmt.Println("MySQL连接字符串测试工具")
	fmt.Println("作者: Go语言代码优化专家")
	fmt.Println("目的: 验证fscan中MySQL连接字符串格式的正确性")
	fmt.Println("=" + strings.Repeat("=", 60))
	
	// 检查必要的包
	fmt.Println("\n检查依赖...")
	fmt.Println("✅ github.com/go-sql-driver/mysql 已导入")
	
	// 执行测试
	TestMySQLConnection()
	
	// 打印优化建议
	printOptimizationSuggestions()
	
	fmt.Println("\n测试完成！")
	fmt.Println("\n使用方法:")
	fmt.Println("1. 确保MySQL服务器运行在127.0.0.1:3306")
	fmt.Println("2. 创建用户: CREATE USER 'root'@'%' IDENTIFIED BY '123456';")
	fmt.Println("3. 授权: GRANT ALL PRIVILEGES ON *.* TO 'root'@'%';")
	fmt.Println("4. 刷新权限: FLUSH PRIVILEGES;")
	fmt.Println("5. 运行: go run mysql_connection_test.go")
}