//go:build plugin_mysql || !plugin_selective

package services

import (
	"context"
	"database/sql"
	"fmt"
	"io"
	"log"
	"net"
	"strconv"
	"strings"
	"time"

	"github.com/go-sql-driver/mysql"
	"github.com/shadow1ng/fscan/common"
	"github.com/shadow1ng/fscan/common/i18n"
	"github.com/shadow1ng/fscan/plugins"
)

type nullWriter struct{}

func (nullWriter) Write(p []byte) (int, error) { return len(p), nil }

func init() {
	// 禁用mysql驱动的错误日志（如unexpected EOF）
	_ = mysql.SetLogger(log.New(&nullWriter{}, "", 0))
}

// MySQLPlugin MySQL数据库扫描插件
type MySQLPlugin struct {
	plugins.BasePlugin
}

func NewMySQLPlugin() *MySQLPlugin {
	return &MySQLPlugin{
		BasePlugin: plugins.NewBasePlugin("mysql"),
	}
}

func (p *MySQLPlugin) Scan(ctx context.Context, info *common.HostInfo, session *common.ScanSession) *ScanResult {
	config := session.Config
	state := session.State
	if config.DisableBrute {
		return p.identifyService(ctx, info, session)
	}

	credentials := GenerateCredentials("mysql", config)
	if len(credentials) == 0 {
		return &ScanResult{
			Success: false,
			Service: "mysql",
			Error:   fmt.Errorf("%s", i18n.GetText("service_no_credentials")),
		}
	}

	target := info.Target()

	// 使用公共框架进行并发凭据测试
	authFn := p.createAuthFunc(info, config, state)
	testConfig := DefaultConcurrentTestConfigWithTarget(config, info)

	result := TestCredentialsConcurrently(ctx, credentials, authFn, "mysql", testConfig)

	if result.Success {
		session.LogVuln(i18n.Tr("mysql_credential", target, result.Username, result.Password))
	}

	return result
}

// createAuthFunc 创建MySQL认证函数
func (p *MySQLPlugin) createAuthFunc(info *common.HostInfo, config *common.Config, state *common.State) AuthFunc {
	return func(ctx context.Context, cred Credential) *AuthResult {
		return p.doMySQLAuth(ctx, info, cred, config, state)
	}
}

// doMySQLAuth 执行MySQL认证
func (p *MySQLPlugin) doMySQLAuth(ctx context.Context, info *common.HostInfo, cred Credential, config *common.Config, state *common.State) *AuthResult {
	connStr, err := mySQLConnString(cred.Username, cred.Password, info, config.ModuleTimeout())
	if err != nil {
		return &AuthResult{
			Success:   false,
			ErrorType: ErrorTypeAuth,
			Error:     err,
		}
	}

	db, err := sql.Open("mysql", connStr)
	if err != nil {
		state.IncrementTCPFailedPacketCount()
		return &AuthResult{
			Success:   false,
			ErrorType: classifyMySQLErrorType(err),
			Error:     err,
		}
	}

	db.SetConnMaxLifetime(config.ModuleTimeout())
	db.SetMaxOpenConns(1)
	db.SetMaxIdleConns(0)

	err = db.PingContext(ctx)
	if err != nil {
		_ = db.Close()
		state.IncrementTCPFailedPacketCount()
		return &AuthResult{
			Success:   false,
			ErrorType: classifyMySQLErrorType(err),
			Error:     err,
		}
	}

	state.IncrementTCPSuccessPacketCount()

	return &AuthResult{
		Success:   true,
		Conn:      &SQLDBWrapper{db},
		ErrorType: ErrorTypeUnknown,
		Error:     nil,
	}
}

func mySQLConnString(username, password string, info *common.HostInfo, timeout time.Duration) (string, error) {
	if strings.ContainsAny(username, ":@/") {
		return "", fmt.Errorf("mysql username contains unsupported DSN delimiter")
	}
	cfg := mysql.NewConfig()
	cfg.User = username
	cfg.Passwd = password
	cfg.Net = "tcp"
	cfg.Addr = net.JoinHostPort(info.Host, strconv.Itoa(info.Port))
	cfg.DBName = "information_schema"
	cfg.Params = map[string]string{"charset": "utf8"}
	cfg.Timeout = timeout
	return cfg.FormatDSN(), nil
}

// classifyMySQLErrorType MySQL错误分类
func classifyMySQLErrorType(err error) ErrorType {
	if err == nil {
		return ErrorTypeUnknown
	}

	mysqlAuthErrors := []string{
		"access denied for user",
		"unknown database",
		"host is not allowed",
		"authentication failed",
		"permission denied",
		"user does not exist",
	}

	mysqlNetworkErrors := append(CommonNetworkErrors,
		"too many connections",
		"can't connect to mysql server",
		"lost connection to mysql server",
		"mysql server has gone away",
	)

	return ClassifyError(err, mysqlAuthErrors, mysqlNetworkErrors)
}

func (p *MySQLPlugin) identifyService(ctx context.Context, info *common.HostInfo, session *common.ScanSession) *ScanResult {
	target := info.Target()

	conn, err := session.DialTCP(ctx, "tcp", target, session.Config.Timeout)
	if err != nil {
		return &ScanResult{
			Success: false,
			Service: "mysql",
			Error:   err,
		}
	}
	defer func() { _ = conn.Close() }()

	if banner := p.readMySQLBanner(conn, session.Config); banner != "" {
		session.LogSuccess(i18n.Tr("mysql_service", target, banner))
		return &ScanResult{
			Type:    plugins.ResultTypeService,
			Success: true,
			Service: "mysql",
			Banner:  banner,
		}
	}

	return &ScanResult{
		Success: false,
		Service: "mysql",
		Error:   fmt.Errorf("%s", i18n.Tr("service_not_identified", "MySQL")),
	}
}

func (p *MySQLPlugin) readMySQLBanner(conn net.Conn, config *common.Config) string {
	_ = conn.SetReadDeadline(time.Now().Add(config.ModuleTimeout()))

	header := make([]byte, 5)
	if _, err := io.ReadFull(conn, header); err != nil {
		return ""
	}

	if header[4] != 10 {
		return ""
	}

	version := make([]byte, 0, 64)
	var b [1]byte
	for len(version) < 250 {
		if _, err := io.ReadFull(conn, b[:]); err != nil {
			return ""
		}
		if b[0] == 0 {
			break
		}
		version = append(version, b[0])
	}

	if len(version) == 0 {
		return ""
	}

	return fmt.Sprintf("MySQL %s", string(version))
}

func init() {
	RegisterPluginWithPorts("mysql", func() Plugin {
		return NewMySQLPlugin()
	}, []int{3306, 3307, 33060})
}