package services

import (
	"context"
	"crypto/tls"
	"fmt"
	"net"
	"net/smtp"
	"strings"
	"time"

	"github.com/shadow1ng/fscan/common"
)

type SMTPPlugin struct {
	name  string
	ports []int
}

func NewSMTPPlugin() *SMTPPlugin {
	return &SMTPPlugin{
		name:  "smtp",
		ports: []int{25, 465, 587, 2525},
	}
}

func (p *SMTPPlugin) Name() string {
	return p.name
}

func (p *SMTPPlugin) GetPorts() []int {
	return p.ports
}

func (p *SMTPPlugin) Scan(ctx context.Context, info *common.HostInfo) *ScanResult {
	target := fmt.Sprintf("%s:%s", info.Host, info.Ports)

	if common.DisableBrute {
		return p.identifyService(ctx, info)
	}

	if result := p.testOpenRelay(ctx, info); result != nil && result.Success {
		common.LogSuccess(fmt.Sprintf("SMTP %s 开放中继", target))
		return result
	}

	credentials := GenerateCredentials("smtp")
	if len(credentials) == 0 {
		return &ScanResult{
			Success: false,
			Service: "smtp",
			Error:   fmt.Errorf("没有可用的测试凭据"),
		}
	}

	for _, cred := range credentials {
		if p.testCredential(ctx, info, cred) {
			common.LogSuccess(fmt.Sprintf("SMTP %s %s:%s", target, cred.Username, cred.Password))

			return &ScanResult{
				Success:  true,
				Service:  "smtp",
				Username: cred.Username,
				Password: cred.Password,
			}
		}
	}

	return &ScanResult{
		Success: false,
		Service: "smtp",
		Error:   fmt.Errorf("未发现弱密码"),
	}
}


func (p *SMTPPlugin) testOpenRelay(ctx context.Context, info *common.HostInfo) *ScanResult {
	target := fmt.Sprintf("%s:%s", info.Host, info.Ports)
	
	client, err := smtp.Dial(target)
	if err != nil {
		return nil
	}
	defer client.Quit()

	if err := client.Hello("fscan.test"); err != nil {
		return nil
	}

	if err := client.Mail("test@fscan.test"); err != nil {
		return nil
	}

	if err := client.Rcpt("external@example.com"); err != nil {
		return nil
	}

	return &ScanResult{
		Success: true,
		Service: "smtp",
		Banner:  "开放中继",
	}
}

func (p *SMTPPlugin) testCredential(ctx context.Context, info *common.HostInfo, cred Credential) bool {
	target := fmt.Sprintf("%s:%s", info.Host, info.Ports)
	
	var client *smtp.Client
	var err error
	
	if info.Ports == "465" {
		conn, err := tls.Dial("tcp", target, &tls.Config{InsecureSkipVerify: true})
		if err != nil {
			return false
		}
		defer conn.Close()
		
		client, err = smtp.NewClient(conn, info.Host)
		if err != nil {
			return false
		}
	} else {
		client, err = smtp.Dial(target)
		if err != nil {
			return false
		}
	}
	defer client.Quit()

	if ok, _ := client.Extension("STARTTLS"); ok {
		if err := client.StartTLS(&tls.Config{InsecureSkipVerify: true}); err != nil {
			
		}
	}

	auth := smtp.PlainAuth("", cred.Username, cred.Password, info.Host)
	if err := client.Auth(auth); err != nil {
		return false
	}

	return true
}

func (p *SMTPPlugin) getServerInfo(ctx context.Context, info *common.HostInfo) string {
	target := fmt.Sprintf("%s:%s", info.Host, info.Ports)
	
	conn, err := net.DialTimeout("tcp", target, time.Duration(common.Timeout)*time.Second)
	if err != nil {
		return ""
	}
	defer conn.Close()

	conn.SetReadDeadline(time.Now().Add(time.Duration(common.Timeout) * time.Second))
	buffer := make([]byte, 1024)
	n, err := conn.Read(buffer)
	if err != nil {
		return ""
	}

	welcome := strings.TrimSpace(string(buffer[:n]))
	if strings.HasPrefix(welcome, "220") {
		return strings.TrimPrefix(welcome, "220 ")
	}

	return welcome
}

func (p *SMTPPlugin) identifyService(ctx context.Context, info *common.HostInfo) *ScanResult {
	target := fmt.Sprintf("%s:%s", info.Host, info.Ports)

	serverInfo := p.getServerInfo(ctx, info)
	var banner string
	
	if serverInfo != "" {
		banner = fmt.Sprintf("SMTP邮件服务 (%s)", serverInfo)
	} else {
		conn, err := net.DialTimeout("tcp", target, time.Duration(common.Timeout)*time.Second)
		if err != nil {
			return &ScanResult{
				Success: false,
				Service: "smtp",
				Error:   err,
			}
		}
		defer conn.Close()
		banner = "SMTP邮件服务"
	}

	common.LogSuccess(fmt.Sprintf("SMTP %s %s", target, banner))

	return &ScanResult{
		Success: true,
		Service: "smtp",
		Banner:  banner,
	}
}

func init() {
	// 使用高效注册方式：直接传递端口信息，避免实例创建
	RegisterPluginWithPorts("smtp", func() Plugin {
		return NewSMTPPlugin()
	}, []int{25, 465, 587, 2525})
}