package services

import (
	"crypto/tls"
	"fmt"
	"net"
	"net/smtp"
	"strconv"
	"strings"
	"time"
)

// SMTPConfig 发送邮件所需参数（与 yz_system_email 字段对应）
type SMTPConfig struct {
	FromAddress string
	FromName    string
	Host        string
	Port        uint
	Password    string
	Encryption  string // ssl / tls / none
	Timeout     uint   // 秒
}

// SendTestEmailSMTP 发送一封简单测试邮件（纯文本 UTF-8）
func SendTestEmailSMTP(cfg SMTPConfig, to string) error {
	to = strings.TrimSpace(to)
	if to == "" {
		return fmt.Errorf("收件人不能为空")
	}
	if cfg.Host == "" || cfg.FromAddress == "" {
		return fmt.Errorf("SMTP 主机或发件人不能为空")
	}
	if cfg.Port == 0 {
		cfg.Port = 465
	}
	timeout := cfg.Timeout
	if timeout == 0 {
		timeout = 30
	}
	d := net.Dialer{Timeout: time.Duration(timeout) * time.Second}
	addr := net.JoinHostPort(cfg.Host, strconv.FormatUint(uint64(cfg.Port), 10))
	enc := strings.ToLower(strings.TrimSpace(cfg.Encryption))
	if enc == "" {
		enc = "ssl"
	}

	var client *smtp.Client
	var err error

	switch enc {
	case "ssl":
		conn, derr := tls.DialWithDialer(&d, "tcp", addr, &tls.Config{ServerName: cfg.Host, MinVersion: tls.VersionTLS12})
		if derr != nil {
			return fmt.Errorf("连接 SMTP 失败: %w", derr)
		}
		defer conn.Close()
		client, err = smtp.NewClient(conn, cfg.Host)
		if err != nil {
			return fmt.Errorf("SMTP 握手失败: %w", err)
		}
	case "tls":
		conn, derr := d.Dial("tcp", addr)
		if derr != nil {
			return fmt.Errorf("连接 SMTP 失败: %w", derr)
		}
		defer conn.Close()
		client, err = smtp.NewClient(conn, cfg.Host)
		if err != nil {
			return fmt.Errorf("SMTP 握手失败: %w", err)
		}
		if ok, _ := client.Extension("STARTTLS"); ok {
			if err = client.StartTLS(&tls.Config{ServerName: cfg.Host, MinVersion: tls.VersionTLS12}); err != nil {
				_ = client.Close()
				return fmt.Errorf("STARTTLS 失败: %w", err)
			}
		}
	case "none":
		conn, derr := d.Dial("tcp", addr)
		if derr != nil {
			return fmt.Errorf("连接 SMTP 失败: %w", derr)
		}
		defer conn.Close()
		client, err = smtp.NewClient(conn, cfg.Host)
		if err != nil {
			return fmt.Errorf("SMTP 握手失败: %w", err)
		}
	default:
		return fmt.Errorf("不支持的加密方式: %s", cfg.Encryption)
	}
	defer func() { _ = client.Close() }()

	auth := smtp.PlainAuth("", cfg.FromAddress, cfg.Password, cfg.Host)
	if err = client.Auth(auth); err != nil {
		return fmt.Errorf("SMTP 认证失败: %w", err)
	}
	if err = client.Mail(cfg.FromAddress); err != nil {
		return fmt.Errorf("MAIL FROM 失败: %w", err)
	}
	if err = client.Rcpt(to); err != nil {
		return fmt.Errorf("RCPT TO 失败: %w", err)
	}
	wc, err := client.Data()
	if err != nil {
		return fmt.Errorf("DATA 失败: %w", err)
	}
	fromName := strings.TrimSpace(cfg.FromName)
	subject := "平台邮箱测试"
	body := "这是一封来自管理后台「邮箱管理」的测试邮件。\r\nThis is a test email from the platform email settings.\r\n"
	headers := fmt.Sprintf("From: %s\r\nTo: %s\r\nSubject: %s\r\nMIME-Version: 1.0\r\nContent-Type: text/plain; charset=UTF-8\r\nContent-Transfer-Encoding: 8bit\r\n\r\n",
		formatFromHeader(fromName, cfg.FromAddress), to, subject)
	if _, err = wc.Write([]byte(headers + body)); err != nil {
		return fmt.Errorf("写入邮件内容失败: %w", err)
	}
	if err = wc.Close(); err != nil {
		return fmt.Errorf("结束 DATA 失败: %w", err)
	}
	return client.Quit()
}

func formatFromHeader(name, addr string) string {
	name = strings.TrimSpace(name)
	if name == "" {
		return addr
	}
	return fmt.Sprintf("%s <%s>", name, addr)
}