package email

import (
	"bytes"
	"crypto/tls"
	"fmt"
	"net"
	"net/smtp"
	"time"

	"git.toowon.com/jimmy/go-common/config"
)

// Email 邮件发送器
type Email struct {
	config *config.EmailConfig
}

// NewEmail 创建邮件发送器
func NewEmail(cfg *config.Config) *Email {
	if cfg == nil || cfg.Email == nil {
		return &Email{config: nil}
	}
	return &Email{config: cfg.Email}
}

// getEmailConfig 获取邮件配置（内部方法）
func (e *Email) getEmailConfig() (*config.EmailConfig, error) {
	if e.config == nil {
		return nil, fmt.Errorf("email config is nil")
	}

	if e.config.Host == "" {
		return nil, fmt.Errorf("email host is required")
	}

	if e.config.Username == "" {
		return nil, fmt.Errorf("email username is required")
	}

	if e.config.Password == "" {
		return nil, fmt.Errorf("email password is required")
	}

	// 设置默认值
	if e.config.Port == 0 {
		e.config.Port = 587
	}
	if e.config.From == "" {
		e.config.From = e.config.Username
	}
	if e.config.Timeout == 0 {
		e.config.Timeout = 30
	}

	return e.config, nil
}

// Message 邮件消息
type Message struct {
	// To 收件人列表
	To []string

	// Cc 抄送列表（可选）
	Cc []string

	// Bcc 密送列表（可选）
	Bcc []string

	// Subject 主题
	Subject string

	// Body 正文（纯文本）
	Body string

	// HTMLBody HTML正文（可选，如果设置了会优先使用）
	HTMLBody string
}

// SendEmail 发送邮件
// to: 收件人列表
// subject: 邮件主题
// body: 邮件正文（纯文本）
// htmlBody: HTML正文（可选，如果设置了会优先使用）
func (e *Email) SendEmail(to []string, subject, body string, htmlBody ...string) error {
	cfg, err := e.getEmailConfig()
	if err != nil {
		return err
	}

	msg := &Message{
		To:      to,
		Subject: subject,
		Body:    body,
	}

	if len(htmlBody) > 0 && htmlBody[0] != "" {
		msg.HTMLBody = htmlBody[0]
	}

	return e.send(msg, cfg)
}

// send 发送邮件（内部方法）
func (e *Email) send(msg *Message, cfg *config.EmailConfig) error {
	if msg == nil {
		return fmt.Errorf("message is nil")
	}

	if len(msg.To) == 0 {
		return fmt.Errorf("recipients are required")
	}

	if msg.Subject == "" {
		return fmt.Errorf("subject is required")
	}

	if msg.Body == "" && msg.HTMLBody == "" {
		return fmt.Errorf("body or HTMLBody is required")
	}

	// 构建邮件内容
	emailBody, err := e.buildEmailBody(msg, cfg)
	if err != nil {
		return fmt.Errorf("failed to build email body: %w", err)
	}

	// 合并收件人列表
	recipients := append(msg.To, msg.Cc...)
	recipients = append(recipients, msg.Bcc...)

	// 连接SMTP服务器
	addr := net.JoinHostPort(cfg.Host, fmt.Sprintf("%d", cfg.Port))
	auth := smtp.PlainAuth("", cfg.Username, cfg.Password, cfg.Host)

	// 创建连接
	conn, err := net.DialTimeout("tcp", addr, time.Duration(cfg.Timeout)*time.Second)
	if err != nil {
		return fmt.Errorf("failed to connect to SMTP server: %w", err)
	}
	defer conn.Close()

	// 创建SMTP客户端
	client, err := smtp.NewClient(conn, cfg.Host)
	if err != nil {
		return fmt.Errorf("failed to create SMTP client: %w", err)
	}
	defer client.Close()

	// TLS/SSL处理
	if cfg.UseSSL {
		// SSL模式（端口通常是465）
		tlsConfig := &tls.Config{
			ServerName: cfg.Host,
		}
		if err := client.StartTLS(tlsConfig); err != nil {
			return fmt.Errorf("failed to start TLS: %w", err)
		}
	} else if cfg.UseTLS {
		// TLS模式（STARTTLS，端口通常是587）
		tlsConfig := &tls.Config{
			ServerName: cfg.Host,
		}
		if err := client.StartTLS(tlsConfig); err != nil {
			return fmt.Errorf("failed to start TLS: %w", err)
		}
	}

	// 认证
	if err := client.Auth(auth); err != nil {
		return fmt.Errorf("failed to authenticate: %w", err)
	}

	// 设置发件人
	if err := client.Mail(cfg.From); err != nil {
		return fmt.Errorf("failed to set sender: %w", err)
	}

	// 设置收件人
	for _, to := range recipients {
		if err := client.Rcpt(to); err != nil {
			return fmt.Errorf("failed to set recipient %s: %w", to, err)
		}
	}

	// 发送邮件内容
	writer, err := client.Data()
	if err != nil {
		return fmt.Errorf("failed to get data writer: %w", err)
	}

	_, err = writer.Write(emailBody)
	if err != nil {
		writer.Close()
		return fmt.Errorf("failed to write email body: %w", err)
	}

	err = writer.Close()
	if err != nil {
		return fmt.Errorf("failed to close writer: %w", err)
	}

	// 退出
	if err := client.Quit(); err != nil {
		return fmt.Errorf("failed to quit: %w", err)
	}

	return nil
}

// buildEmailBody 构建邮件内容
func (e *Email) buildEmailBody(msg *Message, cfg *config.EmailConfig) ([]byte, error) {
	var buf bytes.Buffer

	// 邮件头
	from := cfg.From
	if cfg.FromName != "" {
		from = fmt.Sprintf("%s <%s>", cfg.FromName, cfg.From)
	}
	buf.WriteString(fmt.Sprintf("From: %s\r\n", from))

	// 收件人
	buf.WriteString(fmt.Sprintf("To: %s\r\n", joinEmails(msg.To)))

	// 抄送
	if len(msg.Cc) > 0 {
		buf.WriteString(fmt.Sprintf("Cc: %s\r\n", joinEmails(msg.Cc)))
	}

	// 主题
	buf.WriteString(fmt.Sprintf("Subject: %s\r\n", msg.Subject))

	// 内容类型
	if msg.HTMLBody != "" {
		// 多部分邮件（HTML + 纯文本）
		boundary := "----=_Part_" + fmt.Sprint(time.Now().UnixNano())
		buf.WriteString("MIME-Version: 1.0\r\n")
		buf.WriteString(fmt.Sprintf("Content-Type: multipart/alternative; boundary=\"%s\"\r\n", boundary))
		buf.WriteString("\r\n")

		// 纯文本部分
		buf.WriteString("--" + boundary + "\r\n")
		buf.WriteString("Content-Type: text/plain; charset=UTF-8\r\n")
		buf.WriteString("Content-Transfer-Encoding: quoted-printable\r\n")
		buf.WriteString("\r\n")
		buf.WriteString(msg.Body)
		buf.WriteString("\r\n")

		// HTML部分
		buf.WriteString("--" + boundary + "\r\n")
		buf.WriteString("Content-Type: text/html; charset=UTF-8\r\n")
		buf.WriteString("Content-Transfer-Encoding: quoted-printable\r\n")
		buf.WriteString("\r\n")
		buf.WriteString(msg.HTMLBody)
		buf.WriteString("\r\n")

		buf.WriteString("--" + boundary + "--\r\n")
	} else {
		// 纯文本邮件
		buf.WriteString("Content-Type: text/plain; charset=UTF-8\r\n")
		buf.WriteString("Content-Transfer-Encoding: quoted-printable\r\n")
		buf.WriteString("\r\n")
		buf.WriteString(msg.Body)
		buf.WriteString("\r\n")
	}

	return buf.Bytes(), nil
}

// joinEmails 连接邮箱地址
func joinEmails(emails []string) string {
	if len(emails) == 0 {
		return ""
	}
	result := emails[0]
	for i := 1; i < len(emails); i++ {
		result += ", " + emails[i]
	}
	return result
}