package mailer

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

	"juwan-backend/app/email/mq/internal/config"
)

type Sender struct {
	conf config.MailConf
}

type Message struct {
	To      []string
	Cc      []string
	Bcc     []string
	Subject string
	Body    string
	IsHTML  bool
}

func NewSender(conf config.MailConf) (*Sender, error) {
	if strings.TrimSpace(conf.Host) == "" {
		return nil, fmt.Errorf("mail host is required")
	}
	if conf.Port <= 0 {
		return nil, fmt.Errorf("mail port is required")
	}
	if strings.TrimSpace(conf.FromAddress) == "" {
		return nil, fmt.Errorf("mail from address is required")
	}
	if conf.UseSSL && conf.UseStartTLS {
		return nil, fmt.Errorf("mail config invalid: UseSSL and UseStartTLS cannot both be true")
	}

	return &Sender{conf: conf}, nil
}

func (s *Sender) Send(ctx context.Context, msg Message) error {
	toList := compactAddresses(msg.To)
	if len(toList) == 0 {
		return fmt.Errorf("mail recipients are empty")
	}

	ccList := compactAddresses(msg.Cc)
	bccList := compactAddresses(msg.Bcc)
	allRecipients := append(append([]string{}, toList...), ccList...)
	allRecipients = append(allRecipients, bccList...)

	addr := fmt.Sprintf("%s:%d", s.conf.Host, s.conf.Port)

	var (
		client *smtp.Client
		err    error
	)

	tlsConfig := &tls.Config{
		ServerName:         s.conf.Host,
		InsecureSkipVerify: s.conf.InsecureSkipVerify,
	}

	if s.conf.UseSSL {
		conn, dialErr := tls.DialWithDialer((&net.Dialer{}), "tcp", addr, tlsConfig)
		if dialErr != nil {
			return fmt.Errorf("smtp ssl dial failed(%s): %w", addr, dialErr)
		}
		client, err = smtp.NewClient(conn, s.conf.Host)
	} else {
		dialer := &net.Dialer{}
		conn, dialErr := dialer.DialContext(ctx, "tcp", addr)
		if dialErr != nil {
			return fmt.Errorf("smtp dial failed(%s): %w", addr, dialErr)
		}
		client, err = smtp.NewClient(conn, s.conf.Host)
	}
	if err != nil {
		return fmt.Errorf("smtp create client failed: %w", err)
	}
	defer client.Close()

	if s.conf.UseStartTLS {
		if err = client.StartTLS(tlsConfig); err != nil {
			return fmt.Errorf("smtp starttls failed: %w", err)
		}
	}

	if strings.TrimSpace(s.conf.Username) != "" {
		auth := smtp.PlainAuth("", s.conf.Username, s.conf.Password, s.conf.Host)
		if err = client.Auth(auth); err != nil {
			return fmt.Errorf("smtp auth failed: %w", err)
		}
	}

	if err = client.Mail(s.conf.FromAddress); err != nil {
		return fmt.Errorf("smtp mail from failed: %w", err)
	}
	for _, rcpt := range allRecipients {
		if err = client.Rcpt(rcpt); err != nil {
			return fmt.Errorf("smtp rcpt to(%s) failed: %w", rcpt, err)
		}
	}

	w, err := client.Data()
	if err != nil {
		return fmt.Errorf("smtp data start failed: %w", err)
	}

	bodyType := "text/plain; charset=UTF-8"
	if msg.IsHTML {
		bodyType = "text/html; charset=UTF-8"
	}

	headers := []string{
		fmt.Sprintf("From: %s", formatFrom(s.conf.FromName, s.conf.FromAddress)),
		fmt.Sprintf("To: %s", strings.Join(toList, ",")),
		fmt.Sprintf("Subject: %s", msg.Subject),
		"MIME-Version: 1.0",
		fmt.Sprintf("Content-Type: %s", bodyType),
	}
	if len(ccList) > 0 {
		headers = append(headers, fmt.Sprintf("Cc: %s", strings.Join(ccList, ",")))
	}
	if strings.TrimSpace(s.conf.ReplyTo) != "" {
		headers = append(headers, fmt.Sprintf("Reply-To: %s", strings.TrimSpace(s.conf.ReplyTo)))
	}

	raw := strings.Join(headers, "\r\n") + "\r\n\r\n" + msg.Body
	if _, err = w.Write([]byte(raw)); err != nil {
		_ = w.Close()
		return fmt.Errorf("smtp write body failed: %w", err)
	}
	if err = w.Close(); err != nil {
		return fmt.Errorf("smtp data close failed: %w", err)
	}

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

	return nil
}

func formatFrom(name, address string) string {
	trimmedName := strings.TrimSpace(name)
	trimmedAddress := strings.TrimSpace(address)
	if trimmedName == "" {
		return trimmedAddress
	}

	return fmt.Sprintf("%s <%s>", trimmedName, trimmedAddress)
}

func compactAddresses(input []string) []string {
	result := make([]string, 0, len(input))
	for _, item := range input {
		trimmed := strings.TrimSpace(item)
		if trimmed == "" {
			continue
		}
		result = append(result, trimmed)
	}

	return result
}