package mail

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

	"github.com/imc-vibe/backend/internal/config"
)

type EmailService struct {
	host     string
	port     string
	username string
	password string
	from     string
	baseURL  string
}

func NewEmailService(cfg *config.Config) *EmailService {
	return &EmailService{
		host:     cfg.SMTPHost,
		port:     cfg.SMTPPort,
		username: cfg.SMTPUser,
		password: cfg.SMTPPassword,
		from:     cfg.SMTPFrom,
		baseURL:  cfg.BaseURL,
	}
}

func (s *EmailService) SendPasswordReset(to, token string) error {
	resetURL := fmt.Sprintf("%s/auth/reset-password?token=%s", s.baseURL, token)

	subject := "Password Reset Request"
	body := fmt.Sprintf(`Hi,

You requested a password reset for your account.

Click the link below to reset your password:
%s

This link will expire in 1 hour.

If you didn't request this, please ignore this email.

Best regards,
IMC Vibe Mail Server Admin
`, resetURL)

	return s.send(to, subject, body)
}

func (s *EmailService) send(to, subject, body string) error {
	if s.host == "" || s.username == "" {
		return fmt.Errorf("SMTP not configured")
	}

	addr := fmt.Sprintf("%s:%s", s.host, s.port)

	msg := fmt.Sprintf("From: %s\r\n"+
		"To: %s\r\n"+
		"Subject: %s\r\n"+
		"MIME-Version: 1.0\r\n"+
		"Content-Type: text/plain; charset=\"UTF-8\"\r\n"+
		"\r\n"+
		"%s", s.from, to, subject, body)

	var auth smtp.Auth
	if s.port == "465" {
		err := s.sendWithTLS(addr, to, msg)
		return err
	} else {
		auth = smtp.PlainAuth("", s.username, s.password, s.host)
		err := smtp.SendMail(addr, auth, s.from, []string{to}, []byte(msg))
		return err
	}
}

func (s *EmailService) sendWithTLS(addr, to, msg string) error {
	tlsConfig := &tls.Config{
		ServerName: s.host,
	}

	conn, err := tls.Dial("tcp", addr, tlsConfig)
	if err != nil {
		return err
	}
	defer conn.Close()

	client, err := smtp.NewClient(conn, s.host)
	if err != nil {
		return err
	}
	defer client.Close()

	auth := smtp.PlainAuth("", s.username, s.password, s.host)
	if err := client.Auth(auth); err != nil {
		return err
	}

	if err := client.Mail(s.from); err != nil {
		return err
	}

	if err := client.Rcpt(to); err != nil {
		return err
	}

	w, err := client.Data()
	if err != nil {
		return err
	}

	_, err = w.Write([]byte(msg))
	if err != nil {
		return err
	}

	err = w.Close()
	if err != nil {
		return err
	}

	return client.Quit()
}

func GenerateToken() string {
	b := make([]byte, 32)
	for i := range b {
		b[i] = tokenChars[i%len(tokenChars)]
	}
	return fmt.Sprintf("%x", b)
}

const tokenChars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"

func ValidateToken(token string) bool {
	if len(token) != 64 {
		return false
	}
	for _, c := range token {
		if !strings.ContainsRune(tokenChars, c) {
			return false
		}
	}
	return true
}