byom-golang-lib/pkg/smtp/service.go

package smtp

import (
	"bytes"
	"html/template"
	"strings"

	"github.com/sirupsen/logrus"
	"github.com/wneessen/go-mail"
)

// EmailData holds the data for the default email template
type EmailData struct {
	Subject string
	Body    string
}

// VerificationData holds the data for the verification email template
type VerificationData struct {
	VerificationURL string
}

// WelcomeData holds the data for the welcome email template
type WelcomeData struct {
	Username  string
	Password  string
	WebAppURL string
}

// SMTPService handles email sending operations
type SMTPService struct {
	client *mail.Client
	logger *logrus.Logger
	from   string
}

// NewSMTPService creates a new SMTP service instance
func NewSMTPService(config *Config, logger *logrus.Logger) (*SMTPService, error) {
	if logger == nil {
		return nil, NewError("initialization", ErrInvalidConfig, "logger is required")
	}

	// Validate config
	if config.Host == "" || config.Port == 0 || config.Username == "" || config.Password == "" || config.From == "" {
		return nil, NewError("initialization", ErrInvalidConfig, "missing required configuration")
	}

	// Create mail client with proper configuration
	client, err := mail.NewClient(config.Host,
		mail.WithPort(config.Port),
		mail.WithSMTPAuth(mail.SMTPAuthPlain),
		mail.WithUsername(config.Username),
		mail.WithPassword(config.Password),
		mail.WithTLSPolicy(mail.TLSMandatory), // Enforce TLS
	)
	if err != nil {
		logger.WithError(err).Error("Failed to create SMTP client")
		return nil, NewError("initialization", ErrConnectionFailed, err.Error())
	}

	return &SMTPService{
		client: client,
		logger: logger,
		from:   config.From,
	}, nil
}

// SendEmail sends a basic email using the default template
func (s *SMTPService) SendEmail(to string, data EmailData) error {
	if strings.TrimSpace(to) == "" {
		return NewSendError("send", to, ErrInvalidRecipient, "empty recipient email")
	}

	// Parse and execute template
	tmpl, err := template.New("email").Parse(defaultTemplate)
	if err != nil {
		s.logger.WithError(err).Error("Failed to parse email template")
		return NewTemplateError("send", "default", ErrTemplateParsingFailed, err.Error())
	}

	var body bytes.Buffer
	if err := tmpl.Execute(&body, data); err != nil {
		s.logger.WithError(err).Error("Failed to execute email template")
		return NewTemplateError("send", "default", ErrTemplateExecutionFailed, err.Error())
	}

	// Create and configure message
	msg := mail.NewMsg()
	if err := msg.From(s.from); err != nil {
		return NewError("send", ErrMessageCreationFailed, "failed to set from address")
	}
	if err := msg.To(to); err != nil {
		return NewSendError("send", to, ErrMessageCreationFailed, "failed to set recipient")
	}
	msg.Subject(data.Subject)
	msg.SetBodyString(mail.TypeTextHTML, body.String())

	// Send email
	if err := s.client.DialAndSend(msg); err != nil {
		s.logger.WithError(err).Error("Failed to send email")
		return NewSendError("send", to, ErrSendFailed, err.Error())
	}

	s.logger.WithFields(logrus.Fields{
		"to":      to,
		"subject": data.Subject,
	}).Info("Email sent successfully")

	return nil
}

// SendVerificationEmail sends an email verification message
func (s *SMTPService) SendVerificationEmail(to string, data VerificationData) error {
	if strings.TrimSpace(to) == "" || strings.TrimSpace(data.VerificationURL) == "" {
		return NewError("send_verification", ErrInvalidTemplate, "empty recipient or verification URL")
	}

	// Parse and execute template
	tmpl, err := template.New("verification").Parse(verificationTemplate)
	if err != nil {
		s.logger.WithError(err).Error("Failed to parse verification template")
		return NewTemplateError("send_verification", "verification", ErrTemplateParsingFailed, err.Error())
	}

	var body bytes.Buffer
	if err := tmpl.Execute(&body, data); err != nil {
		s.logger.WithError(err).Error("Failed to execute verification template")
		return NewTemplateError("send_verification", "verification", ErrTemplateExecutionFailed, err.Error())
	}

	// Create and configure message
	msg := mail.NewMsg()
	if err := msg.From(s.from); err != nil {
		return NewError("send_verification", ErrMessageCreationFailed, "failed to set from address")
	}
	if err := msg.To(to); err != nil {
		return NewSendError("send_verification", to, ErrMessageCreationFailed, "failed to set recipient")
	}
	msg.Subject("Verify Your Email Address")
	msg.SetBodyString(mail.TypeTextHTML, body.String())

	// Send email
	if err := s.client.DialAndSend(msg); err != nil {
		s.logger.WithError(err).Error("Failed to send verification email")
		return NewSendError("send_verification", to, ErrSendFailed, err.Error())
	}

	s.logger.WithFields(logrus.Fields{
		"to": to,
	}).Info("Verification email sent successfully")

	return nil
}

// SendWelcomeEmail sends a welcome email with credentials
func (s *SMTPService) SendWelcomeEmail(to string, data WelcomeData) error {
	if strings.TrimSpace(to) == "" || strings.TrimSpace(data.Username) == "" {
		return NewError("send_welcome", ErrInvalidTemplate, "empty recipient or username")
	}

	// Parse and execute template
	tmpl, err := template.New("welcome").Parse(welcomeTemplate)
	if err != nil {
		s.logger.WithError(err).Error("Failed to parse welcome template")
		return NewTemplateError("send_welcome", "welcome", ErrTemplateParsingFailed, err.Error())
	}

	var body bytes.Buffer
	if err := tmpl.Execute(&body, data); err != nil {
		s.logger.WithError(err).Error("Failed to execute welcome template")
		return NewTemplateError("send_welcome", "welcome", ErrTemplateExecutionFailed, err.Error())
	}

	// Create and configure message
	msg := mail.NewMsg()
	if err := msg.From(s.from); err != nil {
		return NewError("send_welcome", ErrMessageCreationFailed, "failed to set from address")
	}
	if err := msg.To(to); err != nil {
		return NewSendError("send_welcome", to, ErrMessageCreationFailed, "failed to set recipient")
	}
	msg.Subject("Welcome to Our Platform!")
	msg.SetBodyString(mail.TypeTextHTML, body.String())

	// Send email
	if err := s.client.DialAndSend(msg); err != nil {
		s.logger.WithError(err).Error("Failed to send welcome email")
		return NewSendError("send_welcome", to, ErrSendFailed, err.Error())
	}

	s.logger.WithFields(logrus.Fields{
		"to":       to,
		"username": data.Username,
	}).Info("Welcome email sent successfully")

	return nil
}

// Close closes the SMTP client connection
func (s *SMTPService) Close() error {
	if s.client != nil {
		if err := s.client.Close(); err != nil {
			s.logger.WithError(err).Error("Failed to close SMTP client")
			return NewError("close", ErrClientClosed, err.Error())
		}
		s.logger.Info("SMTP client closed successfully")
	}
	return nil
}