feat: implemented smtp service;

feat: implemented registration emails;
fix: config variables for password length used the same env variable;
refactor: all available config variables added to docker-compose.yml

backend/internal/services/smtp.go

@@ -17,10 +17,21 @@
 
 package services
 
-import "go.uber.org/zap"
+import (
+	"crypto/tls"
+	"easywish/config"
+	"fmt"
+	"net"
+	"net/smtp"
+	"strings"
+	"time"
+
+	"go.uber.org/zap"
+	errs "easywish/internal/errors"
+)
 
 type SmtpService interface {
-	SendEmail(to string, content string)
+	SendEmail(to string, subject, body string) error
 }
 
 type smtpServiceImpl struct {
@@ -31,7 +42,102 @@ func NewSmtpService(_log *zap.Logger) SmtpService {
 	return &smtpServiceImpl{log: _log}
 }
 
-func (s *smtpServiceImpl) SendEmail(to string, content string) {
-	panic("unimplemented")
-}
+func (s *smtpServiceImpl) SendEmail(to string, subject, body string) error {
+	cfg := config.GetConfig()
 
+	if !cfg.SmtpEnabled {
+		s.log.Error("Attempted to send an email with SMTP disabled in the config")
+		return errs.ErrSmtpDisabled
+	}
+
+	if cfg.SmtpServer == "" || cfg.SmtpPort == 0 || cfg.SmtpFrom == "" {
+		s.log.Error("SMTP service settings or the SMTP From paramater are not set")
+		return errs.ErrSmtpMissingConfiguration
+	}
+
+	toSlice := []string{to}
+
+	headers := map[string]string{
+		"From":         cfg.SmtpFrom,
+		"To":           strings.Join(toSlice, ", "),
+		"Subject":      subject,
+		"MIME-Version": "1.0",
+		"Content-Type": "text/html; charset=UTF-8",
+	}
+
+	var sb strings.Builder
+	for k, v := range headers {
+		sb.WriteString(fmt.Sprintf("%s: %s\r\n", k, v))
+	}
+	sb.WriteString("\r\n" + body)
+	message := []byte(sb.String())
+
+	hostPort := fmt.Sprintf("%s:%d", cfg.SmtpServer, cfg.SmtpPort)
+	var conn net.Conn
+	var err error
+
+	if cfg.SmtpUseSSL {
+		tlsConfig := &tls.Config{ServerName: cfg.SmtpServer}
+		conn, err = tls.Dial("tcp", hostPort, tlsConfig)
+	} else {
+		timeout := time.Duration(cfg.SmtpTimeout) * time.Second
+		conn, err = net.DialTimeout("tcp", hostPort, timeout)
+	}
+	if err != nil {
+		s.log.Error("SMTP connection failure", zap.Error(err))
+		return err
+	}
+	defer conn.Close()
+
+	client, err := smtp.NewClient(conn, cfg.SmtpServer)
+	if err != nil {
+		s.log.Error("SMTP client creation failed", zap.Error(err))
+		return err
+	}
+	defer client.Close()
+
+	if !cfg.SmtpUseSSL && cfg.SmtpUseTLS {
+		tlsConfig := &tls.Config{ServerName: cfg.SmtpServer}
+		if err = client.StartTLS(tlsConfig); err != nil {
+			return err
+		}
+	}
+
+	// Authenticate if credentials exist
+	if cfg.SmtpUser != "" && cfg.SmtpPassword != "" {
+		auth := smtp.PlainAuth("", cfg.SmtpUser, cfg.SmtpPassword, cfg.SmtpServer)
+		if err = client.Auth(auth); err != nil {
+			s.log.Error("SMTP authentication failure", zap.Error(err))
+			return err
+		}
+	}
+
+	if err = client.Mail(cfg.SmtpFrom); err != nil {
+		s.log.Error("SMTP sender set failed", zap.Error(err))
+		return err
+	}
+
+	for _, recipient := range to {
+		if err = client.Rcpt(string(recipient)); err != nil {
+			s.log.Error("SMTP recipient set failed", zap.Error(err))
+			return err
+		}
+	}
+
+	// Send email body
+	w, err := client.Data()
+	if err != nil {
+		s.log.Error("SMTP data command failed", zap.Error(err))
+		return err
+	}
+	if _, err = w.Write(message); err != nil {
+		s.log.Error("SMTP message write failed", zap.Error(err))
+		return err
+	}
+	if err = w.Close(); err != nil {
+		s.log.Error("SMTP message close failed", zap.Error(err))
+		return err
+	}
+
+	return client.Quit()
+}