Add mailer system

Signed-off-by: gearnode <bryan@frimin.fr>

pkg/mailer/mailer.go

@@ -0,0 +1,115 @@
+// Copyright (c) 2025 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package mailer
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"net/smtp"
+	"time"
+
+	"github.com/getprobo/probo/pkg/coredata"
+	"github.com/jhillyerd/enmime"
+	"go.gearno.de/kit/log"
+	"go.gearno.de/kit/pg"
+)
+
+type (
+	Mailer struct {
+		pg  *pg.Client
+		l   *log.Logger
+		cfg Config
+	}
+
+	Config struct {
+		SenderName  string
+		SenderEmail string
+		Addr        string
+	}
+)
+
+func NewMailer(pg *pg.Client, l *log.Logger, cfg Config) *Mailer {
+	return &Mailer{pg: pg, l: l, cfg: cfg}
+}
+
+func (m *Mailer) Run(ctx context.Context) error {
+LOOP:
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-time.After(1 * time.Second):
+		ctx := context.Background()
+		if err := m.batchSendEmails(ctx); err != nil {
+			m.l.ErrorCtx(ctx, "cannot send email", log.Error(err))
+		}
+
+		goto LOOP
+	}
+}
+
+func (m *Mailer) batchSendEmails(ctx context.Context) error {
+	for {
+		err := m.pg.WithTx(
+			ctx,
+			func(tx pg.Conn) error {
+				email := &coredata.Email{}
+				err := email.LoadNextUnsentForUpdate(ctx, tx)
+				if err != nil {
+					return err
+				}
+
+				mail := enmime.Builder().
+					Subject(email.Subject).
+					From(m.cfg.SenderName, m.cfg.SenderEmail).
+					To(email.RecipientName, email.RecipientEmail).
+					Text([]byte(email.TextBody))
+
+				envelope, err := mail.Build()
+				if err != nil {
+					return fmt.Errorf("cannot build email: %w", err)
+				}
+
+				var buf bytes.Buffer
+				if err := envelope.Encode(&buf); err != nil {
+					return fmt.Errorf("cannot encode email: %w", err)
+				}
+
+				if err := smtp.SendMail(m.cfg.Addr, nil, m.cfg.SenderEmail, []string{email.RecipientEmail}, buf.Bytes()); err != nil {
+					return fmt.Errorf("cannot send email: %w", err)
+				}
+
+				now := time.Now()
+				email.SentAt = &now
+				email.UpdatedAt = now
+
+				if err := email.Update(ctx, tx); err != nil {
+					return fmt.Errorf("cannot update email: %w", err)
+				}
+
+				return nil
+			},
+		)
+
+		if errors.Is(err, coredata.ErrNoUnsentEmail) {
+			return nil
+		}
+
+		if err != nil {
+			return err
+		}
+	}
+}