From 78cfc5d87a7dcb762467aaa82fcc80cb4e24974b Mon Sep 17 00:00:00 2001
From: Robin Jarry <robin@jarry.cc>
Date: Sat, 14 Dec 2024 23:53:55 +0100
Subject: [PATCH] email: allow sending raw emails

The current email.Enqueue() function only allows sending messages with
the server's default settings.

In order to support sending any arbitrary message, we need to expose
a lower level API taking a raw message.Entity pointer. This new API will
be reused in a future reimplementation of the lists.sr.ht ingress agent
to forward messages to subscribers.

Add email.EnqueueRaw() that calls email.SendRaw(). Retry sending 10
times in the case of failure.

Signed-off-by: Robin Jarry <robin@jarry.cc>
---
 email/send.go   | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 email/worker.go | 21 +++++++++++++++++++++
 2 files changed, 67 insertions(+)

diff --git a/email/send.go b/email/send.go
index 27fe52ca2824c7c916712c9fb6686b711ec739eb..48b021a91fafe99c37de3fe4ba16e82b44a72b1d 100644
--- a/email/send.go
+++ b/email/send.go
@@ -6,6 +6,7 @@ import (
 	"io"
 	"strconv"
 
+	"github.com/emersion/go-message"
 	_ "github.com/emersion/go-message/charset"
 	"github.com/emersion/go-message/mail"
 	"github.com/emersion/go-sasl"
@@ -131,3 +132,48 @@ func Send(ctx context.Context, msg io.Reader, rcpts []string) error {
 	}
 	return err
 }
+
+// Sends a raw email. Blocks until it's sent or an error occurs.
+func SendRaw(ctx context.Context, email *message.Entity, to []string) error {
+	worker := ForContext(ctx)
+
+	if worker.client == nil || worker.client.Noop() != nil {
+		worker.client = nil
+
+		c, sender, err := mailSetup(ctx)
+		if err != nil {
+			return err
+		}
+		worker.client = c
+		worker.sender = sender
+	}
+
+	var writer io.WriteCloser
+	var err error
+
+	err = worker.client.Mail(worker.sender.Address, nil)
+	if err != nil {
+		goto end
+	}
+	for _, rcpt := range to {
+		if err := worker.client.Rcpt(rcpt, nil); err != nil {
+			return err
+		}
+	}
+	writer, err = worker.client.Data()
+	if err != nil {
+		goto end
+	}
+	err = email.WriteTo(writer)
+	if err != nil {
+		writer.Close()
+		goto end
+	}
+	err = writer.Close()
+end:
+	if err != nil {
+		worker.client.Close()
+		worker.client = nil
+	}
+	return err
+}
diff --git a/email/worker.go b/email/worker.go
index 1c6cda2445c0a846ba1c802224f25b1c473f3af2..3d918721549512592c37f14c68e5a476cccfe0d2 100644
--- a/email/worker.go
+++ b/email/worker.go
@@ -15,6 +15,7 @@ import (
 
 	work "git.sr.ht/~sircmpwn/dowork"
 	"github.com/ProtonMail/go-crypto/openpgp"
+	"github.com/emersion/go-message"
 	_ "github.com/emersion/go-message/charset"
 	"github.com/emersion/go-message/mail"
 	"github.com/emersion/go-pgpmail"
@@ -172,6 +173,26 @@ func EnqueueStd(ctx context.Context, header mail.Header,
 	return queue.Enqueue(NewTask(&buf, rcpts))
 }
 
+func EnqueueRaw(ctx context.Context, email *message.Entity, to []string) error {
+	queue := ForContext(ctx).queue
+	return queue.Enqueue(work.NewTask(func(ctx context.Context) error {
+		err := SendRaw(ctx, email, to)
+		if err != nil {
+			log.Printf("Error sending mail: %v", err)
+		}
+		return err
+	}).Retries(10).After(func(ctx context.Context, task *work.Task) {
+		msgID := email.Header.Get("Message-ID")
+		if task.Result() == nil {
+			log.Printf("Mail %s sent to %d recipients after %d attempts",
+				msgID, len(to), task.Attempts())
+		} else {
+			log.Printf("Mail %s failed after %d attempts: %v",
+				msgID, task.Attempts(), task.Result())
+		}
+	}))
+}
+
 type nopWriteCloser struct {
 	io.Writer
 }