Split the concrete SMTP struct into separate MSA and MTA implementations

internal/smtp/msa.go

@@ -0,0 +1,77 @@
+package smtp
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"sync/atomic"
+
+	"github.com/emersion/go-smtp"
+
+	"ur.gs/crockery/internal/store"
+)
+
+type msa struct {
+	cancel context.CancelFunc
+	store  store.Interface
+	server *smtp.Server
+
+	// Session IDs
+	sid uint64
+}
+
+func NewMSA(cancel context.CancelFunc, datastore store.Interface) Server {
+	out := &msa{
+		cancel: cancel,
+		store:  datastore,
+	}
+
+	out.server = smtp.NewServer(out)
+	out.server.Domain = datastore.Domain()
+	out.server.TLSConfig = datastore.TLSConfig()
+	out.server.Addr = ":587"
+
+	return out
+}
+
+func (m *msa) Run() {
+	if err := m.server.ListenAndServe(); err != nil {
+		log.Printf("Error serving submission %s: %v", m.server.Addr, err)
+	} else {
+		log.Printf("Stopped listening on submission %s", m.server.Addr)
+	}
+
+	m.cancel()
+}
+
+func (m *msa) Close() error {
+	m.cancel() // FIXME: this doesn't touch the server
+
+	return nil
+}
+
+// Backend implementation for go-smtp after this point
+
+func (m *msa) Login(user, pass string) (smtp.User, error) {
+	account, err := m.store.FindAccountWithPassword(user, pass)
+	if err != nil {
+		// Log the real error, but don't show it to the end user
+		log.Printf("Beginning submission session for %s failed: %s", user, err)
+		return nil, fmt.Errorf("Login failed")
+	}
+
+	session := &Session{
+		ID:      atomic.AddUint64(&m.sid, uint64(1)),
+		Account: account,
+		Handler: &Sender{},
+	}
+
+	log.Printf("Beginning submission session %d for %s", session.ID, user)
+	// FIXME: TODO: Track ongoing sessions for termination or notifications
+
+	return session, nil
+}
+
+func (m *msa) AnonymousLogin() (smtp.User, error) {
+	return nil, smtp.AuthRequiredErr
+}