GODT-1779: Remove go-imap

internal/bridge/smtp_backend.go

@@ -0,0 +1,70 @@
+package bridge
+
+import (
+	"sync"
+
+	"github.com/ProtonMail/proton-bridge/v2/internal/user"
+	"github.com/bradenaw/juniper/xslices"
+	"github.com/emersion/go-smtp"
+	"golang.org/x/exp/slices"
+)
+
+type smtpBackend struct {
+	users     []*user.User
+	usersLock sync.RWMutex
+}
+
+func newSMTPBackend() (*smtpBackend, error) {
+	return &smtpBackend{}, nil
+}
+
+func (backend *smtpBackend) Login(state *smtp.ConnectionState, username string, password string) (smtp.Session, error) {
+	backend.usersLock.RLock()
+	defer backend.usersLock.RUnlock()
+
+	for _, user := range backend.users {
+		if slices.Contains(user.Addresses(), username) && user.BridgePass() == password {
+			return user.NewSMTPSession(username)
+		}
+	}
+
+	return nil, ErrNoSuchUser
+}
+
+func (backend *smtpBackend) AnonymousLogin(state *smtp.ConnectionState) (smtp.Session, error) {
+	return nil, ErrNotImplemented
+}
+
+// addUser adds the given user to the backend.
+// It returns an error if a user with the same ID already exists.
+func (backend *smtpBackend) addUser(user *user.User) error {
+	backend.usersLock.Lock()
+	defer backend.usersLock.Unlock()
+
+	for _, u := range backend.users {
+		if u.ID() == user.ID() {
+			return ErrUserAlreadyExists
+		}
+	}
+
+	backend.users = append(backend.users, user)
+
+	return nil
+}
+
+// removeUser removes the given user from the backend.
+// It returns an error if the user doesn't exist.
+func (backend *smtpBackend) removeUser(user *user.User) error {
+	backend.usersLock.Lock()
+	defer backend.usersLock.Unlock()
+
+	idx := xslices.Index(backend.users, user)
+
+	if idx < 0 {
+		return ErrNoSuchUser
+	}
+
+	backend.users = append(backend.users[:idx], backend.users[idx+1:]...)
+
+	return nil
+}