We build too many walls and not enough bridges

internal/imap/backend_cache.go

@@ -0,0 +1,136 @@
+// Copyright (c) 2020 Proton Technologies AG
+//
+// This file is part of ProtonMail Bridge.
+//
+// ProtonMail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// ProtonMail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with ProtonMail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+package imap
+
+import (
+	"encoding/json"
+	"errors"
+	"os"
+	"strings"
+)
+
+// Cache keys.
+const (
+	SubscriptionException = "subscription_exceptions"
+)
+
+// addToCache adds item to existing item list.
+// Starting from following structure:
+//   {
+//		"username": {"label": "item1;item2"}
+//   }
+//
+// After calling addToCache("username", "label", "newItem") we get:
+//   {
+//		"username": {"label": "item1;item2;newItem"}
+//   }
+//
+func (ib *imapBackend) addToCache(userID, label, toAdd string) {
+	list := ib.getCacheList(userID, label)
+
+	if list != "" {
+		list = list + ";" + toAdd
+	} else {
+		list = toAdd
+	}
+
+	ib.imapCacheLock.Lock()
+	ib.imapCache[userID][label] = list
+	ib.imapCacheLock.Unlock()
+
+	if err := ib.saveIMAPCache(); err != nil {
+		log.Info("Backend/userinfo: could not save cache: ", err)
+	}
+}
+
+func (ib *imapBackend) removeFromCache(userID, label, toRemove string) {
+	list := ib.getCacheList(userID, label)
+
+	split := strings.Split(list, ";")
+
+	for i, item := range split {
+		if item == toRemove {
+			split = append(split[:i], split[i+1:]...)
+		}
+	}
+
+	ib.imapCacheLock.Lock()
+	ib.imapCache[userID][label] = strings.Join(split, ";")
+	ib.imapCacheLock.Unlock()
+
+	if err := ib.saveIMAPCache(); err != nil {
+		log.Info("Backend/userinfo: could not save cache: ", err)
+	}
+}
+
+func (ib *imapBackend) getCacheList(userID, label string) (list string) {
+	if err := ib.loadIMAPCache(); err != nil {
+		log.Warn("Could not load cache: ", err)
+	}
+
+	ib.imapCacheLock.Lock()
+	if ib.imapCache == nil {
+		ib.imapCache = map[string]map[string]string{}
+	}
+
+	if ib.imapCache[userID] == nil {
+		ib.imapCache[userID] = map[string]string{}
+		ib.imapCache[userID][SubscriptionException] = ""
+	}
+
+	list = ib.imapCache[userID][label]
+
+	ib.imapCacheLock.Unlock()
+
+	_ = ib.saveIMAPCache()
+	return
+}
+
+func (ib *imapBackend) loadIMAPCache() error {
+	if ib.imapCache != nil {
+		return nil
+	}
+
+	ib.imapCacheLock.Lock()
+	defer ib.imapCacheLock.Unlock()
+
+	f, err := os.Open(ib.imapCachePath)
+	if err != nil {
+		return err
+	}
+	defer f.Close() //nolint[errcheck]
+
+	return json.NewDecoder(f).Decode(&ib.imapCache)
+}
+
+func (ib *imapBackend) saveIMAPCache() error {
+	if ib.imapCache == nil {
+		return errors.New("cannot save cache: cache is nil")
+	}
+
+	ib.imapCacheLock.Lock()
+	defer ib.imapCacheLock.Unlock()
+
+	f, err := os.Create(ib.imapCachePath)
+	if err != nil {
+		return err
+	}
+	defer f.Close() //nolint[errcheck]
+
+	return json.NewEncoder(f).Encode(ib.imapCache)
+}