feat(GODT-2802): IMAP Serivce

Handles all IMAP related tasks. Unlike the previous iteration, this new
service automatically adds and removes users from Gluon by interfacing
with server manager.

internal/services/imapservice/sync_reporter.go

@@ -0,0 +1,72 @@
+// Copyright (c) 2023 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail 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.
+//
+// Proton Mail 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 Proton Mail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+package imapservice
+
+import (
+	"context"
+	"time"
+
+	"github.com/ProtonMail/proton-bridge/v3/internal/events"
+)
+
+type syncReporter struct {
+	userID         string
+	eventPublisher events.EventPublisher
+
+	start time.Time
+	total int
+	count int
+
+	last time.Time
+	freq time.Duration
+}
+
+func newSyncReporter(userID string, eventsPublisher events.EventPublisher, total int, freq time.Duration) *syncReporter {
+	return &syncReporter{
+		userID:         userID,
+		eventPublisher: eventsPublisher,
+
+		start: time.Now(),
+		total: total,
+		freq:  freq,
+	}
+}
+
+func (rep *syncReporter) add(ctx context.Context, delta int) {
+	rep.count += delta
+
+	if time.Since(rep.last) > rep.freq {
+		rep.eventPublisher.PublishEvent(ctx, events.SyncProgress{
+			UserID:    rep.userID,
+			Progress:  float64(rep.count) / float64(rep.total),
+			Elapsed:   time.Since(rep.start),
+			Remaining: time.Since(rep.start) * time.Duration(rep.total-(rep.count+1)) / time.Duration(rep.count+1),
+		})
+
+		rep.last = time.Now()
+	}
+}
+
+func (rep *syncReporter) done(ctx context.Context) {
+	rep.eventPublisher.PublishEvent(ctx, events.SyncProgress{
+		UserID:    rep.userID,
+		Progress:  1,
+		Elapsed:   time.Since(rep.start),
+		Remaining: 0,
+	})
+}