Import/Export backend prep

internal/transfer/provider.go

@@ -0,0 +1,51 @@
+// 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 transfer
+
+// Provider provides interface for common operation with provider.
+type Provider interface {
+	// ID is used for generating transfer ID by combining source and target ID.
+	ID() string
+
+	// Mailboxes returns all available mailboxes.
+	// Provider used as source returns only non-empty maibloxes.
+	// Provider used as target does not return all mail maiblox.
+	Mailboxes(includeEmpty, includeAllMail bool) ([]Mailbox, error)
+}
+
+// SourceProvider provides interface of provider with support of export.
+type SourceProvider interface {
+	Provider
+
+	// TransferTo exports messages based on rules to channel.
+	TransferTo(transferRules, *Progress, chan<- Message)
+}
+
+// TargetProvider provides interface of provider with support of import.
+type TargetProvider interface {
+	Provider
+
+	// DefaultMailboxes returns the default mailboxes for default rules if no other is found.
+	DefaultMailboxes(sourceMailbox Mailbox) (targetMailboxes []Mailbox)
+
+	// CreateMailbox creates new mailbox to be used as target in transfer rules.
+	CreateMailbox(Mailbox) (Mailbox, error)
+
+	// TransferFrom imports messages from channel.
+	TransferFrom(transferRules, *Progress, <-chan Message)
+}