GODT-1146: Refactor header filtering

internal/imap/mailbox_fetch_test.go

@@ -0,0 +1,67 @@
+// Copyright (c) 2021 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 (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFilterHeader(t *testing.T) {
+	const header = "To: somebody\r\nFrom: somebody else\r\nSubject: this is\r\n\ta multiline field\r\n\r\n"
+
+	assert.Equal(t, "To: somebody\r\n\r\n", string(filterHeaderLines([]byte(header), func(field string) bool {
+		return strings.EqualFold(field, "To")
+	})))
+
+	assert.Equal(t, "From: somebody else\r\n\r\n", string(filterHeaderLines([]byte(header), func(field string) bool {
+		return strings.EqualFold(field, "From")
+	})))
+
+	assert.Equal(t, "To: somebody\r\nFrom: somebody else\r\n\r\n", string(filterHeaderLines([]byte(header), func(field string) bool {
+		return strings.EqualFold(field, "To") || strings.EqualFold(field, "From")
+	})))
+
+	assert.Equal(t, "Subject: this is\r\n\ta multiline field\r\n\r\n", string(filterHeaderLines([]byte(header), func(field string) bool {
+		return strings.EqualFold(field, "Subject")
+	})))
+}
+
+// TestFilterHeaderNoNewline tests that we don't include a trailing newline when filtering
+// if the original header also lacks one (which it can legally do if there is no body).
+func TestFilterHeaderNoNewline(t *testing.T) {
+	const header = "To: somebody\r\nFrom: somebody else\r\nSubject: this is\r\n\ta multiline field\r\n"
+
+	assert.Equal(t, "To: somebody\r\n", string(filterHeaderLines([]byte(header), func(field string) bool {
+		return strings.EqualFold(field, "To")
+	})))
+
+	assert.Equal(t, "From: somebody else\r\n", string(filterHeaderLines([]byte(header), func(field string) bool {
+		return strings.EqualFold(field, "From")
+	})))
+
+	assert.Equal(t, "To: somebody\r\nFrom: somebody else\r\n", string(filterHeaderLines([]byte(header), func(field string) bool {
+		return strings.EqualFold(field, "To") || strings.EqualFold(field, "From")
+	})))
+
+	assert.Equal(t, "Subject: this is\r\n\ta multiline field\r\n", string(filterHeaderLines([]byte(header), func(field string) bool {
+		return strings.EqualFold(field, "Subject")
+	})))
+}