Replace hand-rolled IMAP with go-imap

backend/04-imap-source_test.go

@@ -0,0 +1,26 @@
+package backend
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/emersion/go-imap/v2"
+)
+
+func TestSanitizeIMAPFlagsDropsRecentAndWildcard(t *testing.T) {
+	got := sanitizeIMAPFlags([]imap.Flag{imap.FlagSeen, imap.Flag(`\Recent`), imap.FlagWildcard, imap.FlagAnswered})
+	if len(got) != 2 || got[0] != imap.FlagSeen || got[1] != imap.FlagAnswered {
+		t.Fatalf("sanitizeIMAPFlags returned %#v", got)
+	}
+}
+
+func TestMessageIDFallsBackToBodyHash(t *testing.T) {
+	body := []byte("From: a@example.com\r\nSubject: Test\r\n\r\nBody")
+	id := messageID(body)
+	if !strings.HasPrefix(id, "sha256:") {
+		t.Fatalf("expected sha256 fallback, got %q", id)
+	}
+	if id != messageID(body) {
+		t.Fatal("messageID hash fallback is not stable")
+	}
+}