feat: add chat

internal/handler/broadcasting_auth_test.go

@@ -3,6 +3,7 @@ package handler
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -77,6 +78,44 @@ func TestBroadcastingAuth_Authorization(t *testing.T) {
 
 // A prefix match must not be mistaken for authorization: "…user-a-evil" starts
 // with the victim's id but is a different channel.
+// ConversationRule delegates to the chat service's membership check, so the
+// realtime channel and the REST endpoints can never disagree about who is in a
+// thread.
+func TestConversationRule(t *testing.T) {
+	const member, outsider = "member-1", "outsider-1"
+	rule := ConversationRule(func(_ context.Context, userID, conversationID string) (bool, error) {
+		if conversationID == "boom" {
+			return false, errors.New("database down")
+		}
+		return userID == member && conversationID == "conv-1", nil
+	})
+
+	if rule.Prefix != "private-conversation." {
+		t.Errorf("prefix = %q", rule.Prefix)
+	}
+	tests := []struct {
+		name    string
+		user    string
+		suffix  string
+		wantOK  bool
+		wantErr bool
+	}{
+		{"participant", member, "conv-1", true, false},
+		{"outsider", outsider, "conv-1", false, false},
+		{"participant of another thread", member, "conv-2", false, false},
+		{"empty conversation id", member, "", false, false},
+		{"lookup failure is not a denial", member, "boom", false, true},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			ok, err := rule.Authorize(context.Background(), tc.user, tc.suffix)
+			if ok != tc.wantOK || (err != nil) != tc.wantErr {
+				t.Errorf("= (%v, %v), want (%v, err=%v)", ok, err, tc.wantOK, tc.wantErr)
+			}
+		})
+	}
+}
+
 func TestBroadcastingAuth_SuffixIsComparedExactly(t *testing.T) {
 	rec := serve(t, testAuthHandler(t), testUser, "1234.5678", "private-notifications."+testUser+"-evil")
 	if rec.Code != http.StatusForbidden {