added maximum votes limit per comment (#223)

* added maximum votes limit per comment

* added 'max-votes' param description into README

README.md

@@ -124,6 +124,7 @@ _this is the recommended way to run remark42_
 | ssl.cert                | SSL_CERT                |                       | path to cert.pem file                            |
 | ssl.key                 | SSL_KEY                 |                       | path to key.pem file                             |
 | max-comment             | MAX_COMMENT_SIZE        | 2048                  | comment's size limit                             |
+| max-votes               | MAX_VOTES               | `-1`                  | votes limit per comment, `-1` - unlimited        |
 | low-score               | LOW_SCORE               | `-5`                  | low score threshold                              |
 | critical-score          | CRITICAL_SCORE          | `-10`                 | critical score threshold                         |
 | edit-time               | EDIT_TIME               | `5m`                  | edit window                                      |

backend/app/cmd/server.go

@@ -45,6 +45,7 @@ type ServerCommand struct {
 	MaxBackupFiles int           `long:"max-back" env:"MAX_BACKUP_FILES" default:"10" description:"max backups to keep"`
 	ImageProxy     bool          `long:"img-proxy" env:"IMG_PROXY" description:"enable image proxy"`
 	MaxCommentSize int           `long:"max-comment" env:"MAX_COMMENT_SIZE" default:"2048" description:"max comment size"`
+	MaxVotes       int           `long:"max-votes" env:"MAX_VOTES" default:"-1" description:"maximum number of votes per comment"`
 	LowScore       int           `long:"low-score" env:"LOW_SCORE" default:"-5" description:"low score threshold"`
 	CriticalScore  int           `long:"critical-score" env:"CRITICAL_SCORE" default:"-10" description:"critical score threshold"`
 	ReadOnlyAge    int           `long:"read-age" env:"READONLY_AGE" default:"0" description:"read-only age of comments"`
@@ -206,6 +207,7 @@ func (s *ServerCommand) newServerApp() (*serverApp, error) {
 		EditDuration:   s.EditDuration,
 		AdminStore:     adminStore,
 		MaxCommentSize: s.MaxCommentSize,
+		MaxVotes:       s.MaxVotes,
 	}
 
 	loadingCache, err := s.makeCache()

backend/app/store/service/service.go

@@ -18,6 +18,7 @@ type DataStore struct {
 	EditDuration   time.Duration
 	AdminStore     admin.Store
 	MaxCommentSize int
+	MaxVotes       int
 
 	// granular locks
 	scopedLocks struct {
@@ -28,6 +29,7 @@ type DataStore struct {
 }
 
 const defaultCommentMaxSize = 2000
+const defaultVotesLimit = -1 // unlimited
 
 // Create prepares comment and forward to Interface.Create
 func (s *DataStore) Create(comment store.Comment) (commentID string, err error) {
@@ -97,6 +99,15 @@ func (s *DataStore) Vote(locator store.Locator, commentID string, userID string,
 		return comment, errors.Errorf("user %s already voted for %s", userID, commentID)
 	}
 
+	maxVotes := s.MaxVotes
+	if s.MaxVotes <= 0 {
+		maxVotes = defaultVotesLimit
+	}
+
+	if maxVotes >= 0 && len(comment.Votes) >= maxVotes {
+		return comment, errors.Errorf("maximum number of votes exceeded for comment %s", commentID)
+	}
+
 	// reset vote if user changed to opposite
 	if voted && v != val {
 		delete(comment.Votes, userID)

backend/app/store/service/service_test.go

@@ -116,6 +116,24 @@ func TestService_Vote(t *testing.T) {
 	assert.Equal(t, map[string]bool{}, res[0].Votes, "vote reset ok")
 }
 
+func TestService_VoteLimit(t *testing.T) {
+	defer os.Remove(testDb)
+	b := DataStore{Interface: prepStoreEngine(t), AdminStore: admin.NewStaticKeyStore("secret 123"), MaxVotes: 2}
+
+	_, err := b.Vote(store.Locator{URL: "https://radio-t.com", SiteID: "radio-t"}, "id-1", "user2", true)
+	assert.Nil(t, err)
+
+	_, err = b.Vote(store.Locator{URL: "https://radio-t.com", SiteID: "radio-t"}, "id-1", "user3", true)
+	assert.Nil(t, err)
+
+	_, err = b.Vote(store.Locator{URL: "https://radio-t.com", SiteID: "radio-t"}, "id-1", "user4", true)
+	assert.NotNil(t, err, "vote limit reached")
+	assert.True(t, strings.HasPrefix(err.Error(), "maximum number of votes exceeded for comment id-1"))
+
+	_, err = b.Vote(store.Locator{URL: "https://radio-t.com", SiteID: "radio-t"}, "id-2", "user4", true)
+	assert.Nil(t, err)
+}
+
 func TestService_VoteAggressive(t *testing.T) {
 	defer os.Remove(testDb)
 	b := DataStore{Interface: prepStoreEngine(t), AdminStore: admin.NewStaticKeyStore("secret 123")}