Use constants for task keys for better readability

inspector.go

@@ -217,48 +217,62 @@ type ArchivedTask struct {
 	score int64
 }
 
+// Format string used for task key.
+// Format is <prefix>:<uuid>:<score>.
+const taskKeyFormat = "%s:%v:%v"
+
+// Prefix used for task key.
+const (
+	keyPrefixPending   = "p"
+	keyPrefixScheduled = "s"
+	keyPrefixRetry     = "r"
+	keyPrefixArchived  = "a"
+
+	allKeyPrefixes = keyPrefixPending + keyPrefixScheduled + keyPrefixRetry + keyPrefixArchived
+)
+
 // Key returns a key used to delete, and archive the pending task.
 func (t *PendingTask) Key() string {
 	// Note: Pending tasks are stored in redis LIST, therefore no score.
-	// Use zero for the score to preserve the same key format.
-	return fmt.Sprintf("p:%v:%v", t.ID, 0)
+	// Use zero for the score to use the same key format.
+	return fmt.Sprintf(taskKeyFormat, keyPrefixPending, t.ID, 0)
 }
 
 // Key returns a key used to delete, run, and archive the scheduled task.
 func (t *ScheduledTask) Key() string {
-	return fmt.Sprintf("s:%v:%v", t.ID, t.score)
+	return fmt.Sprintf(taskKeyFormat, keyPrefixScheduled, t.ID, t.score)
 }
 
 // Key returns a key used to delete, run, and archive the retry task.
 func (t *RetryTask) Key() string {
-	return fmt.Sprintf("r:%v:%v", t.ID, t.score)
+	return fmt.Sprintf(taskKeyFormat, keyPrefixRetry, t.ID, t.score)
 }
 
 // Key returns a key used to delete and run the archived task.
 func (t *ArchivedTask) Key() string {
-	return fmt.Sprintf("a:%v:%v", t.ID, t.score)
+	return fmt.Sprintf(taskKeyFormat, keyPrefixArchived, t.ID, t.score)
 }
 
 // parseTaskKey parses a key string and returns each part of key with proper
 // type if valid, otherwise it reports an error.
-func parseTaskKey(key string) (id uuid.UUID, score int64, state string, err error) {
+func parseTaskKey(key string) (prefix string, id uuid.UUID, score int64, err error) {
 	parts := strings.Split(key, ":")
 	if len(parts) != 3 {
-		return uuid.Nil, 0, "", fmt.Errorf("invalid id")
+		return "", uuid.Nil, 0, fmt.Errorf("invalid id")
 	}
 	id, err = uuid.Parse(parts[1])
 	if err != nil {
-		return uuid.Nil, 0, "", fmt.Errorf("invalid id")
+		return "", uuid.Nil, 0, fmt.Errorf("invalid id")
 	}
 	score, err = strconv.ParseInt(parts[2], 10, 64)
 	if err != nil {
-		return uuid.Nil, 0, "", fmt.Errorf("invalid id")
+		return "", uuid.Nil, 0, fmt.Errorf("invalid id")
 	}
-	state = parts[0]
-	if len(state) != 1 || !strings.Contains("psra", state) {
-		return uuid.Nil, 0, "", fmt.Errorf("invalid id")
+	prefix = parts[0]
+	if len(prefix) != 1 || !strings.Contains(allKeyPrefixes, prefix) {
+		return "", uuid.Nil, 0, fmt.Errorf("invalid id")
 	}
-	return id, score, state, nil
+	return prefix, id, score, nil
 }
 
 // ListOption specifies behavior of list operation.
@@ -509,18 +523,18 @@ func (i *Inspector) DeleteTaskByKey(qname, key string) error {
 	if err := validateQueueName(qname); err != nil {
 		return err
 	}
-	id, score, state, err := parseTaskKey(key)
+	prefix, id, score, err := parseTaskKey(key)
 	if err != nil {
 		return err
 	}
-	switch state {
-	case "p":
+	switch prefix {
+	case keyPrefixPending:
 		return i.rdb.DeletePendingTask(qname, id)
-	case "s":
+	case keyPrefixScheduled:
 		return i.rdb.DeleteScheduledTask(qname, id, score)
-	case "r":
+	case keyPrefixRetry:
 		return i.rdb.DeleteRetryTask(qname, id, score)
-	case "a":
+	case keyPrefixArchived:
 		return i.rdb.DeleteArchivedTask(qname, id, score)
 	default:
 		return fmt.Errorf("invalid key")
@@ -562,17 +576,19 @@ func (i *Inspector) RunTaskByKey(qname, key string) error {
 	if err := validateQueueName(qname); err != nil {
 		return err
 	}
-	id, score, state, err := parseTaskKey(key)
+	prefix, id, score, err := parseTaskKey(key)
 	if err != nil {
 		return err
 	}
-	switch state {
-	case "s":
+	switch prefix {
+	case keyPrefixScheduled:
 		return i.rdb.RunScheduledTask(qname, id, score)
-	case "r":
+	case keyPrefixRetry:
 		return i.rdb.RunRetryTask(qname, id, score)
-	case "a":
+	case keyPrefixArchived:
 		return i.rdb.RunArchivedTask(qname, id, score)
+	case keyPrefixPending:
+		return fmt.Errorf("task is already pending for run")
 	default:
 		return fmt.Errorf("invalid key")
 	}
@@ -613,19 +629,19 @@ func (i *Inspector) ArchiveTaskByKey(qname, key string) error {
 	if err := validateQueueName(qname); err != nil {
 		return err
 	}
-	id, score, state, err := parseTaskKey(key)
+	prefix, id, score, err := parseTaskKey(key)
 	if err != nil {
 		return err
 	}
-	switch state {
-	case "p":
+	switch prefix {
+	case keyPrefixPending:
 		return i.rdb.ArchivePendingTask(qname, id)
-	case "s":
+	case keyPrefixScheduled:
 		return i.rdb.ArchiveScheduledTask(qname, id, score)
-	case "r":
+	case keyPrefixRetry:
 		return i.rdb.ArchiveRetryTask(qname, id, score)
-	case "a":
-		return fmt.Errorf("task already archived")
+	case keyPrefixArchived:
+		return fmt.Errorf("task is already archived")
 	default:
 		return fmt.Errorf("invalid key")
 	}