merging unrelated objects into one

internal/cli/shell.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"regexp"
 	"strconv"
 	"strings"
 
@@ -77,6 +78,8 @@ func (s musicObjectStore) currentMusicObjects() ([]data.MusicObject, error) {
 	return (s)[len(s)-1], nil
 }
 
+var indexSelectionPattern = regexp.MustCompile(`^[\d ,]+$`)
+
 func interpretCommand(command string, store musicObjectStore) (musicObjectStore, error) {
 	// going back in history
 	if command == ".." {
@@ -88,21 +91,33 @@ func interpretCommand(command string, store musicObjectStore) (musicObjectStore,
 	}
 
 	// fetch special music object
-	if index, err := strconv.Atoi(command); err == nil {
+	if indexSelectionPattern.MatchString(command) {
 		currentMusicObjects, err := store.currentMusicObjects()
 		if err != nil {
 			return store, err
 		}
 
-		if index >= len(currentMusicObjects) || index < 0 {
+		var fetched data.MusicObject
-			return store, errors.New(command + " is out of bounds [0 <= " + strconv.Itoa(index) + " <= " + strconv.Itoa(len(currentMusicObjects)-1) + "]")
-		}
 
-		current := currentMusicObjects[index]
+		for _, stringIndex := range strings.Split(command, ",") {
+			index, _ := strconv.Atoi(strings.TrimSpace(stringIndex))
 
-		fetched, err := plugin.Fetch(current)
+			if index >= len(currentMusicObjects) || index < 0 {
-		if err != nil {
+				return store, errors.New(command + " is out of bounds [0 <= " + strconv.Itoa(index) + " <= " + strconv.Itoa(len(currentMusicObjects)-1) + "]")
-			return store, err
+			}
+
+			current := currentMusicObjects[index]
+
+			newFetched, err := plugin.Fetch(current)
+			if err != nil {
+				return store, err
+			}
+
+			if fetched == nil {
+				fetched = newFetched
+			} else {
+				fetched = fetched.Merge(newFetched)
+			}
 		}
 
 		return append(store, fetched.Related()), nil