rewrite into get and set functions

internal/statsapi/feed.go

@@ -48,7 +48,7 @@ func expand(arr []any, idx int) []any {
 	return all
 }
 
-func setValue(obj any, key string, value any) error {
+func setLeaf(obj any, key string, value any) error {
 	var err error
 	switch v := obj.(type) {
 	case map[string]any:
@@ -72,40 +72,83 @@ func setValue(obj any, key string, value any) error {
 	return err
 }
 
-func patch(obj any, path string, value any) error {
+func getLeaf(key string, obj any) (any, error) {
+	switch v := obj.(type) {
+	case map[string]any:
+		val, ok := v[key]
+		if !ok {
+			return nil, errors.New("invalid key")
+		}
+		return val, nil
+	case []any:
+		idx, err := strconv.Atoi(key)
+		if err != nil {
+			return nil, err
+		}
+
+		if idx < 0 || idx >= len(v) {
+			return nil, errors.New("invalid index")
+		}
+
+		return v[idx], nil
+	default:
+		return nil, errors.New("couldn't determine type")
+	}
+}
+
+func set(path string, obj any, value any) error {
+	elems := strings.Split(path, "/")
+	leaf := elems[len(elems)-1]
+	leafPath := strings.Join(elems[:len(elems)-1], "/")
+
+	parent, err := get(leafPath, obj)
+	if err != nil {
+		return err
+	}
+
+	err = setLeaf(parent, leaf, value)
+	return err
+}
+
+func get(path string, obj any) (any, error) {
 	var err error
 	first, rest, found := strings.Cut(path, "/")
 	log.Println(first, rest)
 	if !found {
-		err = setValue(obj, first, value)
-		return err
+		return getLeaf(first, obj)
 	} else if first == "" {
-		err = patch(obj, rest, value)
-		return err
+		return get(rest, obj)
 	}
 
 	switch v := obj.(type) {
 	case map[string]any:
-		err = patch(v[first], rest, value)
+		val, ok := v[first]
+		if !ok {
+			return v, errors.New("invalid key")
+		}
+		return get(rest, val)
 	case []any:
 		idx, err := strconv.Atoi(first)
 		if err != nil {
 			break
 		}
 
-		v = expand(v, idx)
-		err = patch(v[idx], rest, value)
+		if idx < 0 || idx >= len(v) {
+			return v, errors.New("invalid index")
+		}
+
+		return get(rest, v[idx])
 	default:
 		err = errors.New("couldn't determine type")
 	}
 
-	return err
+	return obj, err
 }
 
 func (f *FeedResponse) Patch(instr *instruction) error {
 	// TODO: need to handle each type of instruction separately: add,
 	// replace, remove, copy, move
 	log.Println("updating", instr.Path)
-	err := patch(map[string]any(*f), instr.Path, instr.Value)
+	err := set(instr.Path, map[string]any(*f), instr.Value)
 	return err
 }