1 files changed, 43 insertions, 0 deletions
diff --git a/query.go b/query.go
new file mode 100644
index 0000000..69b778c
--- /dev/null
+++ b/query.go
@@ -0,0 +1,43 @@
+package json
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+func Query(parent Node, path []string) (Node, error) {
+	if len(path) == 0 {
+		return parent, nil
+	}
+	head, rest := path[0], path[1:]
+	switch parent := parent.(type) {
+	case ObjectNode:
+		next, ok := parent.GetByKey(head)
+		if !ok {
+			return nil, fmt.Errorf("key %s not found at object %v", head, parent)
+		}
+		return Query(next, rest)
+	case ArrayNode:
+		stringIdx := strings.Trim(head, "[]")
+		idx, err := strconv.Atoi(stringIdx)
+		if err != nil {
+			return nil, fmt.Errorf("key %s is invalid index: %w", stringIdx, err)
+		}
+		if idx >= parent.Len() {
+			return nil, fmt.Errorf("index %d is out of range (len=%d)", idx, parent.Len())
+		}
+		next := parent.Index(idx)
+		return Query(next, rest)
+	default:
+		return nil, fmt.Errorf("can't get key=%s from node type = %t", head, parent)
+	}
+}
+
+func MustQuery(parent Node, path []string) Node {
+	n, err := Query(parent, path)
+	if err != nil {
+		panic(err)
+	}
+	return n
+}