Added pick operator

pkg/yqlib/operator_pick.go

@@ -0,0 +1,86 @@
+package yqlib
+
+import (
+	"container/list"
+	"fmt"
+
+	yaml "gopkg.in/yaml.v3"
+)
+
+func pickMap(original *yaml.Node, indices *yaml.Node) *yaml.Node {
+
+	filteredContent := make([]*yaml.Node, 0)
+	for index := 0; index < len(indices.Content); index = index + 1 {
+		keyToFind := indices.Content[index]
+
+		indexInMap := findKeyInMap(original, keyToFind)
+		if indexInMap > -1 {
+			clonedKey := deepClone(original.Content[indexInMap])
+			clonedValue := deepClone(original.Content[indexInMap+1])
+			filteredContent = append(filteredContent, clonedKey, clonedValue)
+		}
+	}
+
+	newNode := deepCloneNoContent(original)
+	newNode.Content = filteredContent
+
+	return newNode
+}
+
+func pickSequence(original *yaml.Node, indices *yaml.Node) (*yaml.Node, error) {
+
+	filteredContent := make([]*yaml.Node, 0)
+	for index := 0; index < len(indices.Content); index = index + 1 {
+		_, indexInArray, err := parseInt(indices.Content[index].Value)
+		if err != nil {
+			return nil, fmt.Errorf("cannot index array with %v", indices.Content[index].Value)
+		}
+
+		if int(indexInArray) > -1 && int(indexInArray) < len(original.Content) {
+			filteredContent = append(filteredContent, deepClone(original.Content[indexInArray]))
+		}
+	}
+
+	newNode := deepCloneNoContent(original)
+	newNode.Content = filteredContent
+
+	return newNode, nil
+}
+
+func pickOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
+	log.Debugf("Pick")
+
+	contextIndicesToPick, err := d.GetMatchingNodes(context, expressionNode.RHS)
+
+	if err != nil {
+		return Context{}, err
+	}
+	indicesToPick := &yaml.Node{}
+	if contextIndicesToPick.MatchingNodes.Len() > 0 {
+		indicesToPick = contextIndicesToPick.MatchingNodes.Front().Value.(*CandidateNode).Node
+	}
+
+	var results = list.New()
+
+	for el := context.MatchingNodes.Front(); el != nil; el = el.Next() {
+		candidate := el.Value.(*CandidateNode)
+		node := unwrapDoc(candidate.Node)
+
+		var replacement *yaml.Node
+		if node.Tag == "!!map" {
+			replacement = pickMap(node, indicesToPick)
+		} else if node.Tag == "!!seq" {
+			replacement, err = pickSequence(node, indicesToPick)
+			if err != nil {
+				return Context{}, err
+			}
+
+		} else {
+			return Context{}, fmt.Errorf("cannot pick indicies from type %v (%v)", node.Tag, candidate.GetNicePath())
+		}
+
+		results.PushBack(candidate.CreateReplacement(replacement))
+	}
+
+	return context.ChildContext(results), nil
+}