From 1f9a3f5f6c7299317266f1c94f2a369b936c05ed Mon Sep 17 00:00:00 2001
From: Mike Farah <mike.farah@encapto.com>
Date: Mon, 13 Apr 2020 10:36:46 +1000
Subject: [PATCH] Added negative index capability

---
 cmd/commands_test.go        | 43 +++++++++++++++++++++++++++++++++++++
 pkg/yqlib/data_navigator.go | 16 +++++++++++---
 scripts/devtools.sh         |  2 +-
 3 files changed, 57 insertions(+), 4 deletions(-)

diff --git a/cmd/commands_test.go b/cmd/commands_test.go
index 3b7cb0c7..5945746e 100644
--- a/cmd/commands_test.go
+++ b/cmd/commands_test.go
@@ -201,6 +201,49 @@ func TestReadArrayCmd(t *testing.T) {
 	test.AssertResult(t, "b.e.[1].name: sam\n", result.Output)
 }
 
+func TestReadArrayBackwardsCmd(t *testing.T) {
+	content := `- one
+- two
+- three`
+	filename := test.WriteTempYamlFile(content)
+	defer test.RemoveTempYamlFile(filename)
+
+	cmd := getRootCommand()
+	result := test.RunCmd(cmd, fmt.Sprintf("read -p pv %s [-1]", filename))
+	if result.Error != nil {
+		t.Error(result.Error)
+	}
+	test.AssertResult(t, "'[-1]': three\n", result.Output)
+}
+
+func TestReadArrayBackwardsNegative0Cmd(t *testing.T) {
+	content := `- one
+- two
+- three`
+	filename := test.WriteTempYamlFile(content)
+	defer test.RemoveTempYamlFile(filename)
+
+	cmd := getRootCommand()
+	result := test.RunCmd(cmd, fmt.Sprintf("read -p pv %s [-0]", filename))
+	if result.Error != nil {
+		t.Error(result.Error)
+	}
+	test.AssertResult(t, "'[0]': one\n", result.Output)
+}
+
+func TestReadArrayBackwardsPastLimitCmd(t *testing.T) {
+	content := `- one
+- two
+- three`
+	filename := test.WriteTempYamlFile(content)
+	defer test.RemoveTempYamlFile(filename)
+
+	cmd := getRootCommand()
+	result := test.RunCmd(cmd, fmt.Sprintf("read -p pv %s [-4]", filename))
+	expectedOutput := "Error reading path in document index 0: Index [-4] out of range, array size is 3"
+	test.AssertResult(t, expectedOutput, result.Error.Error())
+}
+
 func TestReadArrayLengthCmd(t *testing.T) {
 	content := `- things
 - whatever
diff --git a/pkg/yqlib/data_navigator.go b/pkg/yqlib/data_navigator.go
index b0e0a28a..0c5211a1 100644
--- a/pkg/yqlib/data_navigator.go
+++ b/pkg/yqlib/data_navigator.go
@@ -260,11 +260,21 @@ func (n *navigator) appendArray(value *yaml.Node, head interface{}, tail []inter
 }
 
 func (n *navigator) recurseArray(value *yaml.Node, index int64, head interface{}, tail []interface{}, pathStack []interface{}) error {
-	for int64(len(value.Content)) <= index {
+	var contentLength = int64(len(value.Content))
+	for contentLength <= index {
 		value.Content = append(value.Content, &yaml.Node{Kind: guessKind(head, tail, 0)})
 	}
+	var indexToUse = index
 
-	value.Content[index] = n.getOrReplace(value.Content[index], guessKind(head, tail, value.Content[index].Kind))
+	if indexToUse < 0 {
+		indexToUse = contentLength + indexToUse
+	}
 
-	return n.doTraverse(value.Content[index], head, tail, append(pathStack, index))
+	if indexToUse < 0 {
+		return fmt.Errorf("Index [%v] out of range, array size is %v", index, contentLength)
+	}
+
+	value.Content[indexToUse] = n.getOrReplace(value.Content[indexToUse], guessKind(head, tail, value.Content[indexToUse].Kind))
+
+	return n.doTraverse(value.Content[indexToUse], head, tail, append(pathStack, index))
 }
diff --git a/scripts/devtools.sh b/scripts/devtools.sh
index cbd12f36..6e44517f 100755
--- a/scripts/devtools.sh
+++ b/scripts/devtools.sh
@@ -1,4 +1,4 @@
 #!/bin/sh
 set -e
-wget -O- -nv https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s v1.23.1
+wget -O- -nv https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s v1.24.0
 go get golang.org/x/tools/cmd/goimports
\ No newline at end of file