From eeb16443d4a436c3d2ed77505ebfcab0cd01081e Mon Sep 17 00:00:00 2001
From: Mike Farah <mikefarah@gmail.com>
Date: Tue, 29 Sep 2015 10:56:28 +1000
Subject: [PATCH] Can update simple properties (to stdout)

---
 yaml.go      | 26 ++++++++++++++++++++++++++
 yaml_test.go | 11 +++++++++++
 2 files changed, 37 insertions(+)

diff --git a/yaml.go b/yaml.go
index ff15e965..d116fb87 100644
--- a/yaml.go
+++ b/yaml.go
@@ -22,6 +22,12 @@ func main() {
 			Usage:   "read <filename> <path>\n\te.g.: yaml read sample.json a.b.c\n\t(default) reads a property from a given yaml file",
 			Action:  readProperty,
 		},
+		{
+			Name:    "write",
+			Aliases: []string{"w"},
+			Usage:   "write <filename> <path> <value>\n\te.g.: yaml write sample.json a.b.c 5\n\tupdates a property from a given yaml file, outputs to stdout",
+			Action:  writeProperty,
+		},
 	}
 	app.Action = readProperty
 	app.Run(os.Args)
@@ -37,6 +43,18 @@ func readProperty(c *cli.Context) {
 	printYaml(readMap(parsedData, paths[0], paths[1:len(paths)]))
 }
 
+func writeProperty(c *cli.Context) {
+	var parsedData map[interface{}]interface{}
+	readYaml(c, &parsedData)
+
+	var path = c.Args()[1]
+	var paths = strings.Split(path, ".")
+
+	write(parsedData, paths[0], paths[1:len(paths)], c.Args()[2])
+
+	printYaml(parsedData)
+}
+
 func printYaml(context interface{}) {
   out, err := yaml.Marshal(context)
   if err != nil {
@@ -70,6 +88,14 @@ func readFile(filename string) []byte {
 	return rawData
 }
 
+func write(context map[interface{}]interface{}, head string, tail []string, value interface{}) {
+	// e.g. if updating a.b.c, we need to get the 'b' map...
+	toUpdate := readMap(context, head, tail[0:len(tail)-1]).(map[interface{}]interface{})
+	//  and then set the 'c' key.
+	key := (tail[len(tail)-1])
+	toUpdate[key] = value
+}
+
 func readMap(context map[interface{}]interface{}, head string, tail []string) interface{} {
 	value := context[head]
 	if len(tail) > 0 {
diff --git a/yaml_test.go b/yaml_test.go
index ce53d7b9..4f276887 100644
--- a/yaml_test.go
+++ b/yaml_test.go
@@ -39,3 +39,14 @@ func TestReadMap_array(t *testing.T) {
 		t.Error("Excpted 4 but got ", result)
 	}
 }
+
+func TestWrite_simple(t *testing.T) {
+
+	write(parsedData, "b", []string{"c"}, "4")
+
+	b := parsedData["b"].(map[interface{}]interface{})
+	c := b["c"].(string)
+	if c != "4" {
+		t.Error("Excepted 4 but got ", c)
+	}
+}