Add get command and Get function for string input

Resolves #100

Signed-off-by: Yusuke Kuoka <[email protected]>

README.md

@@ -33,12 +33,14 @@ Usage:
   vals [command]
 
 Available Commands:
-  eval		Evaluate a JSON/YAML document and replace any template expressions in it and prints the result
-  exec		Populates the environment variables and executes the command
-  env		Renders environment variables to be consumed by eval or a tool like direnv
-  ksdecode	Decode YAML document(s) by converting Secret resources' "data" to "stringData" for use with "vals eval"
-
-Use "vals [command] --help" for more information about a command
+  eval          Evaluate a JSON/YAML document and replace any template expressions in it and prints the result
+  exec          Populates the environment variables and executes the command
+  env           Renders environment variables to be consumed by eval or a tool like direnv
+  get       Evaluate a string value passed as the first argument and replace any expressiosn in it and prints the result
+  ksdecode      Decode YAML document(s) by converting Secret resources' "data" to "stringData" for use with "vals eval"
+  version       Print vals version
+
+Use "vals [command] --help" for more information about a comman
 ```
 
 `vals` has a collection of providers that each an be referred with a URI scheme looks `ref+<TYPE>`.

cmd/vals/main.go

@@ -26,6 +26,7 @@ Available Commands:
   eval		Evaluate a JSON/YAML document and replace any template expressions in it and prints the result
   exec		Populates the environment variables and executes the command
   env		Renders environment variables to be consumed by eval or a tool like direnv
+  get       Evaluate a string value passed as the first argument and replace any expressiosn in it and prints the result
   ksdecode	Decode YAML document(s) by converting Secret resources' "data" to "stringData" for use with "vals eval"
   version	Print vals version
 
@@ -72,6 +73,7 @@ func main() {
 	flag.Usage = flagUsage
 
 	CmdEval := "eval"
+	CmdGet := "get"
 	CmdExec := "exec"
 	CmdEnv := "env"
 	CmdKsDecode := "ksdecode"
@@ -112,6 +114,22 @@ func main() {
 		}
 
 		writeOrFail(o, res)
+	case CmdGet:
+		getCmd := flag.NewFlagSet(CmdGet, flag.ExitOnError)
+		getCmd.BoolVar(&log.Silent, "s", false, "Silent mode")
+		getCmd.Parse(os.Args[2:])
+
+		code := getCmd.Arg(0)
+		if code == "" {
+			fatal("The first argument of the get command is required")
+		}
+
+		v, err := vals.Get(code)
+		if err != nil {
+			fatal("%v", err)
+		}
+
+		os.Stdout.WriteString(v)
 	case CmdExec:
 		execCmd := flag.NewFlagSet(CmdExec, flag.ExitOnError)
 		f := execCmd.String("f", "", "YAML/JSON file to be loaded to set envvars")

vals.go

@@ -120,8 +120,7 @@ func New(opts Options) (*Runtime, error) {
 	return r, nil
 }
 
-// Eval replaces 'ref+<provider>://xxxxx' entries by their actual values
-func (r *Runtime) Eval(template map[string]interface{}) (map[string]interface{}, error) {
+func (r *Runtime) prepare() (*expansion.ExpandRegexMatch, error) {
 	var err error
 
 	uriToProviderHash := func(uri *url.URL) string {
@@ -360,6 +359,16 @@ func (r *Runtime) Eval(template map[string]interface{}) (map[string]interface{},
 		},
 	}
 
+	return &expand, nil
+}
+
+// Eval replaces 'ref+<provider>://xxxxx' entries by their actual values
+func (r *Runtime) Eval(template map[string]interface{}) (map[string]interface{}, error) {
+	expand, err := r.prepare()
+	if err != nil {
+		return nil, err
+	}
+
 	ret, err := expand.InMap(template)
 	if err != nil {
 		return nil, err
@@ -368,6 +377,20 @@ func (r *Runtime) Eval(template map[string]interface{}) (map[string]interface{},
 	return ret, nil
 }
 
+// Get replaces every occurrence of 'ref+<provider>://xxxxx' within a string with the fetched value
+func (r *Runtime) Get(code string) (string, error) {
+	expand, err := r.prepare()
+	if err != nil {
+		return "", err
+	}
+
+	ret, err := expand.InString(code)
+	if err != nil {
+		return "", err
+	}
+
+	return ret, nil
+}
 func cloneMap(m map[string]interface{}) map[string]interface{} {
 	bs, err := yaml.Marshal(m)
 	if err != nil {
@@ -456,6 +479,14 @@ func Eval(template map[string]interface{}, o ...Options) (map[string]interface{}
 	return runtime.Eval(template)
 }
 
+func Get(code string) (string, error) {
+	runtime, err := New(Options{})
+	if err != nil {
+		return "", err
+	}
+	return runtime.Get(code)
+}
+
 func Load(conf api.StaticConfig, opt ...Option) (map[string]interface{}, error) {
 	ctx := &ctx{}
 	for _, o := range opt {