GCP example + support default values in prompts (#466)

Signed-off-by: David Chung <david.chung@docker.com>

Author: David Chung

examples/cli/gcp/provision-instance.ikc

@@ -1,13 +1,18 @@
 # Input to create instance using the GCP instance plugin
 {{/* =% sh %= */}}
 
-{{ $user := flag "user" "string" "owner" | prompt "Owner?" "string" }}
-{{ $prefix := flag "prefix" "string" "Prefix to use" | prompt "Prefix for hostname:" "string" }}
-{{ $diskSize := flag "disk-size" "int" "Disk size in mb" | prompt "Disk size in MB [60]?" "int"}}
-{{ $machineType := flag "machine-type" "string" "Machine type" | prompt "Machine type [n1-standard-1]?" "string"}}
+{{ $user := flag "user" "string" "owner" | prompt "Owner?" "string" (env "USER") nil }}
+{{ $prefix := flag "prefix" "string" "Prefix to use" | prompt "Prefix for hostname:" "string" (env "USER") }}
+{{ $diskSize := flag "disk-size" "int" "Disk size in mb" | prompt "Disk size in MB?" "int" 100 }}
+{{ $machineType := flag "machine-type" "string" "Machine type" | prompt "Machine type?" "string" "n1-standard-1"}}
+{{ $privateIP := flag "private-ip" "string" "Private IP" | prompt "Private IP address (IPv4)?" "string" "10.128.0.10" nil }}
+{{ $image := flag "image" "string" "Image" | prompt "Image to boot?" "string" "https://www.googleapis.com/compute/v1/projects/ubuntu-os-cloud/global/images/ubuntu-1404-trusty-v20161205" }}
+
+echo "===> Running with {{$user}}, {{$image}}, {{$privateIP}}:"
 
 infrakit --log 3 --log-stack --name instance-gcp instance provision -y - <<EOF
 
+LogicalID : {{ $privateIP }}
 Tags:
   infrakit-user: {{ $user }}
   infrakit-created: {{ now | htmlDate }}
@@ -20,11 +25,12 @@ Init: |
 
 Properties:
   NamePrefix: {{ $prefix }}
+  PrivateIP: {{ $privateIP }}
   Description: Some description
   Network: default
   MachineType: {{ $machineType }}
   DiskSizeMb: {{ $diskSize }}
-  DiskImage: https://www.googleapis.com/compute/v1/projects/ubuntu-os-cloud/global/images/ubuntu-1404-trusty-v20161205
+  DiskImage: {{ $image }}
   Scopes:
     - https://www.googleapis.com/auth/cloudruntimeconfig
     - https://www.googleapis.com/auth/logging.write

pkg/cli/local/context.go

@@ -165,11 +165,23 @@ func parseBool(text string) (bool, error) {
 	return v > 0, err
 }
 
-func (c *Context) prompt(prompt, ftype string) (interface{}, error) {
+func (c *Context) prompt(prompt, ftype string, optional ...interface{}) (interface{}, error) {
+	def, label := "", ""
+	if len(optional) > 0 {
+		def = fmt.Sprintf("%v", optional[0])
+		if def != "" {
+			label = fmt.Sprintf("[%s]", def)
+		}
+	}
+
 	input := bufio.NewReader(c.input)
-	fmt.Fprintf(os.Stderr, "%s ", prompt)
+	fmt.Fprintf(os.Stderr, "%s %s: ", prompt, label)
 	text, _ := input.ReadString('\n')
 	text = strings.Trim(text, " \t\n")
+	if len(text) == 0 {
+		text = def
+	}
+
 	switch ftype {
 	case "string":
 		return text, nil
@@ -229,10 +241,13 @@ func (c *Context) Funcs() []template.Function {
 				if !c.exec {
 					return "", nil
 				}
-				if len(optional) > 0 && !missing(ftype, optional[0]) {
-					return optional[0], nil
+				// The last value in the optional var args is the value from the previous
+				// pipeline.
+				if len(optional) > 0 && !missing(ftype, optional[len(optional)-1]) {
+					return optional[len(optional)-1], nil
 				}
-				return c.prompt(prompt, ftype)
+
+				return c.prompt(prompt, ftype, optional...)
 			},
 		},
 	}