feat(file) read state from stdin when s -

Using the `-s` flag, `-` is a special value now to read the input from
standard input rather than a file.

Fix #8
From #11

cmd/diff.go

@@ -56,7 +56,8 @@ that will be created or updated or deleted.
 func init() {
 	rootCmd.AddCommand(diffCmd)
 	diffCmd.Flags().StringVarP(&diffCmdKongStateFile,
-		"state", "s", "kong.yaml", "file containing Kong's configuration.")
+		"state", "s", "kong.yaml", "file containing Kong's configuration. "+
+			"Use '-' to read from stdin.")
 	diffCmd.Flags().BoolVar(&dumpConfig.SkipConsumers, "skip-consumers",
 		false, "do not diff consumers or "+
 			"any plugins associated with consumers")

cmd/sync.go

@@ -53,7 +53,8 @@ to get Kong's state in sync with the input state.`,
 func init() {
 	rootCmd.AddCommand(syncCmd)
 	syncCmd.Flags().StringVarP(&syncCmdKongStateFile,
-		"state", "s", "kong.yaml", "file containing Kong's configuration.")
+		"state", "s", "kong.yaml", "file containing Kong's configuration. "+
+			"Use '-' to read from stdin.")
 	syncCmd.Flags().BoolVar(&dumpConfig.SkipConsumers, "skip-consumers",
 		false, "do not diff consumers or "+
 			"any plugins associated with consumers")

file/reader.go

@@ -3,6 +3,7 @@ package file
 import (
 	"fmt"
 	"io/ioutil"
+	"os"
 	"strconv"
 
 	"github.com/hbagdi/deck/counter"
@@ -223,7 +224,13 @@ func GetStateFromFile(filename string) (*state.KongState, error) {
 func readFile(kongStateFile string) (*fileStructure, error) {
 
 	var s fileStructure
-	b, err := ioutil.ReadFile(kongStateFile)
+	var b []byte
+	var err error
+	if kongStateFile == "-" {
+		b, err = ioutil.ReadAll(os.Stdin)
+	} else {
+		b, err = ioutil.ReadFile(kongStateFile)
+	}
 	if err != nil {
 		return nil, err
 	}

file/reader_test.go

@@ -1,8 +1,13 @@
 package file
 
 import (
+	"bytes"
+	"io/ioutil"
+	"os"
 	"reflect"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func Test_ensureJSON(t *testing.T) {
@@ -32,3 +37,76 @@ func Test_ensureJSON(t *testing.T) {
 		})
 	}
 }
+
+func TestReadKongStateFromStdinFailsToParseText(t *testing.T) {
+	var filename = "-"
+	assert := assert.New(t)
+	assert.Equal("-", filename)
+
+	var content bytes.Buffer
+	content.Write([]byte("hunter2\n"))
+
+	tmpfile, err := ioutil.TempFile("", "example")
+	if err != nil {
+		panic(err)
+	}
+	defer os.Remove(tmpfile.Name())
+
+	if _, err := tmpfile.Write(content.Bytes()); err != nil {
+		panic(err)
+	}
+
+	if _, err := tmpfile.Seek(0, 0); err != nil {
+		panic(err)
+	}
+
+	oldStdin := os.Stdin
+	defer func() { os.Stdin = oldStdin }() // Restore original Stdin
+
+	os.Stdin = tmpfile
+
+	ks, err := GetStateFromFile(filename)
+	assert.NotNil(err)
+	assert.Nil(ks)
+}
+
+func TestReadKongStateFromStdin(t *testing.T) {
+	var filename = "-"
+	assert := assert.New(t)
+	assert.Equal("-", filename)
+
+	var content bytes.Buffer
+	content.Write([]byte("services:\n- host: test.com\n  name: test service\n"))
+
+	tmpfile, err := ioutil.TempFile("", "example")
+	if err != nil {
+		panic(err)
+	}
+	defer os.Remove(tmpfile.Name())
+
+	if _, err := tmpfile.Write(content.Bytes()); err != nil {
+		panic(err)
+	}
+
+	if _, err := tmpfile.Seek(0, 0); err != nil {
+		panic(err)
+	}
+
+	oldStdin := os.Stdin
+	defer func() { os.Stdin = oldStdin }() // Restore original Stdin
+
+	os.Stdin = tmpfile
+
+	ks, err := GetStateFromFile(filename)
+	assert.NotNil(ks)
+	assert.Nil(err)
+
+	services, err := ks.Services.GetAll()
+	if err != nil {
+		panic(err)
+	}
+	assert.Equal("test.com", *services[0].Host)
+	assert.NotEqual("not.the.same.as.test.com", *services[0].Host)
+	assert.Equal("test service", *services[0].Name)
+	assert.NotEqual("not the same as 'test service'", *services[0].Name)
+}