Add -c/--config flag

Signed-off-by: Andrew Keesler <akeesler@vmware.com>

cmd/placeholder-name/app/app.go

@@ -0,0 +1,70 @@
+/*
+Copyright 2020 VMware, Inc.
+SPDX-License-Identifier: Apache-2.0
+*/
+
+// Package app is the command line entry point for placeholder-name.
+package app
+
+import (
+	"io"
+	"log"
+	"net/http"
+
+	"github.com/spf13/cobra"
+
+	"github.com/suzerain-io/placeholder-name/pkg/handlers"
+)
+
+// App is an object that represents the placeholder-name application.
+type App struct {
+	cmd *cobra.Command
+
+	// runFunc runs the actual program, after the parsing of flags has been done.
+	//
+	// It is mostly a field for the sake of testing.
+	runFunc func(configPath string)
+}
+
+// New constructs a new App with command line args, stdout and stderr.
+func New(args []string, stdout, stderr io.Writer) *App {
+	a := &App{
+		runFunc: func(configPath string) {
+			addr := ":8080"
+			log.Printf("Starting server on %v", addr)
+			log.Fatal(http.ListenAndServe(addr, handlers.New()))
+		},
+	}
+
+	var configPath string
+	cmd := &cobra.Command{
+		Use: `placeholder-name`,
+		Long: `placeholder-name provides a generic API for mapping an external
+credential from somewhere to an internal credential to be used for
+authenticating to the Kubernetes API.`,
+		Run: func(cmd *cobra.Command, args []string) {
+			a.runFunc(configPath)
+		},
+		Args: cobra.NoArgs,
+	}
+
+	cmd.SetArgs(args)
+	cmd.SetOut(stdout)
+	cmd.SetErr(stderr)
+
+	cmd.Flags().StringVarP(
+		&configPath,
+		"config",
+		"c",
+		"placeholder-name.yaml",
+		"path to configuration file",
+	)
+
+	a.cmd = cmd
+
+	return a
+}
+
+func (a *App) Run() error {
+	return a.cmd.Execute()
+}

cmd/placeholder-name/app/app_test.go

@@ -0,0 +1,84 @@
+/*
+Copyright 2020 VMware, Inc.
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package app
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+const knownGoodUsage = `Usage:
+  placeholder-name [flags]
+
+Flags:
+  -c, --config string   path to configuration file (default "placeholder-name.yaml")
+  -h, --help            help for placeholder-name
+`
+
+func TestCommand(t *testing.T) {
+	tests := []struct {
+		name string
+		args []string
+
+		wantConfigPath string
+	}{
+		{
+			name:           "NoArgsSucceeds",
+			args:           []string{},
+			wantConfigPath: "placeholder-name.yaml",
+		},
+		{
+			name: "OneArgFails",
+			args: []string{"tuna"},
+		},
+		{
+			name:           "ShortConfigFlagSucceeds",
+			args:           []string{"-c", "some/path/to/config.yaml"},
+			wantConfigPath: "some/path/to/config.yaml",
+		},
+		{
+			name:           "LongConfigFlagSucceeds",
+			args:           []string{"--config", "some/path/to/config.yaml"},
+			wantConfigPath: "some/path/to/config.yaml",
+		},
+		{
+			name: "OneArgWithConfigFlagFails",
+			args: []string{
+				"--config", "some/path/to/config.yaml",
+				"tuna",
+			},
+		},
+	}
+	for _, theTest := range tests {
+		test := theTest // please the linter :'(
+		t.Run(test.name, func(t *testing.T) {
+			expect := assert.New(t)
+
+			stdout := bytes.NewBuffer([]byte{})
+			stderr := bytes.NewBuffer([]byte{})
+
+			configPaths := make([]string, 0, 1)
+			runFunc := func(configPath string) {
+				configPaths = append(configPaths, configPath)
+			}
+
+			a := New(test.args, stdout, stderr)
+			a.runFunc = runFunc
+			err := a.Run()
+
+			if test.wantConfigPath != "" {
+				if expect.Equal(1, len(configPaths)) {
+					expect.Equal(test.wantConfigPath, configPaths[0])
+				}
+			} else {
+				expect.Error(err)
+				expect.Contains(stdout.String(), knownGoodUsage)
+			}
+		})
+	}
+}

cmd/placeholder-name/main.go

@@ -6,14 +6,13 @@ SPDX-License-Identifier: Apache-2.0
 package main
 
 import (
-	"log"
-	"net/http"
+	"os"
 
-	"github.com/suzerain-io/placeholder-name/pkg/handlers"
+	"github.com/suzerain-io/placeholder-name/cmd/placeholder-name/app"
 )
 
 func main() {
-	addr := ":8080"
-	log.Printf("Starting server on %v", addr)
-	log.Fatal(http.ListenAndServe(addr, handlers.New()))
+	if err := app.New(os.Args[1:], os.Stdout, os.Stderr).Run(); err != nil {
+		os.Exit(1)
+	}
 }