From 16815048d2f7f770a454597a39838e63014132f2 Mon Sep 17 00:00:00 2001
From: Brian Cully <bjc@kublai.com>
Date: Fri, 10 Jul 2015 20:16:11 +0000
Subject: Add builtin 'help' command.

Allows handlers to output helpful information.
---
 cmd_help.go      | 32 ++++++++++++++++++++++++++++++++
 cmd_help_test.go | 29 +++++++++++++++++++++++++++++
 cmd_pid.go       |  4 ++++
 cmd_ping.go      |  4 ++++
 goctl.go         |  1 +
 goctl_test.go    |  4 ++++
 6 files changed, 74 insertions(+)
 create mode 100644 cmd_help.go
 create mode 100644 cmd_help_test.go

diff --git a/cmd_help.go b/cmd_help.go
new file mode 100644
index 0000000..b14471c
--- /dev/null
+++ b/cmd_help.go
@@ -0,0 +1,32 @@
+package goctl
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+)
+
+type cmdHelp struct{}
+
+func (cmd cmdHelp) Name() string {
+	return "help"
+}
+
+func (cmd cmdHelp) Help() string {
+	return "show this message"
+}
+
+func (cmd cmdHelp) Run(gc *Goctl, args []string) string {
+	rc := []string{"Available commands:", ""}
+	cmds := []string{}
+	for _, h := range gc.handlers {
+		cmds = append(cmds, fmt.Sprintf("\t%s\t%s", h.Name(), h.Help()))
+	}
+	sort.Strings(cmds)
+	rc = append(rc, cmds...)
+	return strings.Join(rc, "\n")
+}
+
+func init() {
+	builtinHandlers = append(builtinHandlers, cmdHelp{})
+}
diff --git a/cmd_help_test.go b/cmd_help_test.go
new file mode 100644
index 0000000..9c9a930
--- /dev/null
+++ b/cmd_help_test.go
@@ -0,0 +1,29 @@
+package goctl
+
+import "testing"
+
+func TestHelp(t *testing.T) {
+	gc := start(t)
+	defer gc.Stop()
+
+	c := dial(t)
+	defer c.Close()
+
+	buf := []byte("help")
+	Write(c, buf)
+
+	buf, err := Read(c)
+	if err != nil {
+		t.Fatalf("Couldn't read from socket: %s.", err)
+	}
+
+	got := string(buf)
+	want := `Available commands:
+
+	help	show this message
+	pid	return the Unix process ID of this program
+	ping	checks whether the connection is working`
+	if got != want {
+		t.Errorf("Didn't get proper help response.\nGot:\n'%s',\nWant:\n'%s'", got, want)
+	}
+}
diff --git a/cmd_pid.go b/cmd_pid.go
index d7fd3fe..3bdb1f3 100644
--- a/cmd_pid.go
+++ b/cmd_pid.go
@@ -13,6 +13,10 @@ func (cmd cmdPID) Name() string {
 	return "pid"
 }
 
+func (cmd cmdPID) Help() string {
+	return "return the Unix process ID of this program"
+}
+
 func (cmd cmdPID) Run(_ *Goctl, _ []string) string {
 	return pid
 }
diff --git a/cmd_ping.go b/cmd_ping.go
index c052649..48294ea 100644
--- a/cmd_ping.go
+++ b/cmd_ping.go
@@ -6,6 +6,10 @@ func (cmd *cmdPing) Name() string {
 	return "ping"
 }
 
+func (cmd cmdPing) Help() string {
+	return "checks whether the connection is working"
+}
+
 func (cmd *cmdPing) Run(_ *Goctl, _ []string) string {
 	return "pong"
 }
diff --git a/goctl.go b/goctl.go
index b68734a..6379cd9 100644
--- a/goctl.go
+++ b/goctl.go
@@ -36,6 +36,7 @@ type Goctl struct {
 
 type Handler interface {
 	Name() string
+	Help() string
 	Run(*Goctl, []string) string
 }
 
diff --git a/goctl_test.go b/goctl_test.go
index dce75e7..1ab0238 100644
--- a/goctl_test.go
+++ b/goctl_test.go
@@ -22,6 +22,10 @@ func (th testHandler) Name() string {
 	return th.name
 }
 
+func (th testHandler) Help() string {
+	return ""
+}
+
 func (th testHandler) Run(gc *Goctl, args []string) string {
 	return th.fn(gc, args)
 }
-- 
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