help.go

/*
   Copyright 2014 CoreOS, Inc.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package main

import (
	"flag"
	"fmt"
	"strings"
	"text/template"

	"github.com/coreos/fleet/version"
)

const (
	// used to indicate flag usage should not be printed
	hidden = "hidden"
)

var (
	cmdHelp = &Command{
		Name:        "help",
		Summary:     "Show a list of commands or help for one command",
		Usage:       "[COMMAND]",
		Description: "Show a list of commands or detailed help for one command",
		Run:         runHelp,
	}

	globalUsageTemplate  *template.Template
	commandUsageTemplate *template.Template
	templFuncs           = template.FuncMap{
		"descToLines": func(s string) []string {
			// trim leading/trailing whitespace and split into slice of lines
			return strings.Split(strings.Trim(s, "\n\t "), "\n")
		},
		"printOption": func(name, defvalue, usage string) string {
			if usage == hidden {
				return ""
			}
			prefix := "--"
			if len(name) == 1 {
				prefix = "-"
			}
			return fmt.Sprintf("\n\t%s%s=%s\t%s", prefix, name, defvalue, usage)
		},
	}
)

func init() {
	globalUsageTemplate = template.Must(template.New("global_usage").Funcs(templFuncs).Parse(`
NAME:
{{printf "\t%s - %s" .Executable .Description}}

USAGE: 
{{printf "\t%s" .Executable}} [global options] <command> [command options] [arguments...]

VERSION:
{{printf "\t%s" .Version}}

COMMANDS:{{range .Commands}}
{{printf "\t%s\t%s" .Name .Summary}}{{end}}

GLOBAL OPTIONS:{{range .Flags}}{{printOption .Name .DefValue .Usage}}{{end}}

Global options can also be configured via upper-case environment variables prefixed with "FLEETCTL_"
For example, "some-flag" => "FLEETCTL_SOME_FLAG"

Run "{{.Executable}} help <command>" for more details on a specific command.
`[1:]))
	commandUsageTemplate = template.Must(template.New("command_usage").Funcs(templFuncs).Parse(`
NAME:
{{printf "\t%s - %s" .Cmd.Name .Cmd.Summary}}

USAGE:
{{printf "\t%s %s %s" .Executable .Cmd.Name .Cmd.Usage}}

DESCRIPTION:
{{range $line := descToLines .Cmd.Description}}{{printf "\t%s" $line}}
{{end}}
{{if .CmdFlags}}OPTIONS:{{range .CmdFlags}}
{{printOption .Name .DefValue .Usage}}{{end}}

{{end}}For help on global options run "{{.Executable}} help"
`[1:]))
}

func runHelp(args []string) (exit int) {
	if len(args) < 1 {
		printGlobalUsage()
		return
	}

	var cmd *Command

	for _, c := range commands {
		if c.Name == args[0] {
			cmd = c
			break
		}
	}

	if cmd == nil {
		stderr("Unrecognized command: %s", args[0])
		return 1
	}

	printCommandUsage(cmd)
	return
}

func printGlobalUsage() {
	globalUsageTemplate.Execute(out, struct {
		Executable  string
		Commands    []*Command
		Flags       []*flag.Flag
		Description string
		Version     string
	}{
		cliName,
		commands,
		getAllFlags(),
		cliDescription,
		version.Version,
	})
	out.Flush()
}

func printCommandUsage(cmd *Command) {
	commandUsageTemplate.Execute(out, struct {
		Executable string
		Cmd        *Command
		CmdFlags   []*flag.Flag
	}{
		cliName,
		cmd,
		getFlags(&cmd.Flags),
	})
	out.Flush()
}