help.go

// Copyright 2012 Jesse van den Kieboom. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package flags

import (
	"bufio"
	"fmt"
	"io"
	"strings"
	"unicode/utf8"
)

func (p *Parser) maxLongLen() (int, bool) {
	maxlonglen := 0
	hasshort := false

	for _, grp := range p.Groups {
		for _, info := range grp.Options {
			if info.ShortName != 0 {
				hasshort = true
			}

			l := utf8.RuneCountInString(info.LongName)

			if l > maxlonglen {
				maxlonglen = l
			}
		}
	}

	return maxlonglen, hasshort
}

func (p *Parser) writeHelpOption(writer *bufio.Writer, option *Option, maxlen int, hasshort bool, termcol int) {
	if option.ShortName != 0 {
		writer.WriteString("  -")
		writer.WriteRune(option.ShortName)
	} else if hasshort {
		writer.WriteString("    ")
	}

	written := 0
	prelen := 4

	if option.LongName != "" {
		if option.ShortName != 0 {
			writer.WriteString(", ")
		} else {
			writer.WriteString("  ")
		}

		fmt.Fprintf(writer, "--%s", option.LongName)
		written = utf8.RuneCountInString(option.LongName)

		prelen += written + 4
	}

	if option.Description != "" {
		if written < maxlen {
			dw := maxlen - written

			writer.WriteString(strings.Repeat(" ", dw))
			prelen += dw
		}

		def := convertToString(option.value, option.options)
		var desc string

		if def != "" {
			desc = fmt.Sprintf("%s (%v)", option.Description, def)
		} else {
			desc = option.Description
		}

		writer.WriteString(wrapText(desc,
			termcol-prelen,
			strings.Repeat(" ", prelen)))
	}

	writer.WriteString("\n")
}

// WriteHelp writes a help message containing all the possible options and
// their descriptions to the provided writer. Note that the HelpFlag parser
// option provides a convenient way to add a -h/--help option group to the
// command line parser which will automatically show the help messages using
// this method.
func (p *Parser) WriteHelp(writer io.Writer) {
	if writer == nil {
		return
	}

	wr := bufio.NewWriter(writer)

	if p.ApplicationName != "" {
		wr.WriteString("Usage:\n")
		fmt.Fprintf(wr, "  %s", p.ApplicationName)

		if p.Usage != "" {
			fmt.Fprintf(wr, " %s", p.Usage)
		}

		wr.WriteString("\n")
	}

	maxlonglen, hasshort := p.maxLongLen()
	maxlen := maxlonglen + 4

	termcol := getTerminalColumns()

	for _, grp := range p.Groups {
		wr.WriteString("\n")

		fmt.Fprintf(wr, "%s:\n", grp.Name)

		for _, info := range grp.Options {
			p.writeHelpOption(wr, info, maxlen, hasshort, termcol)
		}
	}

	wr.Flush()
}