prompt.go

// Copyright 2015 Lukas Weber. All rights reserved.
// Use of this source code is governed by the MIT-styled
// license that can be found in the LICENSE file.

package main

import (
	"github.com/laochailan/barely/completion"
	"strings"

	termbox "github.com/nsf/termbox-go"
)

// completionContext keeps track of the current completion attempt.
// It saves the matching results and chooses the next result when cycling
// through them.
type completionContext struct {
	matches  []string
	matchIdx int
}

func (cc *completionContext) query(str []rune) (result []rune) {
	sstr := string(str)

	// Don’t do file path completion if the command is not yet finished.
	if strings.LastIndex(sstr, " ") == -1 {
		return str
	}

	// if the prompt was not changed and there is more than one result,
	// cycle through results
	if len(cc.matches) > 1 && sstr == cc.matches[cc.matchIdx] {
		if cc.matchIdx++; cc.matchIdx >= len(cc.matches) {
			cc.matchIdx = 0
		}
		return []rune(cc.matches[cc.matchIdx])
	}

	cc.matchIdx = 0
	cc.matches = completion.Query(sstr)

	if cc.matches == nil {
		return str
	}

	return []rune(cc.matches[cc.matchIdx])
}

// Prompt represents the command prompt at the bottom of the screen.
type Prompt struct {
	text   []rune
	cursor int

	compCont completionContext
}

// Active returns true if the prompt is on and false if it is off.
func (p *Prompt) Active() bool {
	return p.text != nil
}

// Draw draws the prompt.
func (p *Prompt) Draw() {
	w, h := termbox.Size()
	printLine(0, h-1, ":"+string(p.text)+" ", -1, -1)
	termbox.SetCursor(p.cursor+1, h-1)
	if p.text == nil {
		termbox.HideCursor()
		printLine(0, h-1, " ", -1, -1)
	}
	for x := len(p.text) + 1; x < w; x++ {
		termbox.CellBuffer()[(h-1)*w+x].Ch = 0
	}
}

func (p *Prompt) putChar(ch rune) {
	tail := make([]rune, len(p.text)-p.cursor)
	copy(tail, p.text[p.cursor:])

	p.text = append(p.text[:p.cursor], ch)
	p.text = append(p.text, tail...)
	p.cursor++
}

func (p *Prompt) delChar() {
	if p.cursor > 0 {
		copy(p.text[p.cursor-1:], p.text[p.cursor:])
		p.text = p.text[:len(p.text)-1]
		p.cursor--
	}
}

// HandleEvent handles termbox events. If the prompt is active, key bindings do not work
// and this function gets all the key events.
func (p *Prompt) HandleEvent(e *termbox.Event) (string, []string) {
	if e.Ch == 0 {
		switch e.Key {
		case termbox.KeyEsc:
			p.text = nil
			p.Draw()
		case termbox.KeyEnter:
			fields := strings.Fields(string(p.text))
			p.text = nil
			p.Draw()
			if len(fields) > 0 {
				return fields[0], fields[1:]
			}
		case termbox.KeyBackspace2:
			p.delChar()
		case termbox.KeyDelete:
			if p.cursor < len(p.text) {
				p.cursor++
				p.delChar()
			}
		case termbox.KeyArrowLeft:
			p.cursor--
		case termbox.KeyArrowRight:
			p.cursor++
		case termbox.KeySpace:
			p.putChar(' ')
		case termbox.KeyTab:
			p.text = p.compCont.query(p.text)
			p.cursor = len(p.text)
		}
	} else {
		p.putChar(e.Ch)
	}

	switch {
	case p.cursor < 0:
		p.cursor = 0
	case p.cursor > len(p.text):
		p.cursor = len(p.text)
	}
	p.Draw()
	return "", nil
}

// Activate switches on the prompt with an initial string.
func (p *Prompt) Activate(startstr string) {
	p.text = append(p.text, []rune(startstr+" ")...)
	if startstr == "" {
		p.text = p.text[:0]
	}
	p.cursor = len(p.text)
	p.Draw()
}