elvish/edit/navigation.go

package edit

import (
	"errors"
	"os"
	"path"
	"strings"
	"unicode/utf8"

	"github.com/elves/elvish/parse"
)

// Navigation subsystem.

// Interface.

type navigation struct {
	current    *navColumn
	parent     *navColumn
	dirPreview *navColumn
	showHidden bool
	filtering  bool
	filter     string
}

func (*navigation) Mode() ModeType {
	return modeNavigation
}

func (n *navigation) ModeLine(width int) *buffer {
	s := " NAVIGATING "
	if n.showHidden {
		s += "(show hidden) "
	}
	b := newBuffer(width)
	b.writes(TrimWcWidth(s, width), styleForMode)
	b.writes(" ", "")
	b.writes(n.filter, styleForFilter)
	b.dot = b.cursor()
	return b
}

func startNav(ed *Editor) {
	initNavigation(&ed.navigation)
	ed.mode = &ed.navigation
}

func navUp(ed *Editor) {
	ed.navigation.prev()
}

func navDown(ed *Editor) {
	ed.navigation.next()
}

func navPageUp(ed *Editor) {
	ed.navigation.current.pageUp()
	ed.navigation.refresh()
}

func navPageDown(ed *Editor) {
	ed.navigation.current.pageDown()
	ed.navigation.refresh()
}

func navLeft(ed *Editor) {
	ed.navigation.ascend()
}

func navRight(ed *Editor) {
	ed.navigation.descend()
}

func navTriggerShowHidden(ed *Editor) {
	ed.navigation.showHidden = !ed.navigation.showHidden
	ed.navigation.refresh()
}

func navTriggerFilter(ed *Editor) {
	ed.navigation.filtering = !ed.navigation.filtering
}

func navInsertSelected(ed *Editor) {
	ed.insertAtDot(parse.Quote(ed.navigation.current.selectedName()) + " ")
}

func navigationDefault(ed *Editor) {
	// Use key binding for insert mode without exiting nigation mode.
	k := ed.lastKey
	n := &ed.navigation
	if n.filtering && likeChar(k) {
		n.filter += k.String()
		n.refreshCurrent()
	} else if n.filtering && k == (Key{Backspace, 0}) {
		_, size := utf8.DecodeLastRuneInString(n.filter)
		if size > 0 {
			n.filter = n.filter[:len(n.filter)-size]
			n.refreshCurrent()
		}
	} else if f, ok := keyBindings[modeInsert][k]; ok {
		ed.CallFn(f)
	} else {
		ed.CallFn(keyBindings[modeInsert][Default])
	}
}

// Implementation.
// TODO(xiaq): Support file preview in navigation mode
// TODO(xiaq): Remember which file was selected in each directory.

var (
	errorEmptyCwd      = errors.New("current directory is empty")
	errorNoCwdInParent = errors.New("could not find current directory in ..")
)

func initNavigation(n *navigation) {
	*n = navigation{}
	n.refresh()
}

func (n *navigation) maintainSelected(name string) {
	n.current.selected = 0
	for i, s := range n.current.candidates {
		if s.text > name {
			break
		}
		n.current.selected = i
	}
}

func (n *navigation) refreshCurrent() {
	selectedName := n.current.selectedName()
	all, err := n.loaddir(".")
	if err != nil {
		n.current = newErrNavColumn(err)
		return
	}
	// Try to select the old selected file.
	// XXX(xiaq): This would break when we support alternative ordering.
	n.current = newNavColumn(all, func(i int) bool {
		return i == 0 || all[i].text <= selectedName
	})
	n.current.changeFilter(n.filter)
	n.maintainSelected(selectedName)
}

func (n *navigation) refreshParent() {
	wd, err := os.Getwd()
	if err != nil {
		n.parent = newErrNavColumn(err)
		return
	}
	if wd == "/" {
		n.parent = newNavColumn(nil, nil)
	} else {
		all, err := n.loaddir("..")
		if err != nil {
			n.parent = newErrNavColumn(err)
			return
		}
		cwd, err := os.Stat(".")
		if err != nil {
			n.parent = newErrNavColumn(err)
			return
		}
		n.parent = newNavColumn(all, func(i int) bool {
			d, _ := os.Lstat("../" + all[i].text)
			return os.SameFile(d, cwd)
		})
	}
}

func (n *navigation) refreshDirPreview() {
	if n.current.selected != -1 {
		name := n.current.selectedName()
		fi, err := os.Stat(name)
		if err != nil {
			n.dirPreview = newErrNavColumn(err)
			return
		}
		if fi.Mode().IsDir() {
			all, err := n.loaddir(name)
			if err != nil {
				n.dirPreview = newErrNavColumn(err)
				return
			}
			n.dirPreview = newNavColumn(all, func(int) bool { return false })
		} else {
			// TODO(xiaq): Support regular file preview in navigation mode
			n.dirPreview = nil
		}
	} else {
		n.dirPreview = nil
	}
}

// refresh rereads files in current and parent directories and maintains the
// selected file if possible.
func (n *navigation) refresh() {
	n.refreshCurrent()
	n.refreshParent()
	n.refreshDirPreview()
}

// ascend changes current directory to the parent.
// TODO(xiaq): navigation.{ascend descend} bypasses the cd builtin. This can be
// problematic if cd acquires more functionality (e.g. trigger a hook).
func (n *navigation) ascend() error {
	wd, err := os.Getwd()
	if err != nil {
		return err
	}
	if wd == "/" {
		return nil
	}

	name := n.parent.selectedName()
	err = os.Chdir("..")
	if err != nil {
		return err
	}
	n.filter = ""
	n.refresh()
	n.maintainSelected(name)
	// XXX Refresh dir preview again. We should perhaps not have used refresh
	// above.
	n.refreshDirPreview()
	return nil
}

// descend changes current directory to the selected file, if it is a
// directory.
func (n *navigation) descend() error {
	if n.current.selected == -1 {
		return errorEmptyCwd
	}
	name := n.current.selectedName()
	err := os.Chdir(name)
	if err != nil {
		return err
	}
	n.filter = ""
	n.current.selected = -1
	n.refresh()
	n.refreshDirPreview()
	return nil
}

// prev selects the previous file.
func (n *navigation) prev() {
	if n.current.selected > 0 {
		n.current.selected--
	}
	n.refresh()
}

// next selects the next file.
func (n *navigation) next() {
	if n.current.selected != -1 && n.current.selected < len(n.current.candidates)-1 {
		n.current.selected++
	}
	n.refresh()
}

func (n *navigation) loaddir(dir string) ([]styled, error) {
	f, err := os.Open(dir)
	if err != nil {
		return nil, err
	}
	infos, err := f.Readdir(0)
	if err != nil {
		return nil, err
	}
	var all []styled
	for _, info := range infos {
		if n.showHidden || info.Name()[0] != '.' {
			name := info.Name()
			all = append(all, styled{name, defaultLsColor.getStyle(path.Join(dir, name))})
		}
	}
	sortStyleds(all)

	return all, nil
}

const (
	navigationListingColMargin          = 1
	navigationListingMinWidthForPadding = 5

	parentColumnWeight  = 3.0
	currentColumnWeight = 8.0
	previewColumnWeight = 9.0
	columnWeightsSum    = parentColumnWeight + currentColumnWeight + previewColumnWeight
)

func (nav *navigation) List(width, maxHeight int) *buffer {
	margin := navigationListingColMargin

	w := width - margin*2
	ws := distributeWidths(w,
		[]float64{
			parentColumnWeight, currentColumnWeight, previewColumnWeight},
		[]int{
			nav.parent.FullWidth(maxHeight),
			nav.current.FullWidth(maxHeight),
			nav.dirPreview.FullWidth(maxHeight),
		})
	wParent, wCurrent, wPreview := ws[0], ws[1], ws[2]

	b := nav.parent.List(wParent, maxHeight)

	bCurrent := nav.current.List(wCurrent, maxHeight)
	b.extendHorizontal(bCurrent, wParent+margin)

	if wPreview > 0 {
		bPreview := nav.dirPreview.List(wPreview, maxHeight)
		b.extendHorizontal(bPreview, wParent+wCurrent+2*margin)
	}

	return b
}

// navColumn is a column in the navigation layout.
type navColumn struct {
	listing
	all        []styled
	candidates []styled
	// selected int
	err error
}

func newNavColumn(all []styled, sel func(int) bool) *navColumn {
	nc := &navColumn{all: all, candidates: all}
	nc.provider = nc
	nc.selected = -1
	for i := range all {
		if sel(i) {
			nc.selected = i
		}
	}
	return nc
}

func newErrNavColumn(err error) *navColumn {
	nc := &navColumn{err: err}
	nc.provider = nc
	return nc
}

func (nc *navColumn) Placeholder() string {
	if nc.err != nil {
		return nc.err.Error()
	}
	return ""
}

func (nc *navColumn) Len() int {
	return len(nc.candidates)
}

func (nc *navColumn) Show(i, w int) styled {
	s := nc.candidates[i]
	if w >= navigationListingMinWidthForPadding {
		return styled{" " + ForceWcWidth(s.text, w-2), s.style}
	}
	return styled{ForceWcWidth(s.text, w), s.style}
}

func (nc *navColumn) Filter(filter string) int {
	nc.candidates = nc.candidates[:0]
	for _, s := range nc.all {
		if strings.Contains(s.text, filter) {
			nc.candidates = append(nc.candidates, s)
		}
	}
	return 0
}

func (nc *navColumn) FullWidth(h int) int {
	if nc == nil {
		return 0
	}
	maxw := 0
	for _, s := range nc.candidates {
		maxw = max(maxw, WcWidths(s.text))
	}
	if maxw >= navigationListingMinWidthForPadding {
		maxw += 2
	}
	if len(nc.candidates) > h {
		maxw++
	}
	return maxw
}

func (nc *navColumn) Accept(i int, ed *Editor) {
	// TODO
}

func (nc *navColumn) ModeTitle(i int) string {
	// Not used
	return ""
}

func (nc *navColumn) selectedName() string {
	if nc == nil || nc.selected == -1 || nc.selected >= len(nc.candidates) {
		return ""
	}
	return nc.candidates[nc.selected].text
}