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package main
import (
"unicode"
"github.com/pkg/errors"
"github.com/prodhe/poe/gapbuffer"
)
type Text struct {
buf *gapbuffer.Buffer
cursorpos int
p0, p1 int // not implemented
history History
}
// Sync synchronizes the underlying buffer with the cursor position. This should be called before every call that manipulates data in the buffer.
func (t *Text) Sync() {
t.buf.Seek(t.cursorpos)
}
func (t *Text) Write(p []byte) (int, error) {
c := Change{t.cursorpos, ActionInsert, p}
n, err := t.commit(c)
if err != nil {
return n, err
}
t.history.Do(c)
return n, nil
}
func (t *Text) Delete() (int, error) {
if t.cursorpos <= 0 {
return 0, errors.New("out of range")
}
b, _ := t.buf.ByteAt(t.cursorpos - 1)
c := Change{t.cursorpos, ActionDelete, []byte{b}}
n, err := t.commit(c)
if err != nil {
return n, err
}
t.history.Do(c)
return n, nil
}
func (t *Text) Undo() error {
change, err := t.history.Undo()
if err != nil {
return errors.Wrap(err, "undo")
}
t.commit(change)
return nil
}
func (t *Text) Redo() error {
change, err := t.history.Redo()
if err != nil {
return errors.Wrap(err, "redo")
}
t.commit(change)
return nil
}
func (t *Text) commit(c Change) (int, error) {
switch c.action {
case ActionInsert:
t.SetCursor(c.offset, 0)
t.Sync()
n, err := t.buf.Write(c.content)
if err != nil {
return 0, err
}
t.SetCursor(n, 1)
return n, err
case ActionDelete:
t.SetCursor(c.offset, 0)
t.Sync()
var ds []byte
for i := c.offset; i <= c.offset; i++ {
ds = append(ds, t.buf.Delete())
}
t.SetCursor(len(ds), -1)
return len(ds), nil
default:
return 0, errors.New("invalid action in change")
}
}
// WordOffset returns the absolute offset for the beginning of the word and the end. A word is a letter/digit sequence of bytes separated by anything else. It scans from the current cursor position.
func (t *Text) WordOffset() (start, end int) {
start, end = t.cursorpos, t.cursorpos
c, _ := t.buf.ByteAt(start)
for unicode.IsLetter(rune(c)) || unicode.IsDigit(rune(c)) {
start--
c, _ = t.buf.ByteAt(start)
}
if start < t.cursorpos {
start++
}
c, _ = t.buf.ByteAt(end)
for unicode.IsLetter(rune(c)) || unicode.IsDigit(rune(c)) {
end++
c, _ = t.buf.ByteAt(end)
}
return start, end
}
// NextNL returns number of bytes from given position to the nearest next new line.
func (t *Text) NextNL(start int) int {
if start >= t.buf.Len() {
return 0
}
n := start
offset := 0
if c, _ := t.buf.ByteAt(n); c == '\n' {
n++
offset++
}
for {
c, _ := t.buf.ByteAt(n)
if c == '\n' || n >= t.buf.Len() {
break
}
n++
offset++
}
return offset
}
// PrevNL returns number of bytes from given position to the nearest new line backwards.
func (t *Text) PrevNL(start int) int {
if start == 0 {
return 0
}
if start > t.buf.Len() {
start = t.buf.Len() - 1
}
n := start - 1
offset := 1
if c, _ := t.buf.ByteAt(n); c == '\n' {
return offset
}
for {
c, _ := t.buf.ByteAt(n)
if c == '\n' || n == 0 {
break
}
n--
offset++
}
return offset
}
// SetCursor moves the cursor to different offsets in the text buffer.
//
// A negative whence is backwards from current position, a positive whence is forward and a zero whence sets the absolute position from the start of the buffer.
func (t *Text) SetCursor(pos, whence int) {
switch whence {
case -1:
t.cursorpos -= pos
case 0:
t.cursorpos = pos
case 1:
t.cursorpos += pos
}
// check out of range
if t.cursorpos < 0 {
t.cursorpos = 0
}
if t.cursorpos >= t.buf.Len() {
t.cursorpos = t.buf.Len()
}
}
/* History */
type Action int
const (
ActionInsert Action = iota
ActionDelete
)
type Change struct {
offset int
action Action
content []byte
}
type History struct {
done []Change
recall []Change
}
func (h *History) Do(c Change) {
h.done = append(h.done, c)
h.recall = nil // clear old recall stack on new do
}
func (h *History) Undo() (Change, error) {
if len(h.done) == 0 {
return Change{}, errors.New("no history")
}
lastdone := h.done[len(h.done)-1]
h.recall = append(h.recall, lastdone)
h.done = h.done[:len(h.done)-1] // remove last one
// Reverse the done action so the returned change can be applied directly.
switch lastdone.action {
case ActionInsert:
lastdone.action = ActionDelete
lastdone.offset += len(lastdone.content)
case ActionDelete:
lastdone.action = ActionInsert
lastdone.offset -= len(lastdone.content)
}
return lastdone, nil
}
func (h *History) Redo() (Change, error) {
if len(h.recall) == 0 {
return Change{}, errors.New("no recall history")
}
lastrecall := h.recall[len(h.recall)-1]
h.done = append(h.done, lastrecall)
h.recall = h.recall[:len(h.recall)-1] //remove last one
return lastrecall, nil
}
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