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buffer.go
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buffer.go
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package prompt
import (
"strings"
"github.com/tarantool/go-prompt/internal/debug"
)
// Buffer emulates the console buffer.
type Buffer struct {
workingLines []string // The working lines. Similar to history
workingIndex int
cursorPosition int
cacheDocument *Document
preferredColumn int // Remember the original column for the next up/down movement.
lastKeyStroke Key
}
// Text returns string of the current line.
func (b *Buffer) Text() string {
return b.workingLines[b.workingIndex]
}
// NewLineCount returns the number of `\n` in the buffer text.
func (b *Buffer) NewLineCount() int {
return strings.Count(b.Text(), "\n")
}
// Document method to return document instance from the current text and cursor position.
func (b *Buffer) Document() (d *Document) {
if b.cacheDocument == nil ||
b.cacheDocument.Text != b.Text() ||
b.cacheDocument.cursorPosition != b.cursorPosition {
b.cacheDocument = &Document{
Text: b.Text(),
cursorPosition: b.cursorPosition,
}
}
b.cacheDocument.lastKey = b.lastKeyStroke
return b.cacheDocument
}
// DisplayCursorPosition returns the cursor position on rendered text on terminal emulators.
// So if Document is "日本(cursor)語", DisplayedCursorPosition returns 4 because '日' and '本' are
// double width characters.
func (b *Buffer) DisplayCursorPosition() int {
return b.Document().DisplayCursorPosition()
}
// InsertText insert string from current line.
func (b *Buffer) InsertText(v string, overwrite bool, moveCursor bool) {
or := []rune(b.Text())
oc := b.cursorPosition
if overwrite {
overwritten := string(or[oc : oc+len(v)])
if strings.Contains(overwritten, "\n") {
i := strings.IndexAny(overwritten, "\n")
overwritten = overwritten[:i]
}
b.setText(string(or[:oc]) + v + string(or[oc+len(overwritten):]))
} else {
b.setText(string(or[:oc]) + v + string(or[oc:]))
}
if moveCursor {
b.cursorPosition += len([]rune(v))
}
}
// SetText method to set text and update cursorPosition.
// (When doing this, make sure that the cursor_position is valid for this text.
// text/cursor_position should be consistent at any time, otherwise set a Document instead.)
func (b *Buffer) setText(v string) {
debug.Assert(b.cursorPosition <= len([]rune(v)),
"length of input should be shorter than cursor position")
// replace CR with LF
v = strings.ReplaceAll(v, "\r", "\n")
b.workingLines[b.workingIndex] = v
}
// Set cursor position. Return whether it changed.
func (b *Buffer) setCursorPosition(p int) {
if p > 0 {
b.cursorPosition = p
} else {
b.cursorPosition = 0
}
}
func (b *Buffer) setDocument(d *Document) {
b.cacheDocument = d
b.setCursorPosition(d.cursorPosition) // Call before setText because setText check the relation
// between cursorPosition and line length.
b.setText(d.Text)
}
// CursorLeft move to left on the current line.
func (b *Buffer) CursorLeft(count int) {
l := b.Document().GetCursorLeftPosition(count)
b.cursorPosition += l
}
// CursorRight move to right on the current line.
func (b *Buffer) CursorRight(count int) {
l := b.Document().GetCursorRightPosition(count)
b.cursorPosition += l
}
// CursorUp move cursor to the previous line.
// (for multi-line edit).
func (b *Buffer) CursorUp(count int) {
defer debug.Un(debug.Trace("CursorUp", count))
orig := b.preferredColumn
if b.preferredColumn == -1 { // -1 means nil
orig = b.Document().CursorPositionCol()
}
b.cursorPosition += b.Document().GetCursorUpPosition(count, orig)
// Remember the original column for the next up/down movement.
b.preferredColumn = orig
}
// CursorDown move cursor to the next line.
// (for multi-line edit).
func (b *Buffer) CursorDown(count int) {
orig := b.preferredColumn
if b.preferredColumn == -1 { // -1 means nil
orig = b.Document().CursorPositionCol()
}
b.cursorPosition += b.Document().GetCursorDownPosition(count, orig)
// Remember the original column for the next up/down movement.
b.preferredColumn = orig
}
// DeleteBeforeCursor deletes specified number of characters before cursor
// and returns the deleted text.
func (b *Buffer) DeleteBeforeCursor(count int) (deleted string) {
debug.Assert(count >= 0, "count should be positive")
r := []rune(b.Text())
if b.cursorPosition > 0 {
start := b.cursorPosition - count
if start < 0 {
start = 0
}
deleted = string(r[start:b.cursorPosition])
b.setDocument(&Document{
Text: string(r[:start]) + string(r[b.cursorPosition:]),
cursorPosition: b.cursorPosition - len([]rune(deleted)),
})
}
return
}
// NewLine means CR.
func (b *Buffer) NewLine(copyMargin bool) {
if copyMargin {
b.InsertText("\n"+b.Document().leadingWhitespaceInCurrentLine(), false, true)
} else {
b.InsertText("\n", false, true)
}
}
// Delete specified number of characters and Return the deleted text.
func (b *Buffer) Delete(count int) (deleted string) {
r := []rune(b.Text())
if b.cursorPosition < len(r) {
deleted = b.Document().TextAfterCursor()[:count]
b.setText(string(r[:b.cursorPosition]) + string(r[b.cursorPosition+len(deleted):]))
}
return
}
// JoinNextLine joins the next line to the current one by deleting the line ending after the
// current line.
func (b *Buffer) JoinNextLine(separator string) {
if !b.Document().OnLastLine() {
b.cursorPosition += b.Document().GetEndOfLinePosition()
b.Delete(1)
// Remove spaces
b.setText(b.Document().TextBeforeCursor() + separator +
strings.TrimLeft(b.Document().TextAfterCursor(), " "))
}
}
// SwapCharactersBeforeCursor swaps the last two characters before the cursor.
func (b *Buffer) SwapCharactersBeforeCursor() {
if b.cursorPosition >= 2 {
x := b.Text()[b.cursorPosition-2 : b.cursorPosition-1]
y := b.Text()[b.cursorPosition-1 : b.cursorPosition]
b.setText(b.Text()[:b.cursorPosition-2] + y + x + b.Text()[b.cursorPosition:])
}
}
// SplitWideLines splits lines, whose width is greater than maxWidth to multiple lines.
func (b *Buffer) SplitWideLines(maxWidth int) *Buffer {
textLines := b.Document().Lines()
processedText := strings.Builder{}
currentCursor := 0
cmdCursor := b.cursorPosition
cmdCursorDelta := 0
for _, line := range textLines {
runes := []rune(line)
for j := 0; j < len(runes); j += maxWidth {
size := len(runes) - j
if size > maxWidth {
size = maxWidth
}
processedText.WriteString(string(runes[j : j+size]))
processedText.WriteByte('\n')
if currentCursor+size-1 < cmdCursor && j+size < len(runes) {
// Shifts cursor because of the extra `\n`.
cmdCursorDelta++
}
currentCursor += size
}
if len(runes) == 0 {
processedText.WriteByte('\n')
}
currentCursor++
}
resultStr := processedText.String()
// Remove extra `\n`
resultStr = resultStr[:len(resultStr)-1]
result := NewBuffer()
result.InsertText(resultStr, false, true)
result.setCursorPosition(cmdCursor + cmdCursorDelta)
return result
}
// ReplaceTabs replaces all `\t` characters with spaces.
func (b *Buffer) ReplaceTabs(tabWidth int) *Buffer {
processedText := strings.Builder{}
runes := []rune(b.Text())
processedText.Grow(len(runes))
cmdCursor := b.cursorPosition
cursorDelta := 0
for cursor, r := range runes {
if r == rune('\t') {
for j := 0; j < tabWidth; j++ {
processedText.WriteByte(' ')
}
if cursor < cmdCursor {
cursorDelta += tabWidth - 1
}
} else {
processedText.WriteRune(r)
}
}
result := NewBuffer()
result.InsertText(processedText.String(), false, true)
result.setCursorPosition(cmdCursor + cursorDelta)
return result
}
// NewBuffer is constructor of Buffer struct.
func NewBuffer() (b *Buffer) {
b = &Buffer{
workingLines: []string{""},
workingIndex: 0,
preferredColumn: -1, // -1 means nil
}
return
}