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runereader.go
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runereader.go
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package terminal
import (
"fmt"
"unicode"
"golang.org/x/text/width"
)
type RuneReader struct {
stdio Stdio
cursor *Cursor
state runeReaderState
}
func NewRuneReader(stdio Stdio) *RuneReader {
return &RuneReader{
stdio: stdio,
state: newRuneReaderState(stdio.In),
}
}
func (rr *RuneReader) printChar(char rune, mask rune) {
// if we don't need to mask the input
if mask == 0 {
// just print the character the user pressed
fmt.Fprintf(rr.stdio.Out, "%c", char)
} else {
// otherwise print the mask we were given
fmt.Fprintf(rr.stdio.Out, "%c", mask)
}
}
func (rr *RuneReader) ReadLine(mask rune) ([]rune, error) {
line := []rune{}
// we only care about horizontal displacements from the origin so start counting at 0
index := 0
cursor := &Cursor{
In: rr.stdio.In,
Out: rr.stdio.Out,
}
// we get the terminal width and height (if resized after this point the property might become invalid)
terminalSize, _ := cursor.Size(rr.Buffer())
// we set the current location of the cursor once
cursorCurrent, _ := cursor.Location(rr.Buffer())
increment := func() {
if cursorCurrent.CursorIsAtLineEnd(terminalSize) {
cursorCurrent.X = COORDINATE_SYSTEM_BEGIN
cursorCurrent.Y++
} else {
cursorCurrent.X++
}
}
decrement := func() {
if cursorCurrent.CursorIsAtLineBegin() {
cursorCurrent.X = terminalSize.X
cursorCurrent.Y--
} else {
cursorCurrent.X--
}
}
for {
// wait for some input
r, _, err := rr.ReadRune()
if err != nil {
return line, err
}
// if the user pressed enter or some other newline/termination like ctrl+d
if r == '\r' || r == '\n' || r == KeyEndTransmission {
// delete what's printed out on the console screen (cleanup)
for index > 0 {
if cursorCurrent.CursorIsAtLineBegin() {
EraseLine(rr.stdio.Out, ERASE_LINE_END)
cursor.PreviousLine(1)
cursor.Forward(int(terminalSize.X))
} else {
cursor.Back(1)
}
decrement()
index--
}
// move the cursor the a new line
cursor.MoveNextLine(cursorCurrent, terminalSize)
// we're done processing the input
return line, nil
}
// if the user interrupts (ie with ctrl+c)
if r == KeyInterrupt {
// go to the beginning of the next line
fmt.Fprint(rr.stdio.Out, "\r\n")
// we're done processing the input, and treat interrupt like an error
return line, InterruptErr
}
// allow for backspace/delete editing of inputs
if r == KeyBackspace || r == KeyDelete {
// and we're not at the beginning of the line
if index > 0 && len(line) > 0 {
// if we are at the end of the word
if index == len(line) {
// just remove the last letter from the internal representation
// also count the number of cells the rune before the cursor occupied
cells := runeWidth(line[len(line)-1])
line = line[:len(line)-1]
// go back one
if cursorCurrent.X == 1 {
cursor.PreviousLine(1)
cursor.Forward(int(terminalSize.X))
} else {
cursor.Back(cells)
}
// clear the rest of the line
EraseLine(rr.stdio.Out, ERASE_LINE_END)
} else {
// we need to remove a character from the middle of the word
cells := runeWidth(line[index-1])
// remove the current index from the list
line = append(line[:index-1], line[index:]...)
// save the current position of the cursor, as we have to move the cursor one back to erase the current symbol
// and then move the cursor for each symbol in line[index-1:] to print it out, afterwards we want to restore
// the cursor to its previous location.
cursor.Save()
// clear the rest of the line
cursor.Back(cells)
// print what comes after
for _, char := range line[index-1:] {
//Erase symbols which are left over from older print
EraseLine(rr.stdio.Out, ERASE_LINE_END)
// print characters to the new line appropriately
rr.printChar(char, mask)
}
// erase what's left over from last print
if cursorCurrent.Y < terminalSize.Y {
cursor.NextLine(1)
EraseLine(rr.stdio.Out, ERASE_LINE_END)
}
// restore cursor
cursor.Restore()
if cursorCurrent.CursorIsAtLineBegin() {
cursor.PreviousLine(1)
cursor.Forward(int(terminalSize.X))
} else {
cursor.Back(cells)
}
}
// decrement the index
index--
decrement()
} else {
// otherwise the user pressed backspace while at the beginning of the line
soundBell(rr.stdio.Out)
}
// we're done processing this key
continue
}
// if the left arrow is pressed
if r == KeyArrowLeft {
// if we have space to the left
if index > 0 {
//move the cursor to the prev line if necessary
if cursorCurrent.CursorIsAtLineBegin() {
cursor.PreviousLine(1)
cursor.Forward(int(terminalSize.X))
} else {
cursor.Back(runeWidth(line[index-1]))
}
//decrement the index
index--
decrement()
} else {
// otherwise we are at the beginning of where we started reading lines
// sound the bell
soundBell(rr.stdio.Out)
}
// we're done processing this key press
continue
}
// if the right arrow is pressed
if r == KeyArrowRight {
// if we have space to the right
if index < len(line) {
// move the cursor to the next line if necessary
if cursorCurrent.CursorIsAtLineEnd(terminalSize) {
cursor.NextLine(1)
} else {
cursor.Forward(runeWidth(line[index]))
}
index++
increment()
} else {
// otherwise we are at the end of the word and can't go past
// sound the bell
soundBell(rr.stdio.Out)
}
// we're done processing this key press
continue
}
// the user pressed one of the special keys
if r == SpecialKeyHome {
for index > 0 {
if cursorCurrent.CursorIsAtLineBegin() {
cursor.PreviousLine(1)
cursor.Forward(int(terminalSize.X))
cursorCurrent.Y--
cursorCurrent.X = terminalSize.X
} else {
cursor.Back(runeWidth(line[index-1]))
cursorCurrent.X -= Short(runeWidth(line[index-1]))
}
index--
}
continue
// user pressed end
} else if r == SpecialKeyEnd {
for index != len(line) {
if cursorCurrent.CursorIsAtLineEnd(terminalSize) {
cursor.NextLine(1)
cursorCurrent.Y++
cursorCurrent.X = COORDINATE_SYSTEM_BEGIN
} else {
cursor.Forward(runeWidth(line[index]))
cursorCurrent.X += Short(runeWidth(line[index]))
}
index++
}
continue
// user pressed forward delete key
} else if r == SpecialKeyDelete {
// if index at the end of the line nothing to delete
if index != len(line) {
// save the current position of the cursor, as we have to erase the current symbol
// and then move the cursor for each symbol in line[index:] to print it out, afterwards we want to restore
// the cursor to its previous location.
cursor.Save()
// remove the symbol after the cursor
line = append(line[:index], line[index+1:]...)
// print the updated line
for _, char := range line[index:] {
EraseLine(rr.stdio.Out, ERASE_LINE_END)
// print out the character
rr.printChar(char, mask)
}
// erase what's left on last line
if cursorCurrent.Y < terminalSize.Y {
cursor.NextLine(1)
EraseLine(rr.stdio.Out, ERASE_LINE_END)
}
// restore cursor
cursor.Restore()
if len(line) == 0 || index == len(line) {
EraseLine(rr.stdio.Out, ERASE_LINE_END)
}
}
continue
}
// if the letter is another escape sequence
if unicode.IsControl(r) || r == IgnoreKey {
// ignore it
continue
}
// the user pressed a regular key
// if we are at the end of the line
if index == len(line) {
// just append the character at the end of the line
line = append(line, r)
// save the location of the cursor
index++
increment()
// print out the character
rr.printChar(r, mask)
} else {
// we are in the middle of the word so we need to insert the character the user pressed
line = append(line[:index], append([]rune{r}, line[index:]...)...)
// save the current position of the cursor, as we have to move the cursor back to erase the current symbol
// and then move for each symbol in line[index:] to print it out, afterwards we want to restore
// cursor's location to its previous one.
cursor.Save()
EraseLine(rr.stdio.Out, ERASE_LINE_END)
// remove the symbol after the cursor
// print the updated line
for _, char := range line[index:] {
EraseLine(rr.stdio.Out, ERASE_LINE_END)
// print out the character
rr.printChar(char, mask)
increment()
}
// if we are at the last line, we want to visually insert a new line and append to it.
if cursorCurrent.CursorIsAtLineEnd(terminalSize) && cursorCurrent.Y == terminalSize.Y {
// add a new line to the terminal
fmt.Fprintln(rr.stdio.Out)
// restore the position of the cursor horizontally
cursor.Restore()
// restore the position of the cursor vertically
cursor.PreviousLine(1)
} else {
// restore cursor
cursor.Restore()
}
// check if cursor needs to move to next line
cursorCurrent, _ = cursor.Location(rr.Buffer())
if cursorCurrent.CursorIsAtLineEnd(terminalSize) {
cursor.NextLine(1)
} else {
cursor.Forward(runeWidth(r))
}
// increment the index
index++
increment()
}
}
}
func runeWidth(r rune) int {
switch width.LookupRune(r).Kind() {
case width.EastAsianWide, width.EastAsianFullwidth:
return 2
}
return 1
}