Subversion Repositories openrisc

// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package terminal

import (
        "io"
        "sync"
)

// EscapeCodes contains escape sequences that can be written to the terminal in
// order to achieve different styles of text.
type EscapeCodes struct {
        // Foreground colors
        Black, Red, Green, Yellow, Blue, Magenta, Cyan, White []byte

        // Reset all attributes
        Reset []byte
}

var vt100EscapeCodes = EscapeCodes{
        Black:   []byte{keyEscape, '[', '3', '0', 'm'},
        Red:     []byte{keyEscape, '[', '3', '1', 'm'},
        Green:   []byte{keyEscape, '[', '3', '2', 'm'},
        Yellow:  []byte{keyEscape, '[', '3', '3', 'm'},
        Blue:    []byte{keyEscape, '[', '3', '4', 'm'},
        Magenta: []byte{keyEscape, '[', '3', '5', 'm'},
        Cyan:    []byte{keyEscape, '[', '3', '6', 'm'},
        White:   []byte{keyEscape, '[', '3', '7', 'm'},

        Reset: []byte{keyEscape, '[', '0', 'm'},
}

// Terminal contains the state for running a VT100 terminal that is capable of
// reading lines of input.
type Terminal struct {
        // AutoCompleteCallback, if non-null, is called for each keypress
        // with the full input line and the current position of the cursor.
        // If it returns a nil newLine, the key press is processed normally.
        // Otherwise it returns a replacement line and the new cursor position.
        AutoCompleteCallback func(line []byte, pos, key int) (newLine []byte, newPos int)

        // Escape contains a pointer to the escape codes for this terminal.
        // It's always a valid pointer, although the escape codes themselves
        // may be empty if the terminal doesn't support them.
        Escape *EscapeCodes

        // lock protects the terminal and the state in this object from
        // concurrent processing of a key press and a Write() call.
        lock sync.Mutex

        c      io.ReadWriter
        prompt string

        // line is the current line being entered.
        line []byte
        // pos is the logical position of the cursor in line
        pos int
        // echo is true if local echo is enabled
        echo bool

        // cursorX contains the current X value of the cursor where the left
        // edge is 0. cursorY contains the row number where the first row of
        // the current line is 0.
        cursorX, cursorY int
        // maxLine is the greatest value of cursorY so far.
        maxLine int

        termWidth, termHeight int

        // outBuf contains the terminal data to be sent.
        outBuf []byte
        // remainder contains the remainder of any partial key sequences after
        // a read. It aliases into inBuf.
        remainder []byte
        inBuf     [256]byte
}

// NewTerminal runs a VT100 terminal on the given ReadWriter. If the ReadWriter is
// a local terminal, that terminal must first have been put into raw mode.
// prompt is a string that is written at the start of each input line (i.e.
// "> ").
func NewTerminal(c io.ReadWriter, prompt string) *Terminal {
        return &Terminal{
                Escape:     &vt100EscapeCodes,
                c:          c,
                prompt:     prompt,
                termWidth:  80,
                termHeight: 24,
                echo:       true,
        }
}

const (
        keyCtrlD     = 4
        keyEnter     = '\r'
        keyEscape    = 27
        keyBackspace = 127
        keyUnknown   = 256 + iota
        keyUp
        keyDown
        keyLeft
        keyRight
        keyAltLeft
        keyAltRight
)

// bytesToKey tries to parse a key sequence from b. If successful, it returns
// the key and the remainder of the input. Otherwise it returns -1.
func bytesToKey(b []byte) (int, []byte) {
        if len(b) == 0 {
                return -1, nil
        }

        if b[0] != keyEscape {
                return int(b[0]), b[1:]
        }

        if len(b) >= 3 && b[0] == keyEscape && b[1] == '[' {
                switch b[2] {
                case 'A':
                        return keyUp, b[3:]
                case 'B':
                        return keyDown, b[3:]
                case 'C':
                        return keyRight, b[3:]
                case 'D':
                        return keyLeft, b[3:]
                }
        }

        if len(b) >= 6 && b[0] == keyEscape && b[1] == '[' && b[2] == '1' && b[3] == ';' && b[4] == '3' {
                switch b[5] {
                case 'C':
                        return keyAltRight, b[6:]
                case 'D':
                        return keyAltLeft, b[6:]
                }
        }

        // If we get here then we have a key that we don't recognise, or a
        // partial sequence. It's not clear how one should find the end of a
        // sequence without knowing them all, but it seems that [a-zA-Z] only
        // appears at the end of a sequence.
        for i, c := range b[0:] {
                if c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' {
                        return keyUnknown, b[i+1:]
                }
        }

        return -1, b
}

// queue appends data to the end of t.outBuf
func (t *Terminal) queue(data []byte) {
        t.outBuf = append(t.outBuf, data...)
}

var eraseUnderCursor = []byte{' ', keyEscape, '[', 'D'}
var space = []byte{' '}

func isPrintable(key int) bool {
        return key >= 32 && key < 127
}

// moveCursorToPos appends data to t.outBuf which will move the cursor to the
// given, logical position in the text.
func (t *Terminal) moveCursorToPos(pos int) {
        if !t.echo {
                return
        }

        x := len(t.prompt) + pos
        y := x / t.termWidth
        x = x % t.termWidth

        up := 0
        if y < t.cursorY {
                up = t.cursorY - y
        }

        down := 0
        if y > t.cursorY {
                down = y - t.cursorY
        }

        left := 0
        if x < t.cursorX {
                left = t.cursorX - x
        }

        right := 0
        if x > t.cursorX {
                right = x - t.cursorX
        }

        t.cursorX = x
        t.cursorY = y
        t.move(up, down, left, right)
}

func (t *Terminal) move(up, down, left, right int) {
        movement := make([]byte, 3*(up+down+left+right))
        m := movement
        for i := 0; i < up; i++ {
                m[0] = keyEscape
                m[1] = '['
                m[2] = 'A'
                m = m[3:]
        }
        for i := 0; i < down; i++ {
                m[0] = keyEscape
                m[1] = '['
                m[2] = 'B'
                m = m[3:]
        }
        for i := 0; i < left; i++ {
                m[0] = keyEscape
                m[1] = '['
                m[2] = 'D'
                m = m[3:]
        }
        for i := 0; i < right; i++ {
                m[0] = keyEscape
                m[1] = '['
                m[2] = 'C'
                m = m[3:]
        }

        t.queue(movement)
}

func (t *Terminal) clearLineToRight() {
        op := []byte{keyEscape, '[', 'K'}
        t.queue(op)
}

const maxLineLength = 4096

// handleKey processes the given key and, optionally, returns a line of text
// that the user has entered.
func (t *Terminal) handleKey(key int) (line string, ok bool) {
        switch key {
        case keyBackspace:
                if t.pos == 0 {
                        return
                }
                t.pos--
                t.moveCursorToPos(t.pos)

                copy(t.line[t.pos:], t.line[1+t.pos:])
                t.line = t.line[:len(t.line)-1]
                if t.echo {
                        t.writeLine(t.line[t.pos:])
                }
                t.queue(eraseUnderCursor)
                t.moveCursorToPos(t.pos)
        case keyAltLeft:
                // move left by a word.
                if t.pos == 0 {
                        return
                }
                t.pos--
                for t.pos > 0 {
                        if t.line[t.pos] != ' ' {
                                break
                        }
                        t.pos--
                }
                for t.pos > 0 {
                        if t.line[t.pos] == ' ' {
                                t.pos++
                                break
                        }
                        t.pos--
                }
                t.moveCursorToPos(t.pos)
        case keyAltRight:
                // move right by a word.
                for t.pos < len(t.line) {
                        if t.line[t.pos] == ' ' {
                                break
                        }
                        t.pos++
                }
                for t.pos < len(t.line) {
                        if t.line[t.pos] != ' ' {
                                break
                        }
                        t.pos++
                }
                t.moveCursorToPos(t.pos)
        case keyLeft:
                if t.pos == 0 {
                        return
                }
                t.pos--
                t.moveCursorToPos(t.pos)
        case keyRight:
                if t.pos == len(t.line) {
                        return
                }
                t.pos++
                t.moveCursorToPos(t.pos)
        case keyEnter:
                t.moveCursorToPos(len(t.line))
                t.queue([]byte("\r\n"))
                line = string(t.line)
                ok = true
                t.line = t.line[:0]
                t.pos = 0
                t.cursorX = 0
                t.cursorY = 0
                t.maxLine = 0
        default:
                if t.AutoCompleteCallback != nil {
                        t.lock.Unlock()
                        newLine, newPos := t.AutoCompleteCallback(t.line, t.pos, key)
                        t.lock.Lock()

                        if newLine != nil {
                                if t.echo {
                                        t.moveCursorToPos(0)
                                        t.writeLine(newLine)
                                        for i := len(newLine); i < len(t.line); i++ {
                                                t.writeLine(space)
                                        }
                                        t.moveCursorToPos(newPos)
                                }
                                t.line = newLine
                                t.pos = newPos
                                return
                        }
                }
                if !isPrintable(key) {
                        return
                }
                if len(t.line) == maxLineLength {
                        return
                }
                if len(t.line) == cap(t.line) {
                        newLine := make([]byte, len(t.line), 2*(1+len(t.line)))
                        copy(newLine, t.line)
                        t.line = newLine
                }
                t.line = t.line[:len(t.line)+1]
                copy(t.line[t.pos+1:], t.line[t.pos:])
                t.line[t.pos] = byte(key)
                if t.echo {
                        t.writeLine(t.line[t.pos:])
                }
                t.pos++
                t.moveCursorToPos(t.pos)
        }
        return
}

func (t *Terminal) writeLine(line []byte) {
        for len(line) != 0 {
                remainingOnLine := t.termWidth - t.cursorX
                todo := len(line)
                if todo > remainingOnLine {
                        todo = remainingOnLine
                }
                t.queue(line[:todo])
                t.cursorX += todo
                line = line[todo:]

                if t.cursorX == t.termWidth {
                        t.cursorX = 0
                        t.cursorY++
                        if t.cursorY > t.maxLine {
                                t.maxLine = t.cursorY
                        }
                }
        }
}

func (t *Terminal) Write(buf []byte) (n int, err error) {
        t.lock.Lock()
        defer t.lock.Unlock()

        if t.cursorX == 0 && t.cursorY == 0 {
                // This is the easy case: there's nothing on the screen that we
                // have to move out of the way.
                return t.c.Write(buf)
        }

        // We have a prompt and possibly user input on the screen. We
        // have to clear it first.
        t.move(0, /* up */ 0, /* down */ t.cursorX, /* left */ 0 /* right */ )
        t.cursorX = 0
        t.clearLineToRight()

        for t.cursorY > 0 {
                t.move(1, /* up */ 0, 0, 0)
                t.cursorY--
                t.clearLineToRight()
        }

        if _, err = t.c.Write(t.outBuf); err != nil {
                return
        }
        t.outBuf = t.outBuf[:0]

        if n, err = t.c.Write(buf); err != nil {
                return
        }

        t.queue([]byte(t.prompt))
        chars := len(t.prompt)
        if t.echo {
                t.queue(t.line)
                chars += len(t.line)
        }
        t.cursorX = chars % t.termWidth
        t.cursorY = chars / t.termWidth
        t.moveCursorToPos(t.pos)

        if _, err = t.c.Write(t.outBuf); err != nil {
                return
        }
        t.outBuf = t.outBuf[:0]
        return
}

// ReadPassword temporarily changes the prompt and reads a password, without
// echo, from the terminal.
func (t *Terminal) ReadPassword(prompt string) (line string, err error) {
        t.lock.Lock()
        defer t.lock.Unlock()

        oldPrompt := t.prompt
        t.prompt = prompt
        t.echo = false

        line, err = t.readLine()

        t.prompt = oldPrompt
        t.echo = true

        return
}

// ReadLine returns a line of input from the terminal.
func (t *Terminal) ReadLine() (line string, err error) {
        t.lock.Lock()
        defer t.lock.Unlock()

        return t.readLine()
}

func (t *Terminal) readLine() (line string, err error) {
        // t.lock must be held at this point

        if t.cursorX == 0 && t.cursorY == 0 {
                t.writeLine([]byte(t.prompt))
                t.c.Write(t.outBuf)
                t.outBuf = t.outBuf[:0]
        }

        for {
                rest := t.remainder
                lineOk := false
                for !lineOk {
                        var key int
                        key, rest = bytesToKey(rest)
                        if key < 0 {
                                break
                        }
                        if key == keyCtrlD {
                                return "", io.EOF
                        }
                        line, lineOk = t.handleKey(key)
                }
                if len(rest) > 0 {
                        n := copy(t.inBuf[:], rest)
                        t.remainder = t.inBuf[:n]
                } else {
                        t.remainder = nil
                }
                t.c.Write(t.outBuf)
                t.outBuf = t.outBuf[:0]
                if lineOk {
                        return
                }

                // t.remainder is a slice at the beginning of t.inBuf
                // containing a partial key sequence
                readBuf := t.inBuf[len(t.remainder):]
                var n int

                t.lock.Unlock()
                n, err = t.c.Read(readBuf)
                t.lock.Lock()

                if err != nil {
                        return
                }

                t.remainder = t.inBuf[:n+len(t.remainder)]
        }
        panic("unreachable")
}

// SetPrompt sets the prompt to be used when reading subsequent lines.
func (t *Terminal) SetPrompt(prompt string) {
        t.lock.Lock()
        defer t.lock.Unlock()

        t.prompt = prompt
}

func (t *Terminal) SetSize(width, height int) {
        t.lock.Lock()
        defer t.lock.Unlock()

        t.termWidth, t.termHeight = width, height
}