path: root/vendor/github.com/peterh/liner/input.go

// +build linux darwin openbsd freebsd netbsd

package liner

import (
    "bufio"
    "errors"
    "os"
    "os/signal"
    "strconv"
    "strings"
    "syscall"
    "time"
)

type nexter struct {
    r   rune
    err error
}

// State represents an open terminal
type State struct {
    commonState
    origMode    termios
    defaultMode termios
    next        <-chan nexter
    winch       chan os.Signal
    pending     []rune
    useCHA      bool
}

// NewLiner initializes a new *State, and sets the terminal into raw mode. To
// restore the terminal to its previous state, call State.Close().
func NewLiner() *State {
    var s State
    s.r = bufio.NewReader(os.Stdin)

    s.terminalSupported = TerminalSupported()
    if m, err := TerminalMode(); err == nil {
        s.origMode = *m.(*termios)
    } else {
        s.inputRedirected = true
    }
    if _, err := getMode(syscall.Stdout); err != 0 {
        s.outputRedirected = true
    }
    if s.inputRedirected && s.outputRedirected {
        s.terminalSupported = false
    }
    if s.terminalSupported && !s.inputRedirected && !s.outputRedirected {
        mode := s.origMode
        mode.Iflag &^= icrnl | inpck | istrip | ixon
        mode.Cflag |= cs8
        mode.Lflag &^= syscall.ECHO | icanon | iexten
        mode.ApplyMode()

        winch := make(chan os.Signal, 1)
        signal.Notify(winch, syscall.SIGWINCH)
        s.winch = winch

        s.checkOutput()
    }

    if !s.outputRedirected {
        s.outputRedirected = !s.getColumns()
    }

    return &s
}

var errTimedOut = errors.New("timeout")

func (s *State) startPrompt() {
    if s.terminalSupported {
        if m, err := TerminalMode(); err == nil {
            s.defaultMode = *m.(*termios)
            mode := s.defaultMode
            mode.Lflag &^= isig
            mode.ApplyMode()
        }
    }
    s.restartPrompt()
}

func (s *State) inputWaiting() bool {
    return len(s.next) > 0
}

func (s *State) restartPrompt() {
    next := make(chan nexter, 200)
    go func() {
        for {
            var n nexter
            n.r, _, n.err = s.r.ReadRune()
            next <- n
            // Shut down nexter loop when an end condition has been reached
            if n.err != nil || n.r == '\n' || n.r == '\r' || n.r == ctrlC || n.r == ctrlD {
                close(next)
                return
            }
        }
    }()
    s.next = next
}

func (s *State) stopPrompt() {
    if s.terminalSupported {
        s.defaultMode.ApplyMode()
    }
}

func (s *State) nextPending(timeout <-chan time.Time) (rune, error) {
    select {
    case thing, ok := <-s.next:
        if !ok {
            return 0, ErrInternal
        }
        if thing.err != nil {
            return 0, thing.err
        }
        s.pending = append(s.pending, thing.r)
        return thing.r, nil
    case <-timeout:
        rv := s.pending[0]
        s.pending = s.pending[1:]
        return rv, errTimedOut
    }
}

func (s *State) readNext() (interface{}, error) {
    if len(s.pending) > 0 {
        rv := s.pending[0]
        s.pending = s.pending[1:]
        return rv, nil
    }
    var r rune
    select {
    case thing, ok := <-s.next:
        if !ok {
            return 0, ErrInternal
        }
        if thing.err != nil {
            return nil, thing.err
        }
        r = thing.r
    case <-s.winch:
        s.getColumns()
        return winch, nil
    }
    if r != esc {
        return r, nil
    }
    s.pending = append(s.pending, r)

    // Wait at most 50 ms for the rest of the escape sequence
    // If nothing else arrives, it was an actual press of the esc key
    timeout := time.After(50 * time.Millisecond)
    flag, err := s.nextPending(timeout)
    if err != nil {
        if err == errTimedOut {
            return flag, nil
        }
        return unknown, err
    }

    switch flag {
    case '[':
        code, err := s.nextPending(timeout)
        if err != nil {
            if err == errTimedOut {
                return code, nil
            }
            return unknown, err
        }
        switch code {
        case 'A':
            s.pending = s.pending[:0] // escape code complete
            return up, nil
        case 'B':
            s.pending = s.pending[:0] // escape code complete
            return down, nil
        case 'C':
            s.pending = s.pending[:0] // escape code complete
            return right, nil
        case 'D':
            s.pending = s.pending[:0] // escape code complete
            return left, nil
        case 'F':
            s.pending = s.pending[:0] // escape code complete
            return end, nil
        case 'H':
            s.pending = s.pending[:0] // escape code complete
            return home, nil
        case 'Z':
            s.pending = s.pending[:0] // escape code complete
            return shiftTab, nil
        case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
            num := []rune{code}
            for {
                code, err := s.nextPending(timeout)
                if err != nil {
                    if err == errTimedOut {
                        return code, nil
                    }
                    return nil, err
                }
                switch code {
                case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
                    num = append(num, code)
                case ';':
                    // Modifier code to follow
                    // This only supports Ctrl-left and Ctrl-right for now
                    x, _ := strconv.ParseInt(string(num), 10, 32)
                    if x != 1 {
                        // Can't be left or right
                        rv := s.pending[0]
                        s.pending = s.pending[1:]
                        return rv, nil
                    }
                    num = num[:0]
                    for {
                        code, err = s.nextPending(timeout)
                        if err != nil {
                            if err == errTimedOut {
                                rv := s.pending[0]
                                s.pending = s.pending[1:]
                                return rv, nil
                            }
                            return nil, err
                        }
                        switch code {
                        case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
                            num = append(num, code)
                        case 'C', 'D':
                            // right, left
                            mod, _ := strconv.ParseInt(string(num), 10, 32)
                            if mod != 5 {
                                // Not bare Ctrl
                                rv := s.pending[0]
                                s.pending = s.pending[1:]
                                return rv, nil
                            }
                            s.pending = s.pending[:0] // escape code complete
                            if code == 'C' {
                                return wordRight, nil
                            }
                            return wordLeft, nil
                        default:
                            // Not left or right
                            rv := s.pending[0]
                            s.pending = s.pending[1:]
                            return rv, nil
                        }
                    }
                case '~':
                    s.pending = s.pending[:0] // escape code complete
                    x, _ := strconv.ParseInt(string(num), 10, 32)
                    switch x {
                    case 2:
                        return insert, nil
                    case 3:
                        return del, nil
                    case 5:
                        return pageUp, nil
                    case 6:
                        return pageDown, nil
                    case 7:
                        return home, nil
                    case 8:
                        return end, nil
                    case 15:
                        return f5, nil
                    case 17:
                        return f6, nil
                    case 18:
                        return f7, nil
                    case 19:
                        return f8, nil
                    case 20:
                        return f9, nil
                    case 21:
                        return f10, nil
                    case 23:
                        return f11, nil
                    case 24:
                        return f12, nil
                    default:
                        return unknown, nil
                    }
                default:
                    // unrecognized escape code
                    rv := s.pending[0]
                    s.pending = s.pending[1:]
                    return rv, nil
                }
            }
        }

    case 'O':
        code, err := s.nextPending(timeout)
        if err != nil {
            if err == errTimedOut {
                return code, nil
            }
            return nil, err
        }
        s.pending = s.pending[:0] // escape code complete
        switch code {
        case 'c':
            return wordRight, nil
        case 'd':
            return wordLeft, nil
        case 'H':
            return home, nil
        case 'F':
            return end, nil
        case 'P':
            return f1, nil
        case 'Q':
            return f2, nil
        case 'R':
            return f3, nil
        case 'S':
            return f4, nil
        default:
            return unknown, nil
        }
    case 'b':
        s.pending = s.pending[:0] // escape code complete
        return altB, nil
    case 'f':
        s.pending = s.pending[:0] // escape code complete
        return altF, nil
    case 'y':
        s.pending = s.pending[:0] // escape code complete
        return altY, nil
    default:
        rv := s.pending[0]
        s.pending = s.pending[1:]
        return rv, nil
    }

    // not reached
    return r, nil
}

// Close returns the terminal to its previous mode
func (s *State) Close() error {
    signal.Stop(s.winch)
    if !s.inputRedirected {
        s.origMode.ApplyMode()
    }
    return nil
}

// TerminalSupported returns true if the current terminal supports
// line editing features, and false if liner will use the 'dumb'
// fallback for input.
// Note that TerminalSupported does not check all factors that may
// cause liner to not fully support the terminal (such as stdin redirection)
func TerminalSupported() bool {
    bad := map[string]bool{"": true, "dumb": true, "cons25": true}
    return !bad[strings.ToLower(os.Getenv("TERM"))]
}