package draw

import (
	"bufio"
	"os"
	"unicode/utf8"
)

// Keyboardctl delivers runes typed at the window.
//
// Opening it also turns the console raw. Without that, rio keeps its own
// line editor on the window and echoes what you type into the text layer,
// painting over whatever the program has drawn. Holding consctl open is
// what keeps raw mode; closing it puts the window back as it was.
type Keyboardctl struct {
	C    <-chan rune
	ctl  *os.File
	cons *os.File
}

func OpenKeyboard(dev string) (*Keyboardctl, error) {
	ctl, err := os.OpenFile(dev+"/consctl", os.O_WRONLY, 0)
	if err != nil {
		return nil, err
	}
	if _, err := ctl.WriteString("rawon"); err != nil {
		ctl.Close()
		return nil, err
	}
	cons, err := os.Open(dev + "/cons")
	if err != nil {
		ctl.Close()
		return nil, err
	}

	ch := make(chan rune, 32)
	k := &Keyboardctl{C: ch, ctl: ctl, cons: cons}
	go func() {
		defer close(ch)
		br := bufio.NewReader(cons)
		var buf []byte
		b := make([]byte, 1)
		for {
			n, err := br.Read(b)
			if n == 0 || err != nil {
				return
			}
			buf = append(buf, b[0])
			// a rune may arrive a byte at a time
			if r, sz := utf8.DecodeRune(buf); r != utf8.RuneError || sz > 1 {
				ch <- r
				buf = buf[:0]
			} else if len(buf) >= utf8.UTFMax {
				buf = buf[:0]
			}
		}
	}()
	return k, nil
}

func (k *Keyboardctl) Close() error {
	k.cons.Close()
	// dropping consctl is what restores rio's own line editing
	return k.ctl.Close()
}