#!/usr/bin/env python3
"""Multi-line input reader. C-j inserts newline, C-m (Enter) submits."""
import sys, tty, termios, os, signal

def readchar(fd):
    """Read a single UTF-8 character from fd in raw mode."""
    b = os.read(fd, 1)
    if not b:
        return b
    if b[0] < 0x80:
        return b
    # determine continuation bytes from leading byte
    n = 1
    if b[0] & 0xe0 == 0xc0: n = 1
    elif b[0] & 0xf0 == 0xe0: n = 2
    elif b[0] & 0xf8 == 0xf0: n = 3
    rest = os.read(fd, n)
    return b + rest

def main():
    prompt = sys.argv[1] if len(sys.argv) > 1 else '> '
    cont = sys.argv[2] if len(sys.argv) > 2 else '. '
    fd = sys.stdin.fileno()
    old = termios.tcgetattr(fd)
    lines = ['']
    cur = 0  # current line index

    def redraw_current():
        p = prompt if cur == 0 else cont
        sys.stderr.write('\r\033[K' + p + lines[cur])
        sys.stderr.flush()

    sys.stderr.write(prompt)
    sys.stderr.flush()

    try:
        tty.setraw(fd)
        while True:
            ch = readchar(fd)
            if not ch:
                break
            b = ch[0]

            if b == 0x0d:  # C-m / Enter -> submit
                sys.stderr.write('\r\n')
                sys.stderr.flush()
                break
            elif b == 0x0a:  # C-j -> newline
                sys.stderr.write('\r\n')
                cur += 1
                lines.insert(cur, '')
                redraw_current()
            elif b == 0x03:  # C-c
                sys.stderr.write('\r\n')
                sys.stderr.flush()
                termios.tcsetattr(fd, termios.TCSADRAIN, old)
                os.kill(os.getpid(), signal.SIGINT)
            elif b == 0x04:  # C-d
                if not any(lines):
                    sys.stderr.write('\r\n')
                    sys.stderr.flush()
                    termios.tcsetattr(fd, termios.TCSADRAIN, old)
                    sys.exit(1)
                else:
                    sys.stderr.write('\r\n')
                    sys.stderr.flush()
                    break
            elif b in (0x7f, 0x08):  # backspace
                if lines[cur]:
                    lines[cur] = lines[cur][:-1]
                    redraw_current()
                elif cur > 0:
                    prev = lines[cur - 1]
                    lines.pop(cur)
                    cur -= 1
                    lines[cur] = prev
                    sys.stderr.write('\033[A')
                    redraw_current()
            elif b == 0x15:  # C-u: kill line
                lines[cur] = ''
                redraw_current()
            elif b == 0x17:  # C-w: kill word
                l = lines[cur].rstrip()
                i = l.rfind(' ')
                lines[cur] = l[:i+1] if i >= 0 else ''
                redraw_current()
            elif b == 0x1b:  # escape sequence - consume and ignore
                os.read(fd, 2)
            elif b >= 0x20:
                s = ch.decode('utf-8', errors='replace')
                lines[cur] += s
                sys.stderr.write(s)
                sys.stderr.flush()
    finally:
        termios.tcsetattr(fd, termios.TCSADRAIN, old)

    text = '\n'.join(lines)
    if not text:
        sys.exit(1)
    sys.stdout.write(text)

if __name__ == '__main__':
    main()