#!/usr/bin/env nix-script
#!>python3

##  write to a file in a chat-like fashion

import subprocess
import time
import threading
import readline
import sys
import os

def sprint(*args, **kwargs):
    '''
    Safe print
    Write automagically to stdout while reading
    from stdin without mixing any text.
    '''
    line_length = len(readline.get_line_buffer())+2
    sys.stdout.write('\r' + ' ' * line_length +'\r')
    print(*args, **kwargs)
    sys.stdout.write(prompt() + readline.get_line_buffer())
    sys.stdout.flush()


def clear():
    '''Clear the screen'''
    cmd = 'cls' if sys.platform == 'win32' else "clear && printf '\e[3J'"
    subprocess.call(cmd, shell=True)

def terminal_size():
    '''Get size of terminal window (lines, columns)'''
    def ioctl_GWINSZ(fd):
        try:
            import fcntl, termios, struct, os
            cr = struct.unpack('hh', fcntl.ioctl(fd, termios.TIOCGWINSZ,
        '1234'))
        except:
            return
        return cr
    cr = ioctl_GWINSZ(0) or ioctl_GWINSZ(1) or ioctl_GWINSZ(2)
    if not cr:
        try:
            fd = os.open(os.ctermid(), os.O_RDONLY)
            cr = ioctl_GWINSZ(fd)
            os.close(fd)
        except:
            pass
    if not cr:
        env = os.environ
        cr = (env.get('LINES', 25), env.get('COLUMNS', 80))
    return list(map(int, cr))


def timestamp(message):
    '''Add timestamp to a message'''
    stamp = time.strftime('%d.%m.%y - %H:%M:%S')
    return '{} {}: {}\n'.format(stamp, username, message)


def update():
    '''Keep the console output updated'''
    global previous

    while True:
        time.sleep(0.1)
        file.seek(0)
        current = file.read()
        if current == previous:
            pass
        else:
            clear()
            sprint(current)
        previous = current


def read():
    '''Prompt user for input'''
    global previous
    global username
    text = input(prompt())

    if text.startswith('/'):
        command = text[1:].split()
        if command[0] == 'quit':
            sys.exit()
        elif command[0] == 'setname':
            username = ' '.join(command[1:])
        elif command[0] == 'clear':
            file.seek(0)
            file.truncate()
        clear()
    elif text != '':
        file.write(timestamp(text))
        file.write('\n')
    else:
        previous=file.read()


mod = lambda x: (0 if x<0 else x)

previous = ''
username = 'Michele'

chat_size = lambda: sum(1 for _ in open('log.txt'))
offset    = lambda: '\n' * mod(terminal_size()[0] - chat_size() - 2)
prompt    = lambda: offset() + username + '>> '


file = open('log.txt', 'a+')
thread = threading.Thread(target=update, daemon=True)


if __name__ == '__main__':
    try:
        thread.start()
        clear()
        while True:
            read()
    except KeyboardInterrupt:
        print()