#!/usr/bin/python

from select import select
from subprocess import Popen, PIPE, STDOUT
import sys

# TODO: byte-by-byte I/O is painful. figure out better buffering
# that doesn't break everything

# currently line-buffered
def run(args):
    #return Popen(args, stdin=PIPE, stdout=PIPE, stderr=STDOUT, bufsize=1, universal_newlines=True)
    return Popen(args, stdin=PIPE, stdout=PIPE, stderr=STDOUT, bufsize=0)

def main():
    args = sys.argv[1:]
    if len(args) < 2:
        print('usage: %s ROM SHELL')
        print('')
        print('execute the given uxn terminal program (ROM)')
        print('and start a shell process (SHELL).')
        sys.exit(1)
    rom = args[0]
    shell = args[1]

    term = run(['uxnemu', rom])
    term_out = term.stdout.fileno()

    shell = run([shell])
    shell_out = shell.stdout.fileno()

    while shell.poll() is None and term.poll() is None:
        # wait 100ms to see if anything is ready to write
        ns, _, _ = select([term_out, shell_out], [], [], 0.1)
        for n in ns:
            if n == term_out:
                shell.stdin.write(term.stdout.read(1))
                shell.stdin.flush()
            elif n == shell_out:
                term.stdin.write(shell.stdout.read(1))
                term.stdin.flush()
            else:
                raise Exception('unexpected fileno: %d (expected %d or %d)' % (n, term_out, shell_out))

if __name__ == "__main__":
    main()