#!/usr/bin/python3
"""Prototype of Meckle: a graphical agent speaking text with a principal.

The Meckle agent opens a window to provide a GUI for the principal.
The principal sends commands to the agent, and the agent notifies the
principal of any relevant events such as button clicks.  With the
agent meckling on the display on behalf of the principal, the
principal can happily run on an Arduino, or be a sed script, or a
playback of a previously recorded meckling session.

XXX not sure how to get this to actually work with tkinter.
w.tk.createfilehandler(infile, tkinter.READABLE, callback) would
probably work, at least on Unix, but obviously that isn't what the
Python REPL uses.  Do I need to run the mainloop in a background
thread?  Or do the I/O in a background thread?  Just calling .update()
after every command isn't good enough; it does cause the window to
appear at least, but it isn't interactive until after the next
command.

Meckle is inspired by RIPScrip, NAPLPS, Videotex and similar teletext
systems, HTML forms, SGI’s Buttonfly, Tcl/Tk, text terminals, the MGR
windowing system Caleb Winston’s STDG, Dave Long’s window manager in
awk, and a conversation I had once at a party with someone who I
perhaps mistakenly remembered to be Richard Uhtenwoldt.

"""
from __future__ import print_function
import tkinter


def run_agent(infile, outfile):
    w = tkinter.Tk()
    # Ugh, how do I read input while also displaying the window?  XXX
    while True:
        line = infile.readline()
        if not line:
            break
        if handle(w, line) == 'exit':
            break

        # XXX this doesn't quite work as desired, though it helps a bit...
        w.update()

commands = {}

def handle(w, line):
    words = line.split()
    if len(words) < 1:
        return

    handler = commands.get(words[0])
    if handler is None:
        print("command not understood", words[0])
        return

    return handler(w, words)

def command(f):
    commands[f.__name__] = f
    return f


@command
def button(w, words):
    b = tkinter.Button(w, text=words[1], command=lambda: print("click", words[1]))
    b.pack()

@command
def mainloop(w, words):
    tkinter.mainloop()
    return 'exit'
    

if __name__ == '__main__':
    import sys
    run_agent(sys.stdin, sys.stdout)