#!/usr/bin/env python3
"""Reads hex-framed display data from stdin, writes PBM, auto-launches feh."""

import sys
import os
import signal
import subprocess
import time

WIDTH = 200
HEIGHT = 200
BUFSIZE = (WIDTH * HEIGHT) // 8
OUT = "/tmp/nrfwarch.pbm"
FRAME_START = "!F!"
FRAME_END = "!E!"

feh_proc = None


def write_pbm(data):
    header = f"P4\n{WIDTH} {HEIGHT}\n".encode()
    inverted = bytes((~b) & 0xFF for b in data)
    tmp = OUT + ".tmp"
    with open(tmp, "wb") as f:
        f.write(header)
        f.write(inverted)
    os.replace(tmp, OUT)


def launch_feh():
    global feh_proc
    if feh_proc is not None and feh_proc.poll() is None:
        return
    try:
        feh_proc = subprocess.Popen(
            [
                "feh",
                "--force-aliasing",
                "--scale",
                "auto",
                "--auto-reload",
                "--title", "nrfwarch sim",
                OUT,
            ],
            stdout=subprocess.DEVNULL,
            stderr=subprocess.DEVNULL,
        )
    except FileNotFoundError:
        print("feh not found, writing PBM to " + OUT)


def cleanup(*_):
    global feh_proc
    if feh_proc and feh_proc.poll() is None:
        feh_proc.terminate()
    sys.exit(0)


def main():
    signal.signal(signal.SIGTERM, cleanup)
    signal.signal(signal.SIGINT, cleanup)

    write_pbm(bytes([0xFF] * BUFSIZE))
    launch_feh()

    capturing = False
    hex_buf = ""
    frame_count = 0

    for line in sys.stdin:
        line = line.strip()
        if line == FRAME_START:
            capturing = True
            hex_buf = ""
        elif line == FRAME_END:
            if capturing and hex_buf:
                try:
                    data = bytes.fromhex(hex_buf)
                    if len(data) == BUFSIZE:
                        write_pbm(data)
                        frame_count += 1
                        print(f"  frame {frame_count}", file=sys.stderr)
                except ValueError:
                    pass
            capturing = False
            hex_buf = ""
        elif capturing:
            hex_buf += line


if __name__ == "__main__":
    main()