import subprocess
import threading
from pathlib import Path
import logging
import os
import time
import atexit
import json
import zmq

GLOBAL_METADATA = Path.cwd() / "global-metadata.json"
ZMQ_SOCKET = Path.cwd() / "runusb.sock"

def get_zmq_publisher():
    context = zmq.Context()
    socket = context.socket(zmq.PUB)
    socket.bind("ipc://" + str(ZMQ_SOCKET))
    return socket

def get_zmq_subscriber(topic: str):
    context = zmq.Context()
    socket = context.socket(zmq.SUB)
    socket.setsockopt_string(zmq.SUBSCRIBE, topic)
    socket.connect("ipc://" + str(ZMQ_SOCKET))
    return socket

class UserCodeSupervisor(threading.Thread):
    def __init__(self, process: subprocess.Popen, mountpoint: Path):
        super().__init__()
        self.process = process
        self.logfile = mountpoint / "log.txt"
        self.zmq_publisher = get_zmq_publisher()

    def run(self):
        with self.logfile.open(mode="w") as log_file:
            while self.process.returncode is None:
                stdout_data = self.process.stdout.readline()
                print(stdout_data, end="")
                log_file.write(stdout_data)
                log_file.flush()

                self.zmq_publisher.send_multipart([b"log", stdout_data.encode()])

                self.process.poll()



class RunUSBRegistry:
    process: subprocess.Popen | None = None
    usercode_dir: Path | None = None

    def __init__(self):
        self.lock = threading.Lock()
        self.metadata = {}
        self.update_metadata({})

    def start_user_code(self, mountpoint: Path):
        self.usercode_dir = mountpoint

        entrypoint = mountpoint / "main.py"
        self.process = subprocess.Popen(
            ["python3", entrypoint],
            env={
                **os.environ,
                "PYTHONUNBUFFERED": "1",
                "METADATA_FILE": str(GLOBAL_METADATA)
            },
            cwd=mountpoint,
            stdin=subprocess.DEVNULL,
            stdout=subprocess.PIPE,
            stderr=subprocess.STDOUT,
            universal_newlines=True,
        )

        UserCodeSupervisor(self.process, mountpoint).start()

    def restart_user_code(self):
        mountpoint = self.usercode_dir

        self.stop_user_code()
        self.start_user_code(mountpoint)

    def stop_user_code(self):
        self.process.terminate()

        try:
            self.process.wait(timeout=5)
        except subprocess.TimeoutExpired:
            pass

        if self.process.poll() is not None:
            self.process.kill()

        # Remove the reference
        self.process = None
        self.usercode_dir = None

    def handle_metadata_file(self, metadata_file: Path):
        with metadata_file.open(mode="r") as f:
            self.metadata = json.load(f)

        # Notify with a blank update, as everything is new
        self.update_metadata({})

    def update_metadata(self, new_metadata: dict):
        self.metadata.update(new_metadata)

        with GLOBAL_METADATA.open("w") as f:
            json.dump(self.metadata, f)

    def __enter__(self):
        self.lock.acquire()

    def __exit__(self, *args):
        self.lock.release()

    def close(self):
        self.stop_user_code()


class BusHandler(threading.Thread):
    def __init__(self, registry: RunUSBRegistry):
        super().__init__()
        self.registry = registry
        self.zmq_subscriber = get_zmq_subscriber("")

    def run(self):
        while True:
            topic, message = self.zmq_subscriber.recv_multipart()

            topic = topic.decode()
            message = message.decode()

            # if topic == "log":
            #     continue

            if topic == "restart":
                with registry:
                    registry.restart_user_code()

            else:
                print("Ignoring message with topic", topic, message.strip())



def watch_drive_activity(registry: RunUSBRegistry):
    with registry:
        registry.start_user_code(Path.cwd())

def watch_metadata(registry: RunUSBRegistry):
    with registry:
        registry.handle_metadata_file(Path.cwd() / "metadata.json")


def main():
    logging.basicConfig(level=logging.DEBUG)

    registry = RunUSBRegistry()
    atexit.register(registry.close)

    BusHandler(registry).start()

    watch_drive_activity(registry)
    watch_metadata(registry)

    # Threads are running now

if __name__ == '__main__':
    main()