import threading
import time
import flask
from werkzeug.serving import make_server
import logging

class Server:
    """
    This server does NOT use Flask's built-in development server.
    Instead, it uses Werkzeug's make_server to create a WSGI server.

    This server is thread-safe and can be stopped by setting the stop_event.

    This server works as a chat server by polling, not by using websockets (to keep it simple).
    """

    def __init__(self, host: str, port: int, stop_event: threading.Event):
        self.host = host
        self.port = port
        self.stop_event = stop_event

        # Flask definition
        self.flask = flask.Flask(__name__)
        self.flask.add_url_rule('/status', methods=['POST'], view_func=self.status)
        self.flask.add_url_rule('/send_message', methods=['POST'], view_func=self.send_message)
        self.flask.add_url_rule('/get_messages', methods=['POST'], view_func=self.get_messages)
        self.server = make_server(self.host, self.port, self.flask)
        self.watcher_thread = threading.Thread(target=self.__watcher)
        self.server_thread = threading.Thread(target=self.server.serve_forever)
        self.server_thread.start()
        self.watcher_thread.start()


        log = logging.getLogger('werkzeug')
        log.setLevel(logging.ERROR)
        self.flask.logger.setLevel(logging.ERROR)

        # Message initialization
        self.message_id = 0
        self.messages = self.__init_messages()

    def __watcher(self):
        while not self.stop_event.is_set():
            time.sleep(1)

        self.shutdown()

    def shutdown(self):
        self.__persist_messages()
        self.server.shutdown()

    def __init_messages(self):
        messages = []
        try:
            with open('chat_server/messages.txt', 'r') as f:
                for line in f:
                    parts = line.strip().split('|')
                    messages.append({
                        'id': int(parts[0]),
                        'sender': parts[1],
                        'content': parts[2]
                    })
            self.message_id = messages[-1]['id'] if messages else 0
        except FileNotFoundError:
            with open('chat_server/messages.txt', 'w+') as f:
                pass
        return messages

    def __persist_messages(self):
        with open('chat_server/messages.txt', 'w') as f:
            for message in self.messages:
                f.write(f"{message['id']}|{message['sender']}|{message['content']}\n")

    def status(self):
        return 'OK'

    def send_message(self):
        sender = flask.request.json['sender']
        content = flask.request.json['content']
        self.message_id += 1
        message = {
            'id': self.message_id,
            'sender': sender,
            'content': content
        }
        self.messages.append(message)
        return {'id': self.message_id}

    def get_messages(self):
        try: last_id = flask.request.json.get('last_id')
        # last_id is a mandatory parameter
        except AttributeError: return flask.Response('Last ID not specified', status=400)
        new_messages = [msg for msg in self.messages if msg['id'] > last_id]
        return {'messages': new_messages}