import json
import datetime


class LastMessage:
    def __init__(self, json_filename: str):
        self.filename = json_filename

    def load_from_json(self):
        with open(self.filename, "r") as json_file:
            last_messages_dict = json.loads(json_file.read())
        if not last_messages_dict:
            self.last_messages_dict = {}
        else:
            self.last_messages_dict = last_messages_dict

    def write_to_json(self) -> None:
        with open(self.filename, "w") as json_file:
            json_file.write(json.dumps(self.last_messages_dict))

    def read_last_message(self, chat_id: int) -> int:
        return self.last_messages_dict[chat_id]

    def write_last_message(self, chat_id: int, timestamp: int) -> None:
        self.load_from_json()
        self.last_messages_dict[chat_id] = timestamp
        self.write_to_json()

    def calculate_time(self, timestamp: int) -> datetime.datetime:
        return datetime.datetime.fromtimestamp((datetime.datetime.now().timestamp() - timestamp))

    def get_estimated_time(self, chat_id: int):
        ts = self.read_last_message(chat_id)
        estimated = 5 - self.calculate_time(ts).minute

        return estimated