from pathlib import Path
from api import SubRosaAPI, APIError
from datetime import datetime
import sys
sys.path.insert(0, ".")
from encryption import PrivateKey, PublicKey

class SubRosaUI:
    """A user interface to the SubRosa chat system.
    """
    def __init__(self, private_key_file, url):
        self.api = SubRosaAPI(url)
        if Path(private_key_file).exists():
            self.private_key = PrivateKey.load(private_key_file)
        else:
            self.private_key = PrivateKey.generate()
            self.private_key.save(private_key_file)
        self.public_key = self.private_key.get_public_key()

    def run(self, username):
        """Runs the client UI.
        """
        self.username = username
        self.user = self.get_or_create_user(username)
        print("Welcome to SubRosa.")
        while True:
            choice = self.choose_action_from_menu()
            if choice == 'VIEW':
                self.show_messages()
            elif choice == 'SEND':
                self.send_message()
            print("=" * 80)

    def get_or_create_user(self, username):
        """Gets user info from the server, or creates the user. 
        If the user already exists, checks that our public key matches
        the server's public key for the user. 
        """
        try:
            user = self.api.get_user(username)
            if user['public_key'] != str(self.public_key):
                raise ValueError(f"Invalid key for {username}")
        except APIError:
            user = self.api.create_user(username, str(self.public_key))
        return user

    def choose_action_from_menu(self):
        """Gets a choice from the user. 
        """
        print("What would you like to do?")
        print("1. See messages")
        print("2. Send a message")
        while True:
            choice = input("> ").strip()
            if choice == '1':
                return 'VIEW'
            elif choice == '2': 
                return 'SEND'

    def show_messages(self):
        """Fetches all messages and displays them. 
        Note: The messages arrive from the server encrypted.
        """
        messages = self.api.get_messages(self.username)['messages']
        if messages:
            for i, message in enumerate(messages):
                print('-' * 80)
                print(f"{i}. From {message['sender']}:")
                print(message['ciphertext'])
        else:
            print(f"No messages for {self.username}.")

    def send_message(self):
        """Sends a message.
        """
        try:
            recipient_name = input("Username of recipient: ").strip()
            recipient = self.api.get_user(recipient_name)
        except APIError:
            print(f"No user named {recipient_name}.")
            return
        plaintext = input("Message: ")
        print('-' * 80)
        print(f"Sorry, couldn't send a message to {recipient_name}; this method isn't implemented yet.")

    def get_current_time(self):
        return datetime.utcnow().isoformat()

def main():
    from argparse import ArgumentParser
    parser = ArgumentParser()
    parser.add_argument("username", help="Existing or new username.")
    parser.add_argument("-k", "--key", 
        default="subrosa_private_key.pem", 
        help="Private key file. Will be created if it does not exist."
    )
    parser.add_argument("-s", "--server-url", 
        default="http://subrosa.makingwithcode.org",
        help='Server URL. Use "http://127.0.0.1:5000" for a local server.'
    )
    args = parser.parse_args()
    ui = SubRosaUI(args.key, args.server_url)
    ui.run(args.username)

if __name__ == '__main__':
    main()