import json
import socket
import struct
import sys
import threading
from datetime import datetime

PORT = 1234
HEADER_LENGTH = 2


def receive_fixed_length_msg(sock, msglen):
    message = b''
    while len(message) < msglen:
        chunk = sock.recv(msglen - len(message))  # preberi nekaj bajtov
        if chunk == b'':
            raise RuntimeError("socket connection broken")
        message = message + chunk  # pripni prebrane bajte sporocilu

    return message


def receive_json(sock):
    # preberi glavo sporocila (v prvih 2 bytih je dolzina sporocila)
    header = receive_fixed_length_msg(sock, HEADER_LENGTH)
    message_length = struct.unpack("!H", header)[0]  # pretvori dolzino sporocila v int

    message = None
    if message_length > 0:  # ce je vse OK
        message = receive_fixed_length_msg(sock, message_length)  # preberi sporocilo
        message = message.decode("utf-8")
        message = json.loads(message)

    return message


def send_json(sock, data):
    data["time"] = datetime.now().strftime("%c")

    # pretvori sporocilo v niz bajtov, uporabi UTF-8 kodno tabelo
    encoded_data = json.dumps(data).encode("utf-8")

    # ustvari glavo v prvih 2 bytih je dolzina sporocila (HEADER_LENGTH)
    # metoda pack "!H" : !=network byte order, H=unsigned short
    header = struct.pack("!H", len(encoded_data))

    data = header + encoded_data  # najprj posljemo dolzino sporocilo, sele nato sporocilo samo
    sock.sendall(data)


def send_username(sock, username):
    send_json(sock, {
        "type": "username",
        "data": username,
    })


def send_message(sock, message):
    send_json(sock, {
        "type": "message",
        "data": message,
    })


# message_receiver funkcija tece v loceni niti
def message_receiver():
    while True:
        msg_received = receive_json(sock)

        msg_type = msg_received["type"]
        data = msg_received["data"]
        time = msg_received["time"]
        match msg_type:
            case "message":
                username = msg_received["username"]
                print(f'[{time}] [{username}] : {data}')
            case "error":
                print(f'Error: {data}')


# povezi se na streznik
print("[system] connecting to chat server ...")
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect(("localhost", PORT))
print("[system] connected!")

# zazeni message_receiver funkcijo v loceni niti
thread = threading.Thread(target=message_receiver)
thread.daemon = True
thread.start()

username = input("enter username: ")
send_username(sock, username)

# pocakaj da uporabnik nekaj natipka in poslji na streznik
while True:
    try:
        msg_send = input("")
        send_message(sock, msg_send)
    except KeyboardInterrupt:
        sys.exit()