# Author: Pierce Parker
# Date: 4/22/2024
# Program Name: lightclient.py
# Description: A UDP client that sends motion detection events to a server and receives blink parameters.

import socket
import sys
import struct
import time
from gpiozero import MotionSensor
from datetime import datetime

PIR = MotionSensor(4)

# Utility Functions
def create_packet(sequence_number, ack_number, ack, syn, fin, payload):
    """
    Creates a custom UDP packet with a specified header and payload.
    
    Args:
        sequence_number (int): Sequence number.
        ack_number (int): Acknowledgment number.
        ack (int): ACK flag (1 or 0).
        syn (int): SYN flag (1 or 0).
        fin (int): FIN flag (1 or 0).
        payload (str): Data to include in the packet.
    
    Returns:
        bytes: Packed data ready for transmission.
    """
    data = struct.pack('!I', sequence_number)
    data += struct.pack('!I', ack_number)
    flags = (ack << 2) | (syn << 1) | fin
    data += struct.pack('!I', flags)
    data += payload.encode()
    return data

def parse_packet(packet):
    """
    Parses a received UDP packet and extracts its components.
    
    Args:
        packet (bytes): The received packet data.
    
    Returns:
        tuple: Parsed sequence number, acknowledgment number, flags, and payload.
    """
    sequence_number, ack_number, flags = struct.unpack('!III', packet[:12])
    ack = (flags >> 2) & 1
    syn = (flags >> 1) & 1
    fin = flags & 1
    payload = packet[12:].decode()
    return sequence_number, ack_number, ack, syn, fin, payload

def get_time():
    """Returns the current timestamp in the format 'YYYY-MM-DD-HH-MM-SS'."""
    return datetime.now().strftime("%Y-%m-%d-%H-%M-%S")

# Main Client Logic
def main():
    try:
        # Validate command-line arguments
        if len(sys.argv) != 7:
            print("Usage: python3 lightclient.py -s <SERVER-IP> -p <PORT> -l <LOG FILE LOCATION>")
            sys.exit(1)
        
        # Parse command-line arguments
        server_ip = sys.argv[2]
        port = int(sys.argv[4])
        log_file = sys.argv[6]
        DURATION = .5
        NUMBLINKS = 3

        # Create a UDP socket
        sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        server_address = (server_ip, port)
        
        sequence_number = 1

        # Start Handshake
        print("[CLIENT] Sending connection request (SYN) to server...")
        sock.sendto(create_packet(sequence_number, 0, ack=0, syn=1, fin=0, payload="SYN"), server_address)
        with open(log_file, 'a') as f:
            f.write(f'{get_time()}: "SENT" {sequence_number} 0 [ACK:0 SYN:1 FIN:0] SYN message sent\n')
        sequence_number += 1

        # Receive SYN-ACK
        print("[CLIENT] Waiting for connection acknowledgment (SYN-ACK) from server...")
        data, _ = sock.recvfrom(1024)
        server_seq, ack_number, ack, syn, fin, payload = parse_packet(data)
        with open(log_file, 'a') as f:
            f.write(f'{get_time()}: "RECEIVED" {server_seq} {ack_number} [ACK:{ack} SYN:{syn} FIN:{fin}] {payload}\n')

        # Send ACK
        print("[CLIENT] Confirming connection (ACK) to server...")
        sock.sendto(create_packet(sequence_number, server_seq + 1, ack=1, syn=0, fin=0, payload="ACK"), server_address)
        with open(log_file, 'a') as f:
            f.write(f'{get_time()}: "SENT" {sequence_number} {server_seq + 1} [ACK:1 SYN:0 FIN:0] ACK message sent\n')
        sequence_number += 1

        # Send Blink Parameters
        print("[CLIENT] Sending blink parameters (count and duration) to server...")
        sock.sendto(create_packet(sequence_number, server_seq + 1, ack=1, syn=0, fin=0, payload=f"{NUMBLINKS} {DURATION}"), server_address)
        with open(log_file, 'a') as f:
            f.write(f'{get_time()}: "SENT" {sequence_number} {server_seq + 1} [ACK:1 SYN:0 FIN:0] Blink parameters sent\n')
        sequence_number += 1

        # Receive Blink Parameters Acknowledgment
        print("[CLIENT] Waiting for acknowledgment of blink parameters from server...")
        data, _ = sock.recvfrom(1024)
        server_seq, ack_number, ack, syn, fin, payload = parse_packet(data)
        with open(log_file, 'a') as f:
            f.write(f'{get_time()}: "RECEIVED" {server_seq} {ack_number} [ACK:{ack} SYN:{syn} FIN:{fin}] {payload}\n')

        # Motion Detection Loop
        while True:
            try:
                print("[CLIENT] Monitoring for motion...")
                PIR.wait_for_motion()
                print("[CLIENT] Motion detected. Notifying server...")
                with open(log_file, 'a') as f:
                    f.write(f"{get_time()}: Motion detected\n")
                sock.sendto(
                    create_packet(sequence_number, server_seq + 1, ack=1, syn=0, fin=0, payload=":MotionDetected"),
                    server_address
                )
                with open(log_file, 'a') as f:
                    f.write(f'{get_time()}: "SENT" {sequence_number} {server_seq + 1} [ACK:1 SYN:0 FIN:0] Motion detected message sent\n')
                sequence_number += 1
                time.sleep(NUMBLINKS * DURATION)
                PIR.wait_for_no_motion()

            except KeyboardInterrupt:
                print("[CLIENT] Terminating connection (FIN)...")
                sock.sendto(
                    create_packet(sequence_number, server_seq + 1, ack=1, syn=0, fin=1, payload="FIN"),
                    server_address
                )
                with open(log_file, 'a') as f:
                    f.write(f'{get_time()}: "SENT" {sequence_number} {server_seq + 1} [ACK:1 SYN:0 FIN:1] Termination request sent\n')
                break

    finally:
        sock.close()
        print("[CLIENT] Connection closed.")

if __name__ == "__main__":
    main()