import sys
import argparse
from collections import deque


def handle_print(source, count, is_bytes):
    if is_bytes:
        decoded = bytearray(deque(source, count)).decode('utf-8')
        print(decoded)
    else:
        for l in deque(source, count):
            print(l, end="")        


def tail(filename, count, is_bytes=False):
    if filename:
        try:
            if is_bytes:
                with open(filename, 'rb') as f:
                    handle_print(f.read(), count, is_bytes)
            else:
                with open(filename, 'r') as f:
                    handle_print(f, count, is_bytes)
        except FileNotFoundError:
            print("File not found!")
            exit(1)
    else:
        source = sys.stdin
        if is_bytes:
            source = source.buffer.read()
        handle_print(source, count, is_bytes)



def positive_int(arg):
    try:
        val = int(arg)
    except ValueError:
        raise argparse.ArgumentTypeError("Must be an integer")
    if val < 0:
        raise argparse.ArgumentTypeError("Must be greater than or equal to 0")
    return val



def parse_arguments():
    parser = argparse.ArgumentParser()
    parser.add_argument("--lines", type=positive_int, default=10, help="Number of lines to read from the end")
    parser.add_argument("--bytes", type=positive_int, nargs="?", help="Number of bytes to read from the end", )
    parser.add_argument("filename", nargs="?", help="Path of the file to be read")
    return parser.parse_args()


def main(args):

    if args.bytes is not None:
        tail(args.filename,args.bytes, True)
    
    else:
        tail(args.filename, args.lines)
        

if __name__ == "__main__":
    args = parse_arguments()

    main(args)