#!/usr/bin/env python3
from sys import stdin
from sys import exit as sysexit
from hashlib import blake2b
from io import BytesIO
from subprocess import Popen, PIPE

import click

from identicon import Identicon


DIGEST_SIZE = 20
BUF_SIZE = 65536  # Linux default pipe capacity is 64KiB (64 * 2^10)


@click.command(
    help=(
        'Print OpenSSH style randomart identicon for arbitrary data.\n\n'
        'If TEXT or --file is not supplied, data is read from STDIN.'
    )
)
@click.argument('text', default=None, type=str, required=False)
@click.option(
    '--file', '-f', default=None, type=click.Path(exists=True),
    help='Calculate from file or directory (recursive).'
)
def main(**kwargs):
    if not (stream := get_input_stream(kwargs)):
        print_usage_and_exit()

    digest = get_digest(stream.stream)
    stream.close()

    i = Identicon(digest)
    i.calculate()
    print(i)


def get_input_stream(kwargs):
    stream = None
    if (text := kwargs["text"]) is not None:
        stream = ClosableStream(BytesIO(text.encode()))
    elif file := kwargs["file"]:
        stream = get_deterministic_tar_stream(file)
    elif not stdin.isatty():
        stream = ClosableStream(stdin.buffer)
    return stream


class ClosableStream:
    def __init__(self, stream, close_func=None):
        self.stream = stream
        self._close_func = close_func or (lambda: None)

    def close(self):
        return self._close_func()


def get_deterministic_tar_stream(file):
    # pylint: disable=consider-using-with
    cmd = (
        'tar',
        f'--blocking-factor={BUF_SIZE//512}',
        '--sort=name',
        '--mtime=UTC 1970-01-01',
        '--owner=root:0', '--group=root:0', '--numeric-owner',
        '--mode=a=rwX', '--no-acls', '--no-xattrs', '--no-selinux',
        '-C', file, '-cf', '-', '.'
    )
    p = Popen(cmd, stdout=PIPE, stderr=PIPE)

    def wait_and_check_exitcode():
        exit_code = p.wait()
        if exit_code != 0:
            raise RuntimeError(f"Tar failed: {p.stderr.read().decode()}")

    return ClosableStream(p.stdout, wait_and_check_exitcode)


def print_usage_and_exit():
    command = main
    with click.Context(command) as ctx:
        click.echo(command.get_help(ctx))
    sysexit(1)


def get_digest(stream):
    hasher = blake2b(digest_size=DIGEST_SIZE)
    while data := stream.read(BUF_SIZE):
        hasher.update(data)
    return hasher.digest()



if __name__ == '__main__':
    main()