#!/usr/bin/env python3
# pylint: disable=C0103

"""
From a list of subdomains, output only
the ones resolving to a first-party tracker.
"""

import argparse
import sys
import progressbar
import csv
import typing

# DomainRule = typing.Union[bool, typing.Dict[str, 'DomainRule']]
DomainRule = typing.Union[bool, typing.Dict]

RULES_DICT: DomainRule = dict()

def subdomain_matching(subdomain: str) -> bool:
    parts = subdomain.split('.')
    parts.reverse()
    dic = RULES_DICT
    for part in parts:
        if isinstance(dic, bool) or part not in dic:
            break
        dic = dic[part]
    if isinstance(dic, bool):
        return dic
    return False


def get_matching(chain: typing.List[str], no_explicit: bool = False
                 ) -> typing.Iterable[str]:
    initial = chain[0]
    cname_destinations = chain[1:-1]
    # a_destination = chain[-1]
    initial_matching = subdomain_matching(initial)
    if no_explicit and initial_matching:
        return
    cname_matching = any(map(subdomain_matching, cname_destinations))
    if cname_matching or initial_matching:
        yield initial


def register_rule(subdomain: str) -> None:
    # Make a tree with domain parts
    parts = subdomain.split('.')
    parts.reverse()
    dic = RULES_DICT
    last_part = len(parts) - 1
    for p, part in enumerate(parts):
        if isinstance(dic, bool):
            return
        if p == last_part:
            dic[part] = True
        else:
            dic.setdefault(part, dict())
            dic = dic[part]

if __name__ == '__main__':

    # Parsing arguments
    parser = argparse.ArgumentParser(
        description="Filter first-party trackers from a list of subdomains")
    parser.add_argument(
        '-i', '--input', type=argparse.FileType('r'), default=sys.stdin,
        help="Input file with DNS chains")
    parser.add_argument(
        '-o', '--output', type=argparse.FileType('w'), default=sys.stdout,
        help="Outptut file with one tracking subdomain per line")
    parser.add_argument(
        '-n', '--no-explicit', action='store_true',
        help="Don't output domains already blocked with rules without CNAME")
    parser.add_argument(
        '-r', '--rules', type=argparse.FileType('r'), default='rules',
        help="Rules file")
    args = parser.parse_args()

    # Progress bar
    widgets = [
        progressbar.Percentage(),
        ' ', progressbar.SimpleProgress(),
        ' ', progressbar.Bar(),
        ' ', progressbar.Timer(),
        ' ', progressbar.AdaptiveTransferSpeed(unit='req'),
        ' ', progressbar.AdaptiveETA(),
    ]
    progress = progressbar.ProgressBar(widgets=widgets)

    # Reading rules
    for rule in args.rules:
        register_rule(rule.strip())

    # Approximating line count
    if args.input.seekable():
        lines = 0
        for line in args.input:
            lines += 1
        progress.max_value = lines
        args.input.seek(0)

    # Reading domains to filter
    reader = csv.reader(args.input)
    progress.start()
    for chain in reader:
        for match in get_matching(chain, no_explicit=args.no_explicit):
            print(match, file=args.output)
        progress.update(progress.value + 1)
    progress.finish()