# wikiget - CLI tool for downloading files from Wikimedia sites
# Copyright (C) 2018, 2019 Cody Logan
# SPDX-License-Identifier: GPL-3.0-or-later
#
# Wikiget is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Wikiget is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Wikiget. If not, see <https://www.gnu.org/licenses/>.

"""Main wikiget functions."""

from __future__ import absolute_import, division, print_function, unicode_literals

from builtins import open

from future import standard_library

standard_library.install_aliases()

import argparse
import hashlib
import logging
import os
import re
import sys
from urllib.parse import unquote, urlparse

from mwclient import InvalidResponse, Site, __version__ as mwclient_version
from requests import ConnectionError
from tqdm import tqdm

from wikiget.version import __version__

BLOCKSIZE = 65536
DEFAULT_SITE = "en.wikipedia.org"
USER_AGENT = "wikiget/{} (https://github.com/clpo13/wikiget) " \
             "mwclient/{}".format(__version__, mwclient_version)


def main():
    """
    Main entry point for console script. Automatically compiled by setuptools
    when installed with `pip install` or `python setup.py install`.
    """

    parser = argparse.ArgumentParser(description="""
                                     A tool for downloading files from MediaWiki sites
                                     using the file name or description page URL
                                     """,
                                     epilog="""
                                     Copyright (C) 2018, 2019 Cody Logan. License GPLv3+: GNU GPL
                                     version 3 or later <http://www.gnu.org/licenses/gpl.html>.
                                     This is free software; you are free to change and redistribute
                                     it under certain conditions. There is NO WARRANTY, to the
                                     extent permitted by law.
                                     """)
    parser.add_argument("FILE", help="""
                        name of the file to download with the File: or Image: prefix,
                        or the URL of its file description page
                        """)
    parser.add_argument("-V", "--version", action="version",
                        version="%(prog)s {}".format(__version__))
    output_options = parser.add_mutually_exclusive_group()
    output_options.add_argument("-q", "--quiet", help="suppress warning messages",
                                action="store_true")
    output_options.add_argument("-v", "--verbose",
                                help="print detailed information; use -vv for even more detail",
                                action="count", default=0)
    parser.add_argument("-f", "--force", help="force overwriting existing files",
                        action="store_true")
    parser.add_argument("-s", "--site", default=DEFAULT_SITE,
                        help="MediaWiki site to download from (default: %(default)s)")
    parser.add_argument("-o", "--output", help="write download to OUTPUT")
    parser.add_argument("-a", "--batch", help="treat FILE as a textfile containing multiple files to download, one URL or filename per line",
                        action="store_true")

    args = parser.parse_args()

    # print API and debug messages in verbose mode
    if args.verbose >= 2:
        logging.basicConfig(level=logging.DEBUG)
    elif args.verbose >= 1:
        logging.basicConfig(level=logging.WARNING)

    if args.batch:
        # batch download mode
        input_file = args.FILE
        if args.verbose >= 1:
            print("Info: using batch file '{}'".format(input_file))
        try:
            fd = open(input_file, "r")
        except IOError as e:
            print("File could not be read. The following error was encountered:")
            print(e)
            sys.exit(1)
        else:
            with fd:
                for _, line in enumerate(fd):
                    line = line.strip()
                    download(line, args)
    else:
        # single download mode
        dl = args.FILE
        download(dl, args)


def download(dl, args):
    url = urlparse(dl)

    if url.netloc:
        filename = url.path
        site_name = url.netloc
        if args.site is not DEFAULT_SITE and not args.quiet:
            # this will work even if the user specifies 'en.wikipedia.org'
            print("Warning: target is a URL, ignoring site specified with --site")
    else:
        filename = dl
        site_name = args.site

    file_match = valid_file(filename)
    site_match = valid_site(site_name)

    # check for valid site parameter
    if not site_match:
        print("Only Wikimedia sites (wikipedia.org and wikimedia.org) are currently supported.")
        sys.exit(1)

    # check if this is a valid file
    if file_match and file_match.group(1):
        # has File:/Image: prefix and extension
        filename = file_match.group(2)
    else:
        # no file extension and/or prefix, probably an article
        print("Downloading Wikipedia articles is not currently supported.", end="")
        if file_match and not file_match.group(1):
            # file extension detected, but no prefix
            # TODO: no longer possible to get to this point since file_match is None with no prefix
            print(" If this is a file, please add the 'File:' prefix.")
        else:
            print("\n", end="")
        sys.exit(1)

    filename = unquote(filename)  # remove URL encoding for special characters

    dest = args.output or filename

    if args.verbose >= 2:
        print("User agent: {}".format(USER_AGENT))

    # connect to site and identify ourselves
    try:
        site = Site(site_name, clients_useragent=USER_AGENT)
    except ConnectionError:
        # usually this means there is no such site, or there's no network connection
        print("Error: couldn't connect to specified site.")
        sys.exit(1)
    except InvalidResponse as e:
        # site exists, but we couldn't communicate with the API endpoint
        print(e)
        sys.exit(1)

    # get info about the target file
    file = site.images[filename]

    if file.imageinfo != {}:
        # file exists either locally or at Wikimedia Commons
        file_url = file.imageinfo["url"]
        file_size = file.imageinfo["size"]
        file_sha1 = file.imageinfo["sha1"]

        if args.verbose >= 1:
            print("Info: downloading '{}' "
                  "({} bytes) from {}".format(filename, file_size, site.host), end="")
            if args.output:
                print(" to '{}'".format(dest))
            else:
                print("\n", end="")
            print("Info: {}".format(file_url))

        if os.path.isfile(dest) and not args.force:
            print("File '{}' already exists, skipping download (use -f to ignore)".format(dest))
        else:
            try:
                fd = open(dest, "wb")
            except IOError as e:
                print("File could not be written. The following error was encountered:")
                print(e)
                sys.exit(1)
            else:
                # download the file
                with tqdm(total=file_size, unit="B",
                          unit_scale=True, unit_divisor=1024) as progress_bar:
                    with fd:
                        res = site.connection.get(file_url, stream=True)
                        progress_bar.set_postfix(file=dest, refresh=False)
                        for chunk in res.iter_content(1024):
                            fd.write(chunk)
                            progress_bar.update(len(chunk))

            # verify file integrity and optionally print details
            dl_sha1 = verify_hash(dest)

            if args.verbose >= 1:
                print("Info: downloaded file SHA1 is {}".format(dl_sha1))
                print("Info: server file SHA1 is {}".format(file_sha1))
            if dl_sha1 == file_sha1:
                if args.verbose >= 1:
                    print("Info: hashes match!")
                # at this point, we've successfully downloaded the file
            else:
                print("Error: hash mismatch! Downloaded file may be corrupt.")
                sys.exit(1)

    else:
        # no file information returned
        print("Target '{}' does not appear to be a valid file.".format(filename))
        sys.exit(1)


def valid_file(search_string):
    """
    Determines if the given string contains a valid file name, defined as a string
    ending with a '.' and at least one character, beginning with 'File:' or
    'Image:', the standard file prefixes in MediaWiki.
    :param search_string: string to validate
    :returns: a regex Match object if there's a match or None otherwise
    """
    # second group could also restrict to file extensions with three or more
    # letters with ([^/\r\n\t\f\v]+\.\w{3,})
    file_regex = re.compile(r"(File:|Image:)([^/\r\n\t\f\v]+\.\w+)$", re.I)
    return file_regex.search(search_string)


def valid_site(search_string):
    """
    Determines if the given string contains a valid site name, defined as a string
    ending with 'wikipedia.org' or 'wikimedia.org'. This covers all subdomains of
    those domains. Eventually, it should be possible to support any MediaWiki site,
    regardless of domain name.
    :param search_string: string to validate
    :returns: a regex Match object if there's a match or None otherwise
    """
    site_regex = re.compile(r"wiki[mp]edia\.org$", re.I)
    return site_regex.search(search_string)


def verify_hash(filename):
    """
    Calculates the SHA1 hash of the given file for comparison with a known value.
    :param filename: name of the file to calculate a hash for
    :return: hash digest
    """
    hasher = hashlib.sha1()
    with open(filename, "rb") as dl:
        buf = dl.read(BLOCKSIZE)
        while len(buf) > 0:
            hasher.update(buf)
            buf = dl.read(BLOCKSIZE)
    return hasher.hexdigest()