downloader_extractor.py

#!/usr/bin/env python3
#
# This file is part of SumeCzech corpus <http://hdl.handle.net/11234/1-2615>.
#
# Copyright 2018 Institute of Formal and Applied Linguistics, Faculty of
# Mathematics and Physics, Charles University in Prague, Czech Republic.
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

import json
import hashlib

from downloader_extractor_utils import *

URL = 'url'
HEADLINE = 'headline'
ABSTRACT = 'abstract'
TEXT = 'text'
SECTION = 'section'
SUBDOMAIN = 'subdomain'
FILENAME = 'filename'
OFFSET = 'offset'
LENGTH = 'length'
PUBLISHED = 'published'
DATASET = 'dataset'

class Extractor(object):
    @staticmethod
    def extract_document(input_document):
        parsed_content = Extractor._parse(input_document)
        Extractor._add_checksum(parsed_content)
        return parsed_content

    @staticmethod
    def _parse(entry_dict):
        # Parse, ignoring exceptions
        parsed_document = Extractor._parse_entry(entry_dict)
        # normalize spacing and quotes, and additional replacements
        for section_key in [HEADLINE, ABSTRACT, TEXT]:
            parsed_document[section_key].encode()
            parsed_document[section_key] = parsed_document[section_key].replace('\r', '').replace('&nbsp;', ' ')
            parsed_document[section_key] = re.sub(r'\[celá zpráva]', ' ', parsed_document[section_key], 0, re.I)
            if section_key in [HEADLINE, ABSTRACT]: parsed_document[section_key] = parsed_document[section_key].replace('\n', ' ')
            parsed_document[section_key] = re.sub(r'[ \t\xA0\u2028]+', ' ', parsed_document[section_key].strip())
            parsed_document[section_key] = re.sub(r'[ ]*\n[ ]*', '\n', parsed_document[section_key])
            parsed_document[section_key] = re.sub(r"['`‚‘’]{1,2}", '"', parsed_document[section_key])
            parsed_document[section_key] = re.sub(r"[„“]", '"', parsed_document[section_key])
        return parsed_document

    @staticmethod
    def _parse_entry(contents):
        """Parse one commoncrawl JSON.

           Return:
            - error status
            - text
            - abstract
            - headline
            - subdomain (i.e., domaci.novinky.cz)

            More specifically:
            return status, url, abstract_len, document_len, headline, abstract, document, section, subdomain, filename
        """
        url = contents['url']
        parse = urlparse(url)
        domain = '.'.join(parse.netloc.rsplit('.', maxsplit=2)[-2:])
        subdomain = parse.netloc.replace('www.', '')
        if domain == subdomain:
            section = (parse.path.split('/') + [''])[1]
            if not section.isalnum():
                section = subdomain
        else:
            section = subdomain
            if 'blog' in section:
                section = 'blogs'

        # get domain/subdomain settings
        # some subdomains require specific settings
        # if not, use generic settings for the domain
        domain_settings = domain_settings_dict.get(subdomain, domain_settings_dict.get(domain, None))

        # parse
        # The non-UTF8 pages sometimes are encoded in UTF-8 -- try it first,
        # and fallback to the non-UTF8 encoding
        try:
            warc = contents['content'].encode('latin-1').decode('utf-8')
        except:
            warc = contents['content'].encode('latin-1').decode(domain_settings.encoding)
        html = warc.split('\r\n\r\n', maxsplit=2)[-1].replace('\r', '')
        soup = BeautifulSoup(html, 'html.parser')

        # replace br by a newline
        for br in soup('br'):
            br.replace_with('\n')

        # get headline
        headline_text = domain_settings.headline_extractor(soup)

        # get abstract
        abstract_text = domain_settings.abstract_extractor(soup)

        # get document
        document_text = domain_settings.document_extractor(soup, domain)

        published = domain_settings.date_extractor(soup)
        if published is None: published = ""

        return {URL: url,
                HEADLINE: headline_text,
                ABSTRACT: abstract_text,
                TEXT: document_text,
                SECTION: section,
                SUBDOMAIN: subdomain,
                FILENAME: contents[FILENAME],
                OFFSET: contents[OFFSET],
                LENGTH: contents[LENGTH],
                PUBLISHED: published,
                DATASET: contents[DATASET]}

    @staticmethod
    def _add_checksum(json_data):
        json_data_for_checksum = {}

        for field in ["headline", "abstract", "text", "section", "subdomain", "published", "url"]:
            json_data_for_checksum[field] = json_data[field]

        string_for_checksum = json.dumps(json_data_for_checksum,
                                         ensure_ascii=True,
                                         sort_keys=True,
                                         indent=None,
                                         separators=(",", ":"))

        json_data['md5'] = hashlib.md5(string_for_checksum.encode('utf-8')).hexdigest()

        return json_data