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#! /usr/bin/env python3


# eurostat-fetcher -- Fetch series from Eurostat database
# By: Emmanuel Raviart <emmanuel.raviart@cepremap.org>
#
# Copyright (C) 2017 Cepremap
# https://git.nomics.world/dbnomics-fetchers/eurostat-fetcher
#
# eurostat-fetcher is free software; you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# eurostat-fetcher 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 Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
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# along with this program.  If not, see <https://www.gnu.org/licenses/>.
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"""Fetch series from Eurostat, the statistical office of the European Union, using bulk download and SDMX formats.

http://ec.europa.eu/eurostat/data/database

EUROSTAT bulk download:
- http://ec.europa.eu/eurostat/fr/data/bulkdownload
- http://ec.europa.eu/eurostat/estat-navtree-portlet-prod/BulkDownloadListing

EUROSTAT SDMX documentation:
- http://ec.europa.eu/eurostat/web/sdmx-infospace/welcome
- http://ec.europa.eu/eurostat/web/sdmx-web-services/rest-sdmx-2.1
"""


import argparse
import io
import re
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import shutil
import subprocess
import sys
import zipfile
from pathlib import Path
from dulwich.errors import NotGitRepository
from dulwich.repo import Repo
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from lxml import etree

from dbnomics_data_model.storages import StorageError
from dbnomics_data_model.storages import git as git_storage
log = logging.getLogger(__name__)
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    nt='urn:eu.europa.ec.eurostat.navtree',
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)
prepared_element_re = re.compile('<Prepared>.+</Prepared>')
def iter_datasets_to_download(xml_element, old_xml_element=None):
    """Yield datasets. If old_xml_element is provided, yield only updated datasets."""
    old_last_update_by_dataset_code = {}
    if old_xml_element is not None:
        # Index lastUpdate attributes in old table_of_contents.xml.
        for element in old_xml_element.iterfind('.//nt:leaf[@type="dataset"]', namespaces=nsmap):
            dataset_code = element.findtext("nt:code", namespaces=nsmap)
            old_last_update = element.findtext("nt:lastUpdate", namespaces=nsmap)
            old_last_update_by_dataset_code[dataset_code] = old_last_update

    for leaf_element in xml_element.iterfind('.//nt:leaf[@type="dataset"]', namespaces=nsmap):
        if old_xml_element is None:
            yield leaf_element
        else:
            dataset_code = leaf_element.findtext('nt:code', namespaces=nsmap)
            old_last_update = old_last_update_by_dataset_code.get(dataset_code)
            if old_last_update is None:
                # This leaf_element is new in this version of table_of_contents.xml
                yield leaf_element
            else:
                last_update = leaf_element.findtext("nt:lastUpdate", namespaces=nsmap)
                if last_update != old_last_update:
                    yield leaf_element


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def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('target_dir', type=Path, help='path of target directory containing Eurostat series')
    parser.add_argument('--full', action='store_true',
                        help='download all datasets; default behavior is to download what changed since last commit')
    parser.add_argument('--resume', action='store_true', help='keep existing files in target directory')
    parser.add_argument('-v', '--verbose', action='store_true', default=False, help='display debug logging messages')
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    args = parser.parse_args()
        format="%(levelname)s:%(asctime)s:%(message)s",
        level=logging.DEBUG if args.verbose else logging.INFO,
    )

    assert args.target_dir.is_dir()
    parser = etree.XMLParser(remove_blank_text=True)

    log.info("Mode: {}".format("full" if args.full else "incremental"))
    # Read old table of contents.
    table_of_contents_file_name = 'table_of_contents.xml'

    old_xml_element = None
    if not args.full:
        try:
            repo = Repo(str(args.target_dir))
        except NotGitRepository:
            log.error("%s is not a Git repository. Use --full option to download all the files of the provider.")
            sys.exit(1)
        try:
            tree = git_storage.get_commit_tree(repo, "HEAD", args.target_dir)
        except StorageError:
            log.error("%s is not a Git repository. Use --full option to download all the files of the provider.")
            sys.exit(1)
        table_of_contents_bytes = git_storage.load_text_blob(repo, tree, table_of_contents_file_name, decode=False)
        old_xml_element = etree.fromstring(table_of_contents_bytes)
    # Fetch new table of contents.

    xml_file_path = args.target_dir / table_of_contents_file_name
    xml_url = 'http://ec.europa.eu/eurostat/estat-navtree-portlet-prod/BulkDownloadListing?file={}'.format(
        table_of_contents_file_name)
    log.info('Fetching table of content {}'.format(xml_url))
    response = requests.get(xml_url)
    xml_element = etree.fromstring(response.content, parser=parser)
    with open(str(xml_file_path), 'wb') as xml_file:
        etree.ElementTree(xml_element).write(xml_file, encoding='utf-8', pretty_print=True, xml_declaration=True)
    # Create first-level directories.

    data_dir = args.target_dir / 'data'
    data_dir.mkdir(exist_ok=True)
    datastructures_dir = args.target_dir / 'datastructure'
    datastructures_dir.mkdir(exist_ok=True)

    # Build set of datasets and set of datasets definitions to download.

    datasets = set()
    datastructures = set()
    for leaf_element in iter_datasets_to_download(xml_element, old_xml_element):
        dataset_code = leaf_element.findtext('./nt:code', namespaces=nsmap)
        dataset_url = leaf_element.findtext('./nt:downloadLink[@format="sdmx"]', namespaces=nsmap)
        if dataset_url:
            datasets.add((dataset_code, dataset_url))
        datastructure_url = leaf_element.findtext('./nt:metadata[@format="sdmx"]', namespaces=nsmap)
        if datastructure_url:
            datastructures.add(datastructure_url)

    log.info("Downloading {} datasets and {} datastructures.".format(len(datasets), len(datastructures)))

    # Delete directories of datasets and datasets definitions to download.

    if not args.resume:
        for dataset_code, dataset_url in datasets:
            dataset_dir = data_dir / dataset_code
            if dataset_dir.is_dir():
                shutil.rmtree(str(dataset_dir))
        for datastructure_url in datastructures:
            datastructure_code = datastructure_url.rsplit('/', 1)[-1].split('.', 1)[0]
            datastructure_dir = datastructures_dir / datastructure_code
            if datastructure_dir.is_dir():
                shutil.rmtree(str(datastructure_dir))

    for index, (dataset_code, dataset_url) in enumerate(sorted(datasets), start=1):
        dataset_dir = data_dir / dataset_code
        if args.resume and dataset_dir.is_dir() and list(dataset_dir.iterdir()):
            log.info('Skipping existing dataset {}/{} {}'.format(index, len(datasets), dataset_url))
            dataset_dir.mkdir(exist_ok=True)
            log.info('Fetching dataset {}/{} {}'.format(index, len(datasets), dataset_url))
            response = requests.get(dataset_url)
            response.raise_for_status()
            data_zip_file = zipfile.ZipFile(io.BytesIO(response.content))
            for data_zip_info in data_zip_file.infolist():
                if data_zip_info.filename.endswith('.xml'):
                    with data_zip_file.open(data_zip_info) as data_file:
                        xml_file_path = dataset_dir / data_zip_info.filename
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                        write_normalized_xml_file(xml_file_path, data_file)
                    data_zip_file.extract(data_zip_info, str(dataset_dir))
    # Fetch datasets definitions.
    for index, datastructure_url in enumerate(sorted(datastructures), start=1):
        datastructure_code = datastructure_url.rsplit('/', 1)[-1].split('.', 1)[0]
        datastructure_dir = datastructures_dir / datastructure_code
        if args.resume and datastructure_dir.is_dir() and list(dataset_dir.iterdir()):
            log.info('Skipping existing data structure {}/{} {}'.format(index, len(datastructures), datastructure_url))
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        else:
            datastructure_dir.mkdir(exist_ok=True)
            log.info('Fetching data structure {}/{} {}'.format(index, len(datastructures), datastructure_url))
            response = requests.get(datastructure_url)
            response.raise_for_status()
            metadata_zip_file = zipfile.ZipFile(io.BytesIO(response.content))
            for metadata_zip_info in metadata_zip_file.infolist():
                if metadata_zip_info.filename.endswith('.xml'):
                    with metadata_zip_file.open(metadata_zip_info) as metadata_file:
                        xml_file_path = datastructure_dir / metadata_zip_info.filename
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                        write_normalized_xml_file(xml_file_path, metadata_file)
                    metadata_zip_file.extract(metadata_zip_info, str(datastructure_dir))
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def write_normalized_xml_file(xml_file_path, source_file):
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    """Normalize data that changes at each download, like today date,
    in order to avoid triggering a false commit in source data.
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    Use regexes because lxml raises SerialisationError with too large files.
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    global prepared_element_re
    xml_str = source_file.read().decode('utf-8')
    with open(str(xml_file_path), mode="w") as xml_file:
        xml_file.write(prepared_element_re.sub("<Prepared>1111-11-11T11:11:11</Prepared>", xml_str, 1))
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if __name__ == '__main__':
    sys.exit(main())