Source code for invenio_records_rest.memento

# -*- coding: utf-8 -*-
#
# This file is part of Invenio.
# Copyright (C) 2016 CERN.
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"""Support for Memento response."""

from __future__ import absolute_import, print_function

from flask import after_this_request, request
from invenio_records.api import Record
from link_header import Link, LinkHeader
from werkzeug.http import http_date, parse_date


def get_memento(record, accept_datetime):
    """Return revision of the record for given datetime."""
    if accept_datetime >= record.updated:
        return record
    for revision in reversed(record.revisions):
        updated = revision.updated.replace(microsecond=0)
        if updated <= accept_datetime:
            return revision
    return revision


class MementoRecord(Record):
    """Implement basic Memento protocol.

    The original resource acts as its own TimeGate without distict Memento
    URI (see section 4.1.3).
    """

    @classmethod
    def get_record(cls, *args, **kwargs):
        """Return record object and enhance response."""
        record = super(MementoRecord, cls).get_record(*args, **kwargs)

        if request.method in ('GET', 'HEAD'):
            if 'Accept-Datetime' in request.headers:
                memento = get_memento(record, parse_date(
                    request.headers['Accept-Datetime']
                ))

                @after_this_request
                def memento_datetime(response):
                    """Add Memento-Datetime header."""
                    response.headers['Memento-Datetime'] = http_date(
                        memento.updated
                    )
                    response.headers['Vary'] = 'accept-datetime, accept'
                    response.headers['Link'] = LinkHeader([
                        Link(request.url, rel='original timegate')
                    ])
                    return response
                return memento
        return record