ocrd-galley/ppn2ocr

#!/usr/bin/env python3
"""Get OCR results as a OCR-D workspace for a given PPN"""
import os
import requests
import sys
import lxml.etree as ET
import re
import subprocess
import click
from copy import deepcopy


XMLNS = {
    'mets': 'http://www.loc.gov/METS/',
    'xlink': 'http://www.w3.org/1999/xlink'
}
API_URL = 'https://oai.sbb.berlin'
IDENTIFIER_TEMPLATE = 'oai:digital.staatsbibliothek-berlin.de:%s'


for prefix, uri in XMLNS.items():
    ET.register_namespace(prefix, uri)


def oai_mets(ppn):
    """Retrieve METS metadata for a given PPN."""

    params = {
        'verb': 'GetRecord',
        'metadataPrefix': 'mets',
        'identifier': IDENTIFIER_TEMPLATE % ppn
    }

    s = requests.Session()
    r = s.get(API_URL, params=params)
    mets = ET.XML(r.content).find(f".//{{{XMLNS['mets']}}}mets")
    mets = ET.ElementTree(mets)

    return mets


def iiif_url_for_dms_url(dms_url, ppn, size, format):
    """
    Construct an IIIF URL from a dms URL.

    This function exists to encapsulate the hack of rewriting the URL to get IIIF.
    """
    if ppn not in dms_url:
        raise ValueError(f"Unexpected URL {dms_url}")
    m = re.search(r'/dms/.*/([0-9]+)\.jpg$', dms_url)
    if m:
        page_num = m.group(1)
    else:
        raise ValueError(f"Unexpected URL {dms_url}")
    iiif_identifier = f'{ppn}-{page_num}'
    iiif_quality = 'default'
    iiif_url = f'https://content.staatsbibliothek-berlin.de/dc/{iiif_identifier}/full/{size}/0/{iiif_quality}.{format}'

    return iiif_url


def remove_file_grp(mets, use):
    for bad_fileid in mets.xpath(f'//mets:fileGrp[@USE="{use}"]/mets:file/@ID', namespaces=XMLNS):
        for bad in mets.xpath(f'//mets:fptr[@FILEID="{bad_fileid}"]', namespaces=XMLNS):
            bad.getparent().remove(bad)
    for bad in mets.xpath(f'//mets:fileGrp[@USE="{use}"]', namespaces=XMLNS):
        bad.getparent().remove(bad)


def mime_type_for_format(format_):
    if format_ == 'tif':
        mime_type = 'image/tiff'
    elif format_ == 'jpg':
        mime_type = 'image/jpg'
    else:
        raise ValueError()

    return mime_type


def prune_file_grps(mets):
    """
    Prune unwanted file groups

    We only want to keep the MAX file group (we created it ourselves) and
    possibly ABBYY full texts in FULLTEXT.

    For the PRESENTATION + LOCAL file groups we definitely want to delete
    because they contain local file:/// or file:/ links, which are not handled
    well by "ocrd workspace". They are not explicitly mentioned, as we
    only keep a whitelist.
    """
    wanted_file_grps = ["MAX", "FULLTEXT"]

    for u in mets.xpath('//mets:fileGrp/@USE', namespaces=XMLNS):
        if u not in wanted_file_grps:
            remove_file_grp(mets, u)


def make_workspace(ppn, workspace):
    # Make workspace directory
    os.mkdir(workspace)
    os.chdir(workspace)

    mets = oai_mets(ppn)



    # Delete MAX file group - we assume that, if it exists, it is not as
    # we expect it, e.g. IIIF full URLs
    remove_file_grp(mets, 'MAX')

    # Duplicate DEFAULT file group into a new file group MAX
    format_ = 'tif'
    file_grp_default = mets.find('//mets:fileGrp[@USE="DEFAULT"]', namespaces=XMLNS)

    if file_grp_default is None:
        raise ValueError("This document has no DEFAULT file group, could be a multi-volume work")

    file_grp_best = deepcopy(file_grp_default)

    file_grp_best.attrib['USE'] = 'MAX'
    for f in file_grp_best.findall('./mets:file', namespaces=XMLNS):
        old_id = f.attrib['ID']
        new_id = re.sub('DEFAULT', 'MAX', old_id)
        f.attrib['ID'] = new_id
        f.attrib['MIMETYPE'] = mime_type_for_format(format_)

        for fptr in mets.findall(f'//mets:fptr[@FILEID="{old_id}"]', namespaces=XMLNS):
            new_fptr = deepcopy(fptr)
            new_fptr.attrib['FILEID'] = new_id
            fptr.getparent().append(new_fptr)

        # XXX Need to fumble around with the URL for now
        flocat = f.find(f".//{{{XMLNS['mets']}}}FLocat")
        old_url = flocat.attrib[f"{{{XMLNS['xlink']}}}href"]
        url_iiif_full = iiif_url_for_dms_url(old_url, ppn, 'full', format_)
        flocat.attrib[f"{{{XMLNS['xlink']}}}href"] = url_iiif_full

    mets.find('//mets:fileSec', namespaces=XMLNS).append(file_grp_best)


    prune_file_grps(mets)


    # Write mets.xml
    mets.write('mets.xml', pretty_print=True)

    # TODO
    # Validate workspace
    #ocrd workspace validate mets.xml | grep -v "<notice>Won't download remote image"


def validate_ppn(ctx, param, value):
    """Validate a PPN argument"""
    if not value.startswith('PPN'):
        raise click.BadParameter('PPN must be in format PPNxxxxxxxx')
    else:
        return value


@click.command()
@click.argument('ppn', callback=validate_ppn)
def ppn2ocr(ppn):
    """
    Get METS with best images for a document PPN

    For example, to get the document "PROPOSITIONES PHILOSOPHICAE: [...]" use this:

    \b
    ppn2ocr PPN699887615
    ls PPN699887615
    """
    self_dir = os.path.realpath(os.path.dirname(sys.argv[0]))
    make_workspace(ppn, ppn)

    # XXX
    #  subprocess.run([
    #     os.path.join(self_dir, 'run-docker-hub'),
    #     '-I', 'MAX',
    #     '--skip-validation'
    #  ])


if __name__ == '__main__':
    ppn2ocr()