"""
Utility functions for strings, paths and URL.
"""
import re
import json
from .constants import REGEX_FILE_ID
from .deprecate import deprecation_warning
from warnings import warn
__all__ = [
'assert_file_grp_cardinality',
'concat_padded',
'get_local_filename',
'is_local_filename',
'is_string',
'make_file_id',
'nth_url_segment',
'parse_json_string_or_file',
'parse_json_string_with_comments',
'remove_non_path_from_url',
'safe_filename',
]
[docs]def assert_file_grp_cardinality(grps, n, msg=None):
"""
Assert that a string of comma-separated fileGrps contains exactly ``n`` entries.
"""
if isinstance(grps, str):
grps = grps.split(',')
assert len(grps) == n, \
"Expected exactly %d output file group%s%s, but '%s' has %d" % (
n,
'' if n == 1 else 's',
' (%s)' % msg if msg else '',
grps,
len(grps)
)
[docs]def concat_padded(base, *args):
"""
Concatenate string and zero-padded 4 digit number
"""
ret = base
for n in args:
if is_string(n):
ret = "%s_%s" % (ret, n)
else:
ret = "%s_%04i" % (ret, n)
return ret
[docs]def remove_non_path_from_url(url):
"""
Remove everything from URL after path.
"""
url = url.split('?', 1)[0] # query
url = url.split('#', 1)[0] # fragment identifier
url = re.sub(r"/+$", "", url) # trailing slashes
return url
[docs]def make_file_id(ocrd_file, output_file_grp):
"""
Derive a new file ID for an output file from an existing input file ``ocrd_file``
and the name of the output file's ``fileGrp/@USE``, ``output_file_grp``.
If ``ocrd_file``'s ID contains the input file's fileGrp name, then replace it by ``output_file_grp``.
Else if ``ocrd_file`` has a ``pageId`` but it is not contained in the ``ocrd_file.ID``, then
concatenate ``output_file_grp`` and ``ocrd_file.pageId``.
Otherwise concatenate ``output_file_grp`` with the ``ocrd_file.ID``.
Note: ``make_file_id`` cannot guarantee that the new ID is unique within an actual
:py:class:`ocrd_models.ocrd_mets.OcrdMets`.
The caller is responsible for ensuring uniqueness of files to be added.
Ultimately, ID conflicts will lead to :py:meth:`ocrd_models.ocrd_mets.OcrdMets.add_file`
raising an exception.
This can be avoided if all processors use ``make_file_id`` consistently for ID generation.
Note: ``make_file_id`` generates page-specific IDs. For IDs representing page segments
or ``pc:AlternativeImage`` files, the output of ``make_file_id`` may need to be concatenated
with a unique string for that sub-page element, such as `".IMG"` or the segment ID.
"""
# considerations for this behaviour:
# - uniqueness (in spite of different METS and processor conventions)
# - predictability (i.e. output name can be anticipated from the input name)
# - stability (i.e. output at least as much sorted and consistent as the input)
# ... and all this in spite of --page-id selection and --overwrite
# (i.e. --overwrite should target the existing ID, and input vs output
# IDs should be different, except when overwriting the input fileGrp)
ret = ocrd_file.ID.replace(ocrd_file.fileGrp, output_file_grp)
if ret == ocrd_file.ID and output_file_grp != ocrd_file.fileGrp:
if ocrd_file.pageId and ocrd_file.pageId not in ocrd_file.ID:
ret = output_file_grp + '_' + ocrd_file.pageId
else:
ret = output_file_grp + '_' + ocrd_file.ID
if not REGEX_FILE_ID.fullmatch(ret):
ret = ret.replace(':', '_')
ret = re.sub(r'^([^a-zA-Z_])', r'id_\1', ret)
ret = re.sub(r'[^\w.-]', r'', ret)
return ret
[docs]def nth_url_segment(url, n=-1):
"""
Return the last /-delimited segment of a URL-like string
Arguments:
url (string):
n (integer): index of segment, default: -1
"""
segments = remove_non_path_from_url(url).split('/')
try:
return segments[n]
except IndexError:
return ''
[docs]def get_local_filename(url, start=None):
"""
Return local filename, optionally relative to ``start``
Arguments:
url (string): filename or URL
start (string): Base path to remove from filename. Raise an exception if not a prefix of url
"""
if url.startswith('https://') or url.startswith('http:'):
raise ValueError("Can't determine local filename of http(s) URL")
if url.startswith('file://'):
url = url[len('file://'):]
# Goobi/Kitodo produces those, they are always absolute
if url.startswith('file:/'):
url = url[len('file:'):]
if start:
if not url.startswith(start):
raise ValueError("Cannot remove prefix %s from url %s" % (start, url))
if not start.endswith('/'):
start += '/'
url = url[len(start):]
return url
[docs]def is_local_filename(url):
"""
Whether a url is a local filename.
"""
# deprecation_warning("Deprecated so we spot inconsistent URL/file handling")
return url.startswith('file://') or not('://' in url)
[docs]def is_string(val):
"""
Return whether a value is a ``str``.
"""
return isinstance(val, str)
[docs]def parse_json_string_or_file(*values): # pylint: disable=unused-argument
"""
Parse a string as either the path to a JSON object or a literal JSON object.
Empty strings are equivalent to '{}'
"""
ret = {}
for value in values:
err = None
value_parsed = None
if re.fullmatch(r"\s*", value):
continue
try:
try:
with open(value, 'r') as f:
value_parsed = parse_json_string_with_comments(f.read())
except (FileNotFoundError, OSError):
value_parsed = parse_json_string_with_comments(value.strip())
if not isinstance(value_parsed, dict):
err = ValueError("Not a valid JSON object: '%s' (parsed as '%s')" % (value, value_parsed))
except json.decoder.JSONDecodeError as e:
err = ValueError("Error parsing '%s': %s" % (value, e))
if err:
raise err # pylint: disable=raising-bad-type
ret = {**ret, **value_parsed}
return ret
[docs]def safe_filename(url):
"""
Sanitize input to be safely used as the basename of a local file.
"""
ret = re.sub(r'[^\w]+', '_', url)
ret = re.sub(r'^\.*', '', ret)
ret = re.sub(r'\.\.*', '.', ret)
# print('safe filename: %s -> %s' % (url, ret))
return ret
def generate_range(start, end):
"""
Generate a list of strings by incrementing the number part of ``start`` until including ``end``.
"""
ret = []
try:
start_num, end_num = re.findall(r'\d+', start)[-1], re.findall(r'\d+', end)[-1]
except IndexError:
raise ValueError("Range '%s..%s': could not find numeric part" % (start, end))
if start_num == end_num:
warn("Range '%s..%s': evaluates to the same number")
for i in range(int(start_num), int(end_num) + 1):
ret.append(start.replace(start_num, str(i).zfill(len(start_num))))
return ret
