Merge branch 'feature/upstream' into develop

1 files changed, 809 insertions, 0 deletions

diff --git a/raphodo/generatename.py b/raphodo/generatename.py
new file mode 100644
index 0000000..2057485
--- /dev/null
+++ b/raphodo/generatename.py
@@ -0,0 +1,809 @@
+#!/usr/bin/env python3
+
+# Copyright (C) 2007-2017 Damon Lynch <damonlynch@gmail.com>
+
+# This file is part of Rapid Photo Downloader.
+#
+# Rapid Photo Downloader is free software: you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Rapid Photo Downloader 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 General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Rapid Photo Downloader.  If not,
+# see <http://www.gnu.org/licenses/>.
+### USA
+
+__author__ = 'Damon Lynch'
+__copyright__ = "Copyright 2007-2017, Damon Lynch"
+
+import re
+from datetime import datetime, timedelta
+import string
+from collections import namedtuple
+import logging
+from typing import Sequence, Optional, List, Union
+import locale
+# Use the default locale as defined by the LANG variable
+locale.setlocale(locale.LC_ALL, '')
+
+from gettext import gettext as _
+
+from raphodo.preferences import DownloadsTodayTracker
+from raphodo.problemnotification import (
+    RenamingProblems, FilenameNotFullyGeneratedProblem, make_href,
+    FolderNotFullyGeneratedProblemProblem, Problem
+)
+from raphodo.rpdfile import RPDFile, Photo, Video
+from raphodo.storage import get_uri
+
+from raphodo.generatenameconfig import *
+
+
+MatchedSequences = namedtuple(
+    'MatchedSequences', 'session_sequence_no, sequence_letter, downloads_today, stored_sequence_no'
+)
+
+
+def convert_date_for_strftime(datetime_user_choice):
+    try:
+        return DATE_TIME_CONVERT[LIST_DATE_TIME_L2.index(datetime_user_choice)]
+    except KeyError:
+        raise PrefValueInvalidError(datetime_user_choice)
+
+
+class abstract_attribute():
+    """
+    http://stackoverflow.com/questions/32536176/how-to-define-lazy-variable-in-python-which-will-
+    raise-notimplementederror-for-a/32536493
+    """
+
+    def __get__(self, obj, type):
+        # Now we will iterate over the names on the class,
+        # and all its superclasses, and try to find the attribute
+        # name for this descriptor
+        # traverse the parents in the method resolution order
+        for cls in type.__mro__:
+            # for each cls thus, see what attributes they set
+            for name, value in cls.__dict__.items():
+                # we found ourselves here
+                if value is self:
+                    # if the property gets accessed as Child.variable,
+                    # obj will be done. For this case
+                    # If accessed as a_child.variable, the class Child is
+                    # in the type, and a_child in the obj.
+                    this_obj = obj if obj else type
+
+                    raise NotImplementedError(
+                         "%r does not have the attribute %r "
+                         "(abstract from class %r)" %
+                             (this_obj, name, cls.__name__))
+
+        # we did not find a match, should be rare, but prepare for it
+        raise NotImplementedError(
+            "%s does not set the abstract attribute <unknown>", type.__name__)
+
+
+GenerationErrors = Union[FilenameNotFullyGeneratedProblem, FolderNotFullyGeneratedProblemProblem]
+
+
+class NameGeneration:
+    """
+    Generate the name of a photo. Used as a base class for generating names
+    of videos, as well as subfolder names for both file types
+    """
+
+    def __init__(self,
+                 pref_list: List[str],
+                 problems: Optional[RenamingProblems]=None) -> None:
+        self.pref_list = pref_list
+        self.no_metadata = False
+
+        self.problems = problems
+        self.problem = abstract_attribute()  # type: GenerationErrors
+
+        self.strip_forward_slash = abstract_attribute()
+        self.add_extension = abstract_attribute()
+        self.L1_date_check = abstract_attribute()
+
+        self.L0 = ''
+        self.L1 = ''
+        self.L2 = ''
+
+    def _get_values_from_pref_list(self):
+        for i in range(0, len(self.pref_list), 3):
+            yield (self.pref_list[i], self.pref_list[i + 1], self.pref_list[i + 2])
+
+    def _get_date_component(self) -> str:
+        """
+        Returns portion of new file / subfolder name based on date time.
+        If the date is missing, will attempt to use the fallback date.
+        """
+
+        # step 1: get the correct value from metadata
+        if self.L1 == self.L1_date_check:
+            if self.no_metadata:
+                if self.L2 == SUBSECONDS:
+                    d = datetime.fromtimestamp(self.rpd_file.modification_time)
+                    if not d.microsecond:
+                        d = '00'
+                    try:
+                        d = str(round(int(str(d.microsecond)[:3]) / 10))
+                    except:
+                        d = '00'
+                    return d
+                d = datetime.fromtimestamp(self.rpd_file.ctime)
+            else:
+                if self.L2 == SUBSECONDS:
+                    d = self.rpd_file.metadata.sub_seconds(missing=None)
+                    if d is None:
+                        self.problem.missing_metadata.append(_(self.L2))
+                        return ''
+                    else:
+                        return d
+                else:
+                    d = self.rpd_file.date_time(missing=None)
+
+        elif self.L1 == TODAY:
+            d = datetime.now()
+        elif self.L1 == YESTERDAY:
+            delta = timedelta(days=1)
+            d = datetime.now() - delta
+        elif self.L1 == DOWNLOAD_TIME:
+            d = self.rpd_file.download_start_time
+        else:
+            raise TypeError("Date options invalid")
+
+        # step 2: if have a value, try to convert it to string format
+        if d:
+            try:
+                return d.strftime(convert_date_for_strftime(self.L2))
+            except Exception as e:
+                logging.warning(
+                    "Problem converting date/time value for file %s", self.rpd_file.full_file_name
+                )
+                self.problem.bad_converstion_date_time = True
+                self.problem.bad_conversion_exception = e
+
+        # step 3: handle a missing value using file modification time
+        if self.rpd_file.modification_time:
+            try:
+                d = datetime.fromtimestamp(self.rpd_file.modification_time)
+            except Exception:
+                logging.error(
+                    "Both file modification time and metadata date & time are invalid for file %s",
+                    self.rpd_file.full_file_name
+                )
+                self.problem.invalid_date_time = True
+                return ''
+        else:
+            self.problem.missing_metadata.append(_(self.L1))
+            return ''
+
+        try:
+            return d.strftime(convert_date_for_strftime(self.L2))
+        except:
+            logging.error(
+                "Both file modification time and metadata date & time are invalid for file %s",
+                self.rpd_file.full_file_name
+            )
+            self.problem.invalid_date_time = True
+            return ''
+
+    def _get_associated_file_extension(self, associate_file):
+        """
+        Generates extensions with correct capitalization for files like
+        thumbnail or audio files.
+        """
+
+        if not associate_file:
+            return None
+
+        extension = os.path.splitext(associate_file)[1]
+        if self.rpd_file.generate_extension_case == UPPERCASE:
+            extension = extension.upper()
+        elif self.rpd_file.generate_extension_case == LOWERCASE:
+            extension = extension.lower()
+        # else keep extension case the same as what it originally was
+        return extension
+
+    def _get_thm_extension(self) -> None:
+        """
+        Generates THM extension with correct capitalization, if needed
+        """
+        self.rpd_file.thm_extension = self._get_associated_file_extension(
+            self.rpd_file.thm_full_name
+        )
+
+    def _get_audio_extension(self) -> None:
+        """
+        Generates audio extension with correct capitalization, if needed
+        e.g. WAV or wav
+        """
+        self.rpd_file.audio_extension = self._get_associated_file_extension(
+            self.rpd_file.audio_file_full_name
+        )
+
+    def _get_xmp_extension(self) -> None:
+        """
+        Generates XMP extension with correct capitalization, if needed.
+        """
+
+        self.rpd_file.xmp_extension = self._get_associated_file_extension(
+            self.rpd_file.xmp_file_full_name
+        )
+
+    def _get_log_extension(self) -> None:
+        """
+        Generates LOG extension with correct capitalization, if needed.
+        """
+
+        self.rpd_file.log_extension = self._get_associated_file_extension(
+            self.rpd_file.log_file_full_name
+        )
+
+    def _get_filename_component(self):
+        """
+        Returns portion of new file / subfolder name based on the file name
+        """
+
+        name, extension = os.path.splitext(self.rpd_file.name)
+
+        if self.L1 == NAME:
+            filename = name
+        elif self.L1 == EXTENSION:
+            # Used in subfolder name generation
+            if extension:
+                # having the period when this is used as a part of a
+                # subfolder name
+                # is a bad idea when it is at the start!
+                filename = extension[1:]
+            else:
+                self.problem.missing_extension = True
+                return ""
+        elif self.L1 == IMAGE_NUMBER or self.L1 == VIDEO_NUMBER:
+            n = re.search("(?P<image_number>[0-9]+$)", name)
+            if not n:
+                self.problem.missing_image_no = True
+                return ''
+            else:
+                image_number = n.group("image_number")
+
+                if self.L2 == IMAGE_NUMBER_ALL:
+                    filename = image_number
+                elif self.L2 == IMAGE_NUMBER_1:
+                    filename = image_number[-1]
+                elif self.L2 == IMAGE_NUMBER_2:
+                    filename = image_number[-2:]
+                elif self.L2 == IMAGE_NUMBER_3:
+                    filename = image_number[-3:]
+                else:
+                    assert  self.L2 == IMAGE_NUMBER_4
+                    filename = image_number[-4:]
+        else:
+            raise TypeError("Incorrect filename option")
+
+        if self.L2 == UPPERCASE:
+            filename = filename.upper()
+        elif self.L2 == LOWERCASE:
+            filename = filename.lower()
+
+        return filename
+
+    def _get_metadata_component(self):
+        """
+        Returns portion of new image / subfolder name based on the metadata
+
+        Note: date time metadata found in _getDateComponent()
+        """
+
+        if self.L1 == APERTURE:
+            v = self.rpd_file.metadata.aperture()
+        elif self.L1 == ISO:
+            v = self.rpd_file.metadata.iso()
+        elif self.L1 == EXPOSURE_TIME:
+            v = self.rpd_file.metadata.exposure_time(alternativeFormat=True)
+        elif self.L1 == FOCAL_LENGTH:
+            v = self.rpd_file.metadata.focal_length()
+        elif self.L1 == CAMERA_MAKE:
+            v = self.rpd_file.metadata.camera_make()
+        elif self.L1 == CAMERA_MODEL:
+            v = self.rpd_file.metadata.camera_model()
+        elif self.L1 == SHORT_CAMERA_MODEL:
+            v = self.rpd_file.metadata.short_camera_model()
+        elif self.L1 == SHORT_CAMERA_MODEL_HYPHEN:
+            v = self.rpd_file.metadata.short_camera_model(includeCharacters="\-")
+        elif self.L1 == SERIAL_NUMBER:
+            v = self.rpd_file.metadata.camera_serial()
+        elif self.L1 == SHUTTER_COUNT:
+            v = self.rpd_file.metadata.shutter_count()
+            if v:
+                v = int(v)
+                padding = LIST_SHUTTER_COUNT_L2.index(self.L2) + 3
+                formatter = '%0' + str(padding) + "i"
+                v = formatter % v
+        elif self.L1 == FILE_NUMBER:
+            v = self.rpd_file.metadata.file_number()
+            if v and self.L2 == FILE_NUMBER_FOLDER:
+                v = v[:3]
+        elif self.L1 == OWNER_NAME:
+            v = self.rpd_file.metadata.owner_name()
+        elif self.L1 == ARTIST:
+            v = self.rpd_file.metadata.artist()
+        elif self.L1 == COPYRIGHT:
+            v = self.rpd_file.metadata.copyright()
+        else:
+            raise TypeError("Invalid metadata option specified")
+        if self.L1 in (CAMERA_MAKE, CAMERA_MODEL, SHORT_CAMERA_MODEL, SHORT_CAMERA_MODEL_HYPHEN,
+                        OWNER_NAME, ARTIST, COPYRIGHT):
+            if self.L2 == UPPERCASE:
+                v = v.upper()
+            elif self.L2 == LOWERCASE:
+                v = v.lower()
+        if not v:
+            self.problem.missing_metadata.append(_(self.L1))
+        return v
+
+    def _calculate_letter_sequence(self, sequence):
+
+        def _letters(x):
+            """
+            Adapted from algorithm at
+            http://en.wikipedia.org/wiki/Hexavigesimal
+            """
+            v = ''
+            while x > 25:
+                r = x % 26
+                x = x / 26 - 1
+                v = string.ascii_lowercase[r] + v
+            v = string.ascii_lowercase[x] + v
+
+            return v
+
+
+        v = _letters(sequence)
+        if self.L2 == UPPERCASE:
+            v = v.upper()
+
+        return v
+
+    def _format_sequence_no(self, value, amountToPad):
+        padding = LIST_SEQUENCE_NUMBERS_L2.index(amountToPad) + 1
+        formatter = '%0' + str(padding) + "i"
+        return formatter % value
+
+    def _get_downloads_today(self):
+        return self._format_sequence_no(
+            self.rpd_file.sequences.get_downloads_today(), self.L2
+        )
+
+    def _get_session_sequence_no(self):
+        return self._format_sequence_no(
+            self.rpd_file.sequences.get_session_sequence_no(), self.L2
+        )
+
+    def _get_stored_sequence_no(self):
+        return self._format_sequence_no(
+            self.rpd_file.sequences.get_stored_sequence_no(), self.L2
+        )
+
+    def _get_sequence_letter(self):
+        return self._calculate_letter_sequence(
+            self.rpd_file.sequences.get_sequence_letter()
+        )
+
+    def _get_sequences_component(self):
+        if self.L1 == DOWNLOAD_SEQ_NUMBER:
+            return self._get_downloads_today()
+        elif self.L1 == SESSION_SEQ_NUMBER:
+            return self._get_session_sequence_no()
+        elif self.L1 == STORED_SEQ_NUMBER:
+            return self._get_stored_sequence_no()
+        elif self.L1 == SEQUENCE_LETTER:
+            return self._get_sequence_letter()
+
+    def _get_component(self):
+        try:
+            if self.L0 == DATE_TIME:
+                return self._get_date_component()
+            elif self.L0 == TEXT:
+                return self.L1
+            elif self.L0 == FILENAME:
+                return self._get_filename_component()
+            elif self.L0 == METADATA:
+                return self._get_metadata_component()
+            elif self.L0 == SEQUENCES:
+                return self._get_sequences_component()
+            elif self.L0 == JOB_CODE:
+                return self.rpd_file.job_code
+            elif self.L0 == SEPARATOR:
+                return os.sep
+        except Exception as e:
+            self.problem.component_problem = _(self.L0)
+            self.problem.component_exception = e
+            return ''
+
+    def filter_strip_characters(self, name: str) -> str:
+        """
+        Filter out unwanted chacters from file and subfolder names
+        :param name: full name or name component
+        :return: filtered name
+        """
+
+        # remove any null characters - they are bad news in file names
+        name = name.replace('\x00', '')
+
+        # the user could potentially copy and paste a block of text with a carriage / line return
+        name = name.replace('\n', '')
+
+        if self.rpd_file.strip_characters:
+            for c in r'\:*?"<>|':
+                name = name.replace(c, '')
+
+        if self.strip_forward_slash:
+            name = name.replace('/', '')
+        return name
+
+    def _destination(self, rpd_file: RPDFile, name: str) -> str:
+        # implement in subclass
+        return ''
+
+    def _filter_name(self, name: str, parts: bool) -> str:
+        # implement in subclass if need be
+        return name
+
+    def generate_name(self, rpd_file: RPDFile,
+                      parts: Optional[bool]=False) -> Union[str, List[str]]:
+        """
+        Generate subfolder name(s), and photo/video filenames
+
+        :param rpd_file: rpd file for the name to generate
+        :param parts: if True, return string components in a list
+        :return: complete string or list of name components
+        """
+
+        self.rpd_file = rpd_file
+
+        if parts:
+            name = []
+        else:
+            name = ''
+
+        for self.L0, self.L1, self.L2 in self._get_values_from_pref_list():
+            v = self._get_component()
+            if parts:
+                name.append(self.filter_strip_characters(v))
+            elif v:
+                name += v
+
+        if not parts:
+            name = self.filter_strip_characters(name)
+            # strip any white space from the beginning and end of the name
+            name = name.strip()
+        elif name:
+            # likewise, strip any white space from the beginning and end of the name
+            name[0] = name[0].lstrip()
+            name[-1] = name[-1].rstrip()
+
+        if self.add_extension:
+            case = rpd_file.generate_extension_case
+            extension = os.path.splitext(rpd_file.name)[1]
+            if case == UPPERCASE:
+                extension = extension.upper()
+            elif case == LOWERCASE:
+                extension = extension.lower()
+            if parts:
+                name.append(extension)
+            else:
+                name += extension
+
+            self._get_thm_extension()
+            self._get_audio_extension()
+            self._get_xmp_extension()
+            self._get_log_extension()
+
+        name = self._filter_name(name, parts)
+
+        if self.problem.has_error():
+
+            rpd_file.name_generation_problem = True
+
+            if self.problems is not None:
+                self.problem.destination = self._destination(rpd_file=rpd_file, name=name)
+                self.problem.file_type = rpd_file.title
+                self.problem.source = rpd_file.get_souce_href()
+                self.problems.append(self.problem)
+
+        return name
+
+
+class PhotoName(NameGeneration):
+    """
+    Generate filenames for photos
+    """
+    def __init__(self, pref_list: List[str],
+                 problems: Optional[RenamingProblems]=None) -> None:
+        super().__init__(pref_list, problems)
+
+        self.problem = FilenameNotFullyGeneratedProblem()
+
+        self.strip_forward_slash = True
+        self.add_extension = True
+        self.L1_date_check = IMAGE_DATE  # used in _get_date_component()
+
+    def _destination(self, rpd_file: RPDFile, name: str) -> str:
+        if rpd_file.download_subfolder:
+            return make_href(
+                name=name,
+                uri=get_uri(
+                    full_file_name=os.path.join(
+                        rpd_file.download_folder, rpd_file.download_subfolder, name
+                    )
+                )
+            )
+        else:
+            return name
+
+
+class VideoName(PhotoName):
+    """
+    Generate filenames for videos
+    """
+    def __init__(self, pref_list: List[str],
+                 problems: Optional[RenamingProblems]=None) -> None:
+
+        super().__init__(pref_list, problems)
+
+        self.L1_date_check = VIDEO_DATE  # used in _get_date_component()
+
+    def _get_metadata_component(self):
+        """
+        Returns portion of video / subfolder name based on the metadata
+
+        Note: date time metadata found in _getDateComponent()
+        """
+        return get_video_metadata_component(self)
+
+
+class PhotoSubfolder(NameGeneration):
+    """
+    Generate subfolder names for photo files
+    """
+
+    def __init__(self, pref_list: List[str],
+                 problems: Optional[RenamingProblems]=None,
+                 no_metadata: Optional[bool]=False) -> None:
+        """
+        :param pref_list: subfolder generation preferences list
+        :param no_metadata: if True, halt as soon as the need for metadata
+        or a job code or sequence number becomes necessary
+        """
+
+        super().__init__(pref_list, problems)
+
+        if no_metadata:
+            self.pref_list = truncate_before_unwanted_subfolder_component(pref_list)
+        else:
+            self.pref_list = pref_list
+
+        self.no_metadata = no_metadata
+
+        self.problem = FolderNotFullyGeneratedProblemProblem()
+
+        self.strip_extraneous_white_space = re.compile(r'\s*%s\s*' % os.sep)
+        self.strip_forward_slash = False
+        self.add_extension = False
+        self.L1_date_check = IMAGE_DATE  # used in _get_date_component()
+
+    def _filter_name(self, name: str, parts: bool) -> str:
+        if not parts:
+            return self.filter_subfolder_characters(name)
+        return name
+
+    def _destination(self, rpd_file: RPDFile, name: str) -> str:
+        return make_href(
+                    name=name,
+                    uri = get_uri(path=os.path.join(rpd_file.download_folder, name))
+                )
+
+    def filter_subfolder_characters(self, subfolders: str) -> str:
+        """
+        Remove unwanted characters specific to the generation of subfolders
+        :param subfolders: the complete string containing the subfolders
+         (not component parts)
+        :return: filtered string
+        """
+
+        # subfolder value must never start with a separator, or else any
+        # os.path.join function call will fail to join a subfolder to its
+        # parent folder
+        if subfolders:
+            if subfolders[0] == os.sep:
+                subfolders = subfolders[1:]
+
+        # remove any spaces before and after a directory name
+        if subfolders and self.rpd_file.strip_characters:
+            subfolders = self.strip_extraneous_white_space.sub(os.sep, subfolders)
+
+        # remove any repeated directory separators
+        double_sep = os.sep * 2
+        subfolders = subfolders.replace(double_sep, os.sep)
+
+        # remove any trailing directory separators
+        while subfolders.endswith(os.sep):
+            subfolders = subfolders[:-1]
+
+        return subfolders
+
+
+class VideoSubfolder(PhotoSubfolder):
+    """
+    Generate subfolder names for video files
+    """
+
+    def __init__(self, pref_list: List[str],
+                 problems: Optional[RenamingProblems] = None,
+                 no_metadata: bool=False) -> None:
+        """
+        :param pref_list: subfolder generation preferences list
+        :param no_metadata: if True, halt as soon as the need for metadata
+        or a job code or sequence number becomes necessary
+        """
+        super().__init__(pref_list, problems, no_metadata)
+        self.L1_date_check = VIDEO_DATE  # used in _get_date_component()
+
+
+    def _get_metadata_component(self):
+        """
+        Returns portion of video / subfolder name based on the metadata
+
+        Note: date time metadata found in _getDateComponent()
+        """
+        return get_video_metadata_component(self)
+
+
+def truncate_before_unwanted_subfolder_component(pref_list: List[str]) -> List[str]:
+    r"""
+    truncate the preferences list to remove any subfolder element that
+    contains a metadata or a job code or sequence number
+
+    :param pref_list: subfolder prefs list
+    :return: truncated list
+
+    >>> print(truncate_before_unwanted_subfolder_component(PHOTO_SUBFOLDER_MENU_DEFAULTS_CONV[0]))
+    ['Date time', 'Image date', 'YYYY', '/', '', '', 'Date time', 'Image date', 'YYYYMMDD']
+    >>> print(truncate_before_unwanted_subfolder_component(PHOTO_SUBFOLDER_MENU_DEFAULTS_CONV[1]))
+    ['Date time', 'Image date', 'YYYY', '/', '', '', 'Date time', 'Image date', 'YYYY-MM-DD']
+    >>> print(truncate_before_unwanted_subfolder_component(PHOTO_SUBFOLDER_MENU_DEFAULTS_CONV[2]))
+    ['Date time', 'Image date', 'YYYY', '/', '', '', 'Date time', 'Image date', 'YYYY_MM_DD']
+    >>> print(truncate_before_unwanted_subfolder_component(PHOTO_SUBFOLDER_MENU_DEFAULTS_CONV[3]))
+    ['Date time', 'Image date', 'YYYY']
+    >>> print(truncate_before_unwanted_subfolder_component(PHOTO_SUBFOLDER_MENU_DEFAULTS_CONV[4]))
+    ... # doctest: +NORMALIZE_WHITESPACE
+    ['Date time', 'Image date', 'YYYY', '/', '', '', 'Date time', 'Image date', 'YYYY',
+    'Date time', 'Image date', 'MM']
+    >>> print(truncate_before_unwanted_subfolder_component([JOB_CODE, '', '',]))
+    []
+    >>> pl = [DATE_TIME, IMAGE_DATE, LIST_DATE_TIME_L2[11]]
+    >>> print(truncate_before_unwanted_subfolder_component(pl))
+    ['Date time', 'Image date', 'YYYY']
+    """
+
+    rl = [pref_list[i] for i in range(0, len(pref_list), 3)]
+    truncate = -1
+    for idx, value in enumerate(rl):
+        if value in (METADATA, SEQUENCES, JOB_CODE):
+            break
+        if idx == len(rl) - 1:
+            truncate = idx + 1
+        elif value == SEPARATOR:
+            truncate = idx
+
+    if truncate >= 0:
+        return pref_list[:truncate * 3]
+    return []
+
+
+def get_video_metadata_component(video: Union[VideoSubfolder, VideoName]):
+    """
+    Returns portion of video / subfolder name based on the metadata
+
+    This is outside of a class definition because of the inheritance
+    hierarchy.
+    """
+
+    if video.L1 == CODEC:
+        v = video.rpd_file.metadata.codec()
+    elif video.L1 == WIDTH:
+        v = video.rpd_file.metadata.width()
+    elif video.L1 == HEIGHT:
+        v = video.rpd_file.metadata.height()
+    elif video.L1 == FPS:
+        v = video.rpd_file.metadata.frames_per_second()
+    elif video.L1 == LENGTH:
+        v = video.rpd_file.metadata.length()
+    else:
+        raise TypeError("Invalid metadata option specified")
+    if video.L1 in [CODEC]:
+        if video.L2 == UPPERCASE:
+            v = v.upper()
+        elif video.L2 == LOWERCASE:
+            v = v.lower()
+    if not v:
+        video.problem.missing_metadata.append(_(video.L1))
+    return v
+
+
+class Sequences:
+    """
+    Stores sequence numbers and letters used in generating file names.
+    """
+
+    def __init__(self, downloads_today_tracker: DownloadsTodayTracker,
+                 stored_sequence_no: int) -> None:
+        self.session_sequence_no = 0
+        self.sequence_letter = -1
+        self.downloads_today_tracker = downloads_today_tracker
+        self.stored_sequence_no = stored_sequence_no
+        self.matched_sequences = None
+
+    def set_matched_sequence_value(self, matched_sequences: MatchedSequences) -> None:
+        self.matched_sequences = matched_sequences
+
+    def get_session_sequence_no(self) -> int:
+        if self.matched_sequences is not None:
+            return self.matched_sequences.session_sequence_no
+        else:
+            return self._get_session_sequence_no()
+
+    def _get_session_sequence_no(self) -> int:
+        return self.session_sequence_no + 1
+
+    def get_sequence_letter(self) -> int:
+        if self.matched_sequences is not None:
+            return self.matched_sequences.sequence_letter
+        else:
+            return self._get_sequence_letter()
+
+    def _get_sequence_letter(self) -> int:
+        return self.sequence_letter + 1
+
+    def increment(self, uses_session_sequence_no, uses_sequence_letter) -> None:
+        if uses_session_sequence_no:
+            self.session_sequence_no += 1
+        if uses_sequence_letter:
+            self.sequence_letter += 1
+
+    def get_downloads_today(self) -> int:
+        if self.matched_sequences is not None:
+            return self.matched_sequences.downloads_today
+        else:
+            return self._get_downloads_today()
+
+    def _get_downloads_today(self) -> int:
+        v = self.downloads_today_tracker.get_downloads_today()
+        if v == -1:
+            return 1
+        else:
+            return v + 1
+
+    def get_stored_sequence_no(self) -> int:
+        if self.matched_sequences is not None:
+            return self.matched_sequences.stored_sequence_no
+        else:
+            return self._get_stored_sequence_no()
+
+    def _get_stored_sequence_no(self) -> int:
+        return self.stored_sequence_no
+
+    def create_matched_sequences(self) -> MatchedSequences:
+        return MatchedSequences(
+            session_sequence_no=self._get_session_sequence_no(),
+            sequence_letter=self._get_sequence_letter(),
+            downloads_today=self._get_downloads_today(),
+            stored_sequence_no=self._get_stored_sequence_no())