openlp/openlp/plugins/songs/lib/importers/powersong.py

# -*- coding: utf-8 -*-
# vim: autoindent shiftwidth=4 expandtab textwidth=120 tabstop=4 softtabstop=4

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# OpenLP - Open Source Lyrics Projection                                      #
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# Copyright (c) 2008-2016 OpenLP Developers                                   #
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"""
The :mod:`powersong` module provides the functionality for importing
PowerSong songs into the OpenLP database.
"""
import logging
import fnmatch
import os

from openlp.core.common import translate
from openlp.plugins.songs.lib.importers.songimport import SongImport

log = logging.getLogger(__name__)


class PowerSongImport(SongImport):
    """
    The :class:`PowerSongImport` class provides the ability to import song files
    from PowerSong.

    **PowerSong 1.0 Song File Format:**

    The file has a number of label-field (think key-value) pairs.

    Label and Field strings:

        * Every label and field is a variable length string preceded by an
          integer specifying it's byte length.
        * Integer is 32-bit but is encoded in 7-bit format to save space. Thus
          if length will fit in 7 bits (ie <= 127) it takes up only one byte.

    Metadata fields:

        * Every PowerSong file has a TITLE field.
        * There is zero or more AUTHOR fields.
        * There is always a COPYRIGHTLINE label, but its field may be empty.
          This field may also contain a CCLI number: e.g. "CCLI 176263".

    Lyrics fields:

        * Each verse is contained in a PART field.
        * Lines have Windows line endings ``CRLF`` (0x0d, 0x0a).
        * There is no concept of verse types.

    Valid extensions for a PowerSong song file are:

        * .song
    """
    @staticmethod
    def is_valid_source(import_source):
        """
        Checks if source is a PowerSong 1.0 folder:
            * is a directory
            * contains at least one \*.song file
        """
        if os.path.isdir(import_source):
            for file in os.listdir(import_source):
                if fnmatch.fnmatch(file, '*.song'):
                    return True
        return False

    def do_import(self):
        """
        Receive either a list of files or a folder (unicode) to import.
        """
        from openlp.plugins.songs.lib.importer import SongFormat
        ps_string = SongFormat.get(SongFormat.PowerSong, 'name')
        if isinstance(self.import_source, str):
            if os.path.isdir(self.import_source):
                dir = self.import_source
                self.import_source = []
                for file in os.listdir(dir):
                    if fnmatch.fnmatch(file, '*.song'):
                        self.import_source.append(os.path.join(dir, file))
            else:
                self.import_source = ''
        if not self.import_source or not isinstance(self.import_source, list):
            self.log_error(translate('SongsPlugin.PowerSongImport', 'No songs to import.'),
                           translate('SongsPlugin.PowerSongImport', 'No %s files found.') % ps_string)
            return
        self.import_wizard.progress_bar.setMaximum(len(self.import_source))
        for file in self.import_source:
            if self.stop_import_flag:
                return
            self.set_defaults()
            parse_error = False
            with open(file, 'rb') as song_data:
                while True:
                    try:
                        label = self._read_string(song_data)
                        if not label:
                            break
                        field = self._read_string(song_data)
                    except ValueError:
                        parse_error = True
                        self.log_error(os.path.basename(file), str(
                            translate('SongsPlugin.PowerSongImport', 'Invalid %s file. Unexpected byte value.')) %
                            ps_string)
                        break
                    else:
                        if label == 'TITLE':
                            self.title = field.replace('\n', ' ')
                        elif label == 'AUTHOR':
                            self.parse_author(field)
                        elif label == 'COPYRIGHTLINE':
                            found_copyright = True
                            self._parse_copyright_cCCLI(field)
                        elif label == 'PART':
                            self.add_verse(field)
            if parse_error:
                continue
            # Check that file had TITLE field
            if not self.title:
                self.log_error(os.path.basename(file), str(
                    translate('SongsPlugin.PowerSongImport', 'Invalid %s file. Missing "TITLE" header.')) % ps_string)
                continue
            # Check that file had COPYRIGHTLINE label
            if not found_copyright:
                self.log_error(self.title, str(
                    translate('SongsPlugin.PowerSongImport', 'Invalid %s file. Missing "COPYRIGHTLINE" header.')) %
                    ps_string)
                continue
            # Check that file had at least one verse
            if not self.verses:
                self.log_error(self.title, str(
                    translate('SongsPlugin.PowerSongImport', 'Verses not found. Missing "PART" header.')))
                continue
            if not self.finish():
                self.log_error(self.title)

    def _read_string(self, file_object):
        """
        Reads in next variable-length string.
        """
        string_len = self._read_7_bit_encoded_integer(file_object)
        return str(file_object.read(string_len), 'utf-8', 'ignore')

    def _read_7_bit_encoded_integer(self, file_object):
        """
        Reads in a 32-bit integer in compressed 7-bit format.

        Accomplished by reading the integer 7 bits at a time. The high bit
        of the byte when set means to continue reading more bytes.
        If the integer will fit in 7 bits (ie <= 127), it only takes up one
        byte. Otherwise, it may take up to 5 bytes.

        Reference: .NET method System.IO.BinaryReader.Read7BitEncodedInt
        """
        val = 0
        shift = 0
        i = 0
        while True:
            # Check for corrupted stream (since max 5 bytes per 32-bit integer)
            if i == 5:
                raise ValueError
            byte = self._read_byte(file_object)
            # Strip high bit and shift left
            val += (byte & 0x7f) << shift
            shift += 7
            high_bit_set = byte & 0x80
            if not high_bit_set:
                break
            i += 1
        return val

    def _read_byte(self, file_object):
        """
        Reads in next byte as an unsigned integer

        Note: returns 0 at end of file.
        """
        byte_str = file_object.read(1)
        # If read result is empty, then reached end of file
        if not byte_str:
            return 0
        else:
            return ord(byte_str)

    def _parse_copyright_cCCLI(self, field):
        """
        Look for CCLI song number, and get copyright
        """
        copyright, sep, ccli_no = field.rpartition('CCLI')
        if not sep:
            copyright = ccli_no
            ccli_no = ''
        if copyright:
            self.add_copyright(copyright.rstrip('\n').replace('\n', ' '))
        if ccli_no:
            ccli_no = ccli_no.strip(' :')
            if ccli_no.isdigit():
                self.ccli_number = ccli_no