mudpy/data.py

   1 """Data interface functions for the mudpy engine."""
   2
   3 # Copyright (c) 2004-2017 Jeremy Stanley <fungi@yuggoth.org>. Permission
   4 # to use, copy, modify, and distribute this software is granted under
   5 # terms provided in the LICENSE file distributed with this software.
   6
   7 import os
   8 import re
   9 import stat
  10
  11 import mudpy
  12 import yaml
  13
  14
  15 class _IBSEmitter(yaml.emitter.Emitter):
  16
  17     """Override the default YAML Emitter to indent block sequences."""
  18
  19     def expect_block_sequence(self):
  20         """Match the expectations of the ``yamllint`` style checker."""
  21
  22         # TODO(fungi) Get an option for this implemented upstream in
  23         # the pyyaml library
  24         self.increase_indent(flow=False, indentless=False)
  25         self.state = self.expect_first_block_sequence_item
  26
  27
  28 class _IBSDumper(yaml.SafeDumper, _IBSEmitter):
  29
  30     """Use our _IBSEmitter instead of the default implementation."""
  31
  32     pass
  33
  34
  35 class Data:
  36
  37     """A file containing universe elements and their facets."""
  38
  39     def __init__(self,
  40                  source,
  41                  universe,
  42                  flags=None,
  43                  relative=None,
  44                  ):
  45         self.source = source
  46         self.universe = universe
  47         if flags is None:
  48             self.flags = []
  49         else:
  50             self.flags = flags[:]
  51         self.relative = relative
  52         self.load()
  53
  54     def load(self):
  55         """Read a file, create elements and poplulate facets accordingly."""
  56         self.modified = False
  57         self.source = find_file(
  58                 self.source, relative=self.relative, universe=self.universe)
  59         try:
  60             self.data = yaml.safe_load(open(self.source))
  61         except FileNotFoundError:
  62             # it's normal if the file is one which doesn't exist yet
  63             self.data = {}
  64             log_entry = ("File %s is unavailable." % self.source, 6)
  65             try:
  66                 mudpy.misc.log(*log_entry)
  67             except NameError:
  68                 # happens when we're not far enough along in the init process
  69                 self.universe.setup_loglines.append(log_entry)
  70         if not hasattr(self.universe, "files"):
  71             self.universe.files = {}
  72         self.universe.files[self.source] = self
  73         includes = []
  74         for node in list(self.data):
  75             if node == "_load":
  76                 for included in self.data["_load"]:
  77                     included = find_file(
  78                         included,
  79                         relative=self.source,
  80                         universe=self.universe)
  81                     if included not in includes:
  82                         includes.append(included)
  83                 continue
  84             if node.startswith("_"):
  85                 continue
  86             facet_pos = node.rfind(".") + 1
  87             prefix = node[:facet_pos].strip(".")
  88             try:
  89                 element = self.universe.contents[prefix]
  90             except KeyError:
  91                 element = mudpy.misc.Element(prefix, self.universe, self)
  92             element.set(node[facet_pos:], self.data[node])
  93             if prefix.startswith("mudpy.movement."):
  94                 self.universe.directions.add(
  95                     prefix[prefix.rfind(".") + 1:])
  96         for include_file in includes:
  97             if not os.path.isabs(include_file):
  98                 include_file = find_file(
  99                     include_file,
 100                     relative=self.source,
 101                     universe=self.universe
 102                 )
 103             if (include_file not in self.universe.files or not
 104                     self.universe.files[include_file].is_writeable()):
 105                 Data(include_file, self.universe)
 106
 107     def save(self):
 108         """Write the data, if necessary."""
 109         normal_umask = 0o0022
 110         private_umask = 0o0077
 111         private_file_mode = 0o0600
 112
 113         # when modified, writeable and has content or the file exists
 114         if self.modified and self.is_writeable() and (
 115            self.data or os.path.exists(self.source)
 116            ):
 117
 118             # make parent directories if necessary
 119             if not os.path.exists(os.path.dirname(self.source)):
 120                 old_umask = os.umask(normal_umask)
 121                 os.makedirs(os.path.dirname(self.source))
 122                 os.umask(old_umask)
 123
 124             # backup the file
 125             if "mudpy.limit" in self.universe.contents:
 126                 max_count = self.universe.contents["mudpy.limit"].get(
 127                     "backups", 0)
 128             else:
 129                 max_count = 0
 130             if os.path.exists(self.source) and max_count:
 131                 backups = []
 132                 for candidate in os.listdir(os.path.dirname(self.source)):
 133                     if re.match(
 134                        os.path.basename(self.source) +
 135                        r"""\.\d+$""", candidate
 136                        ):
 137                         backups.append(int(candidate.split(".")[-1]))
 138                 backups.sort()
 139                 backups.reverse()
 140                 for old_backup in backups:
 141                     if old_backup >= max_count - 1:
 142                         os.remove(self.source + "." + str(old_backup))
 143                     elif not os.path.exists(
 144                         self.source + "." + str(old_backup + 1)
 145                     ):
 146                         os.rename(
 147                             self.source + "." + str(old_backup),
 148                             self.source + "." + str(old_backup + 1)
 149                         )
 150                 if not os.path.exists(self.source + ".0"):
 151                     os.rename(self.source, self.source + ".0")
 152
 153             # our data file
 154             if "private" in self.flags:
 155                 old_umask = os.umask(private_umask)
 156                 file_descriptor = open(self.source, "w")
 157                 if oct(stat.S_IMODE(os.stat(
 158                         self.source)[stat.ST_MODE])) != private_file_mode:
 159                     # if it's marked private, chmod it appropriately
 160                     os.chmod(self.source, private_file_mode)
 161             else:
 162                 old_umask = os.umask(normal_umask)
 163                 file_descriptor = open(self.source, "w")
 164             os.umask(old_umask)
 165
 166             # write and close the file
 167             yaml.dump(self.data, Dumper=_IBSDumper, allow_unicode=True,
 168                       default_flow_style=False, explicit_start=True, indent=4,
 169                       stream=file_descriptor)
 170             file_descriptor.close()
 171
 172             # unset the modified flag
 173             self.modified = False
 174
 175     def is_writeable(self):
 176         """Returns True if the _lock is False."""
 177         try:
 178             return not self.data.get("_lock", False)
 179         except KeyError:
 180             return True
 181
 182
 183 def find_file(
 184     file_name=None,
 185     group=None,
 186     prefix=None,
 187     relative=None,
 188     search=None,
 189     stash=None,
 190     universe=None
 191 ):
 192     """Return an absolute file path based on configuration."""
 193
 194     # this is all unnecessary if it's already absolute
 195     if file_name and os.path.isabs(file_name):
 196         return os.path.realpath(file_name)
 197
 198     # if a universe was provided, try to get some defaults from there
 199     if universe:
 200
 201         if hasattr(
 202                 universe, "contents") and "mudpy.filing" in universe.contents:
 203             filing = universe.contents["mudpy.filing"]
 204             if not prefix:
 205                 prefix = filing.get("prefix")
 206             if not search:
 207                 search = filing.get("search")
 208             if not stash:
 209                 stash = filing.get("stash")
 210
 211         # if there's only one file loaded, try to work around a chicken<egg
 212         elif hasattr(universe, "files") and len(
 213             universe.files
 214         ) == 1 and not universe.files[
 215                 list(universe.files.keys())[0]].is_writeable():
 216             data_file = universe.files[list(universe.files.keys())[0]].data
 217
 218             # try for a fallback default directory
 219             if not stash:
 220                 stash = data_file.get(".mudpy.filing.stash", "")
 221
 222             # try for a fallback root path
 223             if not prefix:
 224                 prefix = data_file.get(".mudpy.filing.prefix", "")
 225
 226             # try for a fallback search path
 227             if not search:
 228                 search = data_file.get(".mudpy.filing.search", "")
 229
 230         # another fallback root path, this time from the universe startdir
 231         if hasattr(universe, "startdir"):
 232             if not prefix:
 233                 prefix = universe.startdir
 234             elif not os.path.isabs(prefix):
 235                 prefix = os.path.join(universe.startdir, prefix)
 236
 237     # when no root path is specified, assume the current working directory
 238     if (not prefix or prefix == ".") and hasattr(universe, "startdir"):
 239         prefix = universe.startdir
 240
 241     # make sure it's absolute
 242     prefix = os.path.realpath(prefix)
 243
 244     # if there's no search path, just use the root path and etc
 245     if not search:
 246         search = [prefix, "etc"]
 247
 248     # work on a copy of the search path, to avoid modifying the caller's
 249     else:
 250         search = search[:]
 251
 252     # if there's no default path, use the last component of the search path
 253     if not stash:
 254         stash = search[-1]
 255
 256     # if an existing file or directory reference was supplied, prepend it
 257     if relative:
 258         if os.path.isdir(relative):
 259             search = [relative] + search
 260         else:
 261             search = [os.path.dirname(relative)] + search
 262
 263     # make the search path entries absolute and throw away any dupes
 264     clean_search = []
 265     for each_path in search:
 266         if not os.path.isabs(each_path):
 267             each_path = os.path.realpath(os.path.join(prefix, each_path))
 268         if each_path not in clean_search:
 269             clean_search.append(each_path)
 270
 271     # start hunting for the file now
 272     for each_path in clean_search:
 273
 274         # construct the candidate path
 275         candidate = os.path.join(each_path, file_name)
 276
 277         # if the file exists and is readable, we're done
 278         if os.path.isfile(candidate):
 279             file_name = os.path.realpath(candidate)
 280             break
 281
 282         # if the path is a directory, look for an __init__ file
 283         if os.path.isdir(candidate):
 284             file_name = os.path.realpath(
 285                     os.path.join(candidate, "__init__.yaml"))
 286             break
 287
 288     # it didn't exist after all, so use the default path instead
 289     if not os.path.isabs(file_name):
 290         file_name = os.path.join(stash, file_name)
 291     if not os.path.isabs(file_name):
 292         file_name = os.path.join(prefix, file_name)
 293
 294     # and normalize it last thing before returning
 295     file_name = os.path.realpath(file_name)
 296     return file_name