mudpy/data.py

   1 """Data interface functions for the mudpy engine."""
   2
   3 # Copyright (c) 2004-2018 mudpy authors. Permission to use, copy,
   4 # modify, and distribute this software is granted under terms
   5 # 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             log_entry = ("Loaded file %s into memory." % self.source, 5)
  62         except FileNotFoundError:
  63             # it's normal if the file is one which doesn't exist yet
  64             self.data = {}
  65             log_entry = ("File %s is unavailable." % self.source, 6)
  66         try:
  67             mudpy.misc.log(*log_entry)
  68         except NameError:
  69             # happens when we're not far enough along in the init process
  70             self.universe.setup_loglines.append(log_entry)
  71         if not hasattr(self.universe, "files"):
  72             self.universe.files = {}
  73         self.universe.files[self.source] = self
  74         includes = []
  75         for node in list(self.data):
  76             if node == "_load":
  77                 includes += self.data["_load"]
  78                 continue
  79             if node.startswith("_"):
  80                 continue
  81             facet_pos = node.rfind(".") + 1
  82             prefix = node[:facet_pos].strip(".")
  83             try:
  84                 element = self.universe.contents[prefix]
  85             except KeyError:
  86                 element = mudpy.misc.Element(prefix, self.universe, self)
  87             element.set(node[facet_pos:], self.data[node])
  88             if prefix.startswith("mudpy.movement."):
  89                 self.universe.directions.add(
  90                     prefix[prefix.rfind(".") + 1:])
  91         for include_file in includes:
  92             if not os.path.isabs(include_file):
  93                 include_file = find_file(
  94                     include_file,
  95                     relative=self.source,
  96                     universe=self.universe
  97                 )
  98             if (include_file not in self.universe.files or not
  99                     self.universe.files[include_file].is_writeable()):
 100                 Data(include_file, self.universe)
 101
 102     def save(self):
 103         """Write the data, if necessary."""
 104         normal_umask = 0o0022
 105         private_umask = 0o0077
 106         private_file_mode = 0o0600
 107
 108         # when modified, writeable and has content or the file exists
 109         if self.modified and self.is_writeable() and (
 110            self.data or os.path.exists(self.source)
 111            ):
 112
 113             # make parent directories if necessary
 114             if not os.path.exists(os.path.dirname(self.source)):
 115                 old_umask = os.umask(normal_umask)
 116                 os.makedirs(os.path.dirname(self.source))
 117                 os.umask(old_umask)
 118
 119             # backup the file
 120             if "mudpy.limit" in self.universe.contents:
 121                 max_count = self.universe.contents["mudpy.limit"].get(
 122                     "backups", 0)
 123             else:
 124                 max_count = 0
 125             if os.path.exists(self.source) and max_count:
 126                 backups = []
 127                 for candidate in os.listdir(os.path.dirname(self.source)):
 128                     if re.match(
 129                        os.path.basename(self.source) +
 130                        r"""\.\d+$""", candidate
 131                        ):
 132                         backups.append(int(candidate.split(".")[-1]))
 133                 backups.sort()
 134                 backups.reverse()
 135                 for old_backup in backups:
 136                     if old_backup >= max_count - 1:
 137                         os.remove(self.source + "." + str(old_backup))
 138                     elif not os.path.exists(
 139                         self.source + "." + str(old_backup + 1)
 140                     ):
 141                         os.rename(
 142                             self.source + "." + str(old_backup),
 143                             self.source + "." + str(old_backup + 1)
 144                         )
 145                 if not os.path.exists(self.source + ".0"):
 146                     os.rename(self.source, self.source + ".0")
 147
 148             # our data file
 149             if "private" in self.flags:
 150                 old_umask = os.umask(private_umask)
 151                 file_descriptor = open(self.source, "w")
 152                 if oct(stat.S_IMODE(os.stat(
 153                         self.source)[stat.ST_MODE])) != private_file_mode:
 154                     # if it's marked private, chmod it appropriately
 155                     os.chmod(self.source, private_file_mode)
 156             else:
 157                 old_umask = os.umask(normal_umask)
 158                 file_descriptor = open(self.source, "w")
 159             os.umask(old_umask)
 160
 161             # write and close the file
 162             yaml.dump(self.data, Dumper=_IBSDumper, allow_unicode=True,
 163                       default_flow_style=False, explicit_start=True, indent=4,
 164                       stream=file_descriptor)
 165             file_descriptor.close()
 166
 167             # unset the modified flag
 168             self.modified = False
 169
 170     def is_writeable(self):
 171         """Returns True if the _lock is False."""
 172         try:
 173             return not self.data.get("_lock", False)
 174         except KeyError:
 175             return True
 176
 177
 178 def find_file(
 179     file_name=None,
 180     group=None,
 181     prefix=None,
 182     relative=None,
 183     search=None,
 184     stash=None,
 185     universe=None
 186 ):
 187     """Return an absolute file path based on configuration."""
 188
 189     # this is all unnecessary if it's already absolute
 190     if file_name and os.path.isabs(file_name):
 191         return os.path.realpath(file_name)
 192
 193     # if a universe was provided, try to get some defaults from there
 194     if universe:
 195
 196         if hasattr(
 197                 universe, "contents") and "mudpy.filing" in universe.contents:
 198             filing = universe.contents["mudpy.filing"]
 199             if not prefix:
 200                 prefix = filing.get("prefix")
 201             if not search:
 202                 search = filing.get("search")
 203             if not stash:
 204                 stash = filing.get("stash")
 205
 206         # if there's only one file loaded, try to work around a chicken<egg
 207         elif hasattr(universe, "files") and len(
 208             universe.files
 209         ) == 1 and not universe.files[
 210                 list(universe.files.keys())[0]].is_writeable():
 211             data_file = universe.files[list(universe.files.keys())[0]].data
 212
 213             # try for a fallback default directory
 214             if not stash:
 215                 stash = data_file.get(".mudpy.filing.stash", "")
 216
 217             # try for a fallback root path
 218             if not prefix:
 219                 prefix = data_file.get(".mudpy.filing.prefix", "")
 220
 221             # try for a fallback search path
 222             if not search:
 223                 search = data_file.get(".mudpy.filing.search", "")
 224
 225         # another fallback root path, this time from the universe startdir
 226         if hasattr(universe, "startdir"):
 227             if not prefix:
 228                 prefix = universe.startdir
 229             elif not os.path.isabs(prefix):
 230                 prefix = os.path.join(universe.startdir, prefix)
 231
 232     # when no root path is specified, assume the current working directory
 233     if (not prefix or prefix == ".") and hasattr(universe, "startdir"):
 234         prefix = universe.startdir
 235
 236     # make sure it's absolute
 237     prefix = os.path.realpath(prefix)
 238
 239     # if there's no search path, just use the root path and etc
 240     if not search:
 241         search = [prefix, "etc"]
 242
 243     # work on a copy of the search path, to avoid modifying the caller's
 244     else:
 245         search = search[:]
 246
 247     # if there's no default path, use the last component of the search path
 248     if not stash:
 249         stash = search[-1]
 250
 251     # if an existing file or directory reference was supplied, prepend it
 252     if relative:
 253         if os.path.isdir(relative):
 254             search = [relative] + search
 255         else:
 256             search = [os.path.dirname(relative)] + search
 257
 258     # make the search path entries absolute and throw away any dupes
 259     clean_search = []
 260     for each_path in search:
 261         if not os.path.isabs(each_path):
 262             each_path = os.path.realpath(os.path.join(prefix, each_path))
 263         if each_path not in clean_search:
 264             clean_search.append(each_path)
 265
 266     # start hunting for the file now
 267     for each_path in clean_search:
 268
 269         # construct the candidate path
 270         candidate = os.path.join(each_path, file_name)
 271
 272         # if the file exists and is readable, we're done
 273         if os.path.isfile(candidate):
 274             file_name = os.path.realpath(candidate)
 275             break
 276
 277         # if the path is a directory, look for an __init__ file
 278         if os.path.isdir(candidate):
 279             file_name = os.path.realpath(
 280                     os.path.join(candidate, "__init__.yaml"))
 281             break
 282
 283     # it didn't exist after all, so use the default path instead
 284     if not os.path.isabs(file_name):
 285         file_name = os.path.join(stash, file_name)
 286     if not os.path.isabs(file_name):
 287         file_name = os.path.join(prefix, file_name)
 288
 289     # and normalize it last thing before returning
 290     file_name = os.path.realpath(file_name)
 291     return file_name