EVENT_HOOK_RESTRICT, roverlay.hook

1 files changed, 169 insertions, 0 deletions

diff --git a/roverlay/hook.py b/roverlay/hook.py
new file mode 100644
index 0000000..3b13315
--- /dev/null
+++ b/roverlay/hook.py
@@ -0,0 +1,169 @@
+# R overlay -- run roverlay hooks (shell scripts)
+# -*- coding: utf-8 -*-
+# Copyright (C) 2013 André Erdmann <dywi@mailerd.de>
+# Distributed under the terms of the GNU General Public License;
+# either version 2 of the License, or (at your option) any later version.
+
+import os.path
+import logging
+
+import roverlay.config
+import roverlay.tools.shenv
+
+__all__ = [ 'run_hook', 'phase_allowed', ]
+
+LOGGER = logging.getLogger ( 'event_hook' )
+
+
+_EVENT_SCRIPT = None
+
+# None|iterable _EVENT_RESTRICT
+_EVENT_RESTRICT = None
+
+# int _EVENT_POLICY
+# -1: no policy (allow all)
+#  0: not configured
+#  1: allow unless in _EVENT_RESTRICT (blacklist)
+#  2: deny  unless in _EVENT_RESTRICT (whitelist)
+#  4: deny all
+_EVENT_POLICY = 0
+
+def setup():
+   global _EVENT_SCRIPT
+   global _EVENT_POLICY
+   global _EVENT_RESTRICT
+
+   _EVENT_SCRIPT = roverlay.config.get ( 'EVENT_HOOK.exe', False )
+   if _EVENT_SCRIPT is False:
+      a_dir = roverlay.config.get ( 'OVERLAY.additions_dir', None )
+      if a_dir:
+         s = os.path.join (
+            a_dir,
+            *roverlay.config.get_or_fail ( 'EVENT_HOOK.default_exe_relpath' )
+         )
+         if os.path.isfile ( s ):
+            _EVENT_SCRIPT = s
+   # -- end if _EVENT_SCRIPT
+
+   conf_restrict = roverlay.config.get ( 'EVENT_HOOK.restrict', False )
+
+   if conf_restrict:
+      # tristate None,False,True
+      is_whitelist = None
+      allow = set()
+      deny  = set()
+      for p in conf_restrict:
+         if p == '*':
+            # "allow all"
+            is_whitelist = False
+         elif p == '-*':
+            # "deny all"
+            is_whitelist = True
+         elif p == '-' or p == '+':
+            # empty
+            pass
+         elif p[0] == '-':
+            # deny <k>
+            k = p[1:].lower()
+            deny.add ( k )
+            try:
+               allow.remove ( k )
+            except KeyError:
+               pass
+         else:
+            # allow <k>
+            k = ( p[1:] if p[0] == '+' else p ).lower()
+            allow.add ( k )
+            try:
+               deny.remove ( k )
+            except KeyError:
+               pass
+      # -- end for;
+
+      if is_whitelist is None:
+         # allow is set                   => is whitelist
+         # neither allow nor deny are set => deny allow
+         is_whitelist = bool ( allow or not deny )
+      # -- end if is_whitelist #1
+
+      if is_whitelist:
+         if allow:
+            _EVENT_RESTRICT = frozenset ( allow )
+            _EVENT_POLICY   = 2
+         else:
+            _EVENT_POLICY = 4
+      elif deny:
+         _EVENT_RESTRICT = frozenset ( deny )
+         _EVENT_POLICY   = 1
+      else:
+         _EVENT_POLICY = -1
+      # -- end if is_whitelist #2
+   else:
+      _EVENT_POLICY = -1
+   # -- end if conf_restrict
+# --- end of setup (...) ---
+
+def phase_allowed ( phase ):
+   if _EVENT_POLICY == -1:
+      return True
+   elif _EVENT_POLICY == 1:
+      # allow unless in restrict
+      if phase not in _EVENT_RESTRICT:
+         return True
+      else:
+         LOGGER.debug (
+            "phase {!r} denied by blacklist policy.".format ( phase )
+         )
+   elif _EVENT_POLICY == 2:
+      # deny unless in restrict
+      if phase in _EVENT_RESTRICT:
+         return True
+      else:
+         LOGGER.debug (
+            "phase {!r} denied by whitelist policy.".format ( phase )
+         )
+   elif _EVENT_POLICY == 4:
+      LOGGER.debug (
+         "phase {!r} denied by 'deny all' policy".format ( phase )
+      )
+   else:
+      LOGGER.warning (
+         "phase {!r} denied by undefined policy {} (fix this)".format (
+            phase, _EVENT_POLICY
+         )
+      )
+   # -- end if _EVENT_POLICY
+
+   # default return
+   return False
+# --- end of phase_allowed (...) ---
+
+def phase_allowed_nolog ( phase ):
+   return (
+      _EVENT_POLICY == -1
+   ) or (
+      _EVENT_POLICY == 1 and phase not in _EVENT_RESTRICT
+   ) or (
+      _EVENT_POLICY == 2 and phase in _EVENT_RESTRICT
+   )
+# --- end of phase_allowed_nolog (...) ---
+
+def run ( phase ):
+   if _EVENT_SCRIPT is None:
+      LOGGER.warning (
+         "hook module not initialized - doing that now (FIXME!)"
+      )
+      setup()
+
+
+
+   if _EVENT_SCRIPT and phase_allowed ( phase ):
+      return roverlay.tools.shenv.run_script (
+         _EVENT_SCRIPT, phase, return_success=True
+      )
+   else:
+      # nop
+      return True
+# --- end of run (...) ---
+
+run_hook = run