Implement priorities in utils.add_hook()

This changes world.hooks to store lists of tuples indicating (priority, hook_func).

classes.py

@@ -226,7 +226,8 @@ class PyLinkNetworkCore(structures.DeprecatedAttributesObject, structures.CamelC
                   command, hook_cmd)
 
         # Iterate over registered hook functions, catching errors accordingly.
-        for hook_func in world.hooks[hook_cmd]:
+        for hook_pair in world.hooks[hook_cmd]:
+            hook_func = hook_pair[1]
             try:
                 log.debug('(%s) Calling hook function %s from plugin "%s"', self.name,
                           hook_func, hook_func.__module__)

coremods/corecommands.py

@@ -157,8 +157,9 @@ def unload(irc, source, args):
                         del world.services['pylink'].commands[cmdname]
 
         # Remove any command hooks set by the plugin.
-        for hookname, hookfuncs in world.hooks.copy().items():
-            for hookfunc in hookfuncs:
+        for hookname, hookpairs in world.hooks.copy().items():
+            for hookpair in hookpairs:
+                hookfunc = hookpair[1]
                 if hookfunc.__module__ == modulename:
                     world.hooks[hookname].remove(hookfunc)
                     # If the hookfuncs list is empty, remove it.

utils.py

@@ -44,10 +44,15 @@ def add_cmd(func, name=None, **kwargs):
     world.services['pylink'].add_cmd(func, name=name, **kwargs)
     return func
 
-def add_hook(func, command):
-    """Binds a hook function to the given command name."""
+def add_hook(func, command, priority=100):
+    """
+    Binds a hook function to the given command name.
+
+    A custom priority can also be given (defaults to 100), and hooks with
+    higher priority values will be called first."""
     command = command.upper()
-    world.hooks[command].append(func)
+    world.hooks[command].append((priority, func))
+    world.hooks[command].sort(key=lambda pair: pair[0], reverse=True)
     return func
 
 # DEPRECATED