Add <tag> support to BulletDef and FireDef.

[python-bulletml.git] / bulletml / impl.py

diff --git a/bulletml/impl.py b/bulletml/impl.py
index 0548b9d..6e8138a 100644 (file)
--- a/bulletml/impl.py
+++ b/bulletml/impl.py
@@ -6,15 +6,22 @@ import math
 
 from bulletml import parser
 
-# TODO(jfw): This is very non-Pythonic, it's pretty much just the
-# BulletML reference ActionImpl translated to Python.
-
 PI_2 = math.pi * 2
 
 __all__ = ["Action", "Bullet"]
 
 class Action(object):
-    """Running action implementation."""
+    """Running action implementation.
+
+    To implement new actions,
+
+    - Add a new element/class pair to parser.ActionDef.CONSTRUCTORS.
+      It should support FromXML, __getstate__, and __setstate__.
+    - Subclass impl.Action and override the 'handle' method to handle
+      your custom action type.
+    - Pass the impl.Bullet constructor your Action subclass when
+      creating your root Bullet.
+    """
 
     def __init__(self, owner, parent, actions, params, rank, repeat=1):
         self.actions = actions
@@ -61,9 +68,10 @@ class Action(object):
         self.previous_fire_direction = other.previous_fire_direction
         self.previous_fire_speed = other.previous_fire_speed
 
-    def step(self, owner, rank, created, sin=math.sin, cos=math.cos):
+    def step(self, owner, created, sin=math.sin, cos=math.cos):
         """Advance by one frame."""
         s_params = self.params
+        rank = owner.rank
 
         if self.speed_frames > 0:
             self.speed_frames -= 1
@@ -112,20 +120,21 @@ class Action(object):
 
             if isinstance(action, parser.Repeat):
                 repeat, (actions, params) = action(s_params, rank)
-                child = Action(owner, self, actions, params, rank, repeat)
+                child = self.__class__(
+                    owner, self, actions, params, rank, repeat)
                 owner.replace(self, child)
-                child.step(owner, rank, created, sin, cos)
+                child.step(owner, created, sin, cos)
                 break
 
             elif isinstance(action, (parser.ActionDef, parser.ActionRef)):
                 actions, params = action(s_params, rank)
-                child = Action(owner, self, actions, params, rank)
+                child = self.__class__(owner, self, actions, params, rank)
                 owner.replace(self, child)
-                child.step(owner, rank, created, sin, cos)
+                child.step(owner, created, sin, cos)
                 break
 
             elif isinstance(action, (parser.FireDef, parser.FireRef)):
-                direction, speed, actions, offset = action(s_params, rank)
+                direction, speed, offset, tags, actions = action(s_params, rank)
                 if direction:
                     direction, type = direction
                     if type == "aim" or type is None:
@@ -165,8 +174,10 @@ class Action(object):
                         x += off_x
                         y += off_y
 
-                bullet = Bullet(
-                    x, y, direction, speed, owner.target, actions, self, rank)
+                bullet = owner.__class__(
+                    x=x, y=y, direction=direction, speed=speed,
+                    target=owner.target, actions=actions, rank=rank,
+                    tags=tags, Action=self.__class__)
                 created.append(bullet)
 
             elif isinstance(action, parser.ChangeSpeed):
@@ -251,6 +262,13 @@ class Action(object):
                 owner.vanish()
                 break
 
+            else:
+                self.handle(action, owner, created, sin, cos)
+
+    def handle(self, action, owner, created, sin, cos):
+        """Override in subclasses for new action types."""
+        raise NotImplementedError(action.__class__.__name__)
+
 class Bullet(object):
     """Simple bullet implementation.
 
@@ -268,13 +286,13 @@ class Bullet(object):
     Contructor Arguments:
     x, y, direction, speed, target, rank - same as the attributes
     actions - internal action list
-    parent - parent of actions, None for manually-created bullets
+    Action - custom Action constructor
 
 
     """
 
     def __init__(self, x=0, y=0, direction=0, speed=0, target=None,
-                 actions=(), parent=None, rank=0.5):
+                 actions=(), rank=0.5, tags=(), Action=Action):
         self.x = self.px = x
         self.y = self.py = y
         self.mx = 0
@@ -284,11 +302,19 @@ class Bullet(object):
         self.vanished = False
         self.target = target
         self.rank = rank
-        self.tags = set()
+        self.tags = set(tags)
         # New bullets reset the parent hierarchy.
         self._actions = [Action(self, None, action, params, rank)
                          for action, params in actions]
 
+    @classmethod
+    def FromDocument(cls, doc, x=0, y=0, direction=0, speed=0, target=None,
+                     params=(), rank=0.5, Action=Action):
+        """Construct a new Bullet from a loaded BulletML document."""
+        actions = [a(params, rank) for a in doc.actions]
+        return cls(x=x, y=y, direction=direction, speed=speed,
+                   target=target, actions=actions, rank=rank, Action=Action)
+
     def __repr__(self):
         return ("%s(%r, %r, accel=%r, direction=%r, speed=%r, "
                 "actions=%r, target=%r, vanished=%r)") % (
@@ -298,11 +324,17 @@ class Bullet(object):
 
     @property
     def aim(self):
-        """Angle to the target, in radians."""
-        if self.target is None:
-            return self.direction
+        """Angle to the target, in radians.
+
+        If the target does not exist or cannot be found, return 0.
+        """
+        try:
+            target_x = self.target.x
+            target_y = self.target.y
+        except AttributeError:
+            return 0
         else:
-            return math.atan2(self.target.x - self.x, self.y - self.target.y)
+            return math.atan2(target_x - self.x, self.y - target_y)
 
     @property
     def finished(self):
@@ -352,7 +384,7 @@ class Bullet(object):
         created = []
 
         for action in self._actions:
-            action.step(self, self.rank, created, sin, cos)
+            action.step(self, created, sin, cos)
 
         self.px = self.x
         self.py = self.y