X-Git-Url: https://git.yukkurigames.com/?p=python-bulletml.git;a=blobdiff_plain;f=bulletml%2Fparser.py;h=c8bc990b105bfab652326be334a7db4b0be6a820;hp=0af66943893632fedcd3f5dac68a7defc216cb75;hb=bf5ff1d116840e1330c80894132919ec515596e4;hpb=9104092535823794c1b00f3c0fb16f5181992a00

diff --git a/bulletml/parser.py b/bulletml/parser.py
index 0af6694..c8bc990 100644
--- a/bulletml/parser.py
+++ b/bulletml/parser.py
@@ -1,20 +1,40 @@
 """BulletML parser.
 
-http://www.asahi-net.or.jp/~cs8k-cyu/bulletml/index_e.html
+This is based on the format described at
+http://www.asahi-net.or.jp/~cs8k-cyu/bulletml/bulletml_ref_e.html.
+
+Unless you are adding support for new actions, the only class you
+should care about in here is BulletML.
 """
 
 from __future__ import division
 
+from math import sin, cos, radians, pi as PI
+
 from xml.etree.ElementTree import ElementTree
 
+# Python 3 moved this for no really good reason.
 try:
-    from cStringIO import StringIO
+    from sys import intern
 except ImportError:
-    from StringIO import StringIO
+    pass
+
+try:
+    from io import StringIO
+except ImportError:
+    try:
+        from cStringIO import StringIO
+    except ImportError:
+        from StringIO import StringIO
 
 from bulletml.errors import Error
 from bulletml.expr import NumberDef, INumberDef
 
+
+__all__ = ["ParseError", "BulletML"]
+
+PI_2 = PI * 2
+
 class ParseError(Error):
     """Raised when an error occurs parsing the XML structure."""
     pass
@@ -28,18 +48,18 @@ def realtag(element):
 
 class ParamList(object):
     """List of parameter definitions."""
-    def __init__(self, element):
-        self.params = []
-        if element:
-            for subelem in element:
-                if realtag(subelem) == "param":
-                    self.params.append(NumberDef(subelem.text))
+
+    def __init__(self, params=()):
+        self.params = list(params)
+
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
+        return cls([NumberDef(subelem.text) for subelem in element
+                    if realtag(subelem) == "param"])
 
     def __call__(self, params, rank):
-        new_params = [param(params, rank) for param in self.params]
-        while len(new_params) < len(params):
-            new_params.append(params[len(new_params)])
-        return new_params
+        return [param(params, rank) for param in self.params]
 
     def __repr__(self):
         return "%s(%r)" % (type(self).__name__, self.params)
@@ -47,12 +67,28 @@ class ParamList(object):
 class Direction(object):
     """Raw direction value."""
 
-    def __init__(self, doc, element, type="absolute"):
-        self.type = element.get("type", type)
-        self.value = NumberDef(element.text)
+    VALID_TYPES = ["relative", "absolute", "aim", "sequence"]
+
+    def __init__(self, type, value):
+        if type not in self.VALID_TYPES:
+            raise ValueError("invalid type %r" % type)
+        self.type = intern(type)
+        self.value = value
+
+    def __getstate__(self):
+        return [('type', self.type), ('value', self.value.expr)]
+
+    def __setstate__(self, state):
+        state = dict(state)
+        self.__init__(state["type"], NumberDef(state["value"]))
+
+    @classmethod
+    def FromXML(cls, doc, element, default="absolute"):
+        """Construct using an ElementTree-style element."""
+        return cls(element.get("type", default), NumberDef(element.text))
 
     def __call__(self, params, rank):
-        return (self.value(params, rank), self.type)
+        return (radians(self.value(params, rank)), self.type)
 
     def __repr__(self):
         return "%s(%r, type=%r)" % (
@@ -61,20 +97,54 @@ class Direction(object):
 class ChangeDirection(object):
     """Direction change over time."""
 
-    def __init__(self, doc, element):
+    def __init__(self, term, direction):
+        self.term = term
+        self.direction = direction
+
+    def __getstate__(self):
+        return [('frames', self.term.expr),
+                ('type', self.direction.type),
+                ('value', self.direction.value.expr)]
+
+    def __setstate__(self, state):
+        state = dict(state)
+        self.__init__(INumberDef(state["frames"]),
+                      Direction(state["type"], NumberDef(state["value"])))
+
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
         for subelem in element.getchildren():
             tag = realtag(subelem)
             if tag == "direction":
-                self.direction = Direction(doc, subelem)
+                direction = Direction.FromXML(doc, subelem)
             elif tag == "term":
-                self.term = INumberDef(subelem.text)
+                term = INumberDef(subelem.text)
         try:
-            self.term, self.direction
-        except AttributeError:
-            raise ParseError
+            return cls(term, direction)
+        except UnboundLocalError as exc:
+            raise ParseError(str(exc))
 
-    def __call__(self, params, rank):
-        return self.term(params, rank), self.direction(params, rank)
+    def __call__(self, owner, action, params, rank, created):
+        frames = self.term(params, rank)
+        direction, type = self.direction(params, rank)
+        action.direction_frames = frames
+        action.aiming = False
+        if type == "sequence":
+            action.direction = direction
+        else:
+            if type == "absolute":
+                direction -= owner.direction
+            elif type != "relative": # aim or default
+                action.aiming = True
+                direction += owner.aim - owner.direction
+
+            # Normalize to [-pi, pi).
+            direction = (direction + PI) % PI_2 - PI
+            if frames <= 0:
+                owner.direction += direction
+            else:
+                action.direction = direction / frames
 
     def __repr__(self):
         return "%s(term=%r, direction=%r)" % (
@@ -83,9 +153,25 @@ class ChangeDirection(object):
 class Speed(object):
     """Raw speed value."""
 
-    def __init__(self, doc, element, type="absolute"):
-        self.type = element.get("type", type)
-        self.value = NumberDef(element.text)
+    VALID_TYPES = ["relative", "absolute", "sequence"]
+
+    def __init__(self, type, value):
+        if type not in self.VALID_TYPES:
+            raise ValueError("invalid type %r" % type)
+        self.type = intern(type)
+        self.value = value
+
+    def __getstate__(self):
+        return [('type', self.type), ('value', self.value.expr)]
+
+    def __setstate__(self, state):
+        state = dict(state)
+        self.__init__(state["type"], NumberDef(state["value"]))
+
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
+        return cls(element.get("type", "absolute"), NumberDef(element.text))
 
     def __call__(self, params, rank):
         return (self.value(params, rank), self.type)
@@ -96,20 +182,49 @@ class Speed(object):
 class ChangeSpeed(object):
     """Speed change over time."""
 
-    def __init__(self, doc, element):
+    def __init__(self, term, speed):
+        self.term = term
+        self.speed = speed
+
+    def __getstate__(self):
+        return [('frames', self.term.expr),
+                ('type', self.speed.type),
+                ('value', self.speed.value.expr)]
+
+    def __setstate__(self, state):
+        state = dict(state)
+        self.__init__(INumberDef(state["frames"]),
+                      Speed(state["type"], NumberDef(state["value"])))
+
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
         for subelem in element.getchildren():
             tag = realtag(subelem)
             if tag == "speed":
-                self.speed = Speed(doc, subelem)
+                speed = Speed.FromXML(doc, subelem)
             elif tag == "term":
-                self.term = INumberDef(subelem.text)
+                term = INumberDef(subelem.text)
         try:
-            self.term, self.speed
-        except AttributeError:
-            raise ParseError
+            return cls(term, speed)
+        except UnboundLocalError as exc:
+            raise ParseError(str(exc))
 
-    def __call__(self, params, rank):
-        return self.term(params, rank), self.speed(params, rank)
+    def __call__(self, owner, action, params, rank, created):
+        frames = self.term(params, rank)
+        speed, type = self.speed(params, rank)
+        action.speed_frames = frames
+        if frames <= 0:
+            if type == "absolute":
+                owner.speed = speed
+            elif type == "relative":
+                owner.speed += speed
+        elif type == "sequence":
+            action.speed = speed
+        elif type == "relative":
+            action.speed = speed / frames
+        else:
+            action.speed = (speed - owner.speed) / frames
 
     def __repr__(self):
         return "%s(term=%r, speed=%r)" % (
@@ -117,75 +232,277 @@ class ChangeSpeed(object):
 
 class Wait(object):
     """Wait for some frames."""
-    def __init__(self, doc, element):
-        self.frames = INumberDef(element.text)
 
-    def __call__(self, params, rank):
-        return self.frames(params, rank)
+    def __init__(self, frames):
+        self.frames = frames
+
+    def __getstate__(self):
+        return dict(frames=self.frames.expr)
+
+    def __setstate__(self, state):
+        self.__init__(INumberDef(state["frames"]))
+
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
+        return cls(INumberDef(element.text))
+
+    def __call__(self, owner, action, params, rank, created):
+        action.wait_frames = self.frames(params, rank)
+        return True
 
     def __repr__(self):
         return "%s(%r)" % (type(self).__name__, self.frames)
 
+class Tag(object):
+    """Set a bullet tag."""
+
+    def __init__(self, tag):
+        self.tag = tag
+
+    def __getstate__(self):
+        return dict(tag=self.tag)
+
+    def __setstate__(self, state):
+        self.__init__(state["tag"])
+
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
+        return cls(element.text)
+
+    def __call__(self, owner, action, params, rank, created):
+        owner.tags.add(self.tag)
+
+class Untag(object):
+    """Unset a bullet tag."""
+
+    def __init__(self, tag):
+        self.tag = tag
+        
+    def __getstate__(self):
+        return dict(tag=self.tag)
+
+    def __setstate__(self, state):
+        self.__init__(state["tag"])
+
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
+        return cls(element.text)
+
+    def __call__(self, owner, action, params, rank, created):
+        try:
+            owner.tags.remove(self.tag)
+        except KeyError:
+            pass
+
+class Appearance(object):
+    """Set a bullet appearance."""
+
+    def __init__(self, appearance):
+        self.appearance = appearance
+
+    def __getstate__(self):
+        return dict(appearance=self.appearance)
+
+    def __setstate__(self, state):
+        self.__init__(state["appearance"])
+
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
+        return cls(element.text)
+
+    def __call__(self, owner, action, params, rank, created):
+        owner.apearance = self.appearance
+
 class Vanish(object):
     """Make the owner disappear."""
-    def __init__(self, doc, element):
+
+    def __init__(self):
         pass
 
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
+        return cls()
+
     def __repr__(self):
         return "%s()" % (type(self).__name__)
 
+    def __call__(self, owner, action, params, rank, created):
+        owner.vanish()
+        return True
+
 class Repeat(object):
     """Repeat an action definition."""
 
-    def __init__(self, doc, element):
+    def __init__(self, times, action):
+        self.times = times
+        self.action = action
+
+    def __getstate__(self):
+        return [('times', self.times.expr), ('action', self.action)]
+
+    def __setstate__(self, state):
+        state = dict(state)
+        self.__init__(INumberDef(state["times"]), state["action"])
+    
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
         for subelem in element.getchildren():
             tag = realtag(subelem)
             if tag == "times":
-                self.times = INumberDef(subelem.text)
+                times = INumberDef(subelem.text)
             elif tag == "action":
-                self.action = ActionDef(doc, subelem)
+                action = ActionDef.FromXML(doc, subelem)
             elif tag == "actionRef":
-                self.action = ActionRef(doc, subelem)
-
+                action = ActionRef.FromXML(doc, subelem)
         try:
-            self.times, self.action
-        except AttributeError:
-            raise ParseError
-
-    def __call__(self, params, rank):
-        return self.times(params, rank), self.action(params, rank)
+            return cls(times, action)
+        except UnboundLocalError as exc:
+            raise ParseError(str(exc))
+
+    def __call__(self, owner, action, params, rank, created):
+        repeat = self.times(params, rank)
+        actions, params = self.action(params, rank)
+        child = action.Child(actions, params, rank, repeat)
+        owner.replace(action, child)
+        child.step(owner, created)
+        return True
 
     def __repr__(self):
         return "%s(%r, %r)" % (type(self).__name__, self.times, self.action)
 
+class If(object):
+    """Conditional actions."""
+
+    def __init__(self, cond, then, else_=None):
+        self.cond = cond
+        self.then = then
+        self.else_ = else_
+
+    def __getstate__(self):
+        if self.else_:
+            return [('cond', self.cond.expr),
+                    ('then', self.then),
+                    ('else', self.else_)]
+        else:
+            return [('cond', self.cond.expr), ('then', self.then)]
+
+    def __setstate__(self, state):
+        state = dict(state)
+        state["else_"] = state.pop("else", None)
+        state["cond"] = INumberDef(state["cond"])
+        self.__init__(**state)
+
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
+        else_ = None
+        for subelem in element.getchildren():
+            tag = realtag(subelem)
+            if tag == "cond":
+                cond = INumberDef(subelem.text)
+            elif tag == "then":
+                then = ActionDef.FromXML(doc, subelem)
+            elif tag == "else":
+                else_ = ActionDef.FromXML(doc, subelem)
+        try:
+            return cls(cond, then, else_)
+        except UnboundLocalError as exc:
+            raise ParseError(str(exc))
+
+    def __call__(self, owner, action, params, rank, created):
+        if self.cond(params, rank):
+            branch = self.then
+        else:
+            branch = self.else_
+
+        if branch:
+            actions, params = branch(params, rank)
+            child = action.Child(actions, params, rank)
+            owner.replace(action, child)
+            child.step(owner, created)
+            return True
+        
 class Accel(object):
     """Accelerate over some time."""
 
     horizontal = None
     vertical = None
 
-    def __init__(self, doc, element):
+    def __init__(self, term, horizontal=None, vertical=None):
+        self.term = term
+        self.horizontal = horizontal
+        self.vertical = vertical
+
+    def __getstate__(self):
+        state = [('frames', self.term.expr)]
+        if self.horizontal:
+            state.append(('horizontal', self.horizontal))
+        if self.vertical:
+            state.append(('vertical', self.vertical))
+        return state
+
+    def __setstate__(self, state):
+        state = dict(state)
+        self.__init__(INumberDef(state["frames"]), state.get("horizontal"),
+                      state.get("vertical"))
+
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
+        horizontal = None
+        vertical = None
+
         for subelem in element.getchildren():
             tag = realtag(subelem)
             if tag == "term":
-                self.term = INumberDef(subelem.text)
+                term = INumberDef(subelem.text)
             elif tag == "horizontal":
-                self.horizontal = Speed(doc, subelem)
+                horizontal = Speed.FromXML(doc, subelem)
             elif tag == "vertical":
-                self.vertical = Speed(doc, subelem)
+                vertical = Speed.FromXML(doc, subelem)
 
         try:
-            self.term
+            return cls(term, horizontal, vertical)
         except AttributeError:
             raise ParseError
 
-    def __call__(self, params, rank):
+    def __call__(self, owner, action, params, rank, created):
         frames = self.term(params, rank)
-        horizontal = self.horizontal and (
-            self.horizontal(params, rank), self.horizontal.type)
-        vertical = self.vertical and (
-            self.vertical(params, rank), self.vertical.type)
-        return frames, horizontal, vertical
+        horizontal = self.horizontal and self.horizontal(params, rank)
+        vertical = self.vertical and self.vertical(params, rank)
+        action.accel_frames = frames
+        if horizontal:
+            mx, type = horizontal
+            if frames <= 0:
+                if type == "absolute":
+                    owner.mx = mx
+                elif type == "relative":
+                    owner.mx += mx
+            elif type == "sequence":
+                action.mx = mx
+            elif type == "absolute":
+                action.mx = (mx - owner.mx) / frames
+            elif type == "relative":
+                action.mx = mx / frames
+        if vertical:
+            my, type = vertical
+            if frames <= 0:
+                if type == "absolute":
+                    owner.my = my
+                elif type == "relative":
+                    owner.my += my
+            elif type == "sequence":
+                action.my = my
+            elif type == "absolute":
+                action.my = (my - owner.my) / frames
+            elif type == "relative":
+                action.my = my / frames
 
     def __repr__(self):
         return "%s(%r, horizontal=%r, vertical=%r)" % (
@@ -194,30 +511,62 @@ class Accel(object):
 class BulletDef(object):
     """Bullet definition."""
 
-    direction = None
-    speed = None
+    def __init__(self, actions=(), direction=None, speed=None, tags=(),
+                 appearance=None):
+        self.direction = direction
+        self.speed = speed
+        self.actions = list(actions)
+        self.tags = set(tags)
+        self.appearance = appearance
 
-    def __init__(self, doc, element):
-        self.actions = []
-        doc.bullets[element.get("label")] = self
+    def __getstate__(self):
+        state = []
+        if self.direction:
+            state.append(("direction", self.direction))
+        if self.speed:
+            state.append(("speed", self.speed))
+        if self.actions:
+            state.append(("actions", self.actions))
+        if self.tags:
+            state.append(("tags", list(self.tags)))
+        if self.appearance:
+            state.append(("appearance", self.appearance))
+        return state
+
+    def __setstate__(self, state):
+        state = dict(state)
+        self.__init__(**state)
+
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
+        actions = []
+        speed = None
+        direction = None
+        tags = set()
         for subelem in element.getchildren():
             tag = realtag(subelem)
             if tag == "direction":
-                self.direction = Direction(doc, subelem)
+                direction = Direction.FromXML(doc, subelem)
             elif tag == "speed":
-                self.speed = Speed(doc, subelem)
+                speed = Speed.FromXML(doc, subelem)
             elif tag == "action":
-                self.actions.append(ActionDef(doc, element))
+                actions.append(ActionDef.FromXML(doc, subelem))
             elif tag == "actionRef":
-                self.actions.append(ActionRef(doc, element))
+                actions.append(ActionRef.FromXML(doc, subelem))
+            elif tag == "tag":
+                tags.add(subelem.text)
+        dfn = cls(actions, direction, speed, tags)
+        doc._bullets[element.get("label")] = dfn
+        return dfn
 
     def __call__(self, params, rank):
-        actions = []
-        for action in self.actions:
-            actions.append(action(params, rank))
+        actions = [action(params, rank) for action in self.actions]
         return (
             self.direction and self.direction(params, rank),
             self.speed and self.speed(params, rank),
+            self.tags,
+            self.appearance,
             actions)
 
     def __repr__(self):
@@ -227,10 +576,30 @@ class BulletDef(object):
 class BulletRef(object):
     """Create a bullet by name with parameters."""
 
-    def __init__(self, doc, element):
-        self.bullet = element.get("label")
-        self.params = ParamList(element)
-        doc._bullet_refs.append(self)
+    def __init__(self, bullet, params=None):
+        self.bullet = bullet
+        self.params = ParamList() if params is None else params
+
+    def __getstate__(self):
+        state = []
+        if self.params.params:
+            params = [param.expr for param in self.params.params]
+            state.append(("params", params))
+        state.append(('bullet', self.bullet))
+        return state
+
+    def __setstate__(self, state):
+        state = dict(state)
+        bullet = state["bullet"]
+        params = [NumberDef(param) for param in state.get("params", [])]
+        self.__init__(bullet, ParamList(params))
+
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
+        bullet = cls(element.get("label"), ParamList.FromXML(doc, element))
+        doc._bullet_refs.append(bullet)
+        return bullet
 
     def __call__(self, params, rank):
         return self.bullet(self.params(params, rank), rank)
@@ -240,29 +609,42 @@ class BulletRef(object):
             type(self).__name__, self.params, self.bullet)
 
 class ActionDef(object):
-    """Action definition."""
+    """Action definition.
+
+    To support parsing new actions, add tags to
+    ActionDef.CONSTRUCTORS. It maps tag names to classes with a
+    FromXML classmethod, which take the BulletML instance and
+    ElementTree element as arguments.
+    """
+
+    # This is self-referential, so it's filled in later.
+    CONSTRUCTORS = dict()
+
+    def __init__(self, actions):
+        self.actions = list(actions)
+
+    def __getstate__(self):
+        return dict(actions=self.actions)
+
+    def __setstate__(self, state):
+        state = dict(state)
+        self.__init__(state["actions"])
 
-    def __init__(self, doc, element):
-        doc.actions[element.get("label")] = self
-        self.actions = []
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
+        actions = []
         for subelem in element.getchildren():
             tag = realtag(subelem)
             try:
-                ctr = dict(
-                    repeat=Repeat,
-                    fire=FireDef,
-                    fireRef=FireRef,
-                    changeSpeed=ChangeSpeed,
-                    changeDirection=ChangeDirection,
-                    accel=Accel,
-                    wait=Wait,
-                    vanish=Vanish,
-                    action=ActionDef,
-                    actionRef=ActionRef)[tag]
+                ctr = cls.CONSTRUCTORS[tag]
             except KeyError:
                 continue
             else:
-                self.actions.append(ctr(doc, subelem))
+                actions.append(ctr.FromXML(doc, subelem))
+        dfn = cls(actions)
+        doc._actions[element.get("label")] = dfn
+        return dfn
 
     def __call__(self, params, rank):
         return self.actions, params
@@ -273,10 +655,30 @@ class ActionDef(object):
 class ActionRef(object):
     """Run an action by name with parameters."""
 
-    def __init__(self, doc, element):
-        self.action = element.get("label")
-        self.params = ParamList(element)
-        doc._action_refs.append(self)
+    def __init__(self, action, params=None):
+        self.action = action
+        self.params = params or ParamList()
+
+    def __getstate__(self):
+        state = []
+        if self.params.params:
+            params = [param.expr for param in self.params.params]
+            state.append(("params", params))
+        state.append(('action', self.action))
+        return state
+
+    def __setstate__(self, state):
+        state = dict(state)
+        action = state["action"]
+        params = [NumberDef(param) for param in state.get("params", [])]
+        self.__init__(action, ParamList(params))
+
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
+        action = cls(element.get("label"), ParamList.FromXML(doc, element))
+        doc._action_refs.append(action)
+        return action
 
     def __call__(self, params, rank):
         return self.action(self.params(params, rank), rank)
@@ -285,36 +687,179 @@ class ActionRef(object):
         return "%s(params=%r, action=%r)" % (
             type(self).__name__, self.params, self.action)
 
+class Offset(object):
+    """Provide an offset to a bullet's initial position."""
+
+    VALID_TYPES = ["relative", "absolute"]
+
+    def __init__(self, type, x, y):
+        if type not in self.VALID_TYPES:
+            raise ValueError("invalid type %r" % type)
+        self.type = intern(type)
+        self.x = x
+        self.y = y
+
+    def __getstate__(self):
+        state = [('type', self.type)]
+        if self.x:
+            state.append(('x', self.x.expr))
+        if self.y:
+            state.append(('y', self.y.expr))
+        return state
+
+    def __setstate__(self, state):
+        state = dict(state)
+        x = NumberDef(state["x"]) if "x" in state else None
+        y = NumberDef(state["y"]) if "y" in state else None
+        self.__init__(state["type"], x, y)
+
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
+        type = element.get("type", "relative")
+        x = None
+        y = None
+        for subelem in element:
+            tag = realtag(subelem)
+            if tag == "x":
+                x = NumberDef(subelem.text)
+            elif tag == "y":
+                y = NumberDef(subelem.text)
+        return cls(type, x, y)
+
+    def __call__(self, params, rank):
+        return (self.x(params, rank) if self.x else 0,
+                self.y(params, rank) if self.y else 0)
+
 class FireDef(object):
     """Fire definition (creates a bullet)."""
 
-    direction = None
-    speed = None
+    def __init__(self, bullet, direction=None, speed=None, offset=None,
+                 tags=(), appearance=None):
+        self.bullet = bullet
+        self.direction = direction
+        self.speed = speed
+        self.offset = offset
+        self.tags = set(tags)
+        self.appearance = appearance
+
+    def __getstate__(self):
+        state = []
+        if self.direction:
+            state.append(("direction", self.direction))
+        if self.speed:
+            state.append(("speed", self.speed))
+        if self.offset:
+            state.append(("offset", self.offset))
+        if self.tags:
+            state.append(("tags", list(self.tags)))
+        if self.appearance:
+            state.append(("appearance", self.appearance))
+        try:
+            params = self.bullet.params
+        except AttributeError:
+            state.append(('bullet', self.bullet))
+        else:
+            if params.params:
+                state.append(('bullet', self.bullet))
+            else:
+                # Strip out empty BulletRefs.
+                state.append(('bullet', self.bullet.bullet))
+        return state
+
+    def __setstate__(self, state):
+        state = dict(state)
+        self.__init__(**state)
+
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
+        direction = None
+        speed = None
+        offset = None
+        tags = set()
+        appearance = None
 
-    def __init__(self, doc, element):
-        doc.fires[element.get("label")] = self
         for subelem in element.getchildren():
             tag = realtag(subelem)
             if tag == "direction":
-                self.direction = Direction(doc, subelem)
+                direction = Direction.FromXML(doc, subelem, "aim")
             elif tag == "speed":
-                self.speed = Speed(doc, subelem)
+                speed = Speed.FromXML(doc, subelem)
             elif tag == "bullet":
-                self.bullet = BulletDef(doc, subelem)
+                bullet = BulletDef.FromXML(doc, subelem)
             elif tag == "bulletRef":
-                self.bullet = BulletRef(doc, subelem)
+                bullet = BulletRef.FromXML(doc, subelem)
+            elif tag == "offset":
+                offset = Offset.FromXML(doc, subelem)
+            elif tag == "tag":
+                tags.add(subelem.text)
+            elif tag == "appearance":
+                appearance = subelem.text
         try:
-            self.bullet
-        except AttributeError:
-            raise ParseError
-
-    def __call__(self, params, rank):
-        direction, speed, actions = self.bullet(params, rank)
+            fire = cls(bullet, direction, speed, offset, tags, appearance)
+        except UnboundLocalError as exc:
+            raise ParseError(str(exc))
+        else:
+            doc._fires[element.get("label")] = fire
+            return fire
+
+    def __call__(self, owner, action, params, rank, created):
+        direction, speed, tags, appearance, actions = self.bullet(params, rank)
         if self.direction:
             direction = self.direction(params, rank)
         if self.speed:
             speed = self.speed(params, rank)
-        return direction, speed, actions
+        tags = tags.union(self.tags)
+        if self.appearance:
+            appearance = self.appearance
+
+        if direction:
+            direction, type = direction
+            if type == "aim" or type is None:
+                direction += owner.aim
+            elif type == "sequence":
+                direction += action.previous_fire_direction
+            elif type == "relative":
+                direction += owner.direction
+        else:
+            direction = owner.aim
+        action.previous_fire_direction = direction
+
+        if speed:
+            speed, type = speed
+            if type == "sequence":
+                speed += action.previous_fire_speed
+            elif type == "relative":
+                # The reference Noiz implementation uses
+                # prvFireSpeed here, but the standard is
+                # pretty clear -- "In case of the type is
+                # "relative", ... the speed is relative to the
+                # speed of this bullet."
+                speed += owner.speed
+        else:
+            speed = 1
+        action.previous_fire_speed = speed
+
+        x, y = owner.x, owner.y
+        if self.offset:
+            off_x, off_y = self.offset(params, rank)
+            if self.offset.type == "relative":
+                s = sin(direction)
+                c = cos(direction)
+                x += c * off_x + s * off_y
+                y += s * off_x - c * off_y
+            else:
+                x += off_x
+                y += off_y
+
+        if appearance is None:
+            appearance = owner.appearance
+        bullet = owner.__class__(
+            x=x, y=y, direction=direction, speed=speed,
+            target=owner.target, actions=actions, rank=rank,
+            appearance=appearance, tags=tags, Action=action.__class__)
+        created.append(bullet)
 
     def __repr__(self):
         return "%s(direction=%r, speed=%r, bullet=%r)" % (
@@ -323,14 +868,34 @@ class FireDef(object):
 class FireRef(object):
     """Fire a bullet by name with parameters."""
 
-    def __init__(self, doc, element):
-        self.fire = element.get("label")
-        self.params = ParamList(element)
-        doc._fire_refs.append(self)
-
-    def __call__(self, params, rank):
-        """Generate a Bullet from the FireDef and params."""
-        return self.fire(self.params(params, rank), rank)
+    def __init__(self, fire, params=None):
+        self.fire = fire
+        self.params = params or ParamList()
+
+    def __getstate__(self):
+        state = []
+        if self.params.params:
+            params = [param.expr for param in self.params.params]
+            state.append(("params", params))
+        state.append(('fire', self.fire))
+        return state
+
+    def __setstate__(self, state):
+        state = dict(state)
+        fire = state["fire"]
+        params = [NumberDef(param) for param in state.get("params", [])]
+        self.__init__(fire, ParamList(params))
+
+    @classmethod
+    def FromXML(cls, doc, element):
+        """Construct using an ElementTree-style element."""
+        fired = cls(element.get("label"), ParamList.FromXML(doc, element))
+        doc._fire_refs.append(fired)
+        return fired
+
+    def __call__(self, owner, action, params, rank, created):
+        params = self.params(params, rank)
+        return self.fire(owner, action, params, rank, created)
 
     def __repr__(self):
         return "%s(params=%r, fire=%r)" % (
@@ -339,8 +904,14 @@ class FireRef(object):
 class BulletML(object):
     """BulletML document.
 
-    A BulletML document is a collection of bullets, actions, and
-    firings, as well as a base game type.
+    A BulletML document is a collection of top-level actions and the
+    base game type.
+
+    You can add tags to the BulletML.CONSTRUCTORS dictionary to extend
+    its parsing. It maps tag names to classes with a FromXML
+    classmethod, which take the BulletML instance and ElementTree
+    element as arguments.
+    
     """
 
     CONSTRUCTORS = dict(
@@ -349,49 +920,111 @@ class BulletML(object):
         fire=FireDef,
         )
 
-    def __init__(self, source):
-        self.bullets = {}
-        self.actions = {}
-        self.fires = {}
+    def __init__(self, type="none", actions=None):
+        self.type = intern(type)
+        self.actions = [] if actions is None else actions
+
+    def __getstate__(self):
+        return [('type', self.type), ('actions', self.actions)]
 
-        self._bullet_refs = []
-        self._action_refs = []
-        self._fire_refs = []
+    def __setstate__(self, state):
+        state = dict(state)
+        self.__init__(state["type"], actions=state.get("actions"))
 
-        if isinstance(source, (str, unicode)):
+    @classmethod
+    def FromXML(cls, source):
+        """Return a BulletML instance based on XML."""
+        if not hasattr(source, 'read'):
             source = StringIO(source)
 
         tree = ElementTree()
         root = tree.parse(source)
 
-        self.type = root.get("type", "none")
+        doc = cls(type=root.get("type", "none"))
+
+        doc._bullets = {}
+        doc._actions = {}
+        doc._fires = {}
+        doc._bullet_refs = []
+        doc._action_refs = []
+        doc._fire_refs = []
 
         for element in root.getchildren():
             tag = realtag(element)
-            if tag in self.CONSTRUCTORS:
-                self.CONSTRUCTORS[tag](self, element)
+            if tag in doc.CONSTRUCTORS:
+                doc.CONSTRUCTORS[tag].FromXML(doc, element)
 
         try:
-            for ref in self._bullet_refs:
-                ref.bullet = self.bullets[ref.bullet]
-            for ref in self._fire_refs:
-                ref.fire = self.fires[ref.fire]
-            for ref in self._action_refs:
-                ref.action = self.actions[ref.action]
+            for ref in doc._bullet_refs:
+                ref.bullet = doc._bullets[ref.bullet]
+            for ref in doc._fire_refs:
+                ref.fire = doc._fires[ref.fire]
+            for ref in doc._action_refs:
+                ref.action = doc._actions[ref.action]
         except KeyError as exc:
             raise ParseError("unknown reference %s" % exc)
 
-        del(self._bullet_refs)
-        del(self._action_refs)
-        del(self._fire_refs)
+        doc.actions = [act for name, act in doc._actions.items()
+                        if name and name.startswith("top")]
 
-    @property
-    def top(self):
-        """Get a list of all top-level actions."""
-        return [dfn for name, dfn in self.actions.iteritems()
-                if name and name.startswith("top")]
+        del(doc._bullet_refs)
+        del(doc._action_refs)
+        del(doc._fire_refs)
+        del(doc._bullets)
+        del(doc._actions)
+        del(doc._fires)
+        
+        return doc
+
+    @classmethod
+    def FromYAML(cls, source):
+        """Create a BulletML instance based on YAML."""
+
+        # Late import to avoid a circular dependency.
+        try:
+            import bulletml.bulletyaml
+            import yaml
+        except ImportError:
+            raise ParseError("PyYAML is not available")
+        else:
+            try:
+                return yaml.load(source)
+            except Exception as exc:
+                raise ParseError(str(exc))
+
+    @classmethod
+    def FromDocument(cls, source):
+        """Create a BulletML instance based on a seekable file or string.
+
+        This attempts to autodetect if the stream is XML or YAML.
+        """
+        if not hasattr(source, 'read'):
+            source = StringIO(source)
+        start = source.read(1)
+        source.seek(0)
+        if start == "<":
+            return cls.FromXML(source)
+        elif start == "!" or start == "#":
+            return cls.FromYAML(source)
+        else:
+            raise ParseError("unknown initial character %r" % start)
 
     def __repr__(self):
-        return "%s(type=%r, bullets=%r, actions=%r, fires=%r)" % (
-            type(self).__name__, self.type, self.bullets, self.actions,
-            self.fires)
+        return "%s(type=%r, actions=%r)" % (
+            type(self).__name__, self.type, self.actions)
+
+ActionDef.CONSTRUCTORS = dict(
+    repeat=Repeat,
+    fire=FireDef,
+    fireRef=FireRef,
+    changeSpeed=ChangeSpeed,
+    changeDirection=ChangeDirection,
+    accel=Accel,
+    wait=Wait,
+    vanish=Vanish,
+    tag=Tag,
+    appearance=Appearance,
+    untag=Untag,
+    action=ActionDef,
+    actionRef=ActionRef)
+ActionDef.CONSTRUCTORS["if"] = If