<offset>: Parse, evaluate, and example test case. (Fixes issue #3)

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

diff --git a/bulletml/parser.py b/bulletml/parser.py
index 5e73069..a07cc2d 100644 (file)
--- a/bulletml/parser.py
+++ b/bulletml/parser.py
@@ -375,19 +375,51 @@ 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 = type
+        self.x = x
+        self.y = y
+
+    @classmethod
+    def FromElement(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)."""
 
-    def __init__(self, bullet, direction=None, speed=None):
+    def __init__(self, bullet, direction=None, speed=None, offset=None):
         self.bullet = bullet
         self.direction = direction
         self.speed = speed
+        self.offset = offset
 
     @classmethod
     def FromElement(cls, doc, element):
         """Construct using an ElementTree-style element."""
         direction = None
         speed = None
+        offset = None
 
         for subelem in element.getchildren():
             tag = realtag(subelem)
@@ -399,9 +431,10 @@ class FireDef(object):
                 bullet = BulletDef.FromElement(doc, subelem)
             elif tag == "bulletRef":
                 bullet = BulletRef.FromElement(doc, subelem)
-
+            elif tag == "offset":
+                offset = Offset.FromElement(doc, subelem)
         try:
-            fire = cls(bullet, direction, speed)
+            fire = cls(bullet, direction, speed, offset)
         except UnboundLocalError as exc:
             raise ParseError(str(exc))
         else:
@@ -414,7 +447,7 @@ class FireDef(object):
             direction = self.direction(params, rank)
         if self.speed:
             speed = self.speed(params, rank)
-        return direction, speed, actions
+        return direction, speed, actions, self.offset
 
     def __repr__(self):
         return "%s(direction=%r, speed=%r, bullet=%r)" % (
@@ -435,7 +468,6 @@ class FireRef(object):
         return fired
 
     def __call__(self, params, rank):
-        """Generate a Bullet from the FireDef and params."""
         return self.fire(self.params(params, rank), rank)
 
     def __repr__(self):