Add dynamic statement

game/scripts/cds.rpy

@@ -1,3 +1,59 @@
+python early hide:
+    import inspect
+    __register_params = frozenset(inspect.signature(renpy.register_statement).parameters).difference({"name", "parse"})
+    def register_decorator(cls):
+        """
+        A class decorator which registers a new statement.
+
+        The name of the statement will be the class name unless a `name` class attribute is present, which should be a string.
+
+        The `parse` method should be a static method that returns an object which will be passed to the other methods as `self`.
+        Returning an instance of the class is disabled for now.
+        """
+        # security
+        def raiser(*args, **kwargs):
+            raise NotImplementedError("Returning an instance of the class is disabled")
+        cls.__init__ = raiser
+
+        name = getattr(cls, "name", cls.__name__)
+        parse = getattr(cls, "parse", cls) # left in
+        renpy.register_statement(name,
+            parse=parse,
+            **{k:getattr(cls, k) for k in __register_params.intersection(vars(cls))})
+        return cls
+
+    @register_decorator
+    class dynamic:
+        block = "possible"
+
+        @staticmethod
+        def parse(l):
+            rv = {}
+
+            def parse_simple(ll):
+                target = ll.require(ll.name, "variable name")
+                if target in rv:
+                    ll.error(f"Variable {target} already set in the same dynamic block")
+                ll.require("=", "equals sign")
+                expression = ll.simple_expression()
+                ll.expect_eol()
+                rv[target] = expression
+
+            if l.match(":"):
+                l.expect_block("dynamic block")
+                l.expect_eol()
+                ll = l.subblock_lexer()
+                while ll.advance():
+                    parse_simple(ll)
+            else:
+                parse_simple(l)
+
+            return rv
+
+        def execute(self):
+            evaled = {n: eval(e) for n, e in self.items()}
+            renpy.dynamic(**evaled)
+
 python early:
     def parse_chibi(l):
         who = l.simple_expression()
@@ -72,11 +128,11 @@ python early:
         return {"blocks": blocks}
 
     def next_random(p):
-        blocks = [(block, weight, condition) for block, weight, condition in p["blocks"] if eval(condition)]
-        total_weight = sum(weight for _, weight, _ in blocks)
+        blocks = [(block, weight) for block, weight, condition in p["blocks"] if eval(condition)]
+        total_weight = sum(weight for _, weight in blocks)
         n = renpy.random.random() * total_weight
 
-        for block, weight, _ in blocks:
+        for block, weight in blocks:
             if n <= weight:
                 break
             else: