""" $Id: TreeBuilder.py,v 1.1 2000/10/08 16:48:55 kmacleod Exp $
"""

class TreeBuilder:
    def __init__(self):
        self.node_stack = []
    def __getattr__(self, name):
        if name[0:5] == 'start':
            start_builder = TreeBuilder._StartBuilder(self)
            setattr(self, name, start_builder)
            return start_builder
        elif name[0:3] == 'end':
            end_builder = TreeBuilder._EndBuilder(self)
            setattr(self, name, end_builder)
            return end_builder
        else:
            builder = TreeBuilder._Builder(self)
            setattr(self, name, builder)
            return builder

    class _StartBuilder:
        def __init__(self, builder):
            self._builder = builder

        def __call__(self, node):
            if len(self._builder.node_stack) != 0:
                self._builder.node_stack[-1].contents.append(node)
            self._builder.node_stack.append(node)

    class _Builder:
        def __init__(self, builder):
            self._builder = builder

        def __call__(self, node):
            if len(self._builder.node_stack) == 0:
                raise TypeError, "Data event received before any start* events.\n";
            self._builder.node_stack[-1].contents.append(node)

    class _EndBuilder:
        def __init__(self, builder):
            self._builder = builder

        def __call__(self, node):
            return self._builder.node_stack.pop()