"""
provides node functionality for the eventable odml types
Document, Section, Property and Value

additionally implements change notifications up to the corresponding section
"""
import odml.property
import odml.tools.event as event

def identity_index(obj, val):
    """
    same as obj.index(val) but will only return a position
    if the object val is found in the list

    i.e.
    >>> identity_index(["1"], "1")
    will raise an ValueError because the two strings
    are different objects with the same content

    >>> a = "1"
    >>> identity_index([a], a)
    0

    The difference to obj.index comes apparent here as well:
    >>> a="1", b="1"
    >>> identity_index([a,b], b)
    1
    >>> [a,b].index(b)
    0
    """
    for i, v in enumerate(obj):
        if v is val: return i

    import pdb; pdb.set_trace()
    raise ValueError("%s does not contain the item %s" % (repr(obj), repr(val)))

class RootNode(object):
    @property
    def children(self):
        return self._sections

    def from_path(self, path):
        child = self.children[path[0]]
        if len(path) == 1:
            return child
        return child.from_path(path[1:])

    def to_path(self, parent=None):
        return ()

    def path_to(self, child):
        """return the path from this node to its direct child *child*"""
        return (identity_index(self._sections, child),)

class ParentedNode(RootNode):
    def to_path(self, parent=None):
        if self.parent is parent:
            return self.parent.path_to(self)
        return self.parent.to_path(parent) + self.parent.path_to(self)

    def successor(self):
        return self.parent.children[self.position + 1]

    def next(self):
        """
        returns the next section following in this section's parent's list of sections
        returns None if there is no further element available

        i.e.:
            parent
              sec-a (<- self)
              sec-b

        will return sec-b
        """
        try:
            return self.successor()
        except IndexError:
            return None

    @property
    def position(self):
        return self.parent.path_to(self)[-1]

class SectionNode(ParentedNode):
    """
    SectionNodes are special as they wrap two types of sub-nodes:

    * SubSections (path = (0, idx))
    * Properties  (path = (1, idx))
    """
    def from_path(self, path):
        assert len(path) > 1

        if path[0] == 0: # sections
            return super(SectionNode, self).from_path(path[1:])

        # else: properties
        child = self._props[path[1]]

        if len(path) == 2:
            return child
        return child.from_path(path[2:])


    def path_to(self, child):
        if isinstance(child, odml.property.Property):
            return (1, identity_index(self._props, child))
        return (0, identity_index(self._sections, child))


class PropertyNode(ParentedNode):
    @property
    def children(self):
        return self.values

    def successor(self):
        return self.parent._props[self.position + 1]

    def path_to(self, child):
        return (identity_index(self.values, child),)

class ValueNode(ParentedNode):
    def path_from(self, path):
        raise TypeError("Value objects have no children")

    def path_to(self, child):
        raise TypeError("Value objects have no children")

#TODO? provide this externally?
name = "nodes"
provides = event.provides + ["nodes"]
class Document(event.Document, RootNode): pass
class Value(event.Value, ValueNode): pass
class Property(event.Property, PropertyNode): pass
class Section(event.Section, SectionNode): pass

import sys, odml
odml.addImplementation(sys.modules[__name__])