# Copyright 2006 Google, Inc. All Rights Reserved.

# Licensed to PSF under a Contributor Agreement.

"""Python parse tree definitions.

This is a very concrete parse tree; we need to keep every token and

even the comments and whitespace between tokens.

There's also a pattern matching implementation here.

"""

__author__ = "Guido van Rossum <guido@python.org>"

import sys

from StringIO import StringIO

HUGE = 0x7FFFFFFF  # maximum repeat count, default max

_type_reprs = {}

def type_repr(type_num):

    global _type_reprs

    if not _type_reprs:

        from .pygram import python_symbols

        # printing tokens is possible but not as useful

        # from .pgen2 import token // token.__dict__.items():

        for name, val in python_symbols.__dict__.items():

            if type(val) == int: _type_reprs[val] = name

    return _type_reprs.setdefault(type_num, type_num)

class Base(object):

    """Abstract base class for Node and Leaf.

    This provides some default functionality and boilerplate using the

    template pattern.

    A node may be a subnode of at most one parent.

    """

    # Default values for instance variables

    type = None    # int: token number (< 256) or symbol number (>= 256)

    parent = None  # Parent node pointer, or None

    children = ()  # Tuple of subnodes

    was_changed = False

    def __new__(cls, *args, **kwds):

        """Constructor that prevents Base from being instantiated."""

        assert cls is not Base, "Cannot instantiate Base"

        return object.__new__(cls)

    def __eq__(self, other):

        """Compares two nodes for equality.

        This calls the method _eq().

        """

        if self.__class__ is not other.__class__:

            return NotImplemented

        return self._eq(other)

    def __ne__(self, other):

        """Compares two nodes for inequality.

        This calls the method _eq().

        """

        if self.__class__ is not other.__class__:

            return NotImplemented

        return not self._eq(other)

    def _eq(self, other):

        """Compares two nodes for equality.

        This is called by __eq__ and __ne__.  It is only called if the

        two nodes have the same type.  This must be implemented by the

        concrete subclass.  Nodes should be considered equal if they

        have the same structure, ignoring the prefix string and other

        context information.

        """

        raise NotImplementedError

    def clone(self):

        """Returns a cloned (deep) copy of self.

        This must be implemented by the concrete subclass.

        """

        raise NotImplementedError

    def post_order(self):

        """Returns a post-order iterator for the tree.

        This must be implemented by the concrete subclass.

        """

        raise NotImplementedError

    def pre_order(self):

        """Returns a pre-order iterator for the tree.

        This must be implemented by the concrete subclass.

        """

        raise NotImplementedError

    def set_prefix(self, prefix):

        """Sets the prefix for the node (see Leaf class).

        This must be implemented by the concrete subclass.

        """

        raise NotImplementedError

    def get_prefix(self):

        """Returns the prefix for the node (see Leaf class).

        This must be implemented by the concrete subclass.

        """

        raise NotImplementedError

    def replace(self, new):

        """Replaces this node with a new one in the parent."""

        assert self.parent is not None, str(self)

        assert new is not None

        if not isinstance(new, list):

            new = [new]

        l_children = []

        found = False

        for ch in self.parent.children:

            if ch is self:

                assert not found, (self.parent.children, self, new)

                if new is not None:

                    l_children.extend(new)

                found = True

            else:

                l_children.append(ch)

        assert found, (self.children, self, new)

        self.parent.changed()

        self.parent.children = l_children

        for x in new:

            x.parent = self.parent

        self.parent = None

    def get_lineno(self):

        """Returns the line number which generated the invocant node."""

        node = self

        while not isinstance(node, Leaf):

            if not node.children:

                return

            node = node.children[0]

        return node.lineno

    def changed(self):

        if self.parent:

            self.parent.changed()

        self.was_changed = True

    def remove(self):

        """Remove the node from the tree. Returns the position of the node

        in its parent's children before it was removed."""

        if self.parent:

            for i, node in enumerate(self.parent.children):

                if node is self:

                    self.parent.changed()

                    del self.parent.children[i]

                    self.parent = None

                    return i

    def get_next_sibling(self):

        """Return the node immediately following the invocant in their

        parent's children list. If the invocant does not have a next

        sibling, return None."""

        if self.parent is None:

            return None

        # Can't use index(); we need to test by identity

        for i, child in enumerate(self.parent.children):

            if child is self:

                try:

                    return self.parent.children[i+1]

                except IndexError:

                    return None

    def get_prev_sibling(self):

        """Return the node immediately preceding the invocant in their

        parent's children list. If the invocant does not have a previous

        sibling, return None."""

        if self.parent is None:

            return None

        # Can't use index(); we need to test by identity

        for i, child in enumerate(self.parent.children):

            if child is self:

                if i == 0:

                    return None

                return self.parent.children[i-1]

    def get_suffix(self):

        """Return the string immediately following the invocant node. This

        is effectively equivalent to node.get_next_sibling().get_prefix()"""

        next_sib = self.get_next_sibling()

        if next_sib is None:

            return ""

        return next_sib.get_prefix()

class Node(Base):

    """Concrete implementation for interior nodes."""

    def __init__(self, type, children, context=None, prefix=None):

        """Initializer.

        Takes a type constant (a symbol number >= 256), a sequence of

        child nodes, and an optional context keyword argument.

        As a side effect, the parent pointers of the children are updated.

        """

        assert type >= 256, type

        self.type = type

        self.children = list(children)

        for ch in self.children:

            assert ch.parent is None, repr(ch)

            ch.parent = self

        if prefix is not None:

            self.set_prefix(prefix)

    def __repr__(self):

        """Returns a canonical string representation."""

        return "%s(%s, %r)" % (self.__class__.__name__,

                               type_repr(self.type),

                               self.children)

    def __str__(self):

        """Returns a pretty string representation.

        This reproduces the input source exactly.

        """

        return "".join(map(str, self.children))

    def _eq(self, other):

        """Compares two nodes for equality."""

        return (self.type, self.children) == (other.type, other.children)

    def clone(self):

        """Returns a cloned (deep) copy of self."""

        return Node(self.type, [ch.clone() for ch in self.children])

    def post_order(self):

        """Returns a post-order iterator for the tree."""

        for child in self.children:

            for node in child.post_order():

                yield node

        yield self

    def pre_order(self):

        """Returns a pre-order iterator for the tree."""

        yield self

        for child in self.children:

            for node in child.post_order():

                yield node

    def set_prefix(self, prefix):

        """Sets the prefix for the node.

        This passes the responsibility on to the first child.

        """

        if self.children:

            self.children[0].set_prefix(prefix)

    def get_prefix(self):

        """Returns the prefix for the node.

        This passes the call on to the first child.

        """

        if not self.children:

            return ""

        return self.children[0].get_prefix()

    def set_child(self, i, child):

        """Equivalent to 'node.children[i] = child'. This method also sets the

        child's parent attribute appropriately."""

        child.parent = self

        self.children[i].parent = None

        self.children[i] = child

    def insert_child(self, i, child):

        """Equivalent to 'node.children.insert(i, child)'. This method also

        sets the child's parent attribute appropriately."""

        child.parent = self

        self.children.insert(i, child)

    def append_child(self, child):

        """Equivalent to 'node.children.append(child)'. This method also

        sets the child's parent attribute appropriately."""

        child.parent = self

        self.children.append(child)

class Leaf(Base):

    """Concrete implementation for leaf nodes."""

    # Default values for instance variables

    prefix = ""  # Whitespace and comments preceding this token in the input

    lineno = 0   # Line where this token starts in the input

    column = 0   # Column where this token tarts in the input

    def __init__(self, type, value, context=None, prefix=None):

        """Initializer.

        Takes a type constant (a token number < 256), a string value,

        and an optional context keyword argument.

        """

        assert 0 <= type < 256, type

        if context is not None:

            self.prefix, (self.lineno, self.column) = context

        self.type = type

        self.value = value

        if prefix is not None:

            self.prefix = prefix

    def __repr__(self):

        """Returns a canonical string representation."""

        return "%s(%r, %r)" % (self.__class__.__name__,

                               self.type,

                               self.value)

    def __str__(self):

        """Returns a pretty string representation.

        This reproduces the input source exactly.

        """

        return self.prefix + str(self.value)

    def _eq(self, other):

        """Compares two nodes for equality."""

        return (self.type, self.value) == (other.type, other.value)

    def clone(self):

        """Returns a cloned (deep) copy of self."""

        return Leaf(self.type, self.value,

                    (self.prefix, (self.lineno, self.column)))

    def post_order(self):

        """Returns a post-order iterator for the tree."""

        yield self

    def pre_order(self):

        """Returns a pre-order iterator for the tree."""

        yield self

    def set_prefix(self, prefix):

        """Sets the prefix for the node."""

        self.changed()

        self.prefix = prefix

    def get_prefix(self):

        """Returns the prefix for the node."""

        return self.prefix

def convert(gr, raw_node):

    """Converts raw node information to a Node or Leaf instance.

    This is passed to the parser driver which calls it whenever a

    reduction of a grammar rule produces a new complete node, so that

    the tree is build strictly bottom-up.

    """

    type, value, context, children = raw_node

    if children or type in gr.number2symbol:

        # If there's exactly one child, return that child instead of

        # creating a new node.

        if len(children) == 1:

            return children[0]

        return Node(type, children, context=context)

    else:

        return Leaf(type, value, context=context)

class BasePattern(object):

    """A pattern is a tree matching pattern.

    It looks for a specific node type (token or symbol), and

    optionally for a specific content.

    This is an abstract base class.  There are three concrete

    subclasses:

    - LeafPattern matches a single leaf node;

    - NodePattern matches a single node (usually non-leaf);

    - WildcardPattern matches a sequence of nodes of variable length.

    """

    # Defaults for instance variables

    type = None     # Node type (token if < 256, symbol if >= 256)

    content = None  # Optional content matching pattern

    name = None     # Optional name used to store match in results dict

    def __new__(cls, *args, **kwds):

        """Constructor that prevents BasePattern from being instantiated."""

        assert cls is not BasePattern, "Cannot instantiate BasePattern"

        return object.__new__(cls)

    def __repr__(self):

        args = [type_repr(self.type), self.content, self.name]

        while args and args[-1] is None:

            del args[-1]

        return "%s(%s)" % (self.__class__.__name__, ", ".join(map(repr, args)))

    def optimize(self):

        """A subclass can define this as a hook for optimizations.

        Returns either self or another node with the same effect.

        """

        return self

    def match(self, node, results=None):

        """Does this pattern exactly match a node?

        Returns True if it matches, False if not.

        If results is not None, it must be a dict which will be

        updated with the nodes matching named subpatterns.

        Default implementation for non-wildcard patterns.

        """

        if self.type is not None and node.type != self.type:

            return False

        if self.content is not None:

            r = None

            if results is not None:

                r = {}

            if not self._submatch(node, r):

                return False

            if r:

                results.update(r)

        if results is not None and self.name:

            results[self.name] = node

        return True

    def match_seq(self, nodes, results=None):

        """Does this pattern exactly match a sequence of nodes?

        Default implementation for non-wildcard patterns.

        """

        if len(nodes) != 1:

            return False

        return self.match(nodes[0], results)

    def generate_matches(self, nodes):

        """Generator yielding all matches for this pattern.

        Default implementation for non-wildcard patterns.

        """

        r = {}

        if nodes and self.match(nodes[0], r):

            yield 1, r

class LeafPattern(BasePattern):

    def __init__(self, type=None, content=None, name=None):

        """Initializer.  Takes optional type, content, and name.

        The type, if given must be a token type (< 256).  If not given,

        this matches any *leaf* node; the content may still be required.

        The content, if given, must be a string.

        If a name is given, the matching node is stored in the results

        dict under that key.

        """

        if type is not None:

            assert 0 <= type < 256, type

        if content is not None:

            assert isinstance(content, basestring), repr(content)

        self.type = type

        self.content = content

        self.name = name

    def match(self, node, results=None):

        """Override match() to insist on a leaf node."""

        if not isinstance(node, Leaf):

            return False

        return BasePattern.match(self, node, results)

    def _submatch(self, node, results=None):

        """Match the pattern's content to the node's children.

        This assumes the node type matches and self.content is not None.

        Returns True if it matches, False if not.

        If results is not None, it must be a dict which will be

        updated with the nodes matching named subpatterns.

        When returning False, the results dict may still be updated.

        """

        return self.content == node.value

class NodePattern(BasePattern):

    wildcards = False

    def __init__(self, type=None, content=None, name=None):

        """Initializer.  Takes optional type, content, and name.

        The type, if given, must be a symbol type (>= 256).  If the

        type is None this matches *any* single node (leaf or not),

        except if content is not None, in which it only matches

        non-leaf nodes that also match the content pattern.

        The content, if not None, must be a sequence of Patterns that

        must match the node's children exactly.  If the content is

        given, the type must not be None.

        If a name is given, the matching node is stored in the results

        dict under that key.

        """

        if type is not None:

            assert type >= 256, type

        if content is not None:

            assert not isinstance(content, basestring), repr(content)

            content = list(content)

            for i, item in enumerate(content):

                assert isinstance(item, BasePattern), (i, item)

                if isinstance(item, WildcardPattern):

                    self.wildcards = True

        self.type = type