#!/usr/bin/env python

# -*- coding: utf-8 -*-

# java2python.lang.selector -> declarative AST node selection

#

# This module provides classes for simple AST node selection that can be

# easily combined to form complex, declarative rules for retrieving AST

# nodes.

#

# The classes are similar to CSS selectors, with a nod to Python parsing

# libraries like LEPL and PyParsing. At the moment, only a few very

# basic selector types are implemented, but those that are here already

# provide all of the functionality necessary for use within the package.

#

# Projects using java2python should regard this subpackage as

# experimental. While the interfaces are not expected to change, the

# semantics may. Use with caution.

from java2python.lang import tokens

import collections

class Selector(object):

""" Base class for concrete selectors; provides operator methods. """

def __add__(self, other):

""" E + F

Like CSS "E + F": an F element immediately preceded by an E element

"""

return AdjacentSibling(self, other)

def __and__(self, other):

""" E & F

Like CSS "E F": an F element descendant of an E element

"""

return Descendant(self, other)

def __call__(self, *args, **kwds):

""" Subclasses must implement. """

raise NotImplementedError('Selector class cannot be called.')

def __getitem__(self, key):

""" E[n]

Like CSS "E:nth-child(n)": an E element, the n-th child of its parent

"""

return Nth(self, key)

def __gt__(self, other):

""" E > F

Like CSS: "E > F": an F element child of an E element

"""

return Child(self, other)

def __div__(self, other):

""" E / F

Produces a AnySibling.

"""

return AnySibling(self, other)

def walk(self, tree):

""" Select items from the tree and from the tree children. """

for item in self(tree):

yield item

for child in tree.children:

for item in self.walk(child):

yield item

class Token(Selector):

""" Token(...) -> select tokens by matching attributes.

Token is the most generic and flexible Selector; using it,

arbitrary nodes of any type, line number, position, and/or text

can be selected.

Calling Token() without any keywords is equivalent to:

Token(channel=None, index=None, input=None, line=None,

start=None, stop=None, text=None, type=None)

Note that the value of each keyword can be a constant or a

callable. When callables are specified, they are passed a the

token and should return a bool.

"""

def __init__(self, **attrs):

self.attrs = attrs

## we support strings so that the client can refer to the

## token name that way instead of via lookup or worse, integer.

if isinstance(attrs.get('type'), str):

self.attrs['type'] = getattr(tokens, attrs.get('type'))

def __call__(self, tree):

items = list(self.attrs.items())

token = tree.token

def match_or_call(k, v):

if isinstance(v, collections.Callable):

return v(token)

return getattr(token, k)==v

if all(match_or_call(k, v) for k, v in items if v is not None):

yield tree

def __str__(self):

items = list(self.attrs.items())

keys = ('{}={}'.format(k, v) for k, v in items if v is not None)

return 'Token({})'.format(', '.join(keys))

class Nth(Selector):

""" E[n] -> match any slice n of E

Similar to the :nth-child pseudo selector in CSS, but without the

support for keywords like 'odd', 'even', etc.

"""

def __init__(self, e, key):

self.e, self.key = e, key

def __call__(self, tree):

for etree in self.e(tree):

try:

matches = tree.children[self.key]

except (IndexError, ):

return

if not isinstance(matches, list):

matches = [matches]

for child in matches:

yield child

def __str__(self):

return 'Nth({0})[{1}]'.format(self.e, self.key)

class Child(Selector):

""" E > F select any F that is a child of E """

def __init__(self, e, f):

self.e, self.f = e, f

def __call__(self, tree):

for ftree in self.f(tree):

for etree in self.e(tree.parent):

yield ftree

def __str__(self):

return 'Child({0} > {1})'.format(self.e, self.f)

class Type(Selector):

""" Type(T) select any token of type T

Similar to the type selector in CSS.

"""

def __init__(self, key, value=None):

self.key = key if isinstance(key, int) else getattr(tokens, key)

self.value = value

def __call__(self, tree):

if tree.token.type == self.key:

if self.value is None or self.value == tree.token.text:

yield tree

def __str__(self):

val = '' if self.value is None else '={0}'.format(self.value)

return 'Type({0}{1}:{2})'.format(tokens.map[self.key], val, self.key)

class Star(Selector):

""" * select any

Similar to the * selector in CSS.

"""

def __call__(self, tree):

yield tree

def __str__(self):

return 'Star(*)'

class Descendant(Selector):

""" E & F select any F that is a descendant of E """

def __init__(self, e, f):

self.e, self.f = e, f

def __call__(self, tree):

for ftree in self.f(tree):

root, ftree = ftree, ftree.parent

while ftree:

for etree in self.e(ftree):

yield root

ftree = ftree.parent

def __str__(self):

return 'Descendant({0} & {1})'.format(self.e, self.f)

class AdjacentSibling(Selector):

""" E + F select any F immediately preceded by a sibling E """

def __init__(self, e, f):

self.e, self.f = e, f

def __call__(self, node):

if not node.parent:

return

for ftree in self.f(node):

index = node.parent.children.index(ftree)

if not index:

return

previous = node.parent.children[index-1]

for child in self.e(previous):

yield ftree

def __str__(self):

return 'AdjacentSibling({} + {})'.format(self.e, self.f)

class AnySibling(Selector):

""" E / F select any F preceded by a sibling E """

def __init__(self, e, f):

self.e, self.f = e, f

def __call__(self, node):

if not node.parent:

return

for ftree in self.f(node):

index = node.parent.children.index(ftree)

if not index:

return

for prev in node.parent.children[:index]:

for child in self.e(prev):

yield ftree

def __str__(self):

return 'AnySibling({} / {})'.format(self.e, self.f)