0000004f
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 '    "Utility functions used by the btm_matcher module"

from . import pytree
from .pgen2 import grammar, token
from .pygram import pattern_symbols, python_symbols

syms = pattern_symbols
pysyms = python_symbols
tokens = grammar.opmap
token_labels = token

TYPE_ANY = -1
TYPE_ALTERNATIVES = -2
TYPE_GROUP = -3

class MinNode(object):
    """This class serves as an intermediate representation of the
    pattern tree during the conversion to sets of leaf-to-root
    subpatterns"""

    def __init__(self, type=None, name=None):
        self.type = type
        self.name = name
        self.children = []
        self.leaf = False
        self.parent = None
        self.alternatives = []
        self.group = []

    def __repr__(self):
        return str(self.type) + ' ' + str(self.name)

    def leaf_to_root(self):
        """Internal method. Returns a characteristic path of the
        pattern tree. This method must be run for all leaves until the
        linear subpatterns are merged into a single"""
        node = self
        subp = []
        while node:
            if node.type == TYPE_ALTERNATIVES:
                node.alternatives.append(subp)
                if len(node.alternatives) == len(node.children):
                    #last alternative
                    subp = [tuple(node.alternatives)]
                    node.alternatives = []
                    node = node.parent
                    continue
                else:
                    node = node.parent
                    subp = None
                    break

            if node.type == TYPE_GROUP:
                node.group.append(subp)
                #probably should check the number of leaves
                if len(node.group) == len(node.children):
                    subp = get_characteristic_subpattern(node.group)
                    node.group = []
                    node = node.parent
                    continue
                else:
                    node = node.parent
                    subp = None
                    break

            if node.type == token_labels.NAME and node.name:
                #in case of type=name, use the name instead
                subp.append(node.name)
            else:
                subp.append(node.type)

            node = node.parent
        return subp

    def get_linear_subpattern(self):
        """Drives the leaf_to_root method. The reason that
        leaf_to_root must be run multiple times is because we need to
        reject 'group' matches; for example the alternative form
        (a | b c) creates a group [b c] that needs to be matched. Since
        matching multiple linear patterns overcomes the automaton's
        capabilities, leaf_to_root merges each group into a single
        choice based on 'characteristic'ity,

        i.e. (a|b c) -> (a|b) if b more characteristic than c

        Returns: The most 'characteristic'(as defined by
          get_characteristic_subpattern) path for the compiled pattern
          tree.
        """

        for l in self.leaves():
            subp = l.leaf_to_root()
            if subp:
                return subp

    def leaves(self):
        "Generator that returns the leaves of the tree"
        for child in self.children:
            for x in child.leaves():
                yield x
        if not self.children:
            yield self

def reduce_tree(node, parent=None):
    """
    Internal function. Reduces a compiled pattern tree to an
    intermediate representation suitable for feeding the
    automaton. This also trims off any optional pattern elements(like
    [a], a*).
    """

    new_node = None
    #switch on the node type
    if node.type == syms.Matcher:
        #skip
        node = node.children[0]

    if node.type == syms.Alternatives  :
        #2 cases
        if len(node.children) <= 2:
            #just a single 'Alternative', skip this node
            new_node = reduce_tree(node.children[0], parent)
        else:
            #real alternatives
            new_node = MinNode(type=TYPE_ALTERNATIVES)