#     Copyright 2014, Kay Hayen, mailto:kay.hayen@gmail.com
#
#     Part of "Nuitka", an optimizing Python compiler that is compatible and
#     integrates with CPython, but also works on its own.
#
#     Licensed under the Apache License, Version 2.0 (the "License");
#     you may not use this file except in compliance with the License.
#     You may obtain a copy of the License at
#
#        http://www.apache.org/licenses/LICENSE-2.0
#
#     Unless required by applicable law or agreed to in writing, software
#     distributed under the License is distributed on an "AS IS" BASIS,
#     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#     See the License for the specific language governing permissions and
#     limitations under the License.
#
""" Subscript node.

Subscripts are important when working with lists and dictionaries. Tracking
them can allow to achieve more compact code, or predict results at compile time.

There will be a method "computeExpressionSubscript" to aid predicting them.
"""

from .NodeBases import ExpressionChildrenHavingBase


class ExpressionSubscriptLookup(ExpressionChildrenHavingBase):
    kind = "EXPRESSION_SUBSCRIPT_LOOKUP"

    named_children = (
        "expression",
        "subscript"
    )

    def __init__(self, expression, subscript, source_ref):
        ExpressionChildrenHavingBase.__init__(
            self,
            values     = {
                "expression" : expression,
                "subscript"  : subscript
            },
            source_ref = source_ref
        )

    getLookupSource = ExpressionChildrenHavingBase.childGetter("expression")
    getSubscript = ExpressionChildrenHavingBase.childGetter("subscript")

    def computeExpression(self, constraint_collection):
        lookup_source = self.getLookupSource()

        return lookup_source.computeExpressionSubscript(
            lookup_node           = self,
            subscript             = self.getSubscript(),
            constraint_collection = constraint_collection
        )

    def isKnownToBeIterable(self, count):
        return None
