#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You 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.
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#

from abc import ABCMeta

from pyspark.ml.util import Identifiable


__all__ = ['Param', 'Params']


class Param(object):
    """
    A param with self-contained documentation and optionally default value.
    """

    def __init__(self, parent, name, doc, defaultValue=None):
        if not isinstance(parent, Identifiable):
            raise ValueError("Parent must be identifiable but got type %s." % type(parent).__name__)
        self.parent = parent
        self.name = str(name)
        self.doc = str(doc)
        self.defaultValue = defaultValue

    def __str__(self):
        return str(self.parent) + "-" + self.name

    def __repr__(self):
        return "Param(parent=%r, name=%r, doc=%r, defaultValue=%r)" % \
               (self.parent, self.name, self.doc, self.defaultValue)


class Params(Identifiable):
    """
    Components that take parameters. This also provides an internal
    param map to store parameter values attached to the instance.
    """

    __metaclass__ = ABCMeta

    def __init__(self):
        super(Params, self).__init__()
        #: embedded param map
        self.paramMap = {}

    @property
    def params(self):
        """
        Returns all params. The default implementation uses
        :py:func:`dir` to get all attributes of type
        :py:class:`Param`.
        """
        return filter(lambda attr: isinstance(attr, Param),
                      [getattr(self, x) for x in dir(self) if x != "params"])

    def _merge_params(self, params):
        paramMap = self.paramMap.copy()
        paramMap.update(params)
        return paramMap

    @staticmethod
    def _dummy():
        """
        Returns a dummy Params instance used as a placeholder to generate docs.
        """
        dummy = Params()
        dummy.uid = "undefined"
        return dummy