#
# 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.
    """

    def __init__(self, parent, name, doc):
        if not isinstance(parent, Params):
            raise TypeError("Parent must be a Params but got type %s." % type(parent))
        self.parent = parent
        self.name = str(name)
        self.doc = str(doc)

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

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


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

    __metaclass__ = ABCMeta

    #: internal param map for user-supplied values param map
    paramMap = {}

    #: internal param map for default values
    defaultParamMap = {}

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

    def _explain(self, param):
        """
        Explains a single param and returns its name, doc, and optional
        default value and user-supplied value in a string.
        """
        param = self._resolveParam(param)
        values = []
        if self.isDefined(param):
            if param in self.defaultParamMap:
                values.append("default: %s" % self.defaultParamMap[param])
            if param in self.paramMap:
                values.append("current: %s" % self.paramMap[param])
        else:
            values.append("undefined")
        valueStr = "(" + ", ".join(values) + ")"
        return "%s: %s %s" % (param.name, param.doc, valueStr)

    def explainParams(self):
        """
        Returns the documentation of all params with their optionally
        default values and user-supplied values.
        """
        return "\n".join([self._explain(param) for param in self.params])

    def getParam(self, paramName):
        """
        Gets a param by its name.
        """
        param = getattr(self, paramName)
        if isinstance(param, Param):
            return param
        else:
            raise ValueError("Cannot find param with name %s." % paramName)

    def isSet(self, param):
        """
        Checks whether a param is explicitly set by user.
        """
        param = self._resolveParam(param)
        return param in self.paramMap

    def hasDefault(self, param):
        """
        Checks whether a param has a default value.
        """
        param = self._resolveParam(param)
        return param in self.defaultParamMap

    def isDefined(self, param):
        """
        Checks whether a param is explicitly set by user or has a default value.
        """
        return self.isSet(param) or self.hasDefault(param)

    def getOrDefault(self, param):
        """
        Gets the value of a param in the user-supplied param map or its
        default value. Raises an error if either is set.
        """
        if isinstance(param, Param):
            if param in self.paramMap:
                return self.paramMap[param]
            else:
                return self.defaultParamMap[param]
        elif isinstance(param, str):
            return self.getOrDefault(self.getParam(param))
        else:
            raise KeyError("Cannot recognize %r as a param." % param)

    def extractParamMap(self, extraParamMap={}):
        """
        Extracts the embedded default param values and user-supplied
        values, and then merges them with extra values from input into
        a flat param map, where the latter value is used if there exist
        conflicts, i.e., with ordering: default param values <
        user-supplied values < extraParamMap.
        :param extraParamMap: extra param values
        :return: merged param map
        """
        paramMap = self.defaultParamMap.copy()
        paramMap.update(self.paramMap)
        paramMap.update(extraParamMap)
        return paramMap

    def _shouldOwn(self, param):
        """
        Validates that the input param belongs to this Params instance.
        """
        if param.parent is not self:
            raise ValueError("Param %r does not belong to %r." % (param, self))

    def _resolveParam(self, param):
        """
        Resolves a param and validates the ownership.
        :param param: param name or the param instance, which must
                      belong to this Params instance
        :return: resolved param instance
        """
        if isinstance(param, Param):
            self._shouldOwn(param)
            return param
        elif isinstance(param, str):
            return self.getParam(param)
        else:
            raise ValueError("Cannot resolve %r as a param." % param)

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

    def _set(self, **kwargs):
        """
        Sets user-supplied params.
        """
        for param, value in kwargs.items():
            self.paramMap[getattr(self, param)] = value
        return self

    def _setDefault(self, **kwargs):
        """
        Sets default params.
        """
        for param, value in kwargs.items():
            self.defaultParamMap[getattr(self, param)] = value
        return self