# Source code for pymatgen.core.xcfunc

    # coding: utf-8
    # Copyright (c) Pymatgen Development Team.
    # Distributed under the terms of the MIT License.
    """
    This module provides
    """

    from collections import namedtuple, OrderedDict
    from monty.string import is_string
    from monty.json import MSONable  # , MontyEncoder
    from monty.functools import lazy_property
    from pymatgen.core.libxcfunc import LibxcFunc

    __author__ = "Matteo Giantomassi"
    __copyright__ = "Copyright 2016, The Materials Project"
    __version__ = "3.0.0"  # The libxc version used to generate this file!
    __maintainer__ = "Matteo Giantomassi"
    __email__ = "gmatteo@gmail.com"
    __status__ = "Production"
    __date__ = "May 16, 2016"

    class XcFunc(MSONable):
        """
        This object stores information about the XC correlation functional.
        Client code usually creates the object by calling the class methods:

            - from_name
            - from_type_name

        or code-specific methods such as:

            - from_abinit_ixc

        Ax XcFunc instance is hashable and can therefore be used as key in dictionaries.

        The implementation is based on the libxc conventions
        and is inspired to the XML specification for atomic PAW datasets documented at:

            https://wiki.fysik.dtu.dk/gpaw/setups/pawxml.html

        For convenience, part of the pawxml documentation is reported here.

        The xc_functional element defines the exchange-correlation functional used for
        generating the dataset. It has the two attributes type and name.

        The type attribute can be LDA, GGA, MGGA or HYB.
        The name attribute designates the exchange-correlation functional
        and can be specified in the following ways:

        [1] Taking the names from the LibXC library. The correlation and exchange names
            are stripped from their XC_ part and combined with a + sign.
            Here is an example for an LDA functional:

            <xc_functional type="LDA", name="LDA_X+LDA_C_PW"/>

            and this is what PBE will look like:

            <xc_functional type="GGA", name="GGA_X_PBE+GGA_C_PBE"/>

        [2] Using one of the following pre-defined aliases:

        type    name    LibXC equivalent             Reference
        LDA     PW      LDA_X+LDA_C_PW               LDA exchange; Perdew, Wang, PRB 45, 13244 (1992)
        GGA     PW91    GGA_X_PW91+GGA_C_PW91        Perdew et al PRB 46, 6671 (1992)
        GGA     PBE     GGA_X_PBE+GGA_C_PBE          Perdew, Burke, Ernzerhof, PRL 77, 3865 (1996)
        GGA     RPBE    GGA_X_RPBE+GGA_C_PBE         Hammer, Hansen, Nørskov, PRB 59, 7413 (1999)
        GGA     revPBE  GGA_X_PBE_R+GGA_C_PBE        Zhang, Yang, PRL 80, 890 (1998)
        GGA     PBEsol  GGA_X_PBE_SOL+GGA_C_PBE_SOL  Perdew et al, PRL 100, 136406 (2008)
        GGA     AM05    GGA_X_AM05+GGA_C_AM05        Armiento, Mattsson, PRB 72, 085108 (2005)
        GGA     BLYP    GGA_X_B88+GGA_C_LYP          Becke, PRA 38, 3098 (1988); Lee, Yang, Parr, PRB 37, 785
        """
        type_name = namedtuple("type_name", "type, name")

        xcf = LibxcFunc
        defined_aliases = OrderedDict([  # (x, c) --> type_name
            # LDAs
            ((xcf.LDA_X, xcf.LDA_C_PW), type_name("LDA", "PW")),  # ixc 7
            ((xcf.LDA_X, xcf.LDA_C_PW_MOD), type_name("LDA", "PW_MOD")),
            ((xcf.LDA_X, xcf.LDA_C_PZ), type_name("LDA", "PZ")),  # ixc 2
            ((xcf.LDA_X, xcf.LDA_C_WIGNER), type_name("LDA", "W")),  # ixc 4
            ((xcf.LDA_X, xcf.LDA_C_HL), type_name("LDA", "HL")),  # ixc 5
            ((xcf.LDA_X, xcf.LDA_C_GL), type_name("LDA", "GL")),
            ((xcf.LDA_X, xcf.LDA_C_VWN), type_name("LDA", "VWN")),
            # GGAs
            ((xcf.GGA_X_PW91, xcf.GGA_C_PW91), type_name("GGA", "PW91")),
            ((xcf.GGA_X_PBE, xcf.GGA_C_PBE), type_name("GGA", "PBE")),
            ((xcf.GGA_X_RPBE, xcf.GGA_C_PBE), type_name("GGA", "RPBE")),  # ixc 15
            ((xcf.GGA_X_PBE_R, xcf.GGA_C_PBE), type_name("GGA", "revPBE")),  # ixc 14
            ((xcf.GGA_X_PBE_SOL, xcf.GGA_C_PBE_SOL), type_name("GGA", "PBEsol")),
            ((xcf.GGA_X_AM05, xcf.GGA_C_AM05), type_name("GGA", "AM05")),
            ((xcf.GGA_X_B88, xcf.GGA_C_LYP), type_name("GGA", "BLYP")),
        ])
        del type_name

        # Correspondence between Abinit ixc notation and libxc notation.
        # see: http://www.abinit.org/doc/helpfiles/for-v7.8/input_variables/varbas.html#ixc
        # and 42_libpaw/m_pawpsp.F90 for the implementation.
        # Fortunately, all the other cases are handled with libxc.
        abinitixc_to_libxc = {
            1: dict(xc=xcf.LDA_XC_TETER93),
            2: dict(x=xcf.LDA_X, c=xcf.LDA_C_PZ),  # PZ  001009
            4: dict(x=xcf.LDA_X, c=xcf.LDA_C_WIGNER),  # W
            5: dict(x=xcf.LDA_X, c=xcf.LDA_C_HL),  # HL
            7: dict(x=xcf.LDA_X, c=xcf.LDA_C_PW),  # PW 001012
            11: dict(x=xcf.GGA_X_PBE, c=xcf.GGA_C_PBE),  # PBE
            14: dict(x=xcf.GGA_X_PBE_R, c=xcf.GGA_C_PBE),  # revPBE
            15: dict(x=xcf.GGA_X_RPBE, c=xcf.GGA_C_PBE),  # RPBE
        }
        del xcf

        @classmethod
        def aliases(cls):
            """List of registered names."""
            return [nt.name for nt in cls.defined_aliases.values()]

        @classmethod
        def asxc(cls, obj):
            """Convert object into Xcfunc."""
            if isinstance(obj, cls):
                return obj
            if is_string(obj):
                return cls.from_name(obj)
            raise TypeError("Don't know how to convert <%s:%s> to Xcfunc" % (type(obj), str(obj)))

        @classmethod
        def from_abinit_ixc(cls, ixc):
            """Build the object from Abinit ixc (integer)"""
            ixc = int(ixc)
            if ixc == 0:
                return None
            if ixc > 0:
                return cls(**cls.abinitixc_to_libxc[ixc])

            # libxc notation employed in Abinit: a six-digit number in the form XXXCCC or CCCXXX
            # ixc = str(ixc)
            # assert len(ixc[1:]) == 6
            # first, last = ixc[1:4], ixc[4:]
            ixc = abs(ixc)
            first = ixc // 1000
            last = ixc - first * 1000
            x, c = LibxcFunc(int(first)), LibxcFunc(int(last))
            if not x.is_x_kind:
                x, c = c, x  # Swap
            assert x.is_x_kind and c.is_c_kind
            return cls(x=x, c=c)

        @classmethod
        def from_name(cls, name):
            """Build the object from one of the registered names"""
            return cls.from_type_name(None, name)

        @classmethod
        def from_type_name(cls, typ, name):
            """Build the object from (type, name)."""
            # Try aliases first.
            for k, nt in cls.defined_aliases.items():
                if typ is not None and typ != nt.type:
                    continue
                # print(name, nt.name)
                if name == nt.name:
                    if len(k) == 1:
                        return cls(xc=k)
                    if len(k) == 2:
                        return cls(x=k[0], c=k[1])
                    raise ValueError("Wrong key: %s" % k)

            # At this point, we should have something in the form
            # name="GGA_X_PBE+GGA_C_PBE" or  name=""LDA_XC_TETER93"
            if "+" in name:
                # if typ is not None: raise ValueError("typ: `%s` but name: `%s`" % (typ, name))
                x, c = (s.strip() for s in name.split("+"))
                x, c = LibxcFunc[x], LibxcFunc[c]
                return cls(x=x, c=c)
            # if typ is not None: raise ValueError("typ: `%s` but name: `%s`" % (typ, name))
            xc = LibxcFunc[name]
            return cls(xc=xc)

        @classmethod
        def from_dict(cls, d):
            """
            Makes XcFunc obey the general json interface used in pymatgen for easier serialization.
            """
            return cls(xc=d.get("xc"), x=d.get("x"), c=d.get("c"))

        def as_dict(self):
            """
            Makes XcFunc obey the general json interface used in pymatgen for easier serialization.
            """
            d = {"@module": self.__class__.__module__,
                 "@class": self.__class__.__name__}
            # print("in as_dict", type(self.x), type(self.c), type(self.xc))
            if self.x is not None:
                d["x"] = self.x.as_dict()
            if self.c is not None:
                d["c"] = self.c.as_dict()
            if self.xc is not None:
                d["xc"] = self.xc.as_dict()
            return d

        # def to_json(self):
        #    """
        #    Returns a json string representation of the MSONable object.
        #    """
        #    return json.dumps(self.as_dict()) #, cls=MontyEncoder)

        def __init__(self, xc=None, x=None, c=None):
            """
            Args:
                xc: LibxcFunc for XC functional.
                x, c: LibxcFunc for exchange and correlation part. Mutually exclusive with xc.
            """
            # Consistency check
            if xc is None:
                if x is None or c is None:
                    raise ValueError("x or c must be specified when xc is None")
            else:
                if x is not None or c is not None:
                    raise ValueError("x and c should be None when xc is specified")

            self.xc, self.x, self.c = xc, x, c

        @lazy_property
        def type(self):
            """The type of the functional."""
            if self.xc in self.defined_aliases:
                return self.defined_aliases[self.xc].type
            xc = (self.x, self.c)
            if xc in self.defined_aliases:
                return self.defined_aliases[xc].type

            # If self is not in defined_aliases, use LibxcFunc family
            if self.xc is not None:
                return self.xc.family
            return "+".join([self.x.family, self.c.family])

        @lazy_property
        def name(self):
            """
            The name of the functional. If the functional is not found in the aliases,
            the string has the form X_NAME+C_NAME
            """
            if self.xc in self.defined_aliases:
                return self.defined_aliases[self.xc].name
            xc = (self.x, self.c)
            if xc in self.defined_aliases:
                return self.defined_aliases[xc].name
            if self.xc is not None:
                return self.xc.name
            return "+".join([self.x.name, self.c.name])

        def __repr__(self):
            return "%s" % self.name

        def __hash__(self):
            return hash(self.name)

        def __eq__(self, other):
            if other is None:
                return False
            if isinstance(other, XcFunc):
                return self.name == other.name
            # assume other is a string
            return self.name == other

        def __ne__(self, other):
            return not self == other

        # @property
        # def refs(self):

        # def info_dict()
        #    if self.xc is not None:
        #        return {"xc", self.xc.info_dict}
        #    else:
        #        return {"x", self.x.info_dict, "c", self.c.info_dict}