"""
Environment nodes module.
"""

import abc

from monty.json import MSONable


class AbstractEnvironmentNode(MSONable):
    """
    Abstract class used to define an environment as a node in a graph.
    """

    COORDINATION_ENVIRONMENT = 0
    NUMBER_OF_NEIGHBORING_COORDINATION_ENVIRONMENTS = 1
    NUMBER_OF_NEIGHBORING_CES = NUMBER_OF_NEIGHBORING_COORDINATION_ENVIRONMENTS
    NEIGHBORING_COORDINATION_ENVIRONMENTS = 2
    NEIGHBORING_CES = NEIGHBORING_COORDINATION_ENVIRONMENTS
    NUMBER_OF_LIGANDS_FOR_EACH_NEIGHBORING_COORDINATION_ENVIRONMENT = 3
    NUMBER_OF_LIGANDS_FOR_EACH_NEIGHBORING_CE = NUMBER_OF_LIGANDS_FOR_EACH_NEIGHBORING_COORDINATION_ENVIRONMENT
    LIGANDS_ARRANGEMENT = 4
    NEIGHBORS_LIGANDS_ARRANGEMENT = 5
    ATOM = 6
    CE_NNBCES_NBCES_LIGANDS = -1
    DEFAULT_EXTENSIONS = (ATOM, COORDINATION_ENVIRONMENT)

    def __init__(self, central_site, i_central_site):
        """
        Constructor for the AbstractEnvironmentNode object.

        Args:
            central_site (Site or subclass of Site): central site as a pymatgen Site or
                                                     subclass of Site (e.g. PeriodicSite, ...).
            i_central_site (int): Index of the central site in the structure.
        """
        self.central_site = central_site
        self.i_central_site = i_central_site

    @property
    def isite(self):
        """Index of the central site."""
        return self.i_central_site

    def __hash__(self):
        """Simple hash function based on the hash function of the central site."""
        return self.central_site.__hash__()

    def __eq__(self, other):
        # When relabelling nodes from a str or int to an EnvironmentNode in-place in a graph (e.g. in a
        # ConnectedComponent), the comparison should return False when comparing the already relabelled nodes (e.g. as
        # an EnvironmentNode) with those not yet relabelled (e.g. a str representing the isite). This is useful for
        # serialization as a json/bson object.
        return self.__class__ == other.__class__ and self.isite == other.isite

    def __lt__(self, other):
        # This simple "Less Than" operator allows to strictly sort environment nodes in a graph.
        # This is useful (and actually needed) in the definition of the cycles but does not have
        # any real meaning of a "lower value" environment node.
        return self.isite < other.isite

    def everything_equal(self, other):
        """Checks equality with respect to another AbstractEnvironmentNode using the index of the central site
        as well as the central site itself."""
        return self.__eq__(other) and self.central_site == other.central_site

    @property
    @abc.abstractmethod
    def coordination_environment(self):
        """Coordination environment of this node."""
        return

    @property
    def ce(self):
        """Coordination environment of this node."""
        return self.coordination_environment

    @property
    def mp_symbol(self):
        """Coordination environment of this node."""
        return self.coordination_environment

    @property
    def ce_symbol(self):
        """Coordination environment of this node."""
        return self.coordination_environment

    @property
    def atom_symbol(self):
        """Symbol of the atom on the central site."""
        return self.central_site.specie.symbol

    def __str__(self):
        """String representation of the AbstractEnvironmentNode."""
        return f"Node #{self.isite:d} {self.atom_symbol} ({self.coordination_environment})"


class EnvironmentNode(AbstractEnvironmentNode):
    """
    Class used to define an environment as a node in a graph.
    """

    def __init__(self, central_site, i_central_site, ce_symbol):
        """
        Constructor for the EnvironmentNode object.

        Args:
            central_site (Site or subclass of Site): central site as a pymatgen Site or
                                                     subclass of Site (e.g. PeriodicSite, ...).
            i_central_site (int): Index of the central site in the structure.
            ce_symbol (str): Symbol of the identified environment.
        """
        AbstractEnvironmentNode.__init__(self, central_site, i_central_site)
        self._ce_symbol = ce_symbol

    @property
    def coordination_environment(self):
        """Coordination environment of this node."""
        return self._ce_symbol

    def everything_equal(self, other):
        """Compare with another environment node.

        Returns:
            True if it is equal to the other node, False otherwise.
        """
        return super().everything_equal(other) and self.coordination_environment == other.coordination_environment


# Keep these as they might come in handy later on if we decide to implement specific descriptors
# for specific environments
# class OctahedralEnvironmentNode(AbstractEnvironmentNode):
#
#     CG = AllCoordinationGeometries().get_geometry_from_mp_symbol('O:6')
#
#     def __init__(self, central_site, i_central_site):
#         AbstractEnvironmentNode.__init__(self, central_site, i_central_site)
#
#     @property
#     def coordination_environment(self):
#         return self.CG.mp_symbol
#
#
# class TetrahedralEnvironmentNode(AbstractEnvironmentNode):
#
#     CG = AllCoordinationGeometries().get_geometry_from_mp_symbol('T:4')
#
#     def __init__(self, central_site, i_central_site):
#         AbstractEnvironmentNode.__init__(self, central_site, i_central_site)
#
#     @property
#     def coordination_environment(self):
#         return self.CG.mp_symbol
#
#
# allowed_environment_nodes = {'O:6': OctahedralEnvironmentNode,
#                              'T:4': TetrahedralEnvironmentNode}


def get_environment_node(central_site, i_central_site, ce_symbol):
    """
    Get the EnvironmentNode class or subclass for the given site and symbol.

    Args:
        central_site (Site or subclass of Site): Central site of the environment.
        i_central_site (int): Index of the central site in the structure.
        ce_symbol: Symbol of the environment.
    Returns:
        An EnvironmentNode object.
    """
    return EnvironmentNode(central_site=central_site, i_central_site=i_central_site, ce_symbol=ce_symbol)
