# -*- coding: utf-8 -*-
#
# Copyright (c) 2023, the cclib development team
#
# This file is part of cclib (http://cclib.github.io) and is distributed under
# the terms of the BSD 3-Clause License.

"""Compute Charge Model 5 (CM5) atomic charges and associated properties.

The description of charges is from https://doi.org/10.1021/ct200866d.
"""

import logging

import numpy as np
import periodictable.covalent_radius as covalent_radius

from cclib.method.calculationmethod import Method


class CM5(Method):
    """Compute Charge Model 5 (CM5) atomic charges and associated properties.

    The description of charges is from https://doi.org/10.1021/ct200866d.

    This implementation is derived from https://github.com/hokru/cm5charges
    (https://doi.org/10.5281/zenodo.1193753), which is derived from
    the original CM5PAC code (https://comp.chem.umn.edu/cm5pac/).

    Parameters
    ----------
    data : ccData
        The parsed data to be used for atomic coordinates, numbers, and Hirshfeld charges
    radii : str, default "hokru"
        Specify the set of radii to be used.  One of:
         - "hokru": Values copied from https://github.com/hokru/cm5charges,
           themselves copied from CM5PAC.  The original reference is
             "Atomic Radii of the Elements," M. Mantina, R. Valero, C. J. Cramer, and D. G. Truhlar,
             in CRC Handbook of Chemistry and Physics, 91st Edition (2010-2011),
             edited by W. M. Haynes (CRC Press, Boca Raton, FL, 2010), pages 9-49-9-50;
             corrected Nov. 17, 2010 for the 92nd edition.
         - "Cordero": Values from doi:10.1039/b801115j.
         - "CorderoPyykko": Values averaged from doi:10.1002/chem.200901472 and Cordero.
        The final charges seem relatively insensitive to this choice.

    progress : Optional[cclib.progress.Progress], default None
    loglevel : int, default logging.INFO
    logname : str
    """
    def __init__(self, data, radii: str = "hokru", progress=None, loglevel=logging.INFO, logname="Log"):
        super().__init__(data, progress, loglevel, logname)

        self.required_attrs = ("natom", "atomcoords", "atomnos")

        if radii == "CorderoPyykko":
            self.atomradius = _radii_cordero_pyykko(radii)
        elif radii == "Cordero":
            self.atomradius = _radii_cordero_pyykko(radii)
        elif radii == "hokru":
            self.atomradius = _radii_hokru()
        else:
            raise RuntimeError(f"invalid name for radii: {radii}")

    def charges(self, extended: bool = True):
        """Compute the CM5 atomic charges.

        Parameters
        ----------
        extended : bool, default True
            Should the "extended" set of charges be used?
            The default of true mimics the behavior in the original CM5PAC program.
            If false, only the 26 elements the model was parameterized on
            will have a non-zero atomic model parameter $D_{Z}$ (H-Ca, Zn, Ge-Br, and I).
            If true, all additional elements (except Sc-Cu/21-29) are considered for non-zero atomwise parameters.
            (Even if true, the following are zero: 3, 12, 20-30, 38-48, 56-80, 88-112.)
            Holger Kruse's code does not use the extended set.

        Returns
        -------
        numpy.ndarray
            The final computed CM5 charges
        """
        nat = self.data.natom
        qcm5 = np.zeros(nat)
        z = self.data.atomnos
        xyz = self.data.atomcoords[-1]
        hirshfeld_charges = self.data.atomcharges["hirshfeld"]

        alpha = 2.474  # Angstrom

        for i in range(0, nat):
            s = 0
            for j in range(0, nat):
                if i != j:
                    rij = np.linalg.norm(np.subtract(xyz[i], xyz[j]))
                    # eq. (2) from doi:10.1021/ct200866d
                    bij = np.exp(
                        -alpha * (rij - self.atomradius[z[i]] - self.atomradius[z[j]])
                    )
                    tij = _tij(z[i], z[j], extended=extended)
                    s += tij * bij
            qcm5[i] = hirshfeld_charges[i] + s
        return qcm5


def _tij(i: int, j: int, extended: bool = True) -> float:
    """Compute a single $T_{kk'}$ in eq. (1) from doi:10.1021/ct200866d.

    This term may be computed from special case pairwise values in eq. (3) or
    more generally via eq. (4), depending on the atomic numbers i and j.

    Notation-wise, k and k prime are renamed to i and j.

    These optionally include the extended set of parameters presented in the
    Supporting Information.

    Parameters
    ----------
    i : int
        Atomic number of first index
    j : int
        Atomic number of second index
    extended : bool, default True
        Should the extended set of $D_{Z}$ parameters presented in the
        Supporting Information be used?

    Returns
    -------
    $T_{ij}$ : float
    """

    tij = 0.0

    # A dummy first index is used to match the Fortran implementation.
    #                    H-C     H-N     H-O     C-N     C-O     N-O
    dzz = np.array([0.0, 0.0502, 0.1747, 0.1671, 0.0556, 0.0234, -0.0346])

    # catch special cases
    if i == 1:
        if j == 6:
            tij = dzz[1]
        elif j == 7:
            tij = dzz[2]
        elif j == 8:
            tij = dzz[3]
    elif i == 6:
        if j == 7:
            tij = dzz[4]
        elif j == 8:
            tij = dzz[5]
        elif j == 1:
            tij = -dzz[1]
    elif i == 7:
        if j == 8:
            tij = dzz[6]
        elif j == 1:
            tij = -dzz[2]
        elif j == 6:
            tij = -dzz[4]
    elif i == 8:
        if j == 1:
            tij = -dzz[3]
        elif j == 6:
            tij = -dzz[5]
        elif j == 7:
            tij = -dzz[6]
    else:
        # Indices used here correspond directly to atomic number.
        dz = np.zeros((119,))
        dz[1] = 0.0056
        dz[2] = -0.1543
        dz[4] = 0.0333
        dz[5] = -0.1030
        dz[6] = -0.0446
        dz[7] = -0.1072
        dz[8] = -0.0802
        dz[9] = -0.0629
        dz[10] = -0.1088
        dz[11] = 0.0184
        dz[13] = -0.0726
        dz[14] = -0.0790
        dz[15] = -0.0756
        dz[16] = -0.0565
        dz[17] = -0.0444
        # This (Z=18) is erroneously set as -0.07676 in Holger Kruse's
        # implementation; here it is left as in the original.
        dz[18] = -0.0767
        dz[19] = 0.0130
        if extended:
            dz[31] = -0.0512
        dz[32] = -0.0557
        dz[33] = -0.0533
        dz[34] = -0.0399
        dz[35] = -0.0313
        if extended:
            dz[36] = -0.0541
            dz[37] = 0.0092
            dz[49] = -0.0361
            dz[50] = -0.0393
            dz[51] = -0.0376
            dz[52] = -0.0281
        dz[53] = -0.0220
        if extended:
            dz[54] = -0.0381
            dz[55] = 0.0065
            dz[81] = -0.0255
            dz[82] = -0.0277
            dz[83] = -0.0265
            dz[84] = -0.0198
            dz[85] = -0.0155
            dz[86] = -0.0269
            dz[87] = 0.0046
            dz[113] = -0.0179
            dz[114] = -0.0195
            dz[115] = -0.0187
            dz[116] = -0.0140
            dz[117] = -0.0110
            dz[118] = -0.0189

        tij = dz[i] - dz[j]

    return tij


def _radii_cordero_pyykko(radii: str) -> np.ndarray:
    """Return the covalent radii available in the `periodictable` package from
    Cordero or Pyykko.

    If 'Cordero', use the values directly from doi:10.1039/b801115j.

    If 'CorderoPykko', use the CRC value, which is the average of
    Cordero's value and Pyykko's single-bond value from 10.1002/chem.200901472.
    If an element doesn't have a single-bond value, use just Cordero's.
    """
    atomradius = np.zeros(119)
    atomradius[0] = 0.20

    for line in covalent_radius.CorderoPyykko.split("\n"):
        if line[0] == "#":
            continue
        fields = line.split()
        Z = int(fields[0])

        if len(fields) < 6:
            for _ in range(len(fields), 6):
                fields.append("0.0")

        if fields[2] == "-":
            rC = 0.0
            # drC = 0.0
        else:
            sfields = fields[2].split("(")
            rC = float(sfields[0])
            # drC = float(sfields[1].split(")", 1)[0]) / 100 if len(sfields) == 2 else 0.0

        r1 = float(fields[3])
        r1_avg = (rC + r1) / 2 if r1 != 0.0 else rC
        # r2 = float(fields[4])
        # r3 = float(fields[5])

        if radii == "CorderoPyykko":
            atomradius[Z] = r1_avg
        elif radii == "Cordero":
            atomradius[Z] = rC

    return atomradius


def _radii_hokru() -> np.ndarray:
    """Return the covalent radii found in
    https://github.com/hokru/cm5charges/blob/23f58b728e9f4af2306702c7cd48b1afb4b72b15/cm5.f90#L58."""
    # fmt: off
    atomradius = np.array([
        # dummy
        0.0,
        # H He
        0.32,0.37,
        # Li     Be     B     C       N      O     F      Ne
        1.30,0.99,0.84,0.75,0.71,0.64,0.60,0.62,
        # Na    Mg     Al     Si     P      S       Cl     Ar
        1.60,1.40,1.24,1.14,1.09,1.04,1.00,1.01,
        # K      Ca     Sc     Ti     V      Cr      Mn     Fe     Co    Ni     Cu     Zn     Ga     Ge     As     Se     Br    Kr
        2.00,1.74,1.59,1.48,1.44,1.30,1.29,1.24,1.18,1.17,1.22,1.20,1.23,1.20,1.20,1.18,1.17,1.24,
        #  Rb    Sr     Y      Zr      Nb     Mo    Tc     Ru     Rh     Pd     Ag     Cd     In    Sn      Sb      Te     I     Xe
        2.15,1.90,1.78,1.64,1.56,1.46,1.38,1.36,1.34,1.30,1.36,1.40,1.42,1.40,1.40,1.37,1.32,1.36,
        # Cs Ba
        2.38,2.06,
        # La-Lu
        1.94,1.84,1.90,1.73,1.86,1.85,1.83,1.82,1.81,1.80,1.79,1.77,1.77,1.78,1.74,
        # Hf     Ta     W       Re     Os    Ir     Pt     Au     Hg     Ti     Pb     Bi     Po     At     Rn
        1.64,1.58,1.50,1.41,1.36,1.32,1.30,1.64,1.88,1.48,1.45,1.50,1.42,1.47,1.46,
        # Fr-Pu
        2.42,2.11,2.01,1.90,1.84,1.83,1.80,1.80
    ])
    # fmt: on
    return atomradius
