##############################################################################
# MDTraj: A Python Library for Loading, Saving, and Manipulating
#         Molecular Dynamics Trajectories.
# Copyright 2012-2013 Stanford University and the Authors
#
# Authors: Robert McGibbon, Kyle Beauchamp
# Contributors:
#
# MDTraj is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as
# published by the Free Software Foundation, either version 2.1
# of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with MDTraj. If not, see <http://www.gnu.org/licenses/>.
##############################################################################


##############################################################################
# Imports
##############################################################################

import cython
import warnings
import numpy as np
from mdtraj.utils import ensure_type

from cpython cimport bool
from cython.parallel cimport prange

##############################################################################
# External Declarations
##############################################################################

cdef extern float msd_axis_major(int nrealatoms, int npaddedatoms, int rowstride,
    float* aT, float* bT, float G_a, float G_b) nogil
cdef extern float msd_atom_major(int nrealatoms, int npaddedatoms,  float* a,
    float* b, float G_a, float G_b, int computeRot, float rot[9]) nogil
cdef extern float rot_msd_atom_major(const int n_real_atoms,
    const int n_padded_atoms, const float* a, const float* b, const float rot[9]) nogil
cdef extern float rot_atom_major(const int n_atoms, float* a, const float rot[9]) nogil
cdef extern from "center.h":
    void inplace_center_and_trace_atom_major(float* coords, float* traces,
    const int n_frames, const int n_atoms) nogil
cdef extern from "math.h":
    float sqrtf(float x) nogil


##############################################################################
# External (Public) Functions
##############################################################################


@cython.boundscheck(False)
def rmsd(target, reference, int frame=0, atom_indices=None,
         ref_atom_indices=None, bool parallel=True, bool precentered=False):
    """rmsd(target, reference, frame=0, atom_indices=None, parallel=True, precentered=False)

    Compute RMSD of all conformations in target to a reference conformation.
    Note, this will center the conformations in place.

    Parameters
    ----------
    target : md.Trajectory
        For each conformation in this trajectory, compute the RMSD to
        a particular 'reference' conformation in another trajectory
        object.
    reference : md.Trajectory
        The object containing the reference conformation to measure distances
        to.
    frame : int
        The index of the conformation in `reference` to measure
        distances to.
    atom_indices : array_like, or None
        The indices of the atoms to use in the RMSD calculation. If not
        supplied, all atoms will be used.
    ref_atom_indices : array_like, or None
        Use these indices for the reference trajectory. If not supplied,
        the atom indices will be the same as those for target.
    parallel : bool
        Use OpenMP to calculate each of the RMSDs in parallel over
        multiple cores.
    precentered : bool, default=False
        Assume that the conformations are already centered at the origin, and that
        the "rmsd_traces" have been computed, as is done by
        `Trajectory.center_coordinates`. The "rmsd_traces" are intermediate
        calculations needed for the RMSD calculation which can be computed
        independently on each trajectory. Note that this has the potential to
        be unsafe; if you use Trajectory.center_coordinates and then modify
        the trajectory's coordinates, the center and traces will be out of
        date and the RMSDs will be incorrect.

    Examples
    --------
    >>> import mdtraj as md                                      # doctest: +SKIP
    >>> rmsds = md.rmsd(trajectory, trajectory, 0)               # doctest: +SKIP
    >>> print rmdsds                                             # doctest: +SKIP
    array([ 0.0,  0.03076187,  0.02549562, ...,  0.06230228,
        0.00666826,  0.24364147])

    The calculation is slightly faster if you precenter the trajectory

    >>> trajectory.center_coordinates()
    >>> rmsds = md.rmsd(trajectory, trajectory, 0, precentered=True)

    See Also
    --------
    Trajectory.center_coordinates

    Notes
    -----
    This function uses OpenMP to parallelize the calculation across
    multiple cores. To control the number of threads launched by OpenMP,
    you can set the environment variable ``OMP_NUM_THREADS``.

    Returns
    -------
    rmsds : np.ndarray, shape=(target.n_frames,)
        A 1-D numpy array of the optimal root-mean-square deviations from
        the `frame`-th conformation in reference to each of the conformations
        in target.
    """
    # import time
    cdef bool atom_indices_is_none = False

    if atom_indices is None:
        atom_indices_is_none = True
        atom_indices = slice(None)
    else:
        atom_indices = ensure_type(np.asarray(atom_indices), dtype=np.int, ndim=1, name='atom_indices')
        if not np.all((atom_indices >= 0) *
                              (atom_indices < target.xyz.shape[1]) *
                              (atom_indices < reference.xyz.shape[1])):
            raise ValueError("atom_indices must be valid positive indices")

    if ref_atom_indices is None:
        ref_atom_indices = atom_indices

    if not isinstance(ref_atom_indices, slice):
        ref_atom_indices = ensure_type(np.asarray(ref_atom_indices), dtype=np.int, ndim=1, name='ref_atom_indices')
        if not np.all((ref_atom_indices >= 0) *
                              (ref_atom_indices < target.xyz.shape[1]) *
                              (ref_atom_indices < reference.xyz.shape[1])):
            raise ValueError("ref_atom_indices must be valid positive indices")

    # Error checks
    assert (target.xyz.ndim == 3) and (reference.xyz.ndim == 3) and (target.xyz.shape[2]) == 3 and (reference.xyz.shape[2] == 3)
    if not (target.xyz.shape[1]  == reference.xyz.shape[1]):
        raise ValueError("Input trajectories must have same number of atoms. "
                         "found %d and %d." % (target.xyz.shape[1], reference.xyz.shape[1]))
    if frame >= reference.xyz.shape[0]:
        raise ValueError("Cannot calculate RMSD of frame %d: reference has "
                         "only %d frames." % (frame, reference.xyz.shape[0]))

    # static declarations
    cdef int i
    cdef float msd, ref_g
    cdef float[:, :, :] target_xyz
    cdef float[:, :] ref_xyz_frame
    cdef float[:] target_g
    cdef int target_n_frames = target.xyz.shape[0]
    cdef int n_atoms = target.xyz.shape[1] if np.all(atom_indices == slice(None)) else len(atom_indices)

    # make sure *every* frame in target_xyz is in proper c-major order
    target_xyz = np.asarray(target.xyz[:, atom_indices, :], order='C', dtype=np.float32)
    # only extract the `frame`-th conformation from ref_xyz
    ref_xyz_frame = np.asarray(reference.xyz[frame, ref_atom_indices, :], order='C', dtype=np.float32)

    # t0 = time.time()
    if precentered and (reference._rmsd_traces is not None) and (target._rmsd_traces is not None) and atom_indices_is_none:
        target_g = np.asarray(target._rmsd_traces, order='C', dtype=np.float32)
        ref_g = reference._rmsd_traces[frame]
    else:
        if precentered:
            warnings.warn(
                'in rmsd(), precentered is ignored when atom_indices != None',
                RuntimeWarning)
        target_g = np.empty(target_n_frames, dtype=np.float32)
        inplace_center_and_trace_atom_major(&target_xyz[0,0,0], &target_g[0], target_n_frames, n_atoms)
        inplace_center_and_trace_atom_major(&ref_xyz_frame[0, 0], &ref_g, 1, n_atoms)

    # t1 = time.time()

    cdef float[:] distances = np.zeros(target_n_frames, dtype=np.float32)
    if parallel:
        for i in prange(target_n_frames, nogil=True):
            msd = msd_atom_major(n_atoms, n_atoms, &target_xyz[i, 0, 0], &ref_xyz_frame[0, 0], target_g[i], ref_g, 0, NULL)
            distances[i] = sqrtf(msd)
    else:
        for i in range(target_n_frames):
            msd = msd_atom_major(n_atoms, n_atoms, &target_xyz[i, 0, 0], &ref_xyz_frame[0, 0], target_g[i], ref_g, 0, NULL)
            distances[i] = sqrtf(msd)

    # t2 = time.time()
    # print 'rmsd: %s, centering: %s' % (t2-t1, t1-t0)
    return np.array(distances, copy=False)


def _center_inplace_atom_major(float[:, :, ::1] xyz not None):
    assert xyz.shape[2] == 3
    cdef float[:] traces = np.empty(xyz.shape[0], dtype=np.float32)
    inplace_center_and_trace_atom_major(&xyz[0,0,0], &traces[0], xyz.shape[0], xyz.shape[1])
    return np.array(traces, copy=False)



##############################################################################
# Private Functions
##############################################################################


@cython.boundscheck(False)
@cython.wraparound(False)
def getMultipleRMSDs_axis_major(float[:, :, ::1] xyz1 not None,
                                float[:, :, ::1] xyz2 not None, float[::1] g1,
                                float[::1] g2, int frame, bool parallel=True):
    """getMultipleRMSDs_axis_major(xyz1, xyz2, g1, g, frame, parallel=True)

    Calculate the RMSD of several frames to a single frame, with the
    coordinates laid out in axis-major orders

    Parameters
    ----------
    xyz1 : np.ndarray, shape=(n_frames, 3, n_atoms), dtype=float32
        Coordinates of reference frame.
    xyz2 : np.ndarray, shape=(n_frames, 3, n_atoms), dtype=float32
        Coordinates of frames to iterate over
    g1 : np.ndarray, shape = (n_frames), dtype=float32
        Pre-calculated G factors (traces) for each frame in xyz1
    g2 : np.ndarray, shape = (n_frames), dtype=float32
        Pre-calculated G factors (traces) for each frame in xyz2
    frame : int
        Index of the desired reference frame in xyz1.
    parallel : bool, default True
        If True, use OpenMP parallelization.

    Returns
    -------
    rmsds: np.ndarray, shape=(len(xyz2),)
        RMSDS between xyz1[frame] and all of xyz2
    """

    cdef Py_ssize_t i
    cdef int n_frames = xyz2.shape[0]
    cdef int n_atoms = xyz1.shape[2]
    cdef float msd

    assert xyz1.ndim == 3 and xyz2.ndim == 3 and xyz1.shape[1] == 3 and xyz2.shape[1] == 3
    if not (xyz1.shape[2]  == xyz2.shape[2]):
        raise ValueError("Input arrays must have same number of atoms. "
                         "found %d and %d." % (xyz1.shape[2], xyz2.shape[2]))
    if frame >= xyz1.shape[0]:
        raise ValueError("Cannot calculate RMSD of frame %d: xyz1 has "
                         "only %d frames." % (frame, xyz1.shape[0]))

    cdef float[:] distances = np.zeros(n_frames, dtype=np.float32)

    if parallel == True:
        for i in prange(n_frames, nogil=True):
            msd = msd_axis_major(n_atoms, n_atoms, n_atoms,
                                   &xyz1[frame, 0, 0], &xyz2[i, 0, 0], g1[frame], g2[i])
            distances[i] = sqrtf(msd)
    else:
        for i in range(n_frames):
            msd = msd_axis_major(n_atoms, n_atoms, n_atoms,
                                   &xyz1[frame, 0, 0], &xyz2[i, 0, 0], g1[frame], g2[i])
            distances[i] = sqrtf(msd)

    return np.array(distances, copy=False)


@cython.boundscheck(False)
@cython.wraparound(False)
def getMultipleRMSDs_atom_major(float[:, :, ::1] xyz1 not None, float[:, :, ::1] xyz2 not None,
                                float[::1] g1 not None, float[::1] g2 not None, int frame,
                                bool parallel=True):
    """getMultipleRMSDs_atom_major(xyz1, xyz2, g1, g2, n_atoms, frame, parallel=True)

    Calculate the RMSD of several frames to a single frame, with the
    coordinates laid out in atom-major orders

    Parameters
    ----------
    xyz1 : np.ndarray, shape=(n_frames, n_atoms, 3), dtype=float32
        Coordinates of reference frame.
    xyz2 : np.ndarray, shape=(n_frames, n_atoms, 3), dtype=float32
        Coordinates of frames to iterate over
    g1 : np.ndarray, shape = (n_frames), dtype=float32
        Pre-calculated G factors (traces) for each frame in xyz1
    g2 : np.ndarray, shape = (n_frames), dtype=float32
        Pre-calculated G factors (traces) for each frame in xyz2
    frame : int
        Index of the desired reference frame in xyz1.
    parallel : bool, default True
        If True, use OpenMP parallelization.

    Returns
    -------
    rmsds: np.ndarray, shape=(len(xyz2),)
        RMSDS between xyz1[frame] and all of xyz2
    """

    cdef Py_ssize_t i
    cdef int n_frames = xyz2.shape[0]
    cdef int n_atoms = xyz1.shape[1]
    cdef float msd

    assert xyz1.ndim == 3 and xyz2.ndim == 3 and xyz1.shape[2] == 3 and xyz2.shape[2] == 3
    if not (xyz1.shape[1]  == xyz2.shape[1]):
        raise ValueError("Input arrays must have same number of atoms. "
                         "found %d and %d." % (xyz1.shape[1], xyz2.shape[1]))
    if frame >= xyz1.shape[0]:
        raise ValueError("Cannot calculate RMSD of frame %d: xyz1 has "
                         "only %d frames." % (frame, xyz1.shape[0]))

    cdef float[:] distances = np.zeros(n_frames, dtype=np.float32)

    if parallel == True:
        for i in prange(n_frames, nogil=True):
            msd = msd_atom_major(n_atoms, n_atoms,  &xyz1[frame, 0, 0], &xyz2[i, 0, 0], g1[frame], g2[i], 0, NULL)
            distances[i] = sqrtf(msd)
    else:
        for i in range(n_frames):
            msd = msd_atom_major(n_atoms, n_atoms, &xyz1[frame, 0, 0], &xyz2[i, 0, 0], g1[frame], g2[i], 0, NULL)
            distances[i] = sqrtf(msd)

    return np.array(distances, copy=False)


@cython.boundscheck(False)
@cython.wraparound(False)
def superpose_atom_major(float[:, :, ::1] xyz_align_target not None,
                         float[:, :, ::1] xyz_align_mobile not None,
                         float[::1] g_target not None, float[::1] g_mobile not None,
                         float[:, :, ::1] xyz_displace_mobile not None, int target_frame,
                         bool parallel=True):
    """superpose_atom_major(xyz_target, xyz_mobile, g_target, g_mobile, xyz_mobile_displace)

    Superpose each frame in xyz2 upon a frame in xyz1

    Parameters
    ----------
    xyz_align_target : np.ndarray, shape=(n_frames, n_atoms, 3), dtype=float32
        Coordinates of reference frame to align to.
    xyz_align_mobile: np.ndarray, shape=(n_frames, n_atoms, 3), dtype=float32
        Coordinates of the mobile trajectory to align to target the target.
    g_target : np.ndarray, shape = (n_frames), dtype=float32
        Pre-calculated G factors (traces) for each frame in xyz_target
    g_mobile : np.ndarray, shape = (n_frames), dtype=float32
        Pre-calculated G factors (traces) for each frame in xyz_mobile
    xyz_displace_mobile : np.ndarray, shape=(n_frames, n_atoms, 3), dtype=float32
        The coordinates of the mobile trajectory to displace
    target_frame : int
        The particular frame in xyz_align_target / g_target to align the mobile
        trajectory  to.
    parallel : bool, default=True
        Run the calculation using multiple cores simultaneously.
    """
    cdef int i
    cdef int n_frames = xyz_align_mobile.shape[0]
    cdef int n_atoms_align = xyz_align_target.shape[1]
    cdef int n_atoms_displace = xyz_displace_mobile.shape[1]
    if not (xyz_align_target.shape[1]  == xyz_align_mobile.shape[1]):
        raise ValueError("Input arrays must have same number of atoms. "
                         "found %d and %d." % (
                         xyz_align_target.shape[1],
                         xyz_align_mobile.shape[1]))
    if not xyz_align_mobile.shape[0] == xyz_displace_mobile.shape[0]:
        raise ValueError("xyz_align_mobile and xyz_displace_mobile must contain the same number of frames")

    # we could get away with using less memory here: we only need 1 rotation
    # matrix in serial mode and 1 rotation matrix per thread in parallel mode.
    cdef float[:, :, ::1] rot = np.zeros((n_frames, 3, 3), dtype=np.float32)

    if parallel == True:
        for i in prange(n_frames, nogil=True):
            msd_atom_major(n_atoms_align, n_atoms_align, &xyz_align_mobile[i, 0, 0],
                           &xyz_align_target[target_frame, 0, 0],
                           g_target[target_frame], g_mobile[i], 1, &rot[i, 0, 0])
            rot_atom_major(n_atoms_displace, &xyz_displace_mobile[i, 0, 0], &rot[i, 0, 0])
    else:
        for i in range(n_frames):
            msd_atom_major(n_atoms_align, n_atoms_align, &xyz_align_mobile[i, 0, 0],
                           &xyz_align_target[target_frame, 0, 0],
                           g_target[target_frame], g_mobile[i], 1, &rot[i, 0, 0])
            rot_atom_major(n_atoms_displace, &xyz_displace_mobile[i, 0, 0], &rot[i, 0, 0])


@cython.boundscheck(False)
@cython.wraparound(False)
def getMultipleAlignDisplaceRMSDs_atom_major(float[:, :, ::1] xyz_align1 not None,
    float[:, :, ::1] xyz_align2 not None, float[::1] g_align1 not None,
    float[::1] g_align2 not None, float[:, :, ::1] xyz_displ1 not None,
    float[:, :, ::1] xyz_displ2 not None, int n_atoms_align,
    int n_atoms_displ, int frame, bool parallel=True):
    """getMultipleAlignDisplaceRMSDs_atom_major(xyz_align1, xyz_align2, g_align1, g_align2, xyz_displ1, xyz_displ2, n_atoms_align, n_atoms_displ, frame, parallel=True)

    Calculate the RMSD of several frames to a single frame, with the
    coordinates laid out in atom-major orders, where alignments are computed
    by determining the optimal rotation matrix to align `xyz_align1` against
    `xyz_align2`, and then using this rotation matrix displace `xyz_displ1`,
    and computing its mean-squared-displacement with respect to `xyz_displ2`.

    Parameters
    ----------
    xyz_align1 : np.ndarray, shape=(n_frames, n_atoms_align_padded, 3), dtype=float32
        Alignment coordinates of reference frame.
    xyz_align2 : np.ndarray, shape=(n_frames, n_atoms_align_padded, 3), dtype=float32
        Alignment coordinates of frames to iterate over.
    g_align1 : np.ndarray, shape = (n_frames), dtype=float32
        Pre-calculated G factors (traces) for each frame in xyz1
    g_align2 : np.ndarray, shape = (n_frames), dtype=float32
        Pre-calculated G factors (traces) for each frame in xyz2
    xyz_displ1 : np.ndarray, shape=(n_frames, n_atoms_displ_padded, 3), dtype=float32
        Displacement coordinates of reference frame.
    xyz_displ2 : np.ndarray, shape=(n_frames, n_atoms_displ_padded, 3), dtype=float32
        Displacement coordinates of frames to iterate over.
    n_atoms_align : int
        The number of true atoms in the alignment coordinates
    n_atoms_displ : int
        The number of true atoms in the displacement coordinates
    frame : int
        Index of the desired reference frame in xyz_align1 / xyz_displ1.
    parallel : bool, default True
        If True, use OpenMP parallelization.

    Returns
    -------
    rmsds: np.ndarray, shape=(len(xyz2),)
        RMSDs between xyz_displ1[frame] and all of xyz_displ2, after the alignment that maximizes
        the overlap between xyz_align1[frame] and all of xyz_align2
    rotations: np.ndarray, shape=(len(xyz2), 3, 3)
        The rotation matrix for each of the alignments
    """
    assert (xyz_align1.shape[2] == 3) and (xyz_align2.shape[2] == 3)
    assert (xyz_displ1.shape[2] == 3) and (xyz_displ2.shape[2] == 3)
    if not ((xyz_align1.shape[1] % 4 == 0) & (xyz_align2.shape[1] % 4 == 0)):
        raise ValueError("Input arrays must have middle dimension of 4*n, "
                         "found %d and %d." % (xyz_align1.shape[1], xyz_align2.shape[1]))
    if not ((xyz_displ1.shape[1] % 4 == 0) & (xyz_displ2.shape[1] % 4 == 0)):
        raise ValueError("Input arrays must have middle dimension of 4*n, "
                         "found %d and %d." % (xyz_displ1.shape[1], xyz_displ2.shape[1]))
    if not xyz_align1.shape[0] == xyz_displ1.shape[0]:
        raise ValueError("xyz_align1 and xyz_displ1 must contain the same number of frames")
    if not xyz_align2.shape[0] == xyz_displ2.shape[0]:
        raise ValueError("xyz_align2 and xyz_displ2 must contain the same number of frames")
    if frame >= xyz_align1.shape[0]:
        raise ValueError("Cannot calculate RMSD of frame %d: xyz1 has "
                         "only %d frames." % (frame, xyz_align1.shape[0]))

    cdef float msd
    cdef Py_ssize_t i
    cdef int n_frames = xyz_align2.shape[0]
    cdef int n_align_atoms_padded = xyz_align1.shape[1]
    cdef int n_displ_atoms_padded = xyz_displ1.shape[1]

    cdef float[:, :, ::1] rot = np.zeros((n_frames, 3, 3), dtype=np.float32)
    cdef float[:] distances = np.zeros(n_frames, dtype=np.float32)

    if parallel == True:
        for i in prange(n_frames, nogil=True):
            msd_atom_major(n_atoms_align, n_align_atoms_padded, &xyz_align1[frame, 0, 0], &xyz_align2[i, 0, 0], g_align1[frame], g_align2[i], 1, &rot[i, 0, 0])
            msd = rot_msd_atom_major(n_atoms_displ, n_displ_atoms_padded, &xyz_displ1[frame, 0, 0], &xyz_displ2[i, 0, 0], &rot[i, 0, 0])
            distances[i] = sqrtf(msd)
    else:
        for i in range(n_frames):
            msd_atom_major(n_atoms_align, n_align_atoms_padded, &xyz_align1[frame, 0, 0], &xyz_align2[i, 0, 0], g_align1[frame], g_align2[i], 1, &rot[i, 0, 0])
            msd = rot_msd_atom_major(n_atoms_displ, n_displ_atoms_padded, &xyz_displ1[frame, 0, 0], &xyz_displ2[i, 0, 0], &rot[i, 0, 0])
            distances[i] = sqrtf(msd)

    return np.array(distances, copy=False), np.array(rot, copy=False)

