# -*- coding: utf-8 -*-
"""
Domain adaptation with optimal transport with GPU implementation
"""

import numpy as np
from ..utils import unif
from ..da import OTDA
from .bregman import sinkhorn
import cudamat


def pairwiseEuclideanGPU(a, b, returnAsGPU=False, squared=False):
    """
    Compute the pairwise euclidean distance between matrices a and b.


    Parameters
    ----------
    a : np.ndarray (n, f)
        first matrice
    b : np.ndarray (m, f)
        second matrice
    returnAsGPU : boolean, optional (default False)
        if True, returns cudamat matrix still on GPU, else return np.ndarray
    squared : boolean, optional (default False)
        if True, return squared euclidean distance matrice


    Returns
    -------
    c : (n x m) np.ndarray or cudamat.CUDAMatrix
        pairwise euclidean distance distance matrix
    """
    # a is shape (n, f) and b shape (m, f). Return matrix c of shape (n, m).
    # First compute in c_GPU the squared euclidean distance. And return its
    # square root. At each cell [i,j] of c, we want to have
    # sum{k in range(f)} ( (a[i,k] - b[j,k])^2 ). We know that
    # (a-b)^2 = a^2 -2ab +b^2. Thus we want to have in each cell of c:
    # sum{k in range(f)} ( a[i,k]^2 -2a[i,k]b[j,k] +b[j,k]^2).

    a_GPU = cudamat.CUDAMatrix(a)
    b_GPU = cudamat.CUDAMatrix(b)

    # Multiply a by b transpose to obtain in each cell [i,j] of c the
    # value sum{k in range(f)} ( a[i,k]b[j,k] )
    c_GPU = cudamat.dot(a_GPU, b_GPU.transpose())
    # multiply by -2 to have sum{k in range(f)} ( -2a[i,k]b[j,k] )
    c_GPU.mult(-2)

    # Compute the vectors of the sum of squared elements.
    a_GPU = cudamat.pow(a_GPU, 2).sum(axis=1)
    b_GPU = cudamat.pow(b_GPU, 2).sum(axis=1)

    # Add the vectors in each columns (respectivly rows) of c.
    # sum{k in range(f)} ( a[i,k]^2 -2a[i,k]b[j,k] )
    c_GPU.add_col_vec(a_GPU)
    # sum{k in range(f)} ( a[i,k]^2 -2a[i,k]b[j,k] +b[j,k]^2)
    c_GPU.add_row_vec(b_GPU.transpose())

    if not squared:
        c_GPU = cudamat.sqrt(c_GPU)

    if returnAsGPU:
        return c_GPU
    else:
        return c_GPU.asarray()


def sinkhorn_lpl1_mm(a, labels_a, b, M_GPU, reg, eta=0.1, numItermax=10,
                     numInnerItermax=200, stopInnerThr=1e-9,
                     verbose=False, log=False):
    """
    Solve the entropic regularization optimal transport problem with nonconvex group lasso regularization

    The function solves the following optimization problem:

    .. math::
        \gamma = arg\min_\gamma <\gamma,M>_F + reg\cdot\Omega_e(\gamma)+ \eta \Omega_g(\gamma)

        s.t. \gamma 1 = a

             \gamma^T 1= b

             \gamma\geq 0
    where :

    - M is the (ns,nt) metric cost matrix
    - :math:`\Omega_e` is the entropic regularization term :math:`\Omega_e(\gamma)=\sum_{i,j} \gamma_{i,j}\log(\gamma_{i,j})`
    - :math:`\Omega_g` is the group lasso  regulaization term :math:`\Omega_g(\gamma)=\sum_{i,c} \|\gamma_{i,\mathcal{I}_c}\|^{1/2}_1`   where  :math:`\mathcal{I}_c` are the index of samples from class c in the source domain.
    - a and b are source and target weights (sum to 1)

    The algorithm used for solving the problem is the generalised conditional gradient as proposed in  [5]_ [7]_


    Parameters
    ----------
    a : np.ndarray (ns,)
        samples weights in the source domain
    labels_a : np.ndarray (ns,)
        labels of samples in the source domain
    b : np.ndarray (nt,)
        samples weights in the target domain
    M_GPU : cudamat.CUDAMatrix (ns,nt)
        loss matrix
    reg : float
        Regularization term for entropic regularization >0
    eta : float, optional
        Regularization term  for group lasso regularization >0
    numItermax : int, optional
        Max number of iterations
    numInnerItermax : int, optional
        Max number of iterations (inner sinkhorn solver)
    stopInnerThr : float, optional
        Stop threshold on error (inner sinkhorn solver) (>0)
    verbose : bool, optional
        Print information along iterations
    log : bool, optional
        record log if True


    Returns
    -------
    gamma : (ns x nt) ndarray
        Optimal transportation matrix for the given parameters
    log : dict
        log dictionary return only if log==True in parameters


    References
    ----------

    .. [5] N. Courty; R. Flamary; D. Tuia; A. Rakotomamonjy, "Optimal Transport for Domain Adaptation," in IEEE Transactions on Pattern Analysis and Machine Intelligence , vol.PP, no.99, pp.1-1
    .. [7] Rakotomamonjy, A., Flamary, R., & Courty, N. (2015). Generalized conditional gradient: analysis of convergence and applications. arXiv preprint arXiv:1510.06567.

    See Also
    --------
    ot.lp.emd : Unregularized OT
    ot.bregman.sinkhorn : Entropic regularized OT
    ot.optim.cg : General regularized OT

    """
    p = 0.5
    epsilon = 1e-3
    Nfin = len(b)

    indices_labels = []
    classes = np.unique(labels_a)
    for c in classes:
        idxc, = np.where(labels_a == c)
        indices_labels.append(cudamat.CUDAMatrix(idxc.reshape(1, -1)))

    Mreg_GPU = cudamat.empty(M_GPU.shape)
    W_GPU = cudamat.empty(M_GPU.shape).assign(0)

    for cpt in range(numItermax):
        Mreg_GPU.assign(M_GPU)
        Mreg_GPU.add_mult(W_GPU, eta)
        transp_GPU = sinkhorn(a, b, Mreg_GPU, reg, numItermax=numInnerItermax,
                              stopThr=stopInnerThr, returnAsGPU=True)
        # the transport has been computed. Check if classes are really
        # separated
        W_GPU.assign(1)
        W_GPU = W_GPU.transpose()
        for (i, c) in enumerate(classes):
            (_, nbRow) = indices_labels[i].shape
            tmpC_GPU = cudamat.empty((Nfin, nbRow)).assign(0)
            transp_GPU.transpose().select_columns(indices_labels[i], tmpC_GPU)
            majs_GPU = tmpC_GPU.sum(axis=1).add(epsilon)
            cudamat.pow(majs_GPU, (p-1))
            majs_GPU.mult(p)

            tmpC_GPU.assign(0)
            tmpC_GPU.add_col_vec(majs_GPU)
            W_GPU.set_selected_columns(indices_labels[i], tmpC_GPU)

        W_GPU = W_GPU.transpose()

    return transp_GPU.asarray()


class OTDA_GPU(OTDA):
    def normalizeM(self, norm):
        if norm == "median":
            self.M_GPU.divide(float(np.median(self.M_GPU.asarray())))
        elif norm == "max":
            self.M_GPU.divide(float(np.max(self.M_GPU.asarray())))
        elif norm == "log":
            self.M_GPU.add(1)
            cudamat.log(self.M_GPU)
        elif norm == "loglog":
            self.M_GPU.add(1)
            cudamat.log(self.M_GPU)
            self.M_GPU.add(1)
            cudamat.log(self.M_GPU)


class OTDA_sinkhorn(OTDA_GPU):
    def fit(self, xs, xt, reg=1, ws=None, wt=None, norm=None, **kwargs):
        cudamat.init()
        xs = np.asarray(xs, dtype=np.float64)
        xt = np.asarray(xt, dtype=np.float64)

        self.xs = xs
        self.xt = xt

        if wt is None:
            wt = unif(xt.shape[0])
        if ws is None:
            ws = unif(xs.shape[0])

        self.ws = ws
        self.wt = wt

        self.M_GPU = pairwiseEuclideanGPU(xs, xt, returnAsGPU=True,
                                          squared=True)
        self.normalizeM(norm)
        self.G = sinkhorn(ws, wt, self.M_GPU, reg, **kwargs)
        self.computed = True


class OTDA_lpl1(OTDA_GPU):
    def fit(self, xs, ys, xt, reg=1, eta=1, ws=None, wt=None, norm=None,
            **kwargs):
        cudamat.init()
        xs = np.asarray(xs, dtype=np.float64)
        xt = np.asarray(xt, dtype=np.float64)

        self.xs = xs
        self.xt = xt

        if wt is None:
            wt = unif(xt.shape[0])
        if ws is None:
            ws = unif(xs.shape[0])

        self.ws = ws
        self.wt = wt

        self.M_GPU = pairwiseEuclideanGPU(xs, xt, returnAsGPU=True,
                                          squared=True)
        self.normalizeM(norm)
        self.G = sinkhorn_lpl1_mm(ws, ys, wt, self.M_GPU, reg, eta, **kwargs)
        self.computed = True