#
#------------------------------------------------------------------------------
# Copyright (c) 2013-2014, Christian Therien
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#------------------------------------------------------------------------------
#
# amaps.py - This file is part of the PySptools package.
#

"""
UCLS, NNLS, FCLS functions
"""

import numpy as np


def UCLS(M, U):
    """
    Performs unconstrained least squares abundance estimation.

    Parameters:
        M: `numpy array`
            2D data matrix (N x p).

        U: `numpy array`
            2D matrix of endmembers (q x p).

    Returns: `numpy array`
        An abundance maps (N x q).
     """
    Uinv = np.linalg.pinv(U.T)
    return np.dot(Uinv, M[0:,:].T).T


def NNLS(M, U):
    """
    NNLS performs non-negative constrained least squares of each pixel
    in M using the endmember signatures of U.  Non-negative constrained least
    squares with the abundance nonnegative constraint (ANC).
    Utilizes the method of Bro.

    Parameters:
        M: `numpy array`
            2D data matrix (N x p).

        U: `numpy array`
            2D matrix of endmembers (q x p).

    Returns: `numpy array`
        An abundance maps (N x q).

    References:
        Bro R., de Jong S., Journal of Chemometrics, 1997, 11, 393-401.
    """
    import scipy.optimize as opt

    N, p1 = M.shape
    q, p2 = U.shape

    X = np.zeros((N, q), dtype=np.float32)
    MtM = np.dot(U, U.T)
    for n1 in xrange(N):
        # opt.nnls() return a tuple, the first element is the result
        X[n1] = opt.nnls(MtM, np.dot(U, M[n1]))[0]
    return X


def _numpy_None_vstack(A1, A2):
    if A1 is None:
        return A2
    else:
        return np.vstack([A1, A2])


def _numpy_None_concatenate(A1, A2):
    if A1 is None:
        return A2
    else:
        return np.concatenate([A1, A2])


def _numpy_to_cvxopt_matrix(A):
    from cvxopt import matrix
    A = np.array(A, dtype=np.float64)
    if A.ndim == 1:
        return matrix(A, (A.shape[0], 1), 'd')
    else:
        return matrix(A, A.shape, 'd')


def FCLS(M, U):
    """
    Performs fully constrained least squares of each pixel in M
    using the endmember signatures of U. Fully constrained least squares
    is least squares with the abundance sum-to-one constraint (ASC) and the
    abundance nonnegative constraint (ANC).

    Parameters:
        M: `numpy array`
            2D data matrix (N x p).

        U: `numpy array`
            2D matrix of endmembers (q x p).

    Returns: `numpy array`
        An abundance maps (N x q).

    References:
         Daniel Heinz, Chein-I Chang, and Mark L.G. Fully Constrained
         Least-Squares Based Linear Unmixing. Althouse. IEEE. 1999.

    Notes:
        Three sources were useful to build the algorithm:
            * The function hyperFclsMatlab, part of the Matlab Hyperspectral
              Toolbox of Isaac Gerg.
            * The Matlab (tm) help on lsqlin.
            * And the Python implementation of lsqlin by Valera Vishnevskiy, click:
              http://maggotroot.blogspot.ca/2013/11/constrained-linear-least-squares-in.html
              , it's great code.
    """
    from cvxopt import solvers, matrix, mul
    solvers.options['show_progress'] = False
    N, p1 = M.shape
    nvars, p2 = U.shape

    C = _numpy_to_cvxopt_matrix(U.T)
    Q = C.T * C

    lb_A = -np.eye(nvars)
    lb = np.repeat(0, nvars)
    A = _numpy_None_vstack(None, lb_A)
    b = _numpy_None_concatenate(None, -lb)
    A = _numpy_to_cvxopt_matrix(A)
    b = _numpy_to_cvxopt_matrix(b)

    Aeq = _numpy_to_cvxopt_matrix(np.ones((1,nvars)))
    beq = _numpy_to_cvxopt_matrix(np.ones(1))

    M = np.array(M, dtype=np.float64)
    X = np.zeros((N, nvars), dtype=np.float32)
    for n1 in xrange(N):
        d = matrix(M[n1], (p1, 1), 'd')
        q = - d.T * C
        sol = solvers.qp(Q, q.T, A, b, Aeq, beq, None, None)['x']
        X[n1] = np.array(sol).squeeze()
    return X
