# -*- coding: utf-8 -*-
#
# Copyright © 2019 Stéphane Guillaso
# Licensed under the terms of
# (see ../../LICENSE.md for details)

# import importlib
import numba as nb
import numpy as np

__bands__ = [400, 600]
__filename__ = "_OC_SLOPE_400_600"
__gui__ = "SOC Index: 1/slope(R400 - R600)"
__info__ = "Organic carbon content: \n" + \
           "Calculate the inverse of the slope of a straight line defined\n" + \
           "between the reflectance value at the start of the absorption feature \n" + \
           "and the reflectance value at the centre of the absorption feature:\n\n" + \
           "ind = 1/slope(R_400, R_600)\n\n" + \
           "Bartholomeus, H., Epema, G., Schaepman, M., 2007.\n" + \
           "Determining iron content in Mediterranean soils in partly vegetated\n" + \
           "regions, using spectral reflectance and imaging spectroscopy.\n" + \
           "Int. J. Appl. Earth Observ. Geoinform. 9, 194–203."


def check_bands(ubands, wvl):
    ind0 = int(ubands[0])
    ind1 = int(ubands[1])
    if ind0 == ind1:
        return False, 'Identical band found!\n'
    if (ind1 - ind0) < 2:
        return False, 'Not enough points to calculate crad!\n'
    return True, "Has been calculated!\n"


@nb.jit(nb.float32[:, :](nb.float32[:, :, :], nb.float32[:], nb.int32[:], nb.int32[:, :]), nopython=True, fastmath=True)
def process(cube, wvl, ind, mask):
    ny = cube.shape[1]
    nx = cube.shape[2]
    out = np.zeros((ny, nx), dtype=np.float32)
    for ky in range(ny):
        for kx in range(nx):
            if mask is not None:
                if mask[ky, kx] == 0:
                    out[ky, kx] = np.nan
                    continue
            R400 = cube[ind[0], ky, kx]
            R600 = cube[ind[1], ky, kx]
            W400 = wvl[ind[0]]
            W600 = wvl[ind[1]]
            slope = (R600 - R400) / (W600 - W400)
            if slope > 0:
                out[ky, kx] = 1. / slope
            else:
                out[ky, kx] = np.nan
    return out
