/*
 * Copyright © Canonical Ltd.
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License version 2 or 3,
 * as published by the Free Software Foundation.
 *
 * This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
 */

#include <mir/graphics/gamma_curves.h>

#include <boost/throw_exception.hpp>

#include <algorithm>
#include <limits>
#include <stdexcept>

namespace mg = mir::graphics;

namespace
{
mg::GammaCurves make_linear_ramp(int size)
{
    if (size < 2)
        BOOST_THROW_EXCEPTION(std::logic_error("gamma LUT size is too small"));

    mg::GammaCurve ramp(size);
    auto const step = std::numeric_limits<mg::GammaCurve::value_type>::max() / (size - 1);
    mg::GammaCurve::value_type n = 0;
    std::generate(ramp.begin(), ramp.end(), [&n, step]{ auto current = n; n += step; return current; });

    return {ramp, ramp, ramp};
}
}
mg::GammaCurves::GammaCurves(GammaCurve const& red,
                             GammaCurve const& green,
                             GammaCurve const& blue) :
    red(red),
    green(green),
    blue(blue)
{
    if (red.size() != green.size() ||
        green.size() != blue.size())
    {
        BOOST_THROW_EXCEPTION(std::logic_error("Different gamma LUT sizes"));
    }
}

mg::LinearGammaLUTs::LinearGammaLUTs(int size)
  : GammaCurves(make_linear_ramp(size))
{
}
