/*
 * 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.
 *
 * Copyright 2012-2015 Danny Robson <danny@nerdcruft.net>
 */

#include "worley.hpp"

#include "../../hash/murmur/murmur2.hpp"

using util::noise::basis::worley;


///////////////////////////////////////////////////////////////////////////////
template <typename T>
util::point<2,T>
generate (util::point<2,intmax_t> p, uint64_t seed)
{
    using util::hash::murmur2::mix;

    auto u = mix (seed, mix (uint64_t (p.x), uint64_t (p.y)));
    auto v = mix (u, seed);

    auto r = util::point<2,T> {
        (u & 0xffff) / T{0xffff},
        (v & 0xffff) / T{0xffff}
    };

    CHECK_LIMIT (r, T{0}, T{1});
    return r;
}


///////////////////////////////////////////////////////////////////////////////
template <typename T, size_t F>
worley<T,F>::worley (seed_t _seed):
    seed (_seed)
{ ; }


//-----------------------------------------------------------------------------
template <typename T, size_t F>
worley<T,F>::worley ():
    worley (time (nullptr))
{ ; }


//-----------------------------------------------------------------------------
template <typename T, size_t F>
util::range<T>
worley<T,F>::bounds (void) const
{
    return { 0.0, 1.5 };
}


//-----------------------------------------------------------------------------
template <typename T, size_t F>
T
worley<T,F>::operator() (util::point<2,T> p) const
{
    // extract integer and fractional parts. be careful to always round down
    // (particularly with negatives) and avoid rounding errors.
    auto p_int = p.template cast<intmax_t> ();
    if (p.x < 0) p_int.x -= 1;
    if (p.y < 0) p_int.y -= 1;
    auto p_rem = abs (p - p_int).template as<point> ();

    // setup an array of distances
    static constexpr size_t RADIUS = 1;
    static constexpr size_t COUNT = pow2 (RADIUS * 2 + 1);
    T distances[COUNT] = { std::numeric_limits<T>::quiet_NaN () };
    T *cursor = distances;

    // record the distances to each candidate point
    for (signed y_off = -signed(RADIUS); y_off <= signed(RADIUS) ; ++y_off) {
        for (signed x_off = -signed(RADIUS); x_off <= signed(RADIUS); ++x_off) {
            auto off = vector<2,intmax_t> {x_off, y_off};
            auto pos = generate<T> (p_int + off, this->seed);

            CHECK_LIMIT (pos.x, T{0}, T{1});
            CHECK_LIMIT (pos.y, T{0}, T{1});

            *cursor = distance2 (pos + off, p_rem);
            cursor++;
        }
    }

    // find the f'th lowest value
    static_assert (F < COUNT, "worley order must be less than search radius");
    std::partial_sort (distances, distances + F, distances + COUNT);
    CHECK_GE (distances[F], 0);
    return distances[F];
}


///////////////////////////////////////////////////////////////////////////////
#include "../lerp.hpp"

namespace util { namespace noise { namespace basis {
    template struct worley<float>;
    template struct worley<double>;
} } }