
#include "libimagequant.h"
#include "pam.h"
#include "viter.h"
#include "nearest.h"
#include <stdlib.h>
#include <string.h>

#ifdef _OPENMP
#include <omp.h>
#else
#define omp_get_max_threads() 1
#define omp_get_thread_num() 0
#endif

/*
 * Voronoi iteration: new palette color is computed from weighted average of colors that map to that palette entry.
 */
LIQ_PRIVATE void viter_init(const colormap *map, const unsigned int max_threads, viter_state average_color[])
{
    memset(average_color, 0, sizeof(average_color[0])*(VITER_CACHE_LINE_GAP+map->colors)*max_threads);
}

LIQ_PRIVATE void viter_update_color(const f_pixel acolor, const float value, const colormap *map, unsigned int match, const unsigned int thread, viter_state average_color[])
{
    match += thread * (VITER_CACHE_LINE_GAP+map->colors);
    average_color[match].a += acolor.a * value;
    average_color[match].r += acolor.r * value;
    average_color[match].g += acolor.g * value;
    average_color[match].b += acolor.b * value;
    average_color[match].total += value;
}

LIQ_PRIVATE void viter_finalize(colormap *map, const unsigned int max_threads, const viter_state average_color[])
{
    for (unsigned int i=0; i < map->colors; i++) {
        double a=0, r=0, g=0, b=0, total=0;

        // Aggregate results from all threads
        for(unsigned int t=0; t < max_threads; t++) {
            const unsigned int offset = (VITER_CACHE_LINE_GAP+map->colors) * t + i;

            a += average_color[offset].a;
            r += average_color[offset].r;
            g += average_color[offset].g;
            b += average_color[offset].b;
            total += average_color[offset].total;
        }

        if (total) {
            map->palette[i].acolor = (f_pixel){
                .a = a / total,
                .r = r / total,
                .g = g / total,
                .b = b / total,
            };
        }
        map->palette[i].popularity = total;
    }
}

LIQ_PRIVATE double viter_do_iteration(histogram *hist, colormap *const map, const float min_opaque_val, viter_callback callback, const bool fast_palette)
{
    const unsigned int max_threads = omp_get_max_threads();
    viter_state average_color[(VITER_CACHE_LINE_GAP+map->colors) * max_threads];
    viter_init(map, max_threads, average_color);
    struct nearest_map *const n = nearest_init(map, fast_palette);
    hist_item *const achv = hist->achv;
    const int hist_size = hist->size;

    double total_diff=0;
    #pragma omp parallel for if (hist_size > 3000) \
        schedule(static) default(none) shared(average_color,callback) reduction(+:total_diff)
    for(int j=0; j < hist_size; j++) {
        float diff;
        unsigned int match = nearest_search(n, achv[j].acolor, achv[j].tmp.likely_colormap_index, min_opaque_val, &diff);
        achv[j].tmp.likely_colormap_index = match;
        total_diff += diff * achv[j].perceptual_weight;

        viter_update_color(achv[j].acolor, achv[j].perceptual_weight, map, match, omp_get_thread_num(), average_color);

        if (callback) callback(&achv[j], diff);
    }

    nearest_free(n);
    viter_finalize(map, max_threads, average_color);

    return total_diff / hist->total_perceptual_weight;
}
