#include "light/nl_color.h"

uint16_t nl_cie_level(uint16_t bri)
{
    float lightness, y;
    uint32_t v;

    if (bri == 0)
        return 0;
    if (bri >= NL_BRI_SCALE)
        return 65535;
    lightness = (float)bri / 100.0f; /* 0..100 */
    if (lightness <= 8.0f) {
        y = lightness / 903.3f;
    } else {
        float t = (lightness + 16.0f) / 116.0f;
        y = t * t * t;
    }
    v = (uint32_t)(y * 65535.0f + 0.5f);
    return (uint16_t)(v == 0 ? 1 : (v > 65535 ? 65535 : v));
}

uint16_t nl_ct_cw_fraction(uint16_t ct, uint16_t ct_min, uint16_t ct_max)
{
    uint32_t m, mw, mc;

    if (ct <= ct_min)
        return 0;
    if (ct >= ct_max)
        return 65535;
    m = 1000000u / ct;
    mw = 1000000u / ct_min;
    mc = 1000000u / ct_max;
    return (uint16_t)(((mw - m) * 65535u) / (mw - mc));
}

static uint8_t to8(uint32_t lin)
{
    return (uint8_t)((lin * 255u + 32767u) / 65535u);
}

void nl_visual_to_channels(const nl_visual_t *v, uint16_t ct_min, uint16_t ct_max, uint8_t out[NL_CH_COUNT])
{
    uint32_t level = nl_cie_level(v->bri);

    for (int i = 0; i < NL_CH_COUNT; i++)
        out[i] = 0;
    if (level == 0)
        return;

    if (v->mode == NL_MODE_COLOR) {
        uint32_t lin[3];
        int maxi = 0;
        lin[0] = level * v->r / 255u;
        lin[1] = level * v->g / 255u;
        lin[2] = level * v->b / 255u;
        for (int i = 0; i < 3; i++) {
            out[NL_CH_R + i] = to8(lin[i]);
            if (lin[i] > lin[maxi])
                maxi = i;
        }
        /* keep the lowest brightness step visible */
        if (!out[NL_CH_R] && !out[NL_CH_G] && !out[NL_CH_B] && lin[maxi] > 0)
            out[NL_CH_R + maxi] = 1;
    } else {
        uint32_t cw = level * nl_ct_cw_fraction(v->ct, ct_min, ct_max) / 65535u;
        uint32_t ww = level - cw;
        out[NL_CH_CW] = to8(cw);
        out[NL_CH_WW] = to8(ww);
        if (!out[NL_CH_CW] && !out[NL_CH_WW])
            out[cw >= ww ? NL_CH_CW : NL_CH_WW] = 1;
    }
}