// SPDX-FileCopyrightText: 2025 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only

#include "ColorScale.h"
#include "JFJochException.h"

float luminance(rgb input) {
    return 0.2126f * input.r + 0.7152f * input.g + 0.0722f * input.b;
}

void ColorScale::Select(ColorScaleEnum val) {
    current = val;
}

rgb ColorScale::Apply(float input, const std::vector<rgb> &map) {
    input = std::clamp(input, 0.0f, 1.0f);

    size_t num_colors = map.size();
    if (num_colors < 2) {
        throw std::invalid_argument("Colormap must have at least two colors.");
    }

    float scaled_value = input * (num_colors - 1);
    size_t lower_idx = static_cast<size_t>(scaled_value);
    size_t upper_idx = std::min(lower_idx + 1, num_colors - 1);
    float t = scaled_value - lower_idx; // Fraction for interpolation

    rgb lower = map[lower_idx];
    rgb upper = map[upper_idx];

    return {
            .r = static_cast<uint8_t>(lower.r + t * (upper.r - lower.r)),
            .g = static_cast<uint8_t>(lower.g + t * (upper.g - lower.g)),
            .b = static_cast<uint8_t>(lower.b + t * (upper.b - lower.b))
    };
}

rgb ColorScale::Apply(ColorScaleSpecial input) {
    switch (input) {
        case ColorScaleSpecial::Gap:
            return gap;
        default:
        case ColorScaleSpecial::BadPixel:
            return bad;
    }
}
rgb ColorScale::Apply(float input) const {
    switch (current) {
        case ColorScaleEnum::Viridis:
            return Apply(input, viridis_colormap);
        case ColorScaleEnum::Heat:
            return Apply(input, heat_colormap);
        case ColorScaleEnum::Indigo:
            return Apply(input, white_to_indigo_colormap);
        case ColorScaleEnum::BW:
            return Apply(input, white_to_black_colormap);
        default:
            throw JFJochException(JFJochExceptionCategory::InputParameterInvalid,
                                  "Color scale unknown");
    }
}