// SPDX-FileCopyrightText: 2026 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only

#include <catch2/catch_all.hpp>
#include <cmath>
#include <random>

#include "../image_analysis/image_preprocessing/SaturationCeiling.h"

// A bright tail, P(> v) ~ 1/v, as the cores of Bragg peaks give.
static saturation_ceiling::Histogram Tail(int64_t clip_from, int64_t clip_to) {
    saturation_ceiling::Histogram h{};
    std::mt19937 rng(1);
    std::uniform_real_distribution<double> u(0.0, 1.0);
    for (int i = 0; i < 2000000; i++) {
        auto v = static_cast<int64_t>(std::min(1e9, 100.0 / (1.0 - u(rng))));   // P(> v) ~ 1/v above 100
        if (v >= clip_from) {
            // Clipped at a ceiling of its own, somewhere in [clip_from, clip_to].
            v = clip_from + static_cast<int64_t>(u(rng) * static_cast<double>(clip_to - clip_from));
        }
        saturation_ceiling::Add(h, v);
    }
    return h;
}

TEST_CASE("SaturationCeiling_NoClipping", "[portable]") {
    CHECK(!saturation_ceiling::Ceiling(Tail(INT32_MAX, INT32_MAX)).has_value());
}

TEST_CASE("SaturationCeiling_OneLevel", "[portable]") {
    const auto c = saturation_ceiling::Ceiling(Tail(12000, 12000));
    REQUIRE(c.has_value());
    CHECK(*c <= 12000);
    CHECK(*c > 12000 * 0.98);
}

TEST_CASE("SaturationCeiling_BandPerPixel", "[portable]") {
    // Each pixel stops at its own level - the ADC's limit less that pixel's dark.
    const auto c = saturation_ceiling::Ceiling(Tail(12400, 15600));
    REQUIRE(c.has_value());
    CHECK(*c <= 12400);
    CHECK(*c > 12400 * 0.98);
}

TEST_CASE("SaturationCeiling_MaskedPixelsLeftOut", "[portable]") {
    saturation_ceiling::Histogram h{};
    const std::vector<int32_t> values(1000, 5000);
    saturation_ceiling::Add(h, values, std::vector<uint32_t>(1000, 1));
    CHECK(!saturation_ceiling::Ceiling(h).has_value());
    saturation_ceiling::Add(h, values, {});
    CHECK(saturation_ceiling::Ceiling(h).has_value());
}