#include "fgc/SettleRule.h"

#include <cmath>

namespace fgc {

SettleRule::Verdict SettleRule::add(const FrameStats& f) {
    if (f.brightness < 0) {
        window_.clear();
        return Verdict::Waiting;
    }
    window_.push_back(f);
    const size_t n = p_.frames < 1 ? 1 : static_cast<size_t>(p_.frames);
    while (window_.size() > n) window_.pop_front();
    if (window_.size() < n || !steady()) return Verdict::Waiting;

    bool in_band = true;
    for (const auto& w : window_)
        in_band = in_band && w.brightness >= bandLow() && w.brightness <= bandHigh();
    if (in_band) return Verdict::Settled;
    return atLimit() ? Verdict::AtLimit : Verdict::Waiting;
}

bool SettleRule::steady() const {
    for (size_t i = 1; i < window_.size(); ++i) {
        const double a = window_[i - 1].brightness, b = window_[i].brightness;
        if (std::fabs(b - a) > p_.steady * std::fmax(a, 1.0)) return false;
    }
    return true;
}

bool SettleRule::atLimit() const {
    const FrameStats& f = window_.back();
    if (f.exposure_us < 0 || f.gain_db < 0) return false;
    // A hair of slack: the camera reports quantised exposure and gain.
    if (f.brightness < bandLow() && p_.exposure_max_us > 0 && p_.gain_max_db >= 0)
        return f.exposure_us >= p_.exposure_max_us * 0.99 && f.gain_db >= p_.gain_max_db - 0.1;
    if (f.brightness > bandHigh() && p_.exposure_min_us > 0 && p_.gain_min_db >= 0)
        return f.exposure_us <= p_.exposure_min_us * 1.01 && f.gain_db <= p_.gain_min_db + 0.1;
    return false;
}

}  // namespace fgc