time-to-impact.cpp

class ImpactEstimator {
public:
    // Estimate seconds until missile reaches us
    // Based on how fast intensity is growing
    // Real systems use much more sophisticated kinematics, this is just a hobby project :p
    double estimate(const MissileTracks& track) {

        if (track.history_index < 2) return 99.0;   // not enough data

        // Get last two intensity readings
        int   curr_idx  = (track.history_index - 1) % 16;
        int   prev_idx  = (track.history_index - 2) % 16;
        double current  = track.intensity_history[curr_idx];
        double previous = track.intensity_history[prev_idx];

        if (previous <= 0.0) return 99.0;

        // Intensity grows as inverse square of range
        // If intensity doubled, range decreased by factor of sqrt 2
        double intensity_ratio = current / previous;

        if (intensity_ratio <= 1.0) return 99.0;    // not closing

        // Rough time-to-impact based on growth rate
        // Real systems use full kinematic models
        double growth_per_second = intensity_ratio * 10.0;
        double time_to_impact    = 100.0 / growth_per_second;

        return std::max(1.0, std::min(time_to_impact, 99.0));
    }
};