#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <math.h>

#if defined(_WIN32)
#define SCE_API __declspec(dllexport)
#else
#define SCE_API __attribute__((visibility("default")))
#endif

#ifdef __cplusplus
extern "C" {
#endif

static inline uint64_t fmix64(uint64_t k) {
    k ^= k >> 33;
    k *= 0xff51afd7ed558ccdULL;
    k ^= k >> 33;
    k *= 0xc4ceb9fe1a85ec53ULL;
    k ^= k >> 33;
    return k;
}

SCE_API void sce_holographic_hash(const char* data, size_t len, char* out_hex) {
    uint64_t h = 0x100000001b3ULL;
    const uint8_t* ptr = (const uint8_t*)data;
    for (size_t i = 0; i < len; ++i) {
        h = (h ^ ptr[i]) * 0xCBF29CE484222325ULL;
    }
    h = fmix64(h);
    snprintf(out_hex, 17, "%016llx", (unsigned long long)h);
}

SCE_API void sce_symplectic_step(double* z, double* z_dot, const double* u, int n, double omega, double dt) {
    double omega_sq = omega * omega;
    double two_omega = 2.0 * omega;
    for (int i = 0; i < n; ++i) {
        double acc = omega_sq * (u[i] - z[i]) - two_omega * z_dot[i];
        z_dot[i] += acc * dt;
        z[i] += z_dot[i] * dt;
    }
}

SCE_API double sce_lyapunov_eval(const double* x, const double* P, int dim) {
    double v = 0.0;
    for (int i = 0; i < dim; ++i) {
        double row_sum = 0.0;
        for (int j = 0; j < dim; ++j) {
            row_sum += P[i * dim + j] * x[j];
        }
        v += x[i] * row_sum;
    }
    return v;
}

SCE_API int sce_ucb_prune(const double* v_mean, const double* v_std, double kappa, double tau, int* out_mask, int n) {
    int pruned_count = 0;
    for (int i = 0; i < n; ++i) {
        double ucb = v_mean[i] + kappa * v_std[i];
        if (ucb < tau) {
            out_mask[i] = 0;
            pruned_count++;
        } else {
            out_mask[i] = 1;
        }
    }
    return pruned_count;
}

#ifdef __cplusplus
}
#endif