#include "leveltrack.hpp"

namespace leveltrack {

void iir_first_order(float* x, const double* A, size_t n) {
    double acc = 0.0;
    for (size_t i = 0; i < n; i++) {
        double y = static_cast<double>(x[i]) * A[i] + acc;
        acc = y;
        x[i] = static_cast<float>(y);
    }
}

void iir_bidirectional(float* x, const double* A, size_t n) {
    iir_first_order(x, A, n);
    // reverse pass over reversed indices back into x (keep array order).
    double acc = 0.0;
    for (size_t k = n; k-- > 0;) {
        double y = static_cast<double>(x[k]) * A[k] + acc;
        acc = y;
        x[k] = static_cast<float>(y);
    }
}

void iir_first_order_unrolled4(float* x, const double* A, size_t n) {
    double acc = 0.0;
    size_t i = 0;
    for (; i + 4 <= n;) {
        for (int u = 0; u < 4; u++, i++) {
            double y = static_cast<double>(x[i]) * A[i] + acc;
            acc = y;
            x[i] = static_cast<float>(y);
        }
    }
    for (; i < n; i++) {
        double y = static_cast<double>(x[i]) * A[i] + acc;
        acc = y;
        x[i] = static_cast<float>(y);
    }
}

}  // namespace leveltrack