// C ABI wrapper around the C++ ITWOM entry points so Rust can FFI them
// cleanly. The C++ originals take `double &` / `int &` reference params,
// which have no C equivalent; we translate them to pointers.

#include <cstring>

extern void point_to_point(double elev[], double tht_m, double rht_m,
    double eps_dielect, double sgm_conductivity, double eno_ns_surfref,
    double frq_mhz, int radio_climate, int pol, double conf, double rel,
    double &dbloss, char *strmode, int &errnum);

extern void point_to_point_ITM(double elev[], double tht_m, double rht_m,
    double eps_dielect, double sgm_conductivity, double eno_ns_surfref,
    double frq_mhz, int radio_climate, int pol, double conf, double rel,
    double &dbloss, char *strmode, int &errnum);

extern double ITWOMVersion();

extern "C" {

// The C++ point_to_point / point_to_point_ITM signatures are non-const on
// `elev`, but by inspection of itwom3.0.cpp neither routine writes into
// the elev array — they only read samples (and use scratch space held in
// the thread_local statics we patched in). Passing the caller's buffer
// directly avoids a per-call heap alloc + memcpy that otherwise dominates
// a full map sweep at ~200 M invocations.
//
// If a future upstream update to ITWOM starts mutating `elev`, Rust's
// ownership guarantees still hold: the elev_buf in compute_radial gets
// cleared and refilled at the top of every ITWOM call, so mid-call
// scribbles would be overwritten before being observed.

void splat_point_to_point(double* elev, double tht_m, double rht_m,
    double eps_dielect, double sgm_conductivity, double eno_ns_surfref,
    double frq_mhz, int radio_climate, int pol, double conf, double rel,
    double* dbloss, char* strmode, int strmode_len, int* errnum)
{
    double loss = 0.0;
    int err = 0;
    char mode[64] = {0};

    point_to_point(elev, tht_m, rht_m, eps_dielect, sgm_conductivity,
        eno_ns_surfref, frq_mhz, radio_climate, pol, conf, rel,
        loss, mode, err);

    *dbloss = loss;
    *errnum = err;
    if (strmode && strmode_len > 0) {
        std::strncpy(strmode, mode, (size_t)strmode_len - 1);
        strmode[strmode_len - 1] = '\0';
    }
}

void splat_point_to_point_itm(double* elev, double tht_m, double rht_m,
    double eps_dielect, double sgm_conductivity, double eno_ns_surfref,
    double frq_mhz, int radio_climate, int pol, double conf, double rel,
    double* dbloss, char* strmode, int strmode_len, int* errnum)
{
    double loss = 0.0;
    int err = 0;
    char mode[64] = {0};

    point_to_point_ITM(elev, tht_m, rht_m, eps_dielect, sgm_conductivity,
        eno_ns_surfref, frq_mhz, radio_climate, pol, conf, rel,
        loss, mode, err);

    *dbloss = loss;
    *errnum = err;
    if (strmode && strmode_len > 0) {
        std::strncpy(strmode, mode, (size_t)strmode_len - 1);
        strmode[strmode_len - 1] = '\0';
    }
}

double splat_itwom_version() { return ITWOMVersion(); }

} // extern "C"