lockstep/app/src/main/cpp/jni_stepdetector.cpp

//
// Created by david on 03.03.2026.
//

#include <jni.h>
#include "step_detector.h"
#include <new>
#include <vector>

extern "C" {

jint throwIllegalArgumentException(JNIEnv *env, const char *message)
{
    jclass exClass;
    const char *className = "java/lang/IllegalArgumentException";
    exClass = env->FindClass(className);
    if (exClass == nullptr) {
        return -1;
    }
    return env->ThrowNew(exClass, message);
}

JNIEXPORT jlong JNICALL
Java_at_lockstep_filter_StepDetector_native_1create(
        JNIEnv *env,
        jclass /*unused*/, jlong engineHandle) {
    auto *listener = reinterpret_cast<StepListener *>(engineHandle);
    // We use std::nothrow so `new` returns a nullptr if the engine creation fails
    auto *detector = new(std::nothrow) StepDetector(60.0 /* FPS */, listener); // TODO
    return reinterpret_cast<jlong>(detector);
}

JNIEXPORT void JNICALL
Java_at_lockstep_filter_StepDetector_native_1delete(
        JNIEnv *env,
        jclass /*unused*/, jlong handle) {
    delete reinterpret_cast<StepDetector *>(handle);
}

JNIEXPORT void JNICALL
Java_at_lockstep_filter_StepDetector_native_1filter(
        JNIEnv *env,
        jclass /*unused*/, jlong handle, jlong timestamp, jfloatArray values) {
    if(values == nullptr) throwIllegalArgumentException(env, "values == null");
    float* nativeValues = (float *)env->GetFloatArrayElements(values, 0);
    jsize length = env->GetArrayLength(values);
    std::vector<float> vecValues(nativeValues, nativeValues + length);
    auto *detector = reinterpret_cast<StepDetector *>(handle);
    detector->filter((double) timestamp, vecValues);
}

}