#include "jni.h"

void println_java(JNIEnv *env, const char *msg);

// extern "C" [[gnu::visibility("default")]] [[gnu::used]]
jint JNI_OnLoad(JavaVM *jvm, void *) {
  JNIEnv *env = nullptr;
  jvm->GetEnv((void **)&env, JNI_VERSION_1_6);
  println_java(env, "Hello from JNI!");
  return JNI_VERSION_1_6;
}

void println_java(JNIEnv *env, const char *msg) {
  // Get system class
  jclass syscls = env->FindClass("java/lang/System");
  // Lookup the "out" field
  jfieldID fid = env->GetStaticFieldID(syscls, "out", "Ljava/io/PrintStream;");
  jobject out = env->GetStaticObjectField(syscls, fid);
  // Get PrintStream class
  jclass pscls = env->FindClass("java/io/PrintStream");
  // Lookup printLn(String)
  jmethodID mid = env->GetMethodID(pscls, "println", "(Ljava/lang/String;)V");
  // Invoke the method
  jstring str = env->NewStringUTF(msg);
  env->CallVoidMethod(out, mid, str);
}