#include "jvm_handler.h"
#include <stdlib.h>

JVMLoader::JVMLoader() {

  SetClassPath("-Djava.class.path=*:."); // use current directory as classpath.
}

void JVMLoader::SetClassPath(std::string _classPath) {

  classPath = "-Djava.class.path=.:" + _classPath;
}

bool JVMLoader::isVMReady() { return jvmStatus; }

std::string JVMLoader::VMStatus(int status) {
  if (status != JNI_ERR) {
    jvmStatus = true;
    return "[jvm]: started successfully.";
  } else {
    jvmStatus = false;
    return "[jvm]: error starting virtual machine.";
  }
}

void JVMLoader::ReleaseThread() { vm->DetachCurrentThread(); };

std::string JVMLoader::GetClassPath() { return classPath; };

const std::shared_ptr<JNIEnv> &JVMLoader::GetJNIEnviorment() {

  if (env == nullptr || env == 0x0)
    throw VMError{"JVM: has not been initialize. "};

  int status = vm->GetEnv((void **)&env, JNI_VERSION_1_6);

  if (status == JNI_EDETACHED) {
    if (vm->AttachCurrentThread((void **)&env, NULL) != 0) {
    }

  } else if (status == JNI_OK)
    return env;
  else if (status == JNI_EVERSION)
    throw VMError{"GetEnv: version not supported"};

  return env;
};

#ifdef __linux__
// try to load JVM dynamic library true is success false failiure.
bool LoadJVMLibrary(std::string path, CreateJVM &create_vm) {
  void *handle = dlopen(path.c_str(), RTLD_LAZY);

  if (!handle)
    return false;

  create_vm = (CreateJVM)dlsym(handle, "JNI_CreateJavaVM");

  const char *dlsym_error = dlerror();

  if (dlsym_error)
    dlclose(handle);
  
  return !dlsym_error;
}

#endif

/* use the one loaded */
std::string JVMLoader::Start() {

#ifdef __linux__

  auto env_var = getenv("JAVA_HOME");
  bool loadStatus = false;
  if(env_var !=NULL){
    std::string java_home = env_var;
    loadStatus = LoadJVMLibrary(java_home + "/jre/lib/amd64/server/libjvm.so", create_vm);
  }else{
    loadStatus = LoadJVMLibrary("./jdk/libjvm.so", create_vm);
  }

  if (!loadStatus) {
    throw VMError{"Fatal: Can't load dynamic library libjvm.so"};
  }

#else
  create_vm = JNI_CreateJavaVM;
#endif

  JavaVMOption options[1];
  JavaVMInitArgs vm_args;

  vm_args.version = JNI_VERSION_1_6;
  vm_args.nOptions = 1;

  options[0].optionString = (char *)classPath.c_str();
  vm_args.options = options;

  int status = create_vm((JavaVM **)&vm, (void **)&env, &vm_args);

  return VMStatus(status);
}