/*
 * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

#include "jvmti.h"
#include "jvmti_common.hpp"

#include <atomic>

extern "C" {

// SampledObjectAlloc event might be triggered on any thread
static std::atomic<int> events_counter(0);

JNIEXPORT void JNICALL
SampledObjectAlloc(jvmtiEnv *jvmti, JNIEnv* jni, jthread thread, jobject object, jclass object_klass, jlong size) {
  events_counter++;
  LOG("Sampled object, events_counter = %d\n", events_counter.load());
}

void JNICALL
VMDeath(jvmtiEnv *jvmti, JNIEnv* jni) {
  if (events_counter == 0) {
    fatal(jni, "SampledObjectAlloc events counter shouldn't be zero");
  }
}

jint Agent_Initialize(JavaVM *jvm, char *options, void *reserved) {
  jvmtiEnv* jvmti = nullptr;
  jvmtiCapabilities caps;
  jvmtiEventCallbacks callbacks;
  jvmtiError err;
  jint res;

  LOG("AGENT INIT");
  res = jvm->GetEnv((void **) &jvmti, JVMTI_VERSION_9);
  if (res != JNI_OK || jvmti == nullptr) {
    LOG("Wrong result of a valid call to GetEnv!\n");
    return JNI_ERR;
  }

  memset(&caps, 0, sizeof(caps));
  caps.can_generate_sampled_object_alloc_events = 1;
  if (jvmti->AddCapabilities(&caps) != JVMTI_ERROR_NONE) {
    return JNI_ERR;
  }

  memset(&callbacks, 0, sizeof(callbacks));
  callbacks.SampledObjectAlloc = &SampledObjectAlloc;
  callbacks.VMDeath = &VMDeath;

  err = jvmti->SetEventCallbacks(&callbacks, sizeof(callbacks));
  check_jvmti_error(err, "SetEventCallbacks");
  /*
   * Interval should be small enough to triggger sampling event while objects are init by VM.
   */
  err = jvmti->SetHeapSamplingInterval(10);
  check_jvmti_error(err, "SetHeapSamplingInterval");

  err = jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_VM_DEATH, nullptr);
  check_jvmti_error(err, "SetEventNotificationMode");

  err = jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_SAMPLED_OBJECT_ALLOC, nullptr);
  check_jvmti_error(err, "SetEventNotificationMode");

  return JNI_OK;
}

JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM *jvm, char *options, void *reserved) {
  return Agent_Initialize(jvm, options, reserved);
}

JNIEXPORT jint JNICALL Agent_OnAttach(JavaVM *jvm, char *options, void *reserved) {
  return Agent_Initialize(jvm, options, reserved);
}
}