#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>

#include "jni.h"
#include "jvmti.h"

static char *
getErrorName (jvmtiEnv * jvmti, jvmtiError errnum)
{
  jvmtiError err;
  char *name;

  err = (*jvmti)->GetErrorName (jvmti, errnum, &name);
  if (err != JVMTI_ERROR_NONE)
    {
      printf ("ERROR: JVMTI GetErrorName error err=%d\n", err);
      abort ();
    }
  return name;
}

/* Check for JVMTI error */
#define CHECK_JVMTI_ERROR(jvmti, err) \
checkJvmtiError(jvmti, err, __FILE__, __LINE__)
static void
checkJvmtiError (jvmtiEnv * jvmti, jvmtiError err, char *file, int line)
{
  if (err != JVMTI_ERROR_NONE)
    {
      char *name;

      name = getErrorName (jvmti, err);
      printf ("ERROR: JVMTI error err=%d(%s) in %s:%d\n",
	      err, name, file, line);
      abort ();
    }
}

static jint JNICALL
stringCallback (jlong class_tag,
                jlong size,
                jlong* tag_ptr,
                const jchar* value,
                jint value_length,
                void* user_data) {
  return 0;
}

static void JNICALL
scanStrings (jvmtiEnv * jvmti, JNIEnv* jni_env,
             jthread thread)
{
  static jvmtiHeapCallbacks callbacks;
  callbacks.string_primitive_value_callback = stringCallback;

  int err = (*jvmti)->IterateThroughHeap(jvmti, 0, NULL, &callbacks, NULL);
  CHECK_JVMTI_ERROR (jvmti, err);
}

JNIEXPORT jint JNICALL
Agent_OnLoad (JavaVM * vm, char *options, void *reserved)
{
  jint rc;
  jvmtiError err;
  jvmtiCapabilities capabilities;
  jvmtiEventCallbacks callbacks;
  jvmtiEnv *jvmti;

  jvmti = NULL;
  rc = (*vm)->GetEnv (vm, (void **) &jvmti, JVMTI_VERSION);
  if (rc != JNI_OK)
    {
      printf ("ERROR: Unable to create jvmtiEnv, GetEnv failed, error=%d\n",
	      rc);
      return -1;
    }

  memset (&capabilities, 0, sizeof (jvmtiCapabilities));
  capabilities.can_tag_objects = 1;
  err = (*jvmti)->AddCapabilities (jvmti, &capabilities);
  CHECK_JVMTI_ERROR (jvmti, err);

  memset (&callbacks, 0, sizeof (callbacks));
  callbacks.ThreadEnd = &scanStrings;
  err = (*jvmti)->SetEventCallbacks (jvmti, &callbacks, sizeof (callbacks));
  CHECK_JVMTI_ERROR (jvmti, err);
  err = (*jvmti)->SetEventNotificationMode (jvmti, JVMTI_ENABLE,
					    JVMTI_EVENT_THREAD_END,
					    NULL);
  CHECK_JVMTI_ERROR (jvmti, err);

  printf ("\n\nDemo JVMTI agent loaded and initialized\n\n");

  return 0;
}


JNIEXPORT void JNICALL
Agent_OnUnload (JavaVM * vm)
{
}