// Native-backed emulation core implementation

#include <stdlib.h>
#include <string.h>
#include <jni.h>
#include <vue.h>
#include "vue_NativeVUE.h"



///////////////////////////////////////////////////////////////////////////////
//                                 Constants                                 //
///////////////////////////////////////////////////////////////////////////////

// Memory access type sizes
static const int TYPE_SIZES[] = { 1, 1, 2, 2, 4 };



///////////////////////////////////////////////////////////////////////////////
//                                   Types                                   //
///////////////////////////////////////////////////////////////////////////////

// Core context state type
typedef struct {
    VUE vue; /* Context into the generic C library */
} CORE;



///////////////////////////////////////////////////////////////////////////////
//                            Internal Functions                             //
///////////////////////////////////////////////////////////////////////////////

// Determine the field ID of NativeVUE.pointer
static jfieldID GetPointerID(JNIEnv *env, jobject vue) {
    return (*env)->GetFieldID(env,
        (*env)->GetObjectClass(env, vue), "pointer", "[B");
}

// Retrieve the handle to a NativeVUE's core context
static CORE* GetCore(JNIEnv *env, jobject vue) {
    jbyteArray pointer =
        (*env)->GetObjectField(env, vue, GetPointerID(env, vue));
    jbyte     *elems   = (*env)->GetByteArrayElements(env, pointer, NULL);
    CORE      *core    = *(CORE **)elems;
    (*env)->ReleaseByteArrayElements(env, pointer, elems, 0);
    return core;
}



///////////////////////////////////////////////////////////////////////////////
//                             Method Functions                              //
///////////////////////////////////////////////////////////////////////////////

// Native constructor
JNIEXPORT void JNICALL Java_vue_NativeVUE_construct
  (JNIEnv *env, jobject vue) {

    // Produce and initialize s new core context
    CORE *core = calloc(sizeof (CORE), 1);
    vueInitialize(&core->vue);
    vueReset(&core->vue);

    // Encode the context handle into a byte array
    jbyteArray pointer = (*env)->NewByteArray(env, sizeof (void *));
    jbyte     *elems   = (*env)->GetByteArrayElements(env, pointer, NULL);
    *(CORE **)elems = core;
    (*env)->ReleaseByteArrayElements(env, pointer, elems, 0);
    (*env)->SetObjectField(env, vue, GetPointerID(env, vue), pointer);
}

// Release any used resources
JNIEXPORT void JNICALL Java_vue_NativeVUE_dispose
  (JNIEnv *env, jobject vue) {
    CORE *core = GetCore(env, vue);
    if (core->vue.bus.rom != NULL)
        free(core->vue.bus.rom);
    if (core->vue.bus.sram != NULL)
        free(core->vue.bus.sram);
    free(core);
}

// Retrieve a register value
JNIEXPORT jint JNICALL Java_vue_NativeVUE_getRegister
  (JNIEnv *env, jobject vue, jint index, jboolean system) {
    CORE *core = GetCore(env, vue);
    return vueGetRegister(&core->vue, index, system);;
}

// Retrieve a copy of the ROM data
JNIEXPORT jbyteArray JNICALL Java_vue_NativeVUE_getROM
  (JNIEnv *env, jobject vue) {
    CORE *core = GetCore(env, vue);

    // No ROM data
    if (core->vue.bus.rom == NULL)
        return NULL;

    // Copy the ROM data
    jbyteArray ret   = (*env)->NewByteArray(env, (jint)core->vue.bus.romSize);
    jbyte     *elems = (*env)->GetByteArrayElements(env, ret, NULL);
    memcpy(elems, core->vue.bus.rom, core->vue.bus.romSize);
    (*env)->ReleaseByteArrayElements(env, ret, elems, 0);
    return ret;
}

// Determine whether the context is native-backed
JNIEXPORT jboolean JNICALL Java_vue_NativeVUE_isNative
  (JNIEnv *env, jobject vue) {
    return JNI_TRUE;
}

// Read bytes from the CPU bus
JNIEXPORT jboolean JNICALL Java_vue_NativeVUE_read
  (JNIEnv *env, jobject vue, jint address, jbyteArray data, jint offset,
        jint length) {

    // Error checking
    if (
        data   == NULL ||
        offset <  0    ||
        length <  0    ||
        offset + length > (*env)->GetArrayLength(env, data)
    ) return JNI_FALSE;

    // Perform the operation
    CORE  *core  = GetCore(env, vue);
    jbyte *elems = (*env)->GetByteArrayElements(env, data, NULL);
    vueRead(&core->vue, address, &elems[offset], length);
    (*env)->ReleaseByteArrayElements(env, data, elems, 0);
    return JNI_TRUE;
}

// Initialize all system components
JNIEXPORT void JNICALL Java_vue_NativeVUE_reset
  (JNIEnv *env, jobject vue) {
    CORE *core = GetCore(env, vue);
    vueReset(&core->vue);
}

// Specify a register value
JNIEXPORT jint JNICALL Java_vue_NativeVUE_setRegister
  (JNIEnv *env, jobject vue, jint index, jboolean system, jint value) {
    CORE *core = GetCore(env, vue);
    return vueSetRegister(&core->vue, index, system, value);
}

// Provide new ROM data
JNIEXPORT jboolean JNICALL Java_vue_NativeVUE_setROM
  (JNIEnv *env, jobject vue, jbyteArray data, jint offset, jint length) {

    // Error checking
    if (
        data == NULL  ||
        offset < 0    ||
        length < 1024 || length > 0x01000000 ||
        (length & length - 1) != 0           ||
        offset + length > (*env)->GetArrayLength(env, data)
    ) return JNI_FALSE;

    // Accept the new ROM data
    uint8_t *rom   = calloc(length, 1);
    jbyte   *elems = (*env)->GetByteArrayElements(env, data, NULL);
    memcpy(rom, &elems[offset], length);
    (*env)->ReleaseByteArrayElements(env, data, elems, 0);

    // Transfer the ROM data to the emulation state
    CORE *core = GetCore(env, vue);
    if (core->vue.bus.rom != NULL)
        free(core->vue.bus.rom);
    vueSetROM(&core->vue, rom, length);
    return JNI_TRUE;
}

/* Write bytes to the CPU bus */
JNIEXPORT jboolean JNICALL Java_vue_NativeVUE_write
  (JNIEnv *env, jobject vue, jint address, jbyteArray data, jint offset,
    jint length) {

    // Error checking
    if (
        data   == NULL ||
        offset <  0    ||
        length <  0    ||
        offset + length > (*env)->GetArrayLength(env, data)
    ) return JNI_FALSE;

    // Perform the operation
    CORE  *core  = GetCore(env, vue);
    jbyte *elems = (*env)->GetByteArrayElements(env, data, NULL);
    vueWrite(&core->vue, address, &elems[offset], length);
    (*env)->ReleaseByteArrayElements(env, data, elems, 0);
    return JNI_TRUE;
}