public class MyActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        String dir = this.getCacheDir().getAbsolutePath();
        // dir にはファイル保存可能領域 (internal storage) への絶対パスが入る
    }
}

// +build android

package jni

/*
#cgo LDFLAGS: -landroid
#include <jni.h>
#include <stdlib.h>

JavaVM* current_vm;
jobject current_ctx;

static char *
_lockJNI(uintptr_t* envp, int* attachedp) {
	JNIEnv* env;

	if (current_vm == NULL) {
		return "no current JVM";
	}

	*attachedp = 0;
	switch ((*current_vm)->GetEnv(current_vm, (void**)&env, JNI_VERSION_1_6)) {
	case JNI_OK:
		break;
	case JNI_EDETACHED:
		if ((*current_vm)->AttachCurrentThread(current_vm, &env, 0) != 0) {
			return "cannot attach to JVM";
		}
		*attachedp = 1;
		break;
	case JNI_EVERSION:
		return "bad JNI version";
	default:
		return "unknown JNI error from GetEnv";
	}

	*envp = (uintptr_t)env;
	return NULL;
}

static char *
_checkException(uintptr_t jnienv) {
	jthrowable exc;
	JNIEnv* env = (JNIEnv*)jnienv;
	if (!(*env)->ExceptionCheck(env)) {
		return NULL;
	}

	exc = (*env)->ExceptionOccurred(env);
	(*env)->ExceptionClear(env);

	jclass clazz = (*env)->FindClass(env, "java/lang/Throwable");
	jmethodID toString = (*env)->GetMethodID(env, clazz, "toString", "()Ljava/lang/String;");
	jobject msgStr = (*env)->CallObjectMethod(env, exc, toString);
	return (char*)(*env)->GetStringUTFChars(env, msgStr, 0);
}

void
_unlockJNI() {
	(*current_vm)->DetachCurrentThread(current_vm);
}
*/
import "C"

import (
	"errors"
	"runtime"
	"unsafe"
)

func RunOnJVM(fn func(vm, env, ctx uintptr) error) error {
	errch := make(chan error)
	go func() {
		runtime.LockOSThread()
		defer runtime.UnlockOSThread()

		env := C.uintptr_t(0)
		attached := C.int(0)
		if errStr := C._lockJNI(&env, &attached); errStr != nil {
			errch <- errors.New(C.GoString(errStr))
			return
		}
		if attached != 0 {
			defer C._unlockJNI()
		}

		vm := uintptr(unsafe.Pointer(C.current_vm)) // #nosec
		if err := fn(vm, uintptr(env), uintptr(C.current_ctx)); err != nil {
			errch <- err
			return
		}

		if exc := C._checkException(env); exc != nil {
			errch <- errors.New(C.GoString(exc))
			C.free(unsafe.Pointer(exc)) // #nosec
			return
		}
		errch <- nil
	}()
	return <-errch
}

// +build android

package storage

/*
#include <jni.h>
#include <stdlib.h>

static const char *
getFilesDir(uintptr_t java_vm, uintptr_t jni_env, uintptr_t jni_ctx) {
	JNIEnv* env = (JNIEnv*)jni_env;
	jobject ctx = (jobject)jni_ctx;

	jclass context = (*env)->FindClass(env, "android/content/Context");
	if(context == NULL) {
		return NULL;
	}
	jmethodID getFilesDir = (*env)->GetMethodID(env, context, "getFilesDir", "()Ljava/io/File;");
	if(getFilesDir == NULL){
		return NULL;
	}

	jobject f = (*env)->CallObjectMethod(env, ctx, getFilesDir);
	if (f == NULL) {
		return NULL;
	}

	jclass file = (*env)->FindClass(env, "java/io/File");
	if (file == NULL) {
		return NULL;
	}

	jmethodID getAbsolutePath = (*env)->GetMethodID(env, file, "getAbsolutePath", "()Ljava/lang/String;");
	if (getAbsolutePath == NULL) {
		return NULL;
	}

	jstring path = (jstring)(*env)->CallObjectMethod(env, f, getAbsolutePath);
	return (*env)->GetStringUTFChars(env, path, 0);
}
*/
import "C"

import (
	"unsafe"

	"github.com/pankona/gomo-simra/simra/internal/jni"
	"github.com/pankona/gomo-simra/simra/simlog"
)

type storageAndroid struct{}

func NewStorage() Storager {
	return &storageAndroid{}
}

var path string

func (s *storageAndroid) DirectoryPath() string {
	if path != "" {
		return path
	}
	jni.RunOnJVM(
		func(vm, env, ctx uintptr) error {
			cpath := C.getFilesDir(C.uintptr_t(vm), C.uintptr_t(env), C.uintptr_t(ctx))
			if cpath == nil {
				simlog.Errorf("failed to get FilesDir!")
			}
			path = C.GoString(cpath)
			C.free(unsafe.Pointer(cpath)) // #nosec
			return nil
		})
	return path
}

func f() {
    dir := storage.NewStorage().DirectoryPath()
    fmt.Printf("path to internal storage: %s", dir)
}

func f() {
    dir := os.Getenv("TMPDIR")
    fmt.Printf("path to internal storage (for cache): %s", dir)
}