main/cpp/MethodMetadata.cpp

#include "MethodMetadata.h"
#include "JSIInteropModuleRegistry.h"
#include "JavaScriptValue.h"
#include "JavaScriptObject.h"
#include "JavaScriptTypedArray.h"
#include "JavaReferencesCache.h"
#include "Exceptions.h"

#include <utility>

#include "react/jni/ReadableNativeMap.h"
#include "react/jni/ReadableNativeArray.h"
#include "JSReferencesCache.h"

namespace jni = facebook::jni;
namespace jsi = facebook::jsi;
namespace react = facebook::react;

namespace expo {

// Modified version of the RN implementation
// https://github.com/facebook/react-native/blob/7dceb9b63c0bfd5b13bf6d26f9530729506e9097/ReactCommon/react/nativemodule/core/platform/android/ReactCommon/JavaTurboModule.cpp#L57
jni::local_ref<react::JCxxCallbackImpl::JavaPart> createJavaCallbackFromJSIFunction(
  jsi::Function &&function,
  jsi::Runtime &rt,
  std::shared_ptr<react::CallInvoker> jsInvoker
) {
  auto weakWrapper = react::CallbackWrapper::createWeak(std::move(function), rt,
                                                        std::move(jsInvoker));

  // This needs to be a shared_ptr because:
  // 1. It cannot be unique_ptr. std::function is copyable but unique_ptr is
  // not.
  // 2. It cannot be weak_ptr since we need this object to live on.
  // 3. It cannot be a value, because that would be deleted as soon as this
  // function returns.
  auto callbackWrapperOwner =
    std::make_shared<react::RAIICallbackWrapperDestroyer>(weakWrapper);

  std::function<void(folly::dynamic)> fn =
    [weakWrapper, callbackWrapperOwner, wrapperWasCalled = false](
      folly::dynamic responses) mutable {
      if (wrapperWasCalled) {
        throw std::runtime_error(
          "callback 2 arg cannot be called more than once");
      }

      auto strongWrapper = weakWrapper.lock();
      if (!strongWrapper) {
        return;
      }

      strongWrapper->jsInvoker().invokeAsync(
        [weakWrapper, callbackWrapperOwner, responses]() mutable {
          auto strongWrapper2 = weakWrapper.lock();
          if (!strongWrapper2) {
            return;
          }

          jsi::Value args =
            jsi::valueFromDynamic(strongWrapper2->runtime(), responses);
          auto argsArray = args.getObject(strongWrapper2->runtime())
            .asArray(strongWrapper2->runtime());
          jsi::Value arg = argsArray.getValueAtIndex(strongWrapper2->runtime(), 0);

          strongWrapper2->callback().call(
            strongWrapper2->runtime(),
            (const jsi::Value *) &arg,
            (size_t) 1
          );

          callbackWrapperOwner.reset();
        });

      wrapperWasCalled = true;
    };

  return react::JCxxCallbackImpl::newObjectCxxArgs(fn);
}

jobjectArray MethodMetadata::convertJSIArgsToJNI(
  JSIInteropModuleRegistry *moduleRegistry,
  JNIEnv *env,
  jsi::Runtime &rt,
  const jsi::Value *args,
  size_t count
) {
  auto argumentArray = env->NewObjectArray(
    count,
    JavaReferencesCache::instance()->getJClass("java/lang/Object").clazz,
    nullptr
  );

  std::vector<jobject> result(count);

  for (unsigned int argIndex = 0; argIndex < count; argIndex++) {
    const jsi::Value &arg = args[argIndex];
    auto &type = argTypes[argIndex];
    if (arg.isNull() || arg.isUndefined()) {
      // If value is null or undefined, we just passes a null
      // Kotlin code will check if expected type is nullable.
      result[argIndex] = nullptr;
    } else {
      if (type->converter->canConvert(rt, arg)) {
        auto converterValue = type->converter->convert(rt, env, moduleRegistry, arg);
        env->SetObjectArrayElement(argumentArray, argIndex, converterValue);
        env->DeleteLocalRef(converterValue);
      } else {
        auto stringRepresentation = arg.toString(rt).utf8(rt);
        jni::throwNewJavaException(
          UnexpectedException::create(
            "Cannot convert '" + stringRepresentation + "' to a Kotlin type.").get()
        );
      }
    }
  }

  return argumentArray;
}

MethodMetadata::MethodMetadata(
  std::string name,
  int args,
  bool isAsync,
  jni::local_ref<jni::JArrayClass<ExpectedType>> expectedArgTypes,
  jni::global_ref<jobject> &&jBodyReference
) : name(std::move(name)),
    args(args),
    isAsync(isAsync),
    jBodyReference(std::move(jBodyReference)) {
  argTypes.reserve(args);
  for (size_t i = 0; i < args; i++) {
    auto expectedType = expectedArgTypes->getElement(i);
    argTypes.push_back(
      std::make_unique<AnyType>(std::move(expectedType))
    );
  }
}

MethodMetadata::MethodMetadata(
  std::string name,
  int args,
  bool isAsync,
  std::vector<std::unique_ptr<AnyType>> &&expectedArgTypes,
  jni::global_ref<jobject> &&jBodyReference
) : name(std::move(name)),
    args(args),
    isAsync(isAsync),
    argTypes(std::move(expectedArgTypes)),
    jBodyReference(std::move(jBodyReference)
    ) {}

std::shared_ptr<jsi::Function> MethodMetadata::toJSFunction(
  jsi::Runtime &runtime,
  JSIInteropModuleRegistry *moduleRegistry
) {
  if (body == nullptr) {
    if (isAsync) {
      body = std::make_shared<jsi::Function>(toAsyncFunction(runtime, moduleRegistry));
    } else {
      body = std::make_shared<jsi::Function>(toSyncFunction(runtime, moduleRegistry));
    }
  }

  return body;
}

jsi::Function MethodMetadata::toSyncFunction(
  jsi::Runtime &runtime,
  JSIInteropModuleRegistry *moduleRegistry
) {
  return jsi::Function::createFromHostFunction(
    runtime,
    moduleRegistry->jsRegistry->getPropNameID(runtime, name),
    args,
    [this, moduleRegistry](
      jsi::Runtime &rt,
      const jsi::Value &thisValue,
      const jsi::Value *args,
      size_t count
    ) -> jsi::Value {
      try {
        return this->callSync(
          rt,
          moduleRegistry,
          args,
          count
        );
      } catch (jni::JniException &jniException) {
        rethrowAsCodedError(rt, moduleRegistry, jniException);
      }
    });
}

jsi::Value MethodMetadata::callSync(
  jsi::Runtime &rt,
  JSIInteropModuleRegistry *moduleRegistry,
  const jsi::Value *args,
  size_t count
) {
  if (this->jBodyReference == nullptr) {
    return jsi::Value::undefined();
  }

  JNIEnv *env = jni::Environment::current();

  /**
   * This will push a new JNI stack frame for the LocalReferences in this
   * function call. When the stack frame for this lambda is popped,
   * all LocalReferences are deleted.
   */
  jni::JniLocalScope scope(env, (int) count);

  auto convertedArgs = convertJSIArgsToJNI(moduleRegistry, env, rt, args, count);

  // Cast in this place is safe, cause we know that this function is promise-less.
  auto syncFunction = jni::static_ref_cast<JNIFunctionBody>(this->jBodyReference);
  auto result = syncFunction->invoke(
    convertedArgs
  );

  env->DeleteLocalRef(convertedArgs);
  if (result == nullptr) {
    return jsi::Value::undefined();
  }

  return jsi::valueFromDynamic(rt, result->cthis()->consume())
    .asObject(rt)
    .asArray(rt)
    .getValueAtIndex(rt, 0);
}

jsi::Function MethodMetadata::toAsyncFunction(
  jsi::Runtime &runtime,
  JSIInteropModuleRegistry *moduleRegistry
) {
  return jsi::Function::createFromHostFunction(
    runtime,
    moduleRegistry->jsRegistry->getPropNameID(runtime, name),
    args,
    [this, moduleRegistry](
      jsi::Runtime &rt,
      const jsi::Value &thisValue,
      const jsi::Value *args,
      size_t count
    ) -> jsi::Value {
      JNIEnv *env = jni::Environment::current();

      /**
       * This will push a new JNI stack frame for the LocalReferences in this
       * function call. When the stack frame for this lambda is popped,
       * all LocalReferences are deleted.
       */
      jni::JniLocalScope scope(env, (int) count);

      try {
        auto convertedArgs = convertJSIArgsToJNI(moduleRegistry, env, rt, args, count);
        auto globalConvertedArgs = (jobjectArray) env->NewGlobalRef(convertedArgs);
        env->DeleteLocalRef(convertedArgs);

        auto &Promise = moduleRegistry->jsRegistry->getObject<jsi::Function>(
          JSReferencesCache::JSKeys::PROMISE
        );
        // Creates a JSI promise
        jsi::Value promise = Promise.callAsConstructor(
          rt,
          createPromiseBody(rt, moduleRegistry, globalConvertedArgs)
        );
        return promise;
      } catch (jni::JniException &jniException) {
        rethrowAsCodedError(rt, moduleRegistry, jniException);
      }
    }
  );
}

jsi::Function MethodMetadata::createPromiseBody(
  jsi::Runtime &runtime,
  JSIInteropModuleRegistry *moduleRegistry,
  jobjectArray globalArgs
) {
  return jsi::Function::createFromHostFunction(
    runtime,
    moduleRegistry->jsRegistry->getPropNameID(runtime, "promiseFn"),
    2,
    [this, globalArgs, moduleRegistry](
      jsi::Runtime &rt,
      const jsi::Value &thisVal,
      const jsi::Value *promiseConstructorArgs,
      size_t promiseConstructorArgCount
    ) {
      if (promiseConstructorArgCount != 2) {
        throw std::invalid_argument("Promise fn arg count must be 2");
      }

      jsi::Function resolveJSIFn = promiseConstructorArgs[0].getObject(rt).getFunction(rt);
      jsi::Function rejectJSIFn = promiseConstructorArgs[1].getObject(rt).getFunction(rt);

      auto &runtimeHolder = moduleRegistry->runtimeHolder;
      jobject resolve = createJavaCallbackFromJSIFunction(
        std::move(resolveJSIFn),
        rt,
        runtimeHolder->jsInvoker
      ).release();

      jobject reject = createJavaCallbackFromJSIFunction(
        std::move(rejectJSIFn),
        rt,
        runtimeHolder->jsInvoker
      ).release();

      JNIEnv *env = jni::Environment::current();

      auto &jPromise = JavaReferencesCache::instance()->getJClass(
        "com/facebook/react/bridge/PromiseImpl");
      jmethodID jPromiseConstructor = jPromise.getMethod(
        "<init>",
        "(Lcom/facebook/react/bridge/Callback;Lcom/facebook/react/bridge/Callback;)V"
      );

      // Creates a promise object
      jobject promise = env->NewObject(
        jPromise.clazz,
        jPromiseConstructor,
        resolve,
        reject
      );

      // Cast in this place is safe, cause we know that this function expects promise.
      auto asyncFunction = jni::static_ref_cast<JNIAsyncFunctionBody>(this->jBodyReference);
      asyncFunction->invoke(
        globalArgs,
        promise
      );

      // We have to remove the local reference to the promise object.
      // It doesn't mean that the promise will be deallocated, but rather that we move
      // the ownership to the `JNIAsyncFunctionBody`.
      env->DeleteLocalRef(promise);
      env->DeleteGlobalRef(globalArgs);

      return jsi::Value::undefined();
    }
  );
}
} // namespace expo