#include <node.h>

using namespace v8;

int factorial(int n) {
    if (n == 0) return 1;
    else return n * factorial(n - 1);
}

void Factorial(const FunctionCallbackInfo<Value>& args) {
    Isolate* isolate = Isolate::GetCurrent();
    HandleScope scope(isolate);

    if (args.Length() != 2) {
        isolate->ThrowException(Exception::TypeError(String::NewFromUtf8(isolate, "Wrong number of arguments")));
    } else {
        if (!(args[0]->IsNumber() && args[1]->IsFunction())) {
            isolate->ThrowException(Exception::TypeError(String::NewFromUtf8(isolate, "Wrong arguments type")));
        } else {
            int result = factorial(args[0]->Int32Value());

            Local<Function> callbackFunction = Local<Function>::Cast(args[1]);
            const unsigned argc = 1;
            Local<Value> argv[argc] = { Number::New(isolate, result) };

            callbackFunction->Call(isolate->GetCurrentContext()->Global(), argc, argv);
        }
    }
}

void Init(Handle<Object> exports) {
    NODE_SET_METHOD(exports, "factorial", Factorial);
}

NODE_MODULE(Factorial, Init)

var factorialAddon = require('./addons/Factorial');
factorialAddon.factorial(5, function (result) {
    console.log(result);
});