/*
 *
 * Copyright 2015, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

/* I don't like using #ifndef, but I don't see a better way to do this */
#ifndef GRPC_UV

#include <node.h>
#include <nan.h>

#include "grpc/grpc.h"
#include "grpc/support/log.h"
#include "grpc/support/time.h"
#include "completion_queue.h"
#include "call.h"

namespace grpc {
namespace node {

namespace {

/* A worker that asynchronously calls completion_queue_next, and queues onto the
   node event loop a call to the function stored in the event's tag. */
class CompletionQueueAsyncWorker : public Nan::AsyncWorker {
 public:
  CompletionQueueAsyncWorker();

  ~CompletionQueueAsyncWorker();
  /* Calls completion_queue_next with the provided deadline, and stores the
     event if there was one or sets an error message if there was not */
  void Execute();

  /* Returns the completion queue attached to this class */
  static grpc_completion_queue *GetQueue();

  /* Convenience function to create a worker with the given arguments and queue
     it to run asynchronously */
  static void Next();

  /* Initialize the CompletionQueueAsyncWorker class */
  static void Init(v8::Local<v8::Object> exports);

 protected:
  /* Called when Execute has succeeded (completed without setting an error
     message). Calls the saved callback with the event that came from
     completion_queue_next */
  void HandleOKCallback();

  void HandleErrorCallback();

 private:
  static void TryAddWorker();

  grpc_event result;

  static grpc_completion_queue *queue;

  // Number of grpc_completion_queue_next calls in the thread pool
  static int current_threads;
  // Number of grpc_completion_queue_next calls waiting to enter the thread pool
  static int waiting_next_calls;
};

const int max_queue_threads = 2;

using v8::Function;
using v8::Local;
using v8::Object;
using v8::Value;

grpc_completion_queue *CompletionQueueAsyncWorker::queue;

// Invariants: current_threads <= max_queue_threads
// (current_threads == max_queue_threads) || (waiting_next_calls == 0)

int CompletionQueueAsyncWorker::current_threads;
int CompletionQueueAsyncWorker::waiting_next_calls;

CompletionQueueAsyncWorker::CompletionQueueAsyncWorker()
    : Nan::AsyncWorker(NULL) {}

CompletionQueueAsyncWorker::~CompletionQueueAsyncWorker() {}

void CompletionQueueAsyncWorker::Execute() {
  result =
      grpc_completion_queue_next(queue, gpr_inf_future(GPR_CLOCK_REALTIME), NULL);
  if (!result.success) {
    SetErrorMessage("The async function encountered an error");
  }
}

grpc_completion_queue *CompletionQueueAsyncWorker::GetQueue() { return queue; }

void CompletionQueueAsyncWorker::TryAddWorker() {
  if (current_threads < max_queue_threads && waiting_next_calls > 0) {
    current_threads += 1;
    waiting_next_calls -= 1;
    CompletionQueueAsyncWorker *worker = new CompletionQueueAsyncWorker();
    Nan::AsyncQueueWorker(worker);
  }
  GPR_ASSERT(current_threads <= max_queue_threads);
  GPR_ASSERT((current_threads == max_queue_threads) ||
             (waiting_next_calls == 0));
}

void CompletionQueueAsyncWorker::Next() {
  waiting_next_calls += 1;
  TryAddWorker();
}

void CompletionQueueAsyncWorker::Init(Local<Object> exports) {
  Nan::HandleScope scope;
  current_threads = 0;
  waiting_next_calls = 0;
  queue = grpc_completion_queue_create(NULL);
}

void CompletionQueueAsyncWorker::HandleOKCallback() {
  Nan::HandleScope scope;
  current_threads -= 1;
  TryAddWorker();
  Nan::Callback *callback = GetTagCallback(result.tag);
  Local<Value> argv[] = {Nan::Null(), GetTagNodeValue(result.tag)};
  callback->Call(2, argv);

  DestroyTag(result.tag);
}

void CompletionQueueAsyncWorker::HandleErrorCallback() {
  Nan::HandleScope scope;
  current_threads -= 1;
  TryAddWorker();
  Nan::Callback *callback = GetTagCallback(result.tag);
  Local<Value> argv[] = {Nan::Error(ErrorMessage())};

  callback->Call(1, argv);

  DestroyTag(result.tag);
}

}  // namespace

grpc_completion_queue *GetCompletionQueue() {
  return CompletionQueueAsyncWorker::GetQueue();
}

void CompletionQueueNext() {
  CompletionQueueAsyncWorker::Next();
}

void CompletionQueueInit(Local<Object> exports) {
  CompletionQueueAsyncWorker::Init(exports);
}

}  // namespace node
}  // namespace grpc

#endif  /* GRPC_UV */