/*
 *
 *    Copyright (c) 2017 Nest Labs, Inc.
 *    All rights reserved.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */

/**
 *    @file
 *      This file defines the AsyncDNSResolver, the object that performs
 *      Asynchronous Domain Name System (DNS) resolution in InetLayer.
 *
 */
#ifndef _ASYNC_DNS_SOCKETS_H_
#define _ASYNC_DNS_SOCKETS_H_

#include <InetLayer/IPAddress.h>
#include <InetLayer/InetError.h>

#if INET_CONFIG_ENABLE_DNS_RESOLVER
#include <InetLayer/DNSResolver.h>
#endif // INET_CONFIG_ENABLE_DNS_RESOLVER

#if WEAVE_SYSTEM_CONFIG_USE_SOCKETS
#if INET_CONFIG_ENABLE_DNS_RESOLVER && INET_CONFIG_ENABLE_ASYNC_DNS_SOCKETS
#include <netdb.h>
#include <pthread.h>
#include <semaphore.h>

namespace nl {
namespace Inet {

/**
 *  @class AsyncDNSResolverSockets
 *
 *  @brief
 *    This is an internal class to InetLayer that provides helper APIs for
 *    Asynchronous Domain Name System (DNS) resolution in InetLayer.
 *    There is no public interface available for the application layer.
 *
 */
class AsyncDNSResolverSockets
{
    friend class InetLayer;
    friend class DNSResolver;
public:

    INET_ERROR EnqueueRequest(DNSResolver &resolver);

    INET_ERROR Init(InetLayer *inet);

    INET_ERROR Cancel(DNSResolver &resolver);

    INET_ERROR Shutdown(void);

    INET_ERROR PrepareDNSResolver(DNSResolver &resolver, const char *hostName, uint16_t hostNameLen,
                                  uint8_t options, uint8_t maxAddrs, IPAddress *addrArray,
                                  DNSResolver::OnResolveCompleteFunct onComplete, void *appState);

private:
    pthread_t               mAsyncDNSThreadHandle[INET_CONFIG_DNS_ASYNC_MAX_THREAD_COUNT];
    pthread_mutex_t         mAsyncDNSMutex;      /* Mutex for accessing the DNSResolver queue. */
    pthread_cond_t          mAsyncDNSCondVar;    /* Condition Variable for thread synchronization. */
    volatile DNSResolver    *mAsyncDNSQueueHead; /* The head of the asynchronous DNSResolver object queue. */
    volatile DNSResolver    *mAsyncDNSQueueTail; /* The tail of the asynchronous DNSResolver object queue. */
    InetLayer               *mInet;              /* The pointer to the InetLayer. */
    static void             DNSResultEventHandler(Weave::System::Layer* aLayer, void* aAppState, Weave::System::Error aError); /* Timer event handler function for asynchronous DNS notification */

    INET_ERROR DequeueRequest(DNSResolver **outResolver);

    bool ShouldThreadShutdown(void);

    void Resolve(DNSResolver &resolver);

    void UpdateDNSResult(DNSResolver &resolver, struct addrinfo *lookupRes);

    static void *AsyncDNSThreadRun(void *args);

    static void NotifyWeaveThread(DNSResolver *resolver);

    void AsyncMutexLock(void);

    void AsyncMutexUnlock(void);
};

} // namespace Inet
} // namespace nl
#endif // INET_CONFIG_ENABLE_DNS_RESOLVER && INET_CONFIG_ENABLE_ASYNC_DNS_SOCKETS
#endif // WEAVE_SYSTEM_CONFIG_USE_SOCKETS

#endif // !defined(_ASYNC_DNS_SOCKETS_H_)