/*

 *

 *    Copyright (c) 2020 Project CHIP Authors

 *    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.

 */

#pragma once

#include <app/InteractionModelDelegatePointers.h>

#include <messaging/ExchangeContext.h>

#include <messaging/ExchangeDelegate.h>

#include <system/SystemClock.h>

#include <system/SystemLayer.h>

#include <system/SystemPacketBuffer.h>

#include <transport/raw/MessageHeader.h>

namespace chip {

namespace app {

class TimedHandler;

/**

 * A TimedHandler handles a Timed Request action and then waits for a

 * subsequent Invoke or Write action and hands those on to

 * InteractionModelEngine if they arrive soon enough.

 *

 * Lifetime handling:

 *

 * A TimedHandler is initially allocated when the Timed Request is received and

 * becomes the delegate for that exchange.  After that it remains alive until

 * either the exchange is closed or the interaction is handed on to the

 * InteractionModelEngine.

 */

class TimedHandlerDelegate

{

public:

    virtual ~TimedHandlerDelegate() = default;

    /**

     * Called when a timed invoke is received.  This function takes over all

     * handling of the exchange, status reporting, and so forth.

     */

    virtual void OnTimedInvoke(TimedHandler * apTimedHandler, Messaging::ExchangeContext * apExchangeContext,

                               const PayloadHeader & aPayloadHeader, System::PacketBufferHandle && aPayload) = 0;

    /**

     * Called when a timed write is received.  This function takes over all

     * handling of the exchange, status reporting, and so forth.

     */

    virtual void OnTimedWrite(TimedHandler * apTimedHandler, Messaging::ExchangeContext * apExchangeContext,

                              const PayloadHeader & aPayloadHeader, System::PacketBufferHandle && aPayload) = 0;

    /**

     * Called when a timed interaction has failed (i.e. the exchange it was

     * happening on has closed while the exchange delegate was the timed

     * handler).

     */

    virtual void OnTimedInteractionFailed(TimedHandler * apTimedHandler) = 0;

};

class TimedHandler : public Messaging::ExchangeDelegate

{

public:

    TimedHandler(TimedHandlerDelegate * delegate) : mDelegate(delegate) {}

    ~TimedHandler() override {}

    // ExchangeDelegate implementation.

    CHIP_ERROR OnMessageReceived(Messaging::ExchangeContext * aExchangeContext, const PayloadHeader & aPayloadHeader,

                                 System::PacketBufferHandle && aPayload) override;

private:

    // ExchangeDelegate implementation.

    void OnResponseTimeout(Messaging::ExchangeContext *) override

    { /* We just want to allow the exchange to close */

    }

    void OnExchangeClosing(Messaging::ExchangeContext * aExchangeContext) override;

    void CancelTimer();

    /**

     * Handler for the Timed Request action.  This returns success if the Timed

     * Request action is parsed successfully and the success Status Response

     * action is sent, failure otherwise.

     */

    CHIP_ERROR HandleTimedRequestAction(Messaging::ExchangeContext * aExchangeContext, const PayloadHeader & aPayloadHeader,

                                        System::PacketBufferHandle && aPayload);

    enum class State : uint8_t

    {

        kExpectingTimedAction,     // Initial state: expecting a timed action.

        kReceivedTimedAction,      // Have received the timed action.  This can

                                   // be a terminal state if the action ends up

                                   // malformed.

        kExpectingFollowingAction, // Expecting write or invoke.

    };

    State mState = State::kExpectingTimedAction;

    /// This may be "fake" pointer or a real delegate pointer, depending

    /// on CHIP_CONFIG_STATIC_GLOBAL_INTERACTION_MODEL_ENGINE setting.

    ///

    /// When this is not a real pointer, it checks that the value is always

    /// set to the global InteractionModelEngine and the size of this

    /// member is 1 byte.

    InteractionModelDelegatePointer<TimedHandlerDelegate> mDelegate;

    // We keep track of the time limit for message reception, in case our

    // exchange's "response expected" timer gets delayed and does not fire when

    // the time runs out.

    //

    // NOTE: mTimeLimit needs to be 8-byte aligned on ARM so we place this last,

    //       to allow previous values to potentially use remaining packing space.

    //       Rationale:

    //         -   vtable is 4-byte aligned on 32-bit arm

    //         -   mTimeLimit requires 8-byte aligment

    //         =>  As a result we may gain 4 bytes if we place mTimeLimit last.

    // Expectation of memory layout:

    //   - vtable pointer (4 bytes & 4 byte alignment)

    //   - other members  (2 bytes on embedded "global pointer" arm)

    //                    (2 bytes padding for 8-byte alignment)

    //   - mTimeLimit     (8 bytes & 8 byte alignment)

    System::Clock::Timestamp mTimeLimit;

};

} // namespace app

} // namespace chip