/*
 * Copyright 2010-2016 Amazon.com, Inc. or its affiliates. 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.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file 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 NetworkConnection.hpp
 * @brief Network interface base class for IoT Client
 *
 * Defines an interface to the Network layer to be used by the MQTT client.
 * Starting point for porting the SDK to the networking layer of a new platform.
 */

#pragma once

#include <cstdint>
#include <string>
#include <mutex>
#include <memory>

#include "util/Core_EXPORTS.hpp"
#include "util/memory/stl/String.hpp"
#include "util/memory/stl/Vector.hpp"

#include "ResponseCode.hpp"

namespace awsiotsdk {
    /**
     * @brief Network Connection Class
     *
     * Defines an interface to the Network layer to be used by the MQTT client.
     * Starting point for porting the SDK to the networking layer of a new platform.
     *
     * This is an abstract class and cannot be instantiated.
     */
    AWS_API_EXPORT class NetworkConnection {
    protected:
        /**
         * Both the below mutexes must be locked before connect/disconnect
         */
        std::mutex read_mutex;   ///< Mutex for synchronizing read operations
        std::mutex write_mutex;  ///< Mutex for synchronizing write operations

        /**
         * @brief Create a Network socket and open the connection
         *
         * Internal implementation of the Connect function to be provided by the derived class
         *
         * Creates an open socket connection including Network handshake.
         *
         * @return ResponseCode - successful connection or Network error
         */
        virtual ResponseCode ConnectInternal() = 0;

        /**
         * @brief Write bytes to the network socket
         *
         * Internal implementation of the Write function to be provided by the derived class
         *
         * @param util::String - const reference to buffer which should be written to socket
         * @return size_t - number of bytes written
         * @return ResponseCode - successful write or Network error code
         */
        virtual ResponseCode WriteInternal(const util::String &buf, size_t &size_written_bytes_out) = 0;

        /**
         * @brief Read bytes from the network socket
         *
         * Internal implementation of the Read function to be provided by the derived class
         *
         * @param util::String - reference to buffer where read bytes should be copied
         * @param size_t - number of bytes to read
         * @param size_t - reference to store number of bytes read
         * @return ResponseCode - successful read or Network error code
         */
        virtual ResponseCode ReadInternal(util::Vector<unsigned char> &buf, size_t buf_read_offset,
                                          size_t size_bytes_to_read, size_t &size_read_bytes_out) = 0;

        /**
         * @brief Disconnect from network socket
         *
         * Internal implementation of the Disconnect function to be provided by the derived class
         *
         * @return ResponseCode - successful read or Network error code
         */
        virtual ResponseCode DisconnectInternal() = 0;

    public:
        /**
         * @brief Check if Network layer is still connected
         *
         * Called to check if the Network layer is still connected or not.
         *
         * @return ResponseCode - Network error code indicating status of network physical layer connection
         */
        virtual bool IsConnected() = 0;

        /**
         * @brief Check if Network Physical layer is still connected
         *
         * Called to check if the Network Physical layer is still connected or not.
         *
         * @return bool - indicating status of network physical layer connection
         */
        virtual bool IsPhysicalLayerConnected() = 0;

        /**
         * @brief Create a Network socket and open the connection
         *
         * Calls the internal connect function after obtaining read and write locks
         *
         * @return ResponseCode - successful connection or Network error
         */
        virtual ResponseCode Connect() final;

        /**
         * @brief Write bytes to the network socket
         *
         * Calls the internal write function after obtaining write lock
         *
         * @param util::String - const reference to buffer which should be written to socket
         * @return size_t - number of bytes written or Network error
         * @return ResponseCode - successful write or Network error code
         */
        virtual ResponseCode Write(const util::String &buf, size_t &size_written_bytes_out) final;

        /**
         * @brief Read bytes from the network socket
         *
         * Calls the internal read function after obtaining read lock
         *
         * @param util::String - reference to buffer where read bytes should be copied
         * @param size_t - number of bytes to read
         * @param size_t - reference to store number of bytes read
         * @return ResponseCode - successful read or Network error code
         */
        virtual ResponseCode Read(util::Vector<unsigned char> &buf, size_t buf_read_offset,
                                  size_t size_bytes_to_read, size_t &size_read_bytes_out) final;

        /**
         * @brief Disconnect from network socket
         *
         * Calls the internal disconnect function after obtaining read and write locks
         * This will be called by the SDK for both manual and auto-disconnect.
         * It separates the Disconnect logic from destroy, Network stack is NOT destroyed by this API
         * SDK should still be able to reconnect after Disconnect, but not after Destroy
         *
         * @return ResponseCode - successful read or Network error code
         */
        virtual ResponseCode Disconnect() final;

        virtual ~NetworkConnection() {}
    };
}