#pragma once

#include "common/instance_id.hpp"
#include "common/transport.hpp"
#include "common/types.hpp"
#include "request.hpp"

#include <libpldm/base.h>
#include <sys/socket.h>

#include <phosphor-logging/lg2.hpp>
#include <sdbusplus/timer.hpp>
#include <sdeventplus/event.hpp>
#include <sdeventplus/source/event.hpp>

#include <cassert>
#include <chrono>
#include <deque>
#include <functional>
#include <memory>
#include <mutex>
#include <queue>
#include <tuple>
#include <unordered_map>

PHOSPHOR_LOG2_USING;

namespace pldm
{
namespace requester
{
/** @struct RequestKey
 *
 *  RequestKey uniquely identifies the PLDM request message to match it with the
 *  response and a combination of MCTP endpoint ID, PLDM instance ID, PLDM type
 *  and PLDM command is the key.
 */
struct RequestKey
{
    mctp_eid_t eid;     //!< MCTP endpoint ID
    uint8_t instanceId; //!< PLDM instance ID
    uint8_t type;       //!< PLDM type
    uint8_t command;    //!< PLDM command

    bool operator==(const RequestKey& e) const
    {
        return ((eid == e.eid) && (instanceId == e.instanceId) &&
                (type == e.type) && (command == e.command));
    }
};

/** @struct RequestKeyHasher
 *
 *  This is a simple hash function, since the instance ID generator API
 *  generates unique instance IDs for MCTP endpoint ID.
 */
struct RequestKeyHasher
{
    std::size_t operator()(const RequestKey& key) const
    {
        return (key.eid << 24 | key.instanceId << 16 | key.type << 8 |
                key.command);
    }
};

using ResponseHandler = std::function<void(
    mctp_eid_t eid, const pldm_msg* response, size_t respMsgLen)>;

/** @struct RegisteredRequest
 *
 *  This struct is used to store the registered request to one endpoint.
 */
struct RegisteredRequest
{
    RequestKey key;                  //!< Responder MCTP endpoint ID
    std::vector<uint8_t> reqMsg;     //!< Request messages queue
    ResponseHandler responseHandler; //!< Waiting for response flag
};

/** @struct EndpointMessageQueue
 *
 *  This struct is used to save the list of request messages of one endpoint and
 *  the existing of the request message to the endpoint with its' EID.
 */
struct EndpointMessageQueue
{
    mctp_eid_t eid; //!< Responder MCTP endpoint ID
    std::deque<std::shared_ptr<RegisteredRequest>> requestQueue; //!< Queue
    bool activeRequest; //!< Waiting for response flag

    bool operator==(const mctp_eid_t& mctpEid) const
    {
        return (eid == mctpEid);
    }
};

/** @class Handler
 *
 *  This class handles the lifecycle of the PLDM request message based on the
 *  instance ID expiration interval, number of request retries and the timeout
 *  waiting for a response. The registered response handlers are invoked with
 *  response once the PLDM responder sends the response. If no response is
 *  received within the instance ID expiration interval or any other failure the
 *  response handler is invoked with the empty response.
 *
 * @tparam RequestInterface - Request class type
 */
template <class RequestInterface>
class Handler
{
  public:
    Handler() = delete;
    Handler(const Handler&) = delete;
    Handler(Handler&&) = delete;
    Handler& operator=(const Handler&) = delete;
    Handler& operator=(Handler&&) = delete;
    ~Handler() = default;

    /** @brief Constructor
     *
     *  @param[in] pldm_transport - PLDM requester
     *  @param[in] event - reference to PLDM daemon's main event loop
     *  @param[in] instanceIdDb - reference to an InstanceIdDb
     *  @param[in] verbose - verbose tracing flag
     *  @param[in] instanceIdExpiryInterval - instance ID expiration interval
     *  @param[in] numRetries - number of request retries
     *  @param[in] responseTimeOut - time to wait between each retry
     */
    explicit Handler(
        PldmTransport* pldmTransport, sdeventplus::Event& event,
        pldm::InstanceIdDb& instanceIdDb, bool verbose,
        std::chrono::seconds instanceIdExpiryInterval =
            std::chrono::seconds(INSTANCE_ID_EXPIRATION_INTERVAL),
        uint8_t numRetries = static_cast<uint8_t>(NUMBER_OF_REQUEST_RETRIES),
        std::chrono::milliseconds responseTimeOut =
            std::chrono::milliseconds(RESPONSE_TIME_OUT)) :
        pldmTransport(pldmTransport),
        event(event), instanceIdDb(instanceIdDb), verbose(verbose),
        instanceIdExpiryInterval(instanceIdExpiryInterval),
        numRetries(numRetries), responseTimeOut(responseTimeOut)
    {}

    void instanceIdExpiryCallBack(RequestKey key)
    {
        auto eid = key.eid;
        if (this->handlers.contains(key))
        {
            error("The eid:InstanceID {EID}:{IID} is using.", "EID",
                  (unsigned)key.eid, "IID", (unsigned)key.instanceId);
            auto& [request, responseHandler,
                   timerInstance] = this->handlers[key];
            request->stop();
            auto rc = timerInstance->stop();
            if (rc)
            {
                error("Failed to stop the instance ID expiry timer. RC = {RC}",
                      "RC", static_cast<int>(rc));
            }
            // Call response handler with an empty response to indicate no
            // response
            responseHandler(eid, nullptr, 0);
            this->removeRequestContainer.emplace(
                key,
                std::make_unique<sdeventplus::source::Defer>(
                    event, std::bind(&Handler::removeRequestEntry, this, key)));
            endpointMessageQueues[eid]->activeRequest = false;

            /* try to send new request if the endpoint is free */
            pollEndpointQueue(eid);
        }
        else
        {
            // This condition is not possible, if a response is received
            // before the instance ID expiry, then the response handler
            // is executed and the entry will be removed.
            assert(false);
        }
    }

    /** @brief Send the remaining PLDM request messages in endpoint queue
     *
     *  @param[in] eid - endpoint ID of the remote MCTP endpoint
     */
    int pollEndpointQueue(mctp_eid_t eid)
    {
        if (endpointMessageQueues[eid]->activeRequest ||
            endpointMessageQueues[eid]->requestQueue.empty())
        {
            return PLDM_SUCCESS;
        }

        endpointMessageQueues[eid]->activeRequest = true;
        auto requestMsg = endpointMessageQueues[eid]->requestQueue.front();
        endpointMessageQueues[eid]->requestQueue.pop_front();

        auto request = std::make_unique<RequestInterface>(
            pldmTransport, requestMsg->key.eid, event,
            std::move(requestMsg->reqMsg), numRetries, responseTimeOut,
            verbose);
        auto timer = std::make_unique<sdbusplus::Timer>(
            event.get(), std::bind(&Handler::instanceIdExpiryCallBack, this,
                                   requestMsg->key));

        auto rc = request->start();
        if (rc)
        {
            instanceIdDb.free(requestMsg->key.eid, requestMsg->key.instanceId);
            error("Failure to send the PLDM request message");
            endpointMessageQueues[eid]->activeRequest = false;
            return rc;
        }

        try
        {
            timer->start(duration_cast<std::chrono::microseconds>(
                instanceIdExpiryInterval));
        }
        catch (const std::runtime_error& e)
        {
            instanceIdDb.free(requestMsg->key.eid, requestMsg->key.instanceId);
            error(
                "Failed to start the instance ID expiry timer. RC = {ERR_EXCEP}",
                "ERR_EXCEP", e.what());
            endpointMessageQueues[eid]->activeRequest = false;
            return PLDM_ERROR;
        }

        handlers.emplace(requestMsg->key,
                         std::make_tuple(std::move(request),
                                         std::move(requestMsg->responseHandler),
                                         std::move(timer)));
        return PLDM_SUCCESS;
    }

    /** @brief Register a PLDM request message
     *
     *  @param[in] eid - endpoint ID of the remote MCTP endpoint
     *  @param[in] instanceId - instance ID to match request and response
     *  @param[in] type - PLDM type
     *  @param[in] command - PLDM command
     *  @param[in] requestMsg - PLDM request message
     *  @param[in] responseHandler - Response handler for this request
     *
     *  @return return PLDM_SUCCESS on success and PLDM_ERROR otherwise
     */
    int registerRequest(mctp_eid_t eid, uint8_t instanceId, uint8_t type,
                        uint8_t command, pldm::Request&& requestMsg,
                        ResponseHandler&& responseHandler)
    {
        RequestKey key{eid, instanceId, type, command};

        if (handlers.contains(key))
        {
            error("The eid:InstanceID {EID}:{IID} is using.", "EID",
                  (unsigned)eid, "IID", (unsigned)instanceId);
            return PLDM_ERROR;
        }

        auto inputRequest = std::make_shared<RegisteredRequest>(
            key, std::move(requestMsg), std::move(responseHandler));
        if (endpointMessageQueues.contains(eid))
        {
            endpointMessageQueues[eid]->requestQueue.push_back(inputRequest);
        }
        else
        {
            std::deque<std::shared_ptr<RegisteredRequest>> reqQueue;
            reqQueue.push_back(inputRequest);
            endpointMessageQueues[eid] =
                std::make_shared<EndpointMessageQueue>(eid, reqQueue, false);
        }

        /* try to send new request if the endpoint is free */
        pollEndpointQueue(eid);

        return PLDM_SUCCESS;
    }

    /** @brief Handle PLDM response message
     *
     *  @param[in] eid - endpoint ID of the remote MCTP endpoint
     *  @param[in] instanceId - instance ID to match request and response
     *  @param[in] type - PLDM type
     *  @param[in] command - PLDM command
     *  @param[in] response - PLDM response message
     *  @param[in] respMsgLen - length of the response message
     */
    void handleResponse(mctp_eid_t eid, uint8_t instanceId, uint8_t type,
                        uint8_t command, const pldm_msg* response,
                        size_t respMsgLen)
    {
        RequestKey key{eid, instanceId, type, command};
        if (handlers.contains(key))
        {
            auto& [request, responseHandler, timerInstance] = handlers[key];
            request->stop();
            auto rc = timerInstance->stop();
            if (rc)
            {
                error("Failed to stop the instance ID expiry timer. RC = {RC}",
                      "RC", static_cast<int>(rc));
            }
            responseHandler(eid, response, respMsgLen);
            instanceIdDb.free(key.eid, key.instanceId);
            handlers.erase(key);

            endpointMessageQueues[eid]->activeRequest = false;
            /* try to send new request if the endpoint is free */
            pollEndpointQueue(eid);
        }
        else
        {
            // Got a response for a PLDM request message not registered with the
            // request handler, so freeing up the instance ID, this can be other
            // OpenBMC applications relying on PLDM D-Bus apis like
            // openpower-occ-control and softoff
            instanceIdDb.free(key.eid, key.instanceId);
        }
    }

  private:
    PldmTransport* pldmTransport; //!< PLDM transport object
    sdeventplus::Event& event; //!< reference to PLDM daemon's main event loop
    pldm::InstanceIdDb& instanceIdDb; //!< reference to an InstanceIdDb
    bool verbose;                     //!< verbose tracing flag
    std::chrono::seconds
        instanceIdExpiryInterval;     //!< Instance ID expiration interval
    uint8_t numRetries;               //!< number of request retries
    std::chrono::milliseconds
        responseTimeOut;              //!< time to wait between each retry

    /** @brief Container for storing the details of the PLDM request
     *         message, handler for the corresponding PLDM response and the
     *         timer object for the Instance ID expiration
     */
    using RequestValue =
        std::tuple<std::unique_ptr<RequestInterface>, ResponseHandler,
                   std::unique_ptr<sdbusplus::Timer>>;

    // Manage the requests of responders base on MCTP EID
    std::map<mctp_eid_t, std::shared_ptr<EndpointMessageQueue>>
        endpointMessageQueues;

    /** @brief Container for storing the PLDM request entries */
    std::unordered_map<RequestKey, RequestValue, RequestKeyHasher> handlers;

    /** @brief Container to store information about the request entries to be
     *         removed after the instance ID timer expires
     */
    std::unordered_map<RequestKey, std::unique_ptr<sdeventplus::source::Defer>,
                       RequestKeyHasher>
        removeRequestContainer;

    /** @brief Remove request entry for which the instance ID expired
     *
     *  @param[in] key - key for the Request
     */
    void removeRequestEntry(RequestKey key)
    {
        if (removeRequestContainer.contains(key))
        {
            removeRequestContainer[key].reset();
            instanceIdDb.free(key.eid, key.instanceId);
            handlers.erase(key);
            removeRequestContainer.erase(key);
        }
    }
};

} // namespace requester

} // namespace pldm