presence/rpolicy.hpp

#pragma once

#include "fan.hpp"

namespace phosphor
{
namespace fan
{
namespace presence
{

/**
 * @class RedundancyPolicy
 * @brief Redundancy policy interface.
 *
 * Provide concrete implementations of RedundancyPolicy to realize
 * new redundancy logic.
 *
 * A fan can have multiple ways to detect whether or not it is present.
 * The redundancy policy encapsulates the logic to aggregate those
 * inputs into a single yes or no the fan is present.
 */
class RedundancyPolicy
{
    public:
        RedundancyPolicy(const RedundancyPolicy&) = default;
        RedundancyPolicy& operator=(const RedundancyPolicy&) = default;
        RedundancyPolicy(RedundancyPolicy&&) = default;
        RedundancyPolicy& operator=(RedundancyPolicy&&) = default;
        virtual ~RedundancyPolicy() = default;

        /**
         * @brief Construct a new Redundancy Policy.
         *
         * @param[in] fan - The fan associated with this policy.
         */
        explicit RedundancyPolicy(const Fan& f) : fan(f) {}

        /**
         * @brief stateChanged
         *
         * Typically invoked by presence sensors to signify
         * a change of presence.  Implementations should update
         * the inventory and execute their policy logic.
         *
         * @param[in] present - The new state of the sensor.
         */
        virtual void stateChanged(bool present) = 0;

        /**
         * @brief monitor
         *
         * Implementations should start monitoring the sensors
         * associated with the fan.
         */
        virtual void monitor() = 0;

    protected:
        /** @brief Fan name and inventory path. */
        const Fan& fan;
};

/**
 * @class PolicyAccess
 * @brief Policy association.
 *
 * PolicyAccess can be used to associate a redundancy policy
 * with something else.
 *
 * Wrap the type to be associated with a policy with PolicyAccess.
 *
 * @tparam T - The type to associate with a redundancy policy.
 * @tparam Policy - An array type where the policy is stored.
 */
template <typename T, typename Policy>
class PolicyAccess : public T
{
    public:
        PolicyAccess() = default;
        PolicyAccess(const PolicyAccess&) = default;
        PolicyAccess& operator=(const PolicyAccess&) = default;
        PolicyAccess(PolicyAccess&&) = default;
        PolicyAccess& operator=(PolicyAccess&&) = default;
        ~PolicyAccess() = default;

        /**
         * @brief Construct a new PolicyAccess wrapped object.
         *
         * @param[in] index - The array index in Policy.
         * @tparam Args - Forwarded to wrapped type constructor.
         */
        template <typename...Args>
        PolicyAccess(size_t index, Args&&...args) :
            T(std::forward<Args>(args)...), policy(index) {}

    private:
        /**
         * @brief Get the associated policy.
         */
        RedundancyPolicy& getPolicy() override
        {
            return *Policy::get()[policy];
        }

        /** The associated policy index. */
        size_t policy;
};
} // namespace presence
} // namespace fan
} // namespace phosphor