/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * 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.
 */

#ifndef ANDROID_HARDWARE_MEDIA_BUFFERPOOL_V2_0_ACCESSORIMPL_H
#define ANDROID_HARDWARE_MEDIA_BUFFERPOOL_V2_0_ACCESSORIMPL_H

#include <map>
#include <set>
#include <condition_variable>
#include <utils/Timers.h>
#include "Accessor.h"

namespace android {
namespace hardware {
namespace media {
namespace bufferpool {
namespace V2_0 {
namespace implementation {

struct InternalBuffer;
struct TransactionStatus;

/**
 * An implementation of a buffer pool accessor(or a buffer pool implementation.) */
class Accessor::Impl
    : public std::enable_shared_from_this<Accessor::Impl> {
public:
    Impl(const std::shared_ptr<BufferPoolAllocator> &allocator);

    ~Impl();

    ResultStatus connect(
            const sp<Accessor> &accessor, const sp<IObserver> &observer,
            sp<Connection> *connection,
            ConnectionId *pConnectionId,
            uint32_t *pMsgId,
            const StatusDescriptor** statusDescPtr,
            const InvalidationDescriptor** invDescPtr);

    ResultStatus close(ConnectionId connectionId);

    ResultStatus allocate(ConnectionId connectionId,
                          const std::vector<uint8_t>& params,
                          BufferId *bufferId,
                          const native_handle_t** handle);

    ResultStatus fetch(ConnectionId connectionId,
                       TransactionId transactionId,
                       BufferId bufferId,
                       const native_handle_t** handle);

    void flush();

    void cleanUp(bool clearCache);

    bool isValid();

    void handleInvalidateAck();

    static void createInvalidator();

    static void createEvictor();

private:
    // ConnectionId = pid : (timestamp_created + seqId)
    // in order to guarantee uniqueness for each connection
    static uint32_t sSeqId;

    const std::shared_ptr<BufferPoolAllocator> mAllocator;

    nsecs_t mScheduleEvictTs;

    /**
     * Buffer pool implementation.
     *
     * Handles buffer status messages. Handles buffer allocation/recycling.
     * Handles buffer transfer between buffer pool clients.
     */
    struct BufferPool {
    private:
        std::mutex mMutex;
        int64_t mTimestampUs;
        int64_t mLastCleanUpUs;
        int64_t mLastLogUs;
        BufferId mSeq;
        BufferId mStartSeq;
        bool mValid;
        BufferStatusObserver mObserver;
        BufferInvalidationChannel mInvalidationChannel;

        std::map<ConnectionId, std::set<BufferId>> mUsingBuffers;
        std::map<BufferId, std::set<ConnectionId>> mUsingConnections;

        std::map<ConnectionId, std::set<TransactionId>> mPendingTransactions;
        // Transactions completed before TRANSFER_TO message arrival.
        // Fetch does not occur for the transactions.
        // Only transaction id is kept for the transactions in short duration.
        std::set<TransactionId> mCompletedTransactions;
        // Currently active(pending) transations' status & information.
        std::map<TransactionId, std::unique_ptr<TransactionStatus>>
                mTransactions;

        std::map<BufferId, std::unique_ptr<InternalBuffer>> mBuffers;
        std::set<BufferId> mFreeBuffers;
        std::set<ConnectionId> mConnectionIds;

        struct Invalidation {
            static std::atomic<std::uint32_t> sInvSeqId;

            struct Pending {
                bool mNeedsAck;
                uint32_t mFrom;
                uint32_t mTo;
                size_t mLeft;
                const std::weak_ptr<Accessor::Impl> mImpl;
                Pending(bool needsAck, uint32_t from, uint32_t to, size_t left,
                        const std::shared_ptr<Accessor::Impl> &impl)
                        : mNeedsAck(needsAck),
                          mFrom(from),
                          mTo(to),
                          mLeft(left),
                          mImpl(impl)
                {}

                bool isInvalidated(uint32_t bufferId) {
                    return isBufferInRange(mFrom, mTo, bufferId) && --mLeft == 0;
                }
            };

            std::list<Pending> mPendings;
            std::map<ConnectionId, uint32_t> mAcks;
            std::map<ConnectionId, const sp<IObserver>> mObservers;
            uint32_t mInvalidationId;
            uint32_t mId;

            Invalidation() : mInvalidationId(0), mId(sInvSeqId.fetch_add(1)) {}

            void onConnect(ConnectionId conId, const sp<IObserver> &observer);

            void onClose(ConnectionId conId);

            void onAck(ConnectionId conId, uint32_t msgId);

            void onBufferInvalidated(
                    BufferId bufferId,
                    BufferInvalidationChannel &channel);

            void onInvalidationRequest(
                    bool needsAck, uint32_t from, uint32_t to, size_t left,
                    BufferInvalidationChannel &channel,
                    const std::shared_ptr<Accessor::Impl> &impl);

            void onHandleAck(
                    std::map<ConnectionId, const sp<IObserver>> *observers,
                    uint32_t *invalidationId);
        } mInvalidation;
        /// Buffer pool statistics which tracks allocation and transfer statistics.
        struct Stats {
            /// Total size of allocations which are used or available to use.
            /// (bytes or pixels)
            size_t mSizeCached;
            /// # of cached buffers which are used or available to use.
            size_t mBuffersCached;
            /// Total size of allocations which are currently used. (bytes or pixels)
            size_t mSizeInUse;
            /// # of currently used buffers
            size_t mBuffersInUse;

            /// # of allocations called on bufferpool. (# of fetched from BlockPool)
            size_t mTotalAllocations;
            /// # of allocations that were served from the cache.
            /// (# of allocator alloc prevented)
            size_t mTotalRecycles;
            /// # of buffer transfers initiated.
            size_t mTotalTransfers;
            /// # of transfers that had to be fetched.
            size_t mTotalFetches;

            Stats()
                : mSizeCached(0), mBuffersCached(0), mSizeInUse(0), mBuffersInUse(0),
                  mTotalAllocations(0), mTotalRecycles(0), mTotalTransfers(0), mTotalFetches(0) {}

            /// # of currently unused buffers
            size_t buffersNotInUse() const {
                ALOG_ASSERT(mBuffersCached >= mBuffersInUse);
                return mBuffersCached - mBuffersInUse;
            }

            /// A new buffer is allocated on an allocation request.
            void onBufferAllocated(size_t allocSize) {
                mSizeCached += allocSize;
                mBuffersCached++;

                mSizeInUse += allocSize;
                mBuffersInUse++;

                mTotalAllocations++;
            }

            /// A buffer is evicted and destroyed.
            void onBufferEvicted(size_t allocSize) {
                mSizeCached -= allocSize;
                mBuffersCached--;
            }

            /// A buffer is recycled on an allocation request.
            void onBufferRecycled(size_t allocSize) {
                mSizeInUse += allocSize;
                mBuffersInUse++;

                mTotalAllocations++;
                mTotalRecycles++;
            }

            /// A buffer is available to be recycled.
            void onBufferUnused(size_t allocSize) {
                mSizeInUse -= allocSize;
                mBuffersInUse--;
            }

            /// A buffer transfer is initiated.
            void onBufferSent() {
                mTotalTransfers++;
            }

            /// A buffer fetch is invoked by a buffer transfer.
            void onBufferFetched() {
                mTotalFetches++;
            }
        } mStats;

        bool isValid() {
            return mValid;
        }

        void invalidate(bool needsAck, BufferId from, BufferId to,
                        const std::shared_ptr<Accessor::Impl> &impl);

        static void createInvalidator();

    public:
        /** Creates a buffer pool. */
        BufferPool();

        /** Destroys a buffer pool. */
        ~BufferPool();

        /**
         * Processes all pending buffer status messages, and returns the result.
         * Each status message is handled by methods with 'handle' prefix.
         */
        void processStatusMessages();

        /**
         * Handles a buffer being owned by a connection.
         *
         * @param connectionId  the id of the buffer owning connection.
         * @param bufferId      the id of the buffer.
         *
         * @return {@code true} when the buffer is owned,
         *         {@code false} otherwise.
         */
        bool handleOwnBuffer(ConnectionId connectionId, BufferId bufferId);

        /**
         * Handles a buffer being released by a connection.
         *
         * @param connectionId  the id of the buffer owning connection.
         * @param bufferId      the id of the buffer.
         *
         * @return {@code true} when the buffer ownership is released,
         *         {@code false} otherwise.
         */
        bool handleReleaseBuffer(ConnectionId connectionId, BufferId bufferId);

        /**
         * Handles a transfer transaction start message from the sender.
         *
         * @param message   a buffer status message for the transaction.
         *
         * @result {@code true} when transfer_to message is acknowledged,
         *         {@code false} otherwise.
         */
        bool handleTransferTo(const BufferStatusMessage &message);

        /**
         * Handles a transfer transaction being acked by the receiver.
         *
         * @param message   a buffer status message for the transaction.
         *
         * @result {@code true} when transfer_from message is acknowledged,
         *         {@code false} otherwise.
         */
        bool handleTransferFrom(const BufferStatusMessage &message);

        /**
         * Handles a transfer transaction result message from the receiver.
         *
         * @param message   a buffer status message for the transaction.
         *
         * @result {@code true} when the exisitng transaction is finished,
         *         {@code false} otherwise.
         */
        bool handleTransferResult(const BufferStatusMessage &message);

        /**
         * Handles a connection being closed, and returns the result. All the
         * buffers and transactions owned by the connection will be cleaned up.
         * The related FMQ will be cleaned up too.
         *
         * @param connectionId  the id of the connection.
         *
         * @result {@code true} when the connection existed,
         *         {@code false} otherwise.
         */
        bool handleClose(ConnectionId connectionId);

        /**
         * Recycles a existing free buffer if it is possible.
         *
         * @param allocator the buffer allocator
         * @param params    the allocation parameters.
         * @param pId       the id of the recycled buffer.
         * @param handle    the native handle of the recycled buffer.
         *
         * @return {@code true} when a buffer is recycled, {@code false}
         *         otherwise.
         */
        bool getFreeBuffer(
                const std::shared_ptr<BufferPoolAllocator> &allocator,
                const std::vector<uint8_t> &params,
                BufferId *pId, const native_handle_t **handle);

        /**
         * Adds a newly allocated buffer to bufferpool.
         *
         * @param alloc     the newly allocated buffer.
         * @param allocSize the size of the newly allocated buffer.
         * @param params    the allocation parameters.
         * @param pId       the buffer id for the newly allocated buffer.
         * @param handle    the native handle for the newly allocated buffer.
         *
         * @return OK when an allocation is successfully allocated.
         *         NO_MEMORY when there is no memory.
         *         CRITICAL_ERROR otherwise.
         */
        ResultStatus addNewBuffer(
                const std::shared_ptr<BufferPoolAllocation> &alloc,
                const size_t allocSize,
                const std::vector<uint8_t> &params,
                BufferId *pId,
                const native_handle_t **handle);

        /**
         * Processes pending buffer status messages and performs periodic cache
         * cleaning.
         *
         * @param clearCache    if clearCache is true, it frees all buffers
         *                      waiting to be recycled.
         */
        void cleanUp(bool clearCache = false);

        /**
         * Processes pending buffer status messages and invalidate all current
         * free buffers. Active buffers are invalidated after being inactive.
         */
        void flush(const std::shared_ptr<Accessor::Impl> &impl);

        friend class Accessor::Impl;
    } mBufferPool;

    struct  AccessorInvalidator {
        std::map<uint32_t, const std::weak_ptr<Accessor::Impl>> mAccessors;
        std::mutex mMutex;
        std::condition_variable mCv;
        bool mReady;

        AccessorInvalidator();
        void addAccessor(uint32_t accessorId, const std::weak_ptr<Accessor::Impl> &impl);
        void delAccessor(uint32_t accessorId);
    };

    static std::unique_ptr<AccessorInvalidator> sInvalidator;

    static void invalidatorThread(
        std::map<uint32_t, const std::weak_ptr<Accessor::Impl>> &accessors,
        std::mutex &mutex,
        std::condition_variable &cv,
        bool &ready);

    struct AccessorEvictor {
        std::map<const std::weak_ptr<Accessor::Impl>, nsecs_t, std::owner_less<>> mAccessors;
        std::mutex mMutex;
        std::condition_variable mCv;

        AccessorEvictor();
        void addAccessor(const std::weak_ptr<Accessor::Impl> &impl, nsecs_t ts);
    };

    static std::unique_ptr<AccessorEvictor> sEvictor;

    static void evictorThread(
        std::map<const std::weak_ptr<Accessor::Impl>, nsecs_t, std::owner_less<>> &accessors,
        std::mutex &mutex,
        std::condition_variable &cv);

    void scheduleEvictIfNeeded();

};

}  // namespace implementation
}  // namespace V2_0
}  // namespace ufferpool
}  // namespace media
}  // namespace hardware
}  // namespace android

#endif  // ANDROID_HARDWARE_MEDIA_BUFFERPOOL_V2_0_ACCESSORIMPL_H