// Copyright 2016 Proyectos y Sistemas de Mantenimiento SL (eProsima).

//

// 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.

/**

 * @file CacheChange.hpp

 */

#ifndef FASTDDS_RTPS_COMMON__CACHECHANGE_HPP

#define FASTDDS_RTPS_COMMON__CACHECHANGE_HPP

#include <atomic>

#include <cassert>

#include <limits>

#include <fastdds/rtps/common/ChangeKind_t.hpp>

#include <fastdds/rtps/common/FragmentNumber.hpp>

#include <fastdds/rtps/common/InstanceHandle.hpp>

#include <fastdds/rtps/common/SerializedPayload.hpp>

#include <fastdds/rtps/common/Time_t.hpp>

#include <fastdds/rtps/common/Types.hpp>

#include <fastdds/rtps/common/VendorId_t.hpp>

#include <fastdds/rtps/common/WriteParams.hpp>

#include <fastdds/rtps/history/IPayloadPool.hpp>

namespace eprosima {

namespace fastdds {

namespace rtps {

struct CacheChange_t;

/*!

 * Specific information for a writer.

 */

struct CacheChangeWriterInfo_t

{

    //!Number of DATA / DATA_FRAG submessages sent to the transport (only used in Writers)

    size_t num_sent_submessages = 0;

    //! Used to link with previous node in a list. Used by FlowControllerImpl.

    //! Cannot be cached because there are several comparisons without locking.

    CacheChange_t* volatile previous = nullptr;

    //! Used to link with next node in a list. Used by FlowControllerImpl.

    //! Cannot be cached because there are several comparisons without locking.

    CacheChange_t* volatile next = nullptr;

    //! Used to know if the object is already in a list.

    std::atomic_bool is_linked {false};

};

/*!

 * Specific information for a reader.

 */

struct CacheChangeReaderInfo_t

{

    //!Reception TimeStamp (only used in Readers)

    Time_t receptionTimestamp;

    //! Disposed generation of the instance when this entry was added to it

    int32_t disposed_generation_count;

    //! No-writers generation of the instance when this entry was added to it

    int32_t no_writers_generation_count;

    //! Ownership stregth of its writer when the sample was received.

    uint32_t writer_ownership_strength;

};

/**

 * Structure CacheChange_t, contains information on a specific CacheChange.

 * @ingroup COMMON_MODULE

 */

struct FASTDDS_EXPORTED_API CacheChange_t

{

    //!Kind of change, default value ALIVE.

    ChangeKind_t kind = ALIVE;

    //!GUID_t of the writer that generated this change.

    GUID_t writerGUID{};

    //!Handle of the data associated with this change.

    InstanceHandle_t instanceHandle{};

    //!SequenceNumber of the change

    SequenceNumber_t sequenceNumber{};

    //!Serialized Payload associated with the change.

    SerializedPayload_t serializedPayload{};

    //!CDR serialization of inlined QoS for this change.

    SerializedPayload_t inline_qos{};

    //!Indicates if the cache has been read (only used in READERS)

    bool isRead = false;

    //!Source TimeStamp

    Time_t sourceTimestamp{};

    //! Vendor Id of the writer that generated this change.

    fastdds::rtps::VendorId_t vendor_id = c_VendorId_Unknown;

    union

    {

        CacheChangeReaderInfo_t reader_info;

        CacheChangeWriterInfo_t writer_info;

    };

    WriteParams write_params{};

    bool is_untyped_ = true;

    /*!

     * @brief Default constructor.

     * Creates an empty CacheChange_t.

     */

    CacheChange_t()

        : writer_info()

    {

        inline_qos.encapsulation = DEFAULT_ENDIAN == LITTLEEND ? PL_CDR_LE : PL_CDR_BE;

    }

    CacheChange_t(

            const CacheChange_t&) = delete;

    const CacheChange_t& operator =(

            const CacheChange_t&) = delete;

    /**

     * Constructor with payload size

     * @param payload_size Serialized payload size

     * @param is_untyped Flag to mark the change as untyped.

     */

    CacheChange_t(

            uint32_t payload_size,

            bool is_untyped = false)

        : serializedPayload(payload_size)

        , is_untyped_(is_untyped)

    {

    }

    /*!

     * Copy a different change into this one. All the elements are copied, included the data, allocating new memory.

     * @param [in] ch_ptr Pointer to the change.

     * @return True if correct.

     */

    bool copy(

            const CacheChange_t* ch_ptr)

    {

        kind = ch_ptr->kind;

        writerGUID = ch_ptr->writerGUID;

        instanceHandle = ch_ptr->instanceHandle;

        sequenceNumber = ch_ptr->sequenceNumber;

        sourceTimestamp = ch_ptr->sourceTimestamp;

        reader_info.receptionTimestamp = ch_ptr->reader_info.receptionTimestamp;

        write_params = ch_ptr->write_params;

        isRead = ch_ptr->isRead;

        vendor_id = ch_ptr->vendor_id;

        fragment_size_ = ch_ptr->fragment_size_;

        fragment_count_ = ch_ptr->fragment_count_;

        first_missing_fragment_ = ch_ptr->first_missing_fragment_;

        return serializedPayload.copy(&ch_ptr->serializedPayload, !ch_ptr->is_untyped_);

    }

    /*!

     * Copy information form a different change into this one.

     * All the elements are copied except data.

     * @param [in] ch_ptr Pointer to the change.

     */

    void copy_not_memcpy(

            const CacheChange_t* ch_ptr)

    {

        kind = ch_ptr->kind;

        writerGUID = ch_ptr->writerGUID;

        instanceHandle = ch_ptr->instanceHandle;

        sequenceNumber = ch_ptr->sequenceNumber;

        sourceTimestamp = ch_ptr->sourceTimestamp;

        reader_info.receptionTimestamp = ch_ptr->reader_info.receptionTimestamp;

        write_params = ch_ptr->write_params;

        isRead = ch_ptr->isRead;

        vendor_id = ch_ptr->vendor_id;

        // Copy certain values from serializedPayload

        serializedPayload.encapsulation = ch_ptr->serializedPayload.encapsulation;

        serializedPayload.is_serialized_key = ch_ptr->serializedPayload.is_serialized_key;

        // Copy fragment size and calculate fragment count

        setFragmentSize(ch_ptr->fragment_size_, false);

    }

    virtual ~CacheChange_t() = default;

    /*!

     * Get the number of fragments this change is split into.

     * @return number of fragments.

     */

    uint32_t getFragmentCount() const

    {

        return fragment_count_;

    }

    /*!

     * Get the size of each fragment this change is split into.

     * @return size of fragment (0 means change is not fragmented).

     */

    uint16_t getFragmentSize() const

    {

        return fragment_size_;

    }

    /*!

     * Checks if all fragments have been received.

     * @return true when change is fully assembled (i.e. no missing fragments).

     */

    bool is_fully_assembled()

    {

        return first_missing_fragment_ >= fragment_count_;

    }

    /*! Checks if the first fragment is present.

     * @return true when it contains the first fragment. In other case, false.

     */

    bool contains_first_fragment()

    {

        return 0 < first_missing_fragment_;

    }

    /*!

     * Fills a FragmentNumberSet_t with the list of missing fragments.

     * @param [out] frag_sns FragmentNumberSet_t where result is stored.

     */

    void get_missing_fragments(

            FragmentNumberSet_t& frag_sns)

    {

        // Note: Fragment numbers are 1-based but we keep them 0 based.

        frag_sns.base(first_missing_fragment_ + 1);

        // Traverse list of missing fragments, adding them to frag_sns

        uint32_t current_frag = first_missing_fragment_;

        while (current_frag < fragment_count_)

        {

            frag_sns.add(current_frag + 1);

            current_frag = get_next_missing_fragment(current_frag);

        }

    }

    /*!

     * Set fragment size for this change.

     *

     * @param fragment_size Size of fragments.

     * @param create_fragment_list Whether to create missing fragments list or not.

     *

     * @remarks Parameter create_fragment_list should only be true when receiving the first

     *          fragment of a change.

     */

    void setFragmentSize(

            uint16_t fragment_size,

            bool create_fragment_list = false)

    {

        fragment_size_ = fragment_size;

        fragment_count_ = 0;

        first_missing_fragment_ = 0;

        if (fragment_size > 0)

        {

            // This follows RTPS 8.3.7.3.5

            fragment_count_ = (serializedPayload.length + fragment_size - 1) / fragment_size;

            if (create_fragment_list)

            {

                // Keep index of next fragment on the payload portion at the beginning of each fragment. Last

                // fragment will have fragment_count_ as 'next fragment index'

                size_t offset = 0;

                for (uint32_t i = 1; i <= fragment_count_; i++, offset += fragment_size_)

                {

                    set_next_missing_fragment(i - 1, i);  // index to next fragment in missing list

                }

            }

            else

            {

                // List not created. This means we are going to send this change fragmented, so it is already

                // assembled, and the missing list is empty (i.e. first missing points to fragment count)

                first_missing_fragment_ = fragment_count_;

            }

        }

    }

    bool add_fragments(

            const SerializedPayload_t& incoming_data,

            uint32_t fragment_starting_num,

            uint32_t fragments_in_submessage)

    {

        uint32_t original_offset = (fragment_starting_num - 1) * fragment_size_;

        uint32_t incoming_length = fragment_size_ * fragments_in_submessage;

        uint32_t last_fragment_index = fragment_starting_num + fragments_in_submessage - 1;

        // Validate payload types

        if (serializedPayload.is_serialized_key != incoming_data.is_serialized_key)

        {

            return false;

        }

        // Validate fragment indexes

        if (last_fragment_index > fragment_count_)

        {

            return false;

        }

        // Update incoming length for last fragment

        if (last_fragment_index == fragment_count_)

        {

            incoming_length = serializedPayload.length - original_offset;

        }

        // Validate lengths

        if (incoming_data.length < incoming_length)

        {

            return false;

        }

        if (original_offset + incoming_length > serializedPayload.length)

        {

            return false;

        }

        if (received_fragments(fragment_starting_num - 1, fragments_in_submessage))

        {

            memcpy(

                &serializedPayload.data[original_offset],

                incoming_data.data, incoming_length);

        }

        return is_fully_assembled();

    }

    /**

     * @brief Calculate the minimum required payload size to store a fragmented change.

     *

     * @param[in]  payload_size       Size of the full payload.

     * @param[in]  fragment_size      Size of each fragment.

     * @param[out] min_required_size  Minimum required size to store the fragmented payload.

     */

    static bool calculate_required_fragmented_payload_size(

            uint32_t payload_size,

            uint16_t fragment_size,

            uint32_t& min_required_size)

    {

        if ((0 == fragment_size) || (payload_size <= fragment_size))

        {

            min_required_size = payload_size;

            return true;

        }

        // In order to avoid overflow on the calculations, we limit the maximum payload size

        constexpr uint32_t MAX_PAYLOAD_SIZE = std::numeric_limits<uint32_t>::max() - 4u - 3u;

        if (payload_size > MAX_PAYLOAD_SIZE)

        {

            return false;

        }

        // Ensure fragment size is at least 4 bytes to store fragment index

        if (fragment_size < 4u)

        {

            return false;

        }

        // Calculate number of fragments without risk of overflow

        uint32_t fragment_count = payload_size / fragment_size;

        if (0 != (payload_size % fragment_size))

        {

            ++fragment_count;

        }

        // This cannot overflow as the result will always be <= payload_size

        uint32_t last_fragment_offset = (fragment_count - 1) * fragment_size;

        // Since we will write a fragment index at the beginning of each fragment,

        // we need to ensure there is space for it in the last fragment.

        // Note: we already imposed limits to ensure no overflow occurs.

        min_required_size = (last_fragment_offset + 3u) & ~3u; // Align last fragment size to 4 bytes

        min_required_size += 4u; // Add fragment index size

        // Ensure minimum size is at least payload size

        if (min_required_size < payload_size)

        {

            min_required_size = payload_size;

        }

        return true;

    }

private:

    // Fragment size

    uint16_t fragment_size_ = 0;

    // Number of fragments

    uint32_t fragment_count_ = 0;

    // First fragment in missing list

    uint32_t first_missing_fragment_ = 0;

    uint32_t get_next_missing_fragment(

            uint32_t fragment_index)

    {

        uint32_t* ptr = next_fragment_pointer(fragment_index);

        return *ptr;

    }

    void set_next_missing_fragment(

            uint32_t fragment_index,

            uint32_t next_fragment_index)

    {

        uint32_t* ptr = next_fragment_pointer(fragment_index);

        *ptr = next_fragment_index;

    }

    uint32_t* next_fragment_pointer(

            uint32_t fragment_index)

    {

        size_t offset = fragment_size_;

        offset *= fragment_index;

        offset = (offset + 3u) & ~3u;

        return reinterpret_cast<uint32_t*>(&serializedPayload.data[offset]);

    }

    /*!

     * Mark a set of consecutive fragments as received.

     * This will remove a set of consecutive fragments from the missing list.

     * Should be called BEFORE copying the received data into the serialized payload.

     *

     * @param initial_fragment Index (0-based) of first received fragment.

     * @param num_of_fragments Number of received fragments. Should be strictly positive.

     * @return true if the list of missing fragments was modified, false otherwise.

     */

    bool received_fragments(

            uint32_t initial_fragment,

            uint32_t num_of_fragments)

    {

        bool at_least_one_changed = false;

        if ((fragment_size_ > 0) && (initial_fragment < fragment_count_))

        {

            uint32_t last_fragment = initial_fragment + num_of_fragments;

            if (last_fragment > fragment_count_)

            {

                last_fragment = fragment_count_;

            }

            if (initial_fragment <= first_missing_fragment_)

            {

                // Perform first = *first until first >= last_received

                while (first_missing_fragment_ < last_fragment)

                {

                    first_missing_fragment_ = get_next_missing_fragment(first_missing_fragment_);

                    at_least_one_changed = true;

                }

            }

            else

            {

                // Find prev in missing list

                uint32_t current_frag = first_missing_fragment_;

                while (current_frag < initial_fragment)

                {

                    uint32_t next_frag = get_next_missing_fragment(current_frag);

                    if (next_frag >= initial_fragment)

                    {

                        // This is the fragment previous to initial_fragment.

                        // Find future value for next by repeating next = *next until next >= last_fragment.

                        uint32_t next_missing_fragment = next_frag;

                        while (next_missing_fragment < last_fragment)

                        {

                            next_missing_fragment = get_next_missing_fragment(next_missing_fragment);

                            at_least_one_changed = true;

                        }

                        // Update next and finish loop

                        if (at_least_one_changed)

                        {

                            set_next_missing_fragment(current_frag, next_missing_fragment);

                        }

                        break;

                    }

                    current_frag = next_frag;

                }

            }

        }

        return at_least_one_changed;

    }

};

} // namespace rtps

} // namespace fastdds

} // namespace eprosima

#endif // FASTDDS_RTPS_COMMON__CACHECHANGE_HPP