text: // Copyright (c) 2014-2019, The Monero Project
  //
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  // permitted provided that the following conditions are met:
  //
  // 1. Redistributions of source code must retain the above copyright notice, this list of
  //    conditions and the following disclaimer.
  //
  // 2. Redistributions in binary form must reproduce the above copyright notice, this list
  //    of conditions and the following disclaimer in the documentation and/or other
  //    materials provided with the distribution.
  //
  // 3. Neither the name of the copyright holder nor the names of its contributors may be
  //    used to endorse or promote products derived from this software without specific
  //    prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
  // EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  // MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
  // THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  // PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  // STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
  // THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  //
  // Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers
  
  #pragma once
  #include "include_base_utils.h"
  
  #include <set>
  #include <unordered_map>
  #include <unordered_set>
  #include <queue>
  #include <boost/serialization/version.hpp>
  
  #include "string_tools.h"
  #include "syncobj.h"
  #include "math_helper.h"
  #include "cryptonote_basic/cryptonote_basic_impl.h"
  #include "cryptonote_basic/verification_context.h"
  #include "blockchain_db/blockchain_db.h"
  #include "crypto/hash.h"
  #include "rpc/core_rpc_server_commands_defs.h"
  #include "rpc/message_data_structs.h"
  #include "tx_blink.h"
  #include "worktips_economy.h"
  
  namespace cryptonote
  {
    class Blockchain;
    /************************************************************************/
    /*                                                                      */
    /************************************************************************/
  
    using namespace std::literals;
  
    //! tuple of <deregister, transaction fee, receive time> for organization
    typedef std::pair<std::tuple<bool, double, std::time_t>, crypto::hash> tx_by_fee_and_receive_time_entry;
  
    class txCompare
    {
    public:
      bool operator()(const tx_by_fee_and_receive_time_entry& a, const tx_by_fee_and_receive_time_entry& b) const
      {
        // Sort order:         non-standard txes,     fee (descending),      arrival time,         hash
        return std::make_tuple(!std::get<0>(a.first), -std::get<1>(a.first), std::get<2>(a.first), a.second)
             < std::make_tuple(!std::get<0>(b.first), -std::get<1>(b.first), std::get<2>(b.first), b.second);
      }
    };
  
    //! container for sorting transactions by fee per unit size
    typedef std::set<tx_by_fee_and_receive_time_entry, txCompare> sorted_tx_container;
  
    /// Argument passed into add_tx specifying different requires on the transaction
    struct tx_pool_options {
      bool kept_by_block = false; ///< has this transaction been in a block?
      bool relayed = false; ///< was this transaction from the network or a local client?
      bool do_not_relay = false; ///< to avoid relaying the transaction to the network
      bool approved_blink = false; ///< signals that this is a blink tx and so should be accepted even if it conflicts with mempool or recent txes in non-immutable block; typically specified indirectly (via core.handle_incoming_txs())
      uint64_t fee_percent = 100; ///< the required miner tx fee in percent relative to the base required miner tx fee; must be >= 100.
      uint64_t burn_fixed = 0; ///< a required minimum amount that must be burned (in atomic currency)
      uint64_t burn_percent = 0; ///< a required amount as a percentage of the base required miner tx fee that must be burned (additive with burn_fixed, if both > 0)
  
      static tx_pool_options from_block() { tx_pool_options o; o.kept_by_block = true; o.relayed = true; return o; }
      static tx_pool_options from_peer() { tx_pool_options o; o.relayed = true; return o; }
      static tx_pool_options new_tx(bool do_not_relay = false) { tx_pool_options o; o.do_not_relay = do_not_relay; return o; }
      static tx_pool_options new_blink(bool approved, uint8_t hf_version) {
        tx_pool_options o;
        o.do_not_relay = !approved;
        o.approved_blink = approved;
        o.fee_percent = BLINK_MINER_TX_FEE_PERCENT;
        o.burn_percent = hf_version <= network_version_14_blink ? BLINK_BURN_TX_FEE_PERCENT_OLD : BLINK_BURN_TX_FEE_PERCENT;
        o.burn_fixed = BLINK_BURN_FIXED;
        return o;
      }
    };
  
    /**
     * @brief Transaction pool, handles transactions which are not part of a block
     *
     * This class handles all transactions which have been received, but not as
     * part of a block.
     *
     * This handling includes:
     *   storing the transactions
     *   organizing the transactions by fee per weight unit
     *   taking/giving transactions to and from various other components
     *   saving the transactions to disk on shutdown
     *   helping create a new block template by choosing transactions for it
     *
     */
    class tx_memory_pool
    {
    public:
      /**
       * @brief Constructor
       *
       * @param bchs a Blockchain class instance, for getting chain info
       */
      tx_memory_pool(Blockchain& bchs);
  
      // Non-copyable
      tx_memory_pool(const tx_memory_pool &) = delete;
      tx_memory_pool &operator=(const tx_memory_pool &) = delete;
  
      /**
       * @copydoc add_tx(transaction&, tx_verification_context&, const tx_pool_options &, uint8_t)
       *
       * @param id the transaction's hash
       * @param tx_weight the transaction's weight
       * @param blink_rollback_height if tx is a blink that conflicts with a recent (non-immutable)
       * block tx then set this pointer to the required new height: that is, all blocks with height
       * `block_rollback_height` and above must be removed.
       */
      bool add_tx(transaction &tx, const crypto::hash &id, const cryptonote::blobdata &blob, size_t tx_weight, tx_verification_context& tvc, const tx_pool_options &opts, uint8_t hf_version, uint64_t *blink_rollback_height = nullptr);
  
      /**
       * @brief add a transaction to the transaction pool
       *
       * Most likely the transaction will come from the network, but it is
       * also possible for transactions to come from popped blocks during
       * a reorg, or from local clients creating a transaction and
       * submitting it to the network
       *
       * @param tx the transaction to be added
       * @param tvc return-by-reference status about the transaction verification
       * @param opts the options controlling how this tx will be accepted/added
       * @param hf_version the hard fork version used to create the transaction
       *
       * @return true if the transaction passes validations, otherwise false
       */
      bool add_tx(transaction &tx, tx_verification_context& tvc, const tx_pool_options &opts, uint8_t hf_version);
  
      /**
       * @brief attempts to add a blink transaction to the transaction pool.
       *
       * This method must be called without a held blink lock.
       *
       * This is only for use for new transactions that should not exist yet on the chain or mempool
       * (and will fail if already does).  See `add_existing_blink` instead to add blink data about a
       * transaction that already exists.  This is only meant to be called during the SN blink signing
       * phase (and requires that the `tx` transaction be properly set to a full transaction);
       * ordinary nodes receiving a blink tx from the network should be going through
       * core.handle_incoming_blinks instead.
       *
       * Whether or not the transaction is added to the known blinks or marked for relaying depends on
       * whether the passed-in transaction has an `.approved()` status: if it does, the transaction is
       * set for relaying and added to the active blinks immediately; otherwise it is not added to the
       * known blinks and will not be relayed.
       *
       * The transaction is *not* added to the known blinks or marked for relaying unless it is passed
       * in with an `.approved()` status.
       *
       * @param blink - a shared_ptr to the blink details
       * @param tvc - the verification results
       * @param blink_exists - will be set to true if the addition fails because the blink tx already
       * exists
       *
       * @return true if the tx passes validations and has been added to the tx pool.
       */
      bool add_new_blink(const std::shared_ptr<blink_tx> &blink, tx_verification_context& tvc, bool &blink_exists);
  
      /**
       * @brief attempts to add blink transaction information about an existing blink transaction
       *
       * You *must* already hold a blink_unique_lock().
       *
       * This method takes an approved blink_tx and records it in the known blinks data.  No check is
       * done that the transaction actually exists on the blockchain or mempool.  It is assumed that
       * the given shared_ptr is a new blink that is not yet shared between threads (and thus doesn't
       * need locking): sharing is expected only after it is added to the blinks via this method.
       *
       * NB: this function assumes that the given blink tx is valid and approved (signed) but does
       * *not* check it (except as an assert when compiling in debug mode).
       *
       * @param blink the blink_tx shared_ptr
       *
       * @return true if the blink data was recorded, false if the given blink was already known.
       */
      bool add_existing_blink(std::shared_ptr<blink_tx> blink);
  
      /**
       * @brief accesses blink tx details if the given tx hash is a known, approved blink tx, nullptr
       * otherwise.
       *
       * You *must* already hold a blink_shared_lock() or blink_unique_lock().
       *
       * @param tx_hash the hash of the tx to access
       */
      std::shared_ptr<blink_tx> get_blink(const crypto::hash &tx_hash) const;
  
      /**
       * Equivalent to `(bool) get_blink(...)`, but slightly more efficient when the blink information
       * isn't actually needed beyond an existance test (as it avoids copying the shared_ptr).
       *
       * You *must* already hold a blink_shared_lock() or blink_unique_lock().
       */
      bool has_blink(const crypto::hash &tx_hash) const;
  
      /**
       * @brief modifies a vector of tx hashes to remove any that have known valid blink signatures
       *
       * Must not currently hold a blink lock.
       *
       * @param txs the tx hashes to check
       */
      void keep_missing_blinks(std::vector<crypto::hash> &tx_hashes) const;
  
      /**
       * @brief returns checksums of blink txes included in recently mined blocks and in the mempool
       *
       * Must not currently hold a blink lock.
       *
       * The returned map consists of height => hashsum pairs where the height is the height in which
       * the blink transactions were mined and the hashsum is a checksum of all the blink txes mined
       * at that height.  Unmined mempool blink txes are included at a height of 0.  Only heights
       * since the immutable checkpoint block are included.  Any block height (including the special
       * "0" height) that has no blink tx in it is not included.
       */
      std::map<uint64_t, crypto::hash> get_blink_checksums() const;
  
      /**
       * @brief returns the hashes of any non-immutable blink transactions mined in the given heights.
       * A height of 0 is allowed: it indicates blinks in the mempool.
       *
       * Must not currently hold a blink lock.
       *
       * Note that this returned hashes by MINED HEIGHTS, not BLINK HEIGHTS where are a different
       * concept.
       *
       * @param set of heights
       *
       * @return vector of hashes
       */
      std::vector<crypto::hash> get_mined_blinks(const std::set<uint64_t> &heights) const;
  
      /**
       * @brief takes a transaction with the given hash from the pool
       *
       * @param id the hash of the transaction
       * @param tx return-by-reference the transaction taken
       * @param txblob return-by-reference the transaction as a blob
       * @param tx_weight return-by-reference the transaction's weight
       * @param fee the transaction fee
       * @param relayed return-by-reference was transaction relayed to us by the network?
       * @param do_not_relay return-by-reference is transaction not to be relayed to the network?
       * @param double_spend_seen return-by-reference was a double spend seen for that transaction?
       *
       * @return true unless the transaction cannot be found in the pool
       */
      bool take_tx(const crypto::hash &id, transaction &tx, cryptonote::blobdata &txblob, size_t& tx_weight, uint64_t& fee, bool &relayed, bool &do_not_relay, bool &double_spend_seen);
  
      /**
       * @brief checks if the pool has a transaction with the given hash
       *
       * @param id the hash to look for
       *
       * @return true if the transaction is in the pool, otherwise false
       */
      bool have_tx(const crypto::hash &id) const;
  
      /**
       * @brief determines whether the given tx hashes are in the mempool
       *
       * @param hashes vector of tx hashes
       *
       * @return vector of the same size as `hashes` of true (1) or false (0) values.  (Not using
       * std::vector<bool> because it is broken by design).
       */
      std::vector<uint8_t> have_txs(const std::vector<crypto::hash> &hashes) const;
  
      /**
       * @brief action to take when notified of a block added to the blockchain
       *
       * @param new_block_height the height of the blockchain after the change
       * @param top_block_id the hash of the new top block
       *
       * @return true
       */
      bool on_blockchain_inc(block const &blk);
  
      /**
       * @brief action to take when notified of a block removed from the blockchain
       *
       * @param new_block_height the height of the blockchain after the change
       * @param top_block_id the hash of the new top block
       *
       * @return true
       */
      bool on_blockchain_dec();
  
      /**
       * @brief action to take periodically
       *
       * Currently checks transaction pool for stale ("stuck") transactions
       */
      void on_idle();
  
      /**
       * @brief locks the transaction pool
       */
      void lock() const { m_transactions_lock.lock(); }
  
      /**
       * @brief unlocks the transaction pool
       */
      void unlock() const { m_transactions_lock.unlock(); }
  
      /**
       * @briefs does a non-blocking attempt to lock the transaction pool
       */
      bool try_lock() const { return m_transactions_lock.try_lock(); }
  
      /* These are needed as a workaround for boost::lock not considering the type lockable if const
       * versions are defined.  When we switch to std::lock these can go. */
      void lock() { m_transactions_lock.lock(); }
      void unlock() { m_transactions_lock.unlock(); }
      bool try_lock() { return m_transactions_lock.try_lock(); }
  
      /**
       * @brief obtains a unique lock on the approved blink tx pool
       */
      template <typename... Args>
      auto blink_unique_lock(Args &&...args) const { return std::unique_lock<boost::shared_mutex>{m_blinks_mutex, std::forward<Args>(args)...}; }
  
      /**
       * @brief obtains a shared lock on the approved blink tx pool
       */
      template <typename... Args>
      auto blink_shared_lock(Args &&...args) const { return std::shared_lock<boost::shared_mutex>{m_blinks_mutex, std::forward<Args>(args)...}; }
  
  
      // load/store operations
  
      /**
       * @brief loads pool state (if any) from disk, and initializes pool
       *
       * @param max_txpool_weight the max weight in bytes
       *
       * @return true
       */
      bool init(size_t max_txpool_weight = 0);
  
      /**
       * @brief attempts to save the transaction pool state to disk
       *
       * Currently fails (returns false) if the data directory from init()
       * does not exist and cannot be created, but returns true even if
       * saving to disk is unsuccessful.
       *
       * @return true in most cases (see above)
       */
      bool deinit();
  
      /**
       * @brief Chooses transactions for a block to include
       *
       * @param bl return-by-reference the block to fill in with transactions
       * @param median_weight the current median block weight
       * @param already_generated_coins the current total number of coins "minted"
       * @param total_weight return-by-reference the total weight of the new block
       * @param fee return-by-reference the total of fees from the included transactions
       * @param expected_reward return-by-reference the total reward awarded to the miner finding this block, including transaction fees
       * @param version hard fork version to use for consensus rules
       *
       * @return true
       */
      bool fill_block_template(block &bl, size_t median_weight, uint64_t already_generated_coins, size_t &total_weight, uint64_t &fee, uint64_t &expected_reward, uint8_t version, uint64_t height);
  
      /**
       * @brief get a list of all transactions in the pool
       *
       * @param txs return-by-reference the list of transactions
       * @param include_unrelayed_txes include unrelayed txes in the result
       *
       */
      void get_transactions(std::vector<transaction>& txs, bool include_unrelayed_txes = true) const;
  
      /**
       * @brief get a list of all transaction hashes in the pool
       *
       * @param txs return-by-reference the list of transactions
       * @param include_unrelayed_txes include unrelayed txes in the result
       *
       */
      void get_transaction_hashes(std::vector<crypto::hash>& txs, bool include_unrelayed_txes = true) const;
  
      /**
       * @brief get (weight, fee, receive time) for all transaction in the pool
       *
       * @param txs return-by-reference that data
       * @param include_unrelayed_txes include unrelayed txes in the result
       *
       */
      void get_transaction_backlog(std::vector<tx_backlog_entry>& backlog, bool include_unrelayed_txes = true) const;
  
      /**
       * @brief get a summary statistics of all transaction hashes in the pool
       *
       * @param stats return-by-reference the pool statistics
       * @param include_unrelayed_txes include unrelayed txes in the result
       *
       */
      void get_transaction_stats(struct txpool_stats& stats, bool include_unrelayed_txes = true) const;
  
      /**
       * @brief get information about all transactions and key images in the pool
       *
       * see documentation on tx_info and spent_key_image_info for more details
       *
       * @param tx_infos return-by-reference the transactions' information
       * @param key_image_infos return-by-reference the spent key images' information
       * @param include_sensitive_data include unrelayed txes and fields that are sensitive to the node privacy
       *
       * @return true
       */
      bool get_transactions_and_spent_keys_info(std::vector<tx_info>& tx_infos, std::vector<spent_key_image_info>& key_image_infos, bool include_sensitive_data = true) const;
  
      /**
       * @brief get information about all transactions and key images in the pool
       *
       * see documentation on tx_in_pool and key_images_with_tx_hashes for more details
       *
       * @param tx_infos [out] the transactions' information
       * @param key_image_infos [out] the spent key images' information
       *
       * @return true
       */
      bool get_pool_for_rpc(std::vector<cryptonote::rpc::tx_in_pool>& tx_infos, cryptonote::rpc::key_images_with_tx_hashes& key_image_infos) const;
  
      /**
       * @brief check for presence of key images in the pool
       *
       * @param key_images [in] vector of key images to check
       * @param spent [out] vector of bool to return
       *
       * @return true
       */
      bool check_for_key_images(const std::vector<crypto::key_image>& key_images, std::vector<bool> spent) const;
  
      /**
       * @brief get a specific transaction from the pool
       *
       * @param h the hash of the transaction to get
       * @param tx return-by-reference the transaction blob requested
       *
       * @return true if the transaction is found, otherwise false
       */
      bool get_transaction(const crypto::hash& h, cryptonote::blobdata& txblob) const;
  
      /**
       * @brief get specific transactions from the pool
       *
       * @param hashes - tx hashes of desired transactions
       * @param txblobs - vector of blobdata (i.e. std::strings) to which found blobs should be
       * appended.  The vector is *not* cleared of existing values.
       *
       * @return number of transactions added to txblobs
       */
      int find_transactions(const std::vector<crypto::hash> &tx_hashes, std::vector<cryptonote::blobdata> &txblobs) const;
  
      /**
       * @brief get a list of all relayable transactions and their hashes
       *
       * "relayable" in this case means:
       *   nonzero fee -or- a zero-fee SN state change tx
       *   hasn't been relayed too recently
       *   isn't old enough that relaying it is considered harmful
       *   doesn't have do_not_relay set
       *
       * @param txs return-by-reference the transactions and their hashes
       *
       * @return true
       */
      bool get_relayable_transactions(std::vector<std::pair<crypto::hash, cryptonote::blobdata>>& txs) const;
  
      /**
       * @brief clear transactions' `do_not_relay` flags (if set) so that they can start being
       * relayed.  (Note that it still must satisfy the other conditions of
       * `get_relayable_transactions` to actually be relayable).
       *
       * @return the number of txes that were found with an active `do_not_relay` flag that was
       * cleared.
       */
      int set_relayable(const std::vector<crypto::hash> &tx_hashes);
  
      /**
       * @brief tell the pool that certain transactions were just relayed
       *
       * @param txs the list of transactions (and their hashes)
       */
      void set_relayed(const std::vector<std::pair<crypto::hash, cryptonote::blobdata>>& txs);
  
      /**
       * @brief get the total number of transactions in the pool
       *
       * @return the number of transactions in the pool
       */
      size_t get_transactions_count(bool include_unrelayed_txes = true) const;
  
      /**
       * @brief remove transactions from the pool which are no longer valid
       *
       * With new versions of the currency, what conditions render a transaction
       * invalid may change.  This function clears those which were received
       * before a version change and no longer conform to requirements.
       *
       * @param version the version the transactions must conform to
       *
       * @return the number of transactions removed
       */
      size_t validate(uint8_t version);
  
       /**
        * @brief return the cookie
        *
        * @return the cookie
        */
      uint64_t cookie() const { return m_cookie; }
  
      /**
       * @brief get the cumulative txpool weight in bytes
       *
       * @return the cumulative txpool weight in bytes
       */
      size_t get_txpool_weight() const;
  
      /**
       * @brief set the max cumulative txpool weight in bytes
       *
       * @param bytes the max cumulative txpool weight in bytes
       */
      void set_txpool_max_weight(size_t bytes);
    private:
  
      /**
       * @brief insert key images into m_spent_key_images
       *
       * @return true on success, false on error
       */
      bool insert_key_images(const transaction_prefix &tx, const crypto::hash &txid, bool kept_by_block);
  
      /**
       * @brief remove old transactions from the pool
       *
       * After a certain time, it is assumed that a transaction which has not
       * yet been mined will likely not be mined.  These transactions are removed
       * from the pool to avoid buildup.
       *
       * @return true
       */
      bool remove_stuck_transactions();
  
      /**
       * @brief check if a transaction in the pool has a given spent key image
       *
       * @param key_im the spent key image to look for
       *
       * @return true if the spent key image is present, otherwise false
       */
      bool have_tx_keyimg_as_spent(const crypto::key_image& key_im) const;
  
      /**
       * @brief check if a tx that does not have a key-image component has a duplicate in the pool
  
       * @return true if it already exists
       *
       */
      bool have_duplicated_non_standard_tx(transaction const &tx, uint8_t hard_fork_version) const;
  
      /**
       * @brief check if any spent key image in a transaction is in the pool
       *
       * Checks if any of the spent key images in a given transaction are present
       * in any of the transactions in the transaction pool.
       *
       * @note see tx_pool::have_tx_keyimg_as_spent
       *
       * @param tx the transaction to check spent key images of
       * @param found if specified, append the hashes of all conflicting mempool txes here
       *
       * @return true if any spent key images are present in the pool, otherwise false
       */
      bool have_tx_keyimges_as_spent(const transaction& tx, std::vector<crypto::hash> *conflicting = nullptr) const;
  
      /**
       * @brief forget a transaction's spent key images
       *
       * Spent key images are stored separately from transactions for
       * convenience/speed, so this is part of the process of removing
       * a transaction from the pool.
       *
       * @param tx the transaction
       * @param txid the transaction's hash
       *
       * @return false if any key images to be removed cannot be found, otherwise true
       */
      bool remove_transaction_keyimages(const transaction_prefix& tx, const crypto::hash &txid);
  
      /**
       * @brief check if any of a transaction's spent key images are present in a given set
       *
       * @param kic the set of key images to check against
       * @param tx the transaction to check
       *
       * @return true if any key images present in the set, otherwise false
       */
      static bool have_key_images(const std::unordered_set<crypto::key_image>& kic, const transaction_prefix& tx);
  
      /**
       * @brief append the key images from a transaction to the given set
       *
       * @param kic the set of key images to append to
       * @param tx the transaction
       *
       * @return false if any append fails, otherwise true
       */
      static bool append_key_images(std::unordered_set<crypto::key_image>& kic, const transaction_prefix& tx);
  
      /**
       * @brief check if a transaction is a valid candidate for inclusion in a block
       *
       * @param txd the transaction to check (and info about it)
       * @param txid the txid of the transaction to check
       * @param txblob the transaction blob to check
       * @param tx the parsed transaction, if successful
       *
       * @return true if the transaction is good to go, otherwise false
       */
      bool is_transaction_ready_to_go(txpool_tx_meta_t& txd, const crypto::hash &txid, const cryptonote::blobdata &txblob, transaction&tx) const;
  
      /**
       * @brief mark all transactions double spending the one passed
       */
      void mark_double_spend(const transaction &tx);
  
      /**
       * @brief remove a transaction from the mempool
       *
       * This is called when pruning the mempool to reduce its size, and when deleting transactions
       * from the mempool because of a conflicting blink transaction arriving.  Transactions lock and
       * blockchain lock must be held by the caller.
       *
       * @param txid the transaction id to remove
       * @param meta optional pointer to txpool_tx_meta_t; will be looked up if omitted
       * @param stc_it an optional iterator to the tx's entry in m_txs_by_fee_and_receive_time to save
       * a (linear) scan to find it when already available.  The given iterator will be invalidated if
       * removed.
       *
       * @return true if the transaction was removed, false on failure.
       */
      bool remove_tx(const crypto::hash &txid, const txpool_tx_meta_t *meta = nullptr, const sorted_tx_container::iterator *stc_it = nullptr);
  
      /**
       * @brief prune lowest fee/byte txes till we're not above bytes
       *
       * @param skip don't prune the given ID this time (because it was just added)
       */
      void prune(const crypto::hash &skip);
  
      /**
       * @brief Attempt to add a blink tx "by force", removing conflicting non-blink txs
       *
       * The given transactions are removed from the mempool, if possible, to make way for this blink
       * transactions.  In order for any removal to happen, all the conflicting txes must be non-blink
       * transactions, and must either:
       * - be a mempool transaction
       * - be a mined, non-blink transaction in the recent (mutable) section of the chain
       *
       * If all conflicting txs satisfy the above then conflicting mempool txs are removed and the
       * blink_rollback_height pointer is updated to the required rollback height to eject any mined
       * txs (if not already at that height or lower).  True is returned.
       *
       * If any txs are found that do not satisfy the above then nothing is removed and false is
       * returned.
       *
       * @param the id of the incoming blink tx
       * @param conflict_txs vector of conflicting transaction hashes that are preventing the blink tx
       * @param blink_rollback_height a pointer to update to the new required height if a chain
       * rollback is needed for the blink tx.  (That is, all blocks with height >=
       * blink_rollback_height need to be popped).
       *
       * This method is *not* called with a blink lock held.
       *
       * @return true if the conflicting transactions have been removed (and/or the rollback height
       * set), false if tx removal and/or rollback are insufficient to eliminate conflicting txes.
       */
      bool remove_blink_conflicts(const crypto::hash &id, const std::vector<crypto::hash> &conflict_txs, uint64_t *blink_rollback_height);
  
      //TODO: confirm the below comments and investigate whether or not this
      //      is the desired behavior
      //! map key images to transactions which spent them
      /*! this seems odd, but it seems that multiple transactions can exist
       *  in the pool which both have the same spent key.  This would happen
       *  in the event of a reorg where someone creates a new/different
       *  transaction on the assumption that the original will not be in a
       *  block again.
       */
      typedef std::unordered_map<crypto::key_image, std::unordered_set<crypto::hash> > key_images_container;
  
      mutable boost::recursive_mutex m_transactions_lock;  //!< mutex for the pool
  
      //! container for spent key images from the transactions in the pool
      key_images_container m_spent_key_images;  
  
      //TODO: this time should be a named constant somewhere, not hard-coded
      //! interval on which to check for stale/"stuck" transactions
      epee::math_helper::periodic_task m_remove_stuck_tx_interval{30s};
  
      //TODO: look into doing this better
      //!< container for transactions organized by fee per size and receive time
      sorted_tx_container m_txs_by_fee_and_receive_time;
  
      std::atomic<uint64_t> m_cookie; //!< incremented at each change
  
      /**
       * @brief get an iterator to a transaction in the sorted container
       *
       * @param id the hash of the transaction to look for
       *
       * @return an iterator, possibly to the end of the container if not found
       */
      sorted_tx_container::iterator find_tx_in_sorted_container(const crypto::hash& id) const;
  
      //! cache/call Blockchain::check_tx_inputs results
      bool check_tx_inputs(const std::function<cryptonote::transaction&()> &get_tx, const crypto::hash &txid, uint64_t &max_used_block_height, crypto::hash &max_used_block_id, tx_verification_context &tvc, bool kept_by_block = false, uint64_t* blink_rollback_height = nullptr) const;
  
      //! transactions which are unlikely to be included in blocks
      /*! These transactions are kept in RAM in case they *are* included
       *  in a block eventually, but this container is not saved to disk.
       */
      std::unordered_set<crypto::hash> m_timed_out_transactions;
  
      Blockchain& m_blockchain;  //!< reference to the Blockchain object
  
      size_t m_txpool_max_weight;
      size_t m_txpool_weight;
  
      mutable std::unordered_map<crypto::hash, std::tuple<bool, tx_verification_context, uint64_t, crypto::hash>> m_input_cache;
  
      std::unordered_map<crypto::hash, transaction> m_parsed_tx_cache;
  
      mutable boost::shared_mutex m_blinks_mutex;
  
      // Contains blink metadata for approved blink transactions. { txhash => blink_tx, ... }.
      mutable std::unordered_map<crypto::hash, std::shared_ptr<cryptonote::blink_tx>> m_blinks;
  
      // Helper method: retrieves hashes and mined heights of blink txes since the immutable block;
      // mempool blinks are included with a height of 0.  Also takes care of cleaning up any blinks
      // that have become immutable.  Blink lock must not be already held.
      std::pair<std::vector<crypto::hash>, std::vector<uint64_t>> get_blink_hashes_and_mined_heights() const;
    };
  }
  