text: // Copyright (c) 2018-2019 The GleecBTC Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #ifndef GLEECBTC_INTERFACES_CHAIN_H
  #define GLEECBTC_INTERFACES_CHAIN_H
  
  #include <optional.h>               // For Optional and nullopt
  #include <primitives/transaction.h> // For CTransactionRef
  
  #include <memory>
  #include <stddef.h>
  #include <stdint.h>
  #include <string>
  #include <vector>
  
  class CBlock;
  class CFeeRate;
  class CRPCCommand;
  class CScheduler;
  class CValidationState;
  class Coin;
  class uint256;
  enum class RBFTransactionState;
  struct CBlockLocator;
  struct FeeCalculation;
  
  namespace interfaces {
  
  class Handler;
  class Wallet;
  
  //! Interface giving clients (wallet processes, maybe other analysis tools in
  //! the future) ability to access to the chain state, receive notifications,
  //! estimate fees, and submit transactions.
  //!
  //! TODO: Current chain methods are too low level, exposing too much of the
  //! internal workings of the gleecbtc node, and not being very convenient to use.
  //! Chain methods should be cleaned up and simplified over time. Examples:
  //!
  //! * The Chain::lock() method, which lets clients delay chain tip updates
  //!   should be removed when clients are able to respond to updates
  //!   asynchronously
  //!   (https://github.com/gleecbtc/gleecbtc/pull/10973#issuecomment-380101269).
  //!
  //! * The initMessages() and loadWallet() methods which the wallet uses to send
  //!   notifications to the GUI should go away when GUI and wallet can directly
  //!   communicate with each other without going through the node
  //!   (https://github.com/gleecbtc/gleecbtc/pull/15288#discussion_r253321096).
  //!
  //! * The handleRpc, registerRpcs, rpcEnableDeprecated methods and other RPC
  //!   methods can go away if wallets listen for HTTP requests on their own
  //!   ports instead of registering to handle requests on the node HTTP port.
  class Chain
  {
  public:
      virtual ~Chain() {}
  
      //! Interface for querying locked chain state, used by legacy code that
      //! assumes state won't change between calls. New code should avoid using
      //! the Lock interface and instead call higher-level Chain methods
      //! that return more information so the chain doesn't need to stay locked
      //! between calls.
      class Lock
      {
      public:
          virtual ~Lock() {}
  
          //! Get current chain height, not including genesis block (returns 0 if
          //! chain only contains genesis block, nullopt if chain does not contain
          //! any blocks).
          virtual Optional<int> getHeight() = 0;
  
          //! Get block height above genesis block. Returns 0 for genesis block,
          //! 1 for following block, and so on. Returns nullopt for a block not
          //! included in the current chain.
          virtual Optional<int> getBlockHeight(const uint256& hash) = 0;
  
          //! Get block depth. Returns 1 for chain tip, 2 for preceding block, and
          //! so on. Returns 0 for a block not included in the current chain.
          virtual int getBlockDepth(const uint256& hash) = 0;
  
          //! Get block hash. Height must be valid or this function will abort.
          virtual uint256 getBlockHash(int height) = 0;
  
          //! Get block time. Height must be valid or this function will abort.
          virtual int64_t getBlockTime(int height) = 0;
  
          //! Get block median time past. Height must be valid or this function
          //! will abort.
          virtual int64_t getBlockMedianTimePast(int height) = 0;
  
          //! Check that the block is available on disk (i.e. has not been
          //! pruned), and contains transactions.
          virtual bool haveBlockOnDisk(int height) = 0;
  
          //! Return height of the first block in the chain with timestamp equal
          //! or greater than the given time and height equal or greater than the
          //! given height, or nullopt if there is no block with a high enough
          //! timestamp and height. Also return the block hash as an optional output parameter
          //! (to avoid the cost of a second lookup in case this information is needed.)
          virtual Optional<int> findFirstBlockWithTimeAndHeight(int64_t time, int height, uint256* hash) = 0;
  
          //! Return height of last block in the specified range which is pruned, or
          //! nullopt if no block in the range is pruned. Range is inclusive.
          virtual Optional<int> findPruned(int start_height = 0, Optional<int> stop_height = nullopt) = 0;
  
          //! Return height of the specified block if it is on the chain, otherwise
          //! return the height of the highest block on chain that's an ancestor
          //! of the specified block, or nullopt if there is no common ancestor.
          //! Also return the height of the specified block as an optional output
          //! parameter (to avoid the cost of a second hash lookup in case this
          //! information is desired).
          virtual Optional<int> findFork(const uint256& hash, Optional<int>* height) = 0;
  
          //! Get locator for the current chain tip.
          virtual CBlockLocator getTipLocator() = 0;
  
          //! Return height of the highest block on chain in common with the locator,
          //! which will either be the original block used to create the locator,
          //! or one of its ancestors.
          virtual Optional<int> findLocatorFork(const CBlockLocator& locator) = 0;
  
          //! Check if transaction will be final given chain height current time.
          virtual bool checkFinalTx(const CTransaction& tx) = 0;
      };
  
      //! Return Lock interface. Chain is locked when this is called, and
      //! unlocked when the returned interface is freed.
      virtual std::unique_ptr<Lock> lock(bool try_lock = false) = 0;
  
      //! Return whether node has the block and optionally return block metadata
      //! or contents.
      //!
      //! If a block pointer is provided to retrieve the block contents, and the
      //! block exists but doesn't have data (for example due to pruning), the
      //! block will be empty and all fields set to null.
      virtual bool findBlock(const uint256& hash,
          CBlock* block = nullptr,
          int64_t* time = nullptr,
          int64_t* max_time = nullptr) = 0;
  
      //! Look up unspent output information. Returns coins in the mempool and in
      //! the current chain UTXO set. Iterates through all the keys in the map and
      //! populates the values.
      virtual void findCoins(std::map<COutPoint, Coin>& coins) = 0;
  
      //! Estimate fraction of total transactions verified if blocks up to
      //! the specified block hash are verified.
      virtual double guessVerificationProgress(const uint256& block_hash) = 0;
  
      //! Check if transaction is RBF opt in.
      virtual RBFTransactionState isRBFOptIn(const CTransaction& tx) = 0;
  
      //! Check if transaction has descendants in mempool.
      virtual bool hasDescendantsInMempool(const uint256& txid) = 0;
  
      //! Transaction is added to memory pool, if the transaction fee is below the
      //! amount specified by max_tx_fee, and broadcast to all peers if relay is set to true.
      //! Return false if the transaction could not be added due to the fee or for another reason.
      virtual bool broadcastTransaction(const CTransactionRef& tx, std::string& err_string, const CAmount& max_tx_fee, bool relay) = 0;
  
      //! Calculate mempool ancestor and descendant counts for the given transaction.
      virtual void getTransactionAncestry(const uint256& txid, size_t& ancestors, size_t& descendants) = 0;
  
      //! Check if transaction will pass the mempool's chain limits.
      virtual bool checkChainLimits(const CTransactionRef& tx) = 0;
  
      //! Estimate smart fee.
      virtual CFeeRate estimateSmartFee(int num_blocks, bool conservative, FeeCalculation* calc = nullptr) = 0;
  
      //! Fee estimator max target.
      virtual unsigned int estimateMaxBlocks() = 0;
  
      //! Mempool minimum fee.
      virtual CFeeRate mempoolMinFee() = 0;
  
      //! Relay current minimum fee (from -minrelaytxfee and -incrementalrelayfee settings).
      virtual CFeeRate relayMinFee() = 0;
  
      //! Relay incremental fee setting (-incrementalrelayfee), reflecting cost of relay.
      virtual CFeeRate relayIncrementalFee() = 0;
  
      //! Relay dust fee setting (-dustrelayfee), reflecting lowest rate it's economical to spend.
      virtual CFeeRate relayDustFee() = 0;
  
      //! Check if any block has been pruned.
      virtual bool havePruned() = 0;
  
      //! Check if the node is ready to broadcast transactions.
      virtual bool isReadyToBroadcast() = 0;
  
      //! Check if in IBD.
      virtual bool isInitialBlockDownload() = 0;
  
      //! Check if shutdown requested.
      virtual bool shutdownRequested() = 0;
  
      //! Get adjusted time.
      virtual int64_t getAdjustedTime() = 0;
  
      //! Send init message.
      virtual void initMessage(const std::string& message) = 0;
  
      //! Send init warning.
      virtual void initWarning(const std::string& message) = 0;
  
      //! Send init error.
      virtual void initError(const std::string& message) = 0;
  
      //! Send wallet load notification to the GUI.
      virtual void loadWallet(std::unique_ptr<Wallet> wallet) = 0;
  
      //! Send progress indicator.
      virtual void showProgress(const std::string& title, int progress, bool resume_possible) = 0;
  
      //! Chain notifications.
      class Notifications
      {
      public:
          virtual ~Notifications() {}
          virtual void TransactionAddedToMempool(const CTransactionRef& tx) {}
          virtual void TransactionRemovedFromMempool(const CTransactionRef& ptx) {}
          virtual void BlockConnected(const CBlock& block, const std::vector<CTransactionRef>& tx_conflicted) {}
          virtual void BlockDisconnected(const CBlock& block) {}
          virtual void UpdatedBlockTip() {}
          virtual void ChainStateFlushed(const CBlockLocator& locator) {}
      };
  
      //! Register handler for notifications.
      virtual std::unique_ptr<Handler> handleNotifications(Notifications& notifications) = 0;
  
      //! Wait for pending notifications to be processed unless block hash points to the current
      //! chain tip, or to a possible descendant of the current chain tip that isn't currently
      //! connected.
      virtual void waitForNotificationsIfNewBlocksConnected(const uint256& old_tip) = 0;
  
      //! Register handler for RPC. Command is not copied, so reference
      //! needs to remain valid until Handler is disconnected.
      virtual std::unique_ptr<Handler> handleRpc(const CRPCCommand& command) = 0;
  
      //! Check if deprecated RPC is enabled.
      virtual bool rpcEnableDeprecated(const std::string& method) = 0;
  
      //! Run function after given number of seconds. Cancel any previous calls with same name.
      virtual void rpcRunLater(const std::string& name, std::function<void()> fn, int64_t seconds) = 0;
  
      //! Current RPC serialization flags.
      virtual int rpcSerializationFlags() = 0;
  
      //! Synchronously send TransactionAddedToMempool notifications about all
      //! current mempool transactions to the specified handler and return after
      //! the last one is sent. These notifications aren't coordinated with async
      //! notifications sent by handleNotifications, so out of date async
      //! notifications from handleNotifications can arrive during and after
      //! synchronous notifications from requestMempoolTransactions. Clients need
      //! to be prepared to handle this by ignoring notifications about unknown
      //! removed transactions and already added new transactions.
      virtual void requestMempoolTransactions(Notifications& notifications) = 0;
  };
  
  //! Interface to let node manage chain clients (wallets, or maybe tools for
  //! monitoring and analysis in the future).
  class ChainClient
  {
  public:
      virtual ~ChainClient() {}
  
      //! Register rpcs.
      virtual void registerRpcs() = 0;
  
      //! Check for errors before loading.
      virtual bool verify() = 0;
  
      //! Load saved state.
      virtual bool load() = 0;
  
      //! Start client execution and provide a scheduler.
      virtual void start(CScheduler& scheduler) = 0;
  
      //! Save state to disk.
      virtual void flush() = 0;
  
      //! Shut down client.
      virtual void stop() = 0;
  };
  
  //! Return implementation of Chain interface.
  std::unique_ptr<Chain> MakeChain();
  
  //! Return implementation of ChainClient interface for a wallet client. This
  //! function will be undefined in builds where ENABLE_WALLET is false.
  //!
  //! Currently, wallets are the only chain clients. But in the future, other
  //! types of chain clients could be added, such as tools for monitoring,
  //! analysis, or fee estimation. These clients need to expose their own
  //! MakeXXXClient functions returning their implementations of the ChainClient
  //! interface.
  std::unique_ptr<ChainClient> MakeWalletClient(Chain& chain, std::vector<std::string> wallet_filenames);
  
  } // namespace interfaces
  
  #endif // GLEECBTC_INTERFACES_CHAIN_H
  