// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2018 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_VALIDATIONINTERFACE_H
#define BITCOIN_VALIDATIONINTERFACE_H

#include <primitives/transaction.h> // CTransaction(Ref)

#include <functional>
#include <memory>

class CBlock;
class CBlockIndex;
struct CBlockLocator;
class CBlockIndex;
class CConnman;
class CReserveScript;
class CValidationInterface;
class CValidationState;
class uint256;
class CScheduler;
class CTxMemPool;
enum class MemPoolRemovalReason;

// These functions dispatch to one or all registered wallets

/** Register a wallet to receive updates from core */
void RegisterValidationInterface(CValidationInterface* pwalletIn);
/** Unregister a wallet from core */
void UnregisterValidationInterface(CValidationInterface* pwalletIn);
/** Unregister all wallets from core */
void UnregisterAllValidationInterfaces();
/**
 * Pushes a function to callback onto the notification queue, guaranteeing any
 * callbacks generated prior to now are finished when the function is called.
 *
 * Be very careful blocking on func to be called if any locks are held -
 * validation interface clients may not be able to make progress as they often
 * wait for things like cs_main, so blocking until func is called with cs_main
 * will result in a deadlock (that DEBUG_LOCKORDER will miss).
 */
void CallFunctionInValidationInterfaceQueue(std::function<void ()> func);
/**
 * This is a synonym for the following, which asserts certain locks are not
 * held:
 *     std::promise<void> promise;
 *     CallFunctionInValidationInterfaceQueue([&promise] {
 *         promise.set_value();
 *     });
 *     promise.get_future().wait();
 */
void SyncWithValidationInterfaceQueue();

/**
 * Implement this to subscribe to events generated in validation
 *
 * Each CValidationInterface() subscriber will receive event callbacks
 * in the order in which the events were generated by validation.
 * Furthermore, each ValidationInterface() subscriber may assume that
 * callbacks effectively run in a single thread with single-threaded
 * memory consistency. That is, for a given ValidationInterface()
 * instantiation, each callback will complete before the next one is
 * invoked. This means, for example when a block is connected that the
 * UpdatedBlockTip() callback may depend on an operation performed in
 * the BlockConnected() callback without worrying about explicit
 * synchronization. No ordering should be assumed across
 * ValidationInterface() subscribers.
 */
class CValidationInterface {
protected:
    /**
     * Protected destructor so that instances can only be deleted by derived classes.
     * If that restriction is no longer desired, this should be made public and virtual.
     */
    ~CValidationInterface() = default;
    /**
     * Notifies listeners when the block chain tip advances.
     *
     * When multiple blocks are connected at once, UpdatedBlockTip will be called on the final tip
     * but may not be called on every intermediate tip. If the latter behavior is desired,
     * subscribe to BlockConnected() instead.
     *
     * Called on a background thread.
     */
    virtual void UpdatedBlockTip(const CBlockIndex *pindexNew, const CBlockIndex *pindexFork, bool fInitialDownload) {}
    /**
     * Notifies listeners of a transaction having been added to mempool.
     *
     * Called on a background thread.
     */
    virtual void TransactionAddedToMempool(const CTransactionRef &ptxn) {}
    /**
     * Notifies listeners of a transaction leaving mempool.
     *
     * This only fires for transactions which leave mempool because of expiry,
     * size limiting, reorg (changes in lock times/coinbase maturity), or
     * replacement. This does not include any transactions which are included
     * in BlockConnectedDisconnected either in block->vtx or in txnConflicted.
     *
     * Called on a background thread.
     */
    virtual void TransactionRemovedFromMempool(const CTransactionRef &ptx) {}
    /**
     * Notifies listeners of a block being connected.
     * Provides a vector of transactions evicted from the mempool as a result.
     *
     * Called on a background thread.
     */
    virtual void BlockConnected(const std::shared_ptr<const CBlock> &block, const CBlockIndex *pindex, const std::vector<CTransactionRef> &txnConflicted) {}
    /**
     * Notifies listeners of a block being disconnected
     *
     * Called on a background thread.
     */
    virtual void BlockDisconnected(const std::shared_ptr<const CBlock> &block) {}
    /**
     * Notifies listeners of the new active block chain on-disk.
     *
     * Prior to this callback, any updates are not guaranteed to persist on disk
     * (ie clients need to handle shutdown/restart safety by being able to
     * understand when some updates were lost due to unclean shutdown).
     *
     * When this callback is invoked, the validation changes done by any prior
     * callback are guaranteed to exist on disk and survive a restart, including
     * an unclean shutdown.
     *
     * Provides a locator describing the best chain, which is likely useful for
     * storing current state on disk in client DBs.
     *
     * Called on a background thread.
     */
    virtual void ChainStateFlushed(const CBlockLocator &locator) {}
    /** Tells listeners to broadcast their data. */
    virtual void ResendWalletTransactions(int64_t nBestBlockTime, CConnman* connman) {}
    /**
     * Notifies listeners of a block validation result.
     * If the provided CValidationState IsValid, the provided block
     * is guaranteed to be the current best block at the time the
     * callback was generated (not necessarily now)
     */
    virtual void BlockChecked(const CBlock&, const CValidationState&) {}
    /**
     * Notifies listeners that a block which builds directly on our current tip
     * has been received and connected to the headers tree, though not validated yet */
    virtual void NewPoWValidBlock(const CBlockIndex *pindex, const std::shared_ptr<const CBlock>& block) {};
    friend void ::RegisterValidationInterface(CValidationInterface*);
    friend void ::UnregisterValidationInterface(CValidationInterface*);
    friend void ::UnregisterAllValidationInterfaces();
};

struct MainSignalsInstance;
class CMainSignals {
private:
    std::unique_ptr<MainSignalsInstance> m_internals;

    friend void ::RegisterValidationInterface(CValidationInterface*);
    friend void ::UnregisterValidationInterface(CValidationInterface*);
    friend void ::UnregisterAllValidationInterfaces();
    friend void ::CallFunctionInValidationInterfaceQueue(std::function<void ()> func);

    void MempoolEntryRemoved(CTransactionRef tx, MemPoolRemovalReason reason);

public:
    /** Register a CScheduler to give callbacks which should run in the background (may only be called once) */
    void RegisterBackgroundSignalScheduler(CScheduler& scheduler);
    /** Unregister a CScheduler to give callbacks which should run in the background - these callbacks will now be dropped! */
    void UnregisterBackgroundSignalScheduler();
    /** Call any remaining callbacks on the calling thread */
    void FlushBackgroundCallbacks();

    size_t CallbacksPending();

    /** Register with mempool to call TransactionRemovedFromMempool callbacks */
    void RegisterWithMempoolSignals(CTxMemPool& pool);
    /** Unregister with mempool */
    void UnregisterWithMempoolSignals(CTxMemPool& pool);

    void UpdatedBlockTip(const CBlockIndex *, const CBlockIndex *, bool fInitialDownload);
    void TransactionAddedToMempool(const CTransactionRef &);
    void BlockConnected(const std::shared_ptr<const CBlock> &, const CBlockIndex *pindex, const std::shared_ptr<const std::vector<CTransactionRef>> &);
    void BlockDisconnected(const std::shared_ptr<const CBlock> &);
    void ChainStateFlushed(const CBlockLocator &);
    void Broadcast(int64_t nBestBlockTime, CConnman* connman);
    void BlockChecked(const CBlock&, const CValidationState&);
    void NewPoWValidBlock(const CBlockIndex *, const std::shared_ptr<const CBlock>&);
};

CMainSignals& GetMainSignals();

#endif // BITCOIN_VALIDATIONINTERFACE_H