CensorshipDetector.h

#pragma once
 
#include <xrpl/basics/algorithm.h>
 
#include <algorithm>
#include <functional>
#include <utility>
#include <vector>
 
namespace xrpl {
 
template <class TxID, class Sequence>
class CensorshipDetector
{
public:
    struct TxIDSeq
    {
        TxID txid;
        Sequence seq;
 
        TxIDSeq(TxID const& txid, Sequence const& seq) : txid(txid), seq(seq)
        {
        }
    };
 
    friend bool
    operator<(TxIDSeq const& lhs, TxIDSeq const& rhs)
    {
        if (lhs.txid != rhs.txid)
            return lhs.txid < rhs.txid;
        return lhs.seq < rhs.seq;
    }
 
    friend bool
    operator<(TxIDSeq const& lhs, TxID const& rhs)
    {
        return lhs.txid < rhs;
    }
 
    friend bool
    operator<(TxID const& lhs, TxIDSeq const& rhs)
    {
        return lhs < rhs.txid;
    }
 
    using TxIDSeqVec = std::vector<TxIDSeq>;
 
private:
    TxIDSeqVec tracker_;
 
public:
    CensorshipDetector() = default;

    void
    propose(TxIDSeqVec proposed)
    {
        // We want to remove any entries that we proposed in a previous round
        // that did not make it in yet if we are no longer proposing them.
        // And we also want to preserve the Sequence of entries that we proposed
        // in the last round and want to propose again.
        std::sort(proposed.begin(), proposed.end());
        generalizedSetIntersection(
            proposed.begin(),
            proposed.end(),
            tracker_.cbegin(),
            tracker_.cend(),
            [](auto& x, auto const& y) { x.seq = y.seq; },
            [](auto const& x, auto const& y) { return x.txid < y.txid; });
        tracker_ = std::move(proposed);
    }

    template <class Predicate>
    void
    check(std::vector<TxID> accepted, Predicate&& pred)
    {
        auto acceptTxid = accepted.begin();
        auto const ae = accepted.end();
        std::sort(acceptTxid, ae);
 
        // We want to remove all tracking entries for transactions that were
        // accepted as well as those which match the predicate.
 
        auto i = removeIfIntersectOrMatch(
            tracker_.begin(),
            tracker_.end(),
            accepted.begin(),
            accepted.end(),
            [&pred](auto const& x) { return pred(x.txid, x.seq); },
            std::less<void>{});
        tracker_.erase(i, tracker_.end());
    }

    void
    reset()
    {
        tracker_.clear();
    }
};
 
}  // namespace xrpl