// Copyright (c) 2023-present The Bitcoin Core developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or https://opensource.org/license/mit/.

#include <private_broadcast.h>

#include <util/check.h>

#include <algorithm>

#include <ranges>

PrivateBroadcast::AddResult PrivateBroadcast::Add(const CTransactionRef& tx)

    EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)

{

    LOCK(m_mutex);

    // Cleanup finished transactions

    std::erase_if(m_transactions, [this](const auto& entry) {

        const auto& state{entry.second};

        return state.resolved && !IsPending(state) &&

               std::ranges::all_of(state.send_statuses, [](const auto& status) { return status.disconnected; });

    });

    if (const auto it{m_transactions.find(tx)}; it != m_transactions.end()) {

        if (it->second.send_statuses.size() < m_max_send_attempts) return AddResult::AlreadyPresent;

        // A transaction that has reached m_max_send_attempts can be explicitly retried by adding it again.

        it->second.time_added = NodeClock::now();

        it->second.send_statuses.clear();

        it->second.planned_sends = INITIAL_CONNECTION_COUNT;

        it->second.resolved = false;

        return AddResult::Added;

    }

    if (m_transactions.size() >= m_max_transactions) return AddResult::QueueFull;

    m_transactions.try_emplace(tx);

    return AddResult::Added;

}

std::optional<size_t> PrivateBroadcast::Remove(const CTransactionRef& tx)

    EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)

{

    LOCK(m_mutex);

    const auto handle{m_transactions.extract(tx)};

    if (handle) {

        const auto& state{handle.mapped()};

        const size_t planned{std::min(state.planned_sends, m_max_send_attempts)};

        const size_t actual{state.send_statuses.size()};

        return planned > actual ? planned - actual : 0;

    }

    return std::nullopt;

}

bool PrivateBroadcast::MarkResolved(const CTransactionRef& tx)

{

    LOCK(m_mutex);

    const auto it{m_transactions.find(tx)};

    if (it == m_transactions.end()) return false;

    it->second.resolved = true;

    return true;

}

void PrivateBroadcast::NodeDisconnected(NodeId nodeid)

{

    LOCK(m_mutex);

    if (const auto entry{GetSendStatusByNode(nodeid)}) {

        entry->send_status.disconnected = true;

    }

}

bool PrivateBroadcast::TryGrantRetry(const CTransactionRef& tx)

{

    LOCK(m_mutex);

    const auto it{m_transactions.find(tx)};

    if (it == m_transactions.end() ||

        it->second.resolved ||

        IsPending(it->second) ||

        it->second.planned_sends >= m_max_send_attempts) return false;

    ++it->second.planned_sends;

    return true;

}

std::optional<CTransactionRef> PrivateBroadcast::PickTxForSend(const NodeId& will_send_to_nodeid, const CService& will_send_to_address)

    EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)

{

    LOCK(m_mutex);

    if (GetSendStatusByNode(will_send_to_nodeid).has_value()) { // nodeid reuse, shouldn't send >1 tx to a given node

        Assume(false);

        return std::nullopt;

    }

    auto pending_transactions{m_transactions | std::views::filter([this](const auto& entry) { return IsPending(entry.second); })};

    const auto it{std::ranges::max_element(

            pending_transactions,

            [](const auto& a, const auto& b) { return a < b; },

            [](const auto& el) { return DerivePriority(el.second.send_statuses); })};

    if (it != pending_transactions.end()) {

        auto& [tx, state]{*it};

        state.send_statuses.emplace_back(will_send_to_nodeid, will_send_to_address, NodeClock::now());

        return tx;

    }

    return std::nullopt;

}

std::optional<CTransactionRef> PrivateBroadcast::GetTxForNode(const NodeId& nodeid)

    EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)

{

    LOCK(m_mutex);

    const auto tx_and_status{GetSendStatusByNode(nodeid)};

    if (tx_and_status.has_value()) {

        return tx_and_status.value().tx;

    }

    return std::nullopt;

}

void PrivateBroadcast::NodeConfirmedReception(const NodeId& nodeid)

    EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)

{

    LOCK(m_mutex);

    const auto tx_and_status{GetSendStatusByNode(nodeid)};

    if (tx_and_status.has_value()) {

        tx_and_status.value().send_status.confirmed = NodeClock::now();

    }

}

bool PrivateBroadcast::HavePendingTransactions()

    EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)

{

    LOCK(m_mutex);

    return std::ranges::any_of(m_transactions, [this](const auto& entry) { return IsPending(entry.second); });

}

std::vector<CTransactionRef> PrivateBroadcast::GetStale() const

    EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)

{

    LOCK(m_mutex);

    const auto now{NodeClock::now()};

    std::vector<CTransactionRef> stale;

    for (const auto& [tx, state] : m_transactions) {

        if (state.resolved || state.planned_sends >= m_max_send_attempts) continue;

        const Priority p{DerivePriority(state.send_statuses)};

        if (p.num_confirmed == 0) {

            if (state.time_added < now - INITIAL_STALE_DURATION) stale.push_back(tx);

        } else {

            if (p.last_confirmed < now - STALE_DURATION) stale.push_back(tx);

        }

    }

    return stale;

}

std::vector<PrivateBroadcast::TxBroadcastInfo> PrivateBroadcast::GetBroadcastInfo() const

    EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)

{

    LOCK(m_mutex);

    std::vector<TxBroadcastInfo> entries;

    entries.reserve(m_transactions.size());

    for (const auto& [tx, state] : m_transactions) {

        if (state.resolved) continue;

        std::vector<PeerSendInfo> peers;

        peers.reserve(state.send_statuses.size());

        for (const auto& status : state.send_statuses) {

            peers.emplace_back(PeerSendInfo{.address = status.address, .sent = status.picked, .received = status.confirmed});

        }

        const size_t attempts_remaining{m_max_send_attempts - std::min(state.send_statuses.size(), m_max_send_attempts)};

        entries.emplace_back(TxBroadcastInfo{.tx = tx, .time_added = state.time_added, .attempts_remaining = attempts_remaining, .peers = std::move(peers)});

    }

    return entries;

}

bool PrivateBroadcast::IsPending(const TxSendStatus& status) const

{

    // Deliberately ignore resolved so all initially scheduled connections can complete.

    const size_t limit{std::min(status.planned_sends, m_max_send_attempts)};

    return status.send_statuses.size() < limit;

}

PrivateBroadcast::Priority PrivateBroadcast::DerivePriority(const std::vector<SendStatus>& sent_to)

{

    Priority p;

    p.num_picked = sent_to.size();

    for (const auto& send_status : sent_to) {

        p.last_picked = std::max(p.last_picked, send_status.picked);

        if (send_status.confirmed.has_value()) {

            ++p.num_confirmed;

            p.last_confirmed = std::max(p.last_confirmed, send_status.confirmed.value());

        }

    }

    return p;

}

std::optional<PrivateBroadcast::TxAndSendStatusForNode> PrivateBroadcast::GetSendStatusByNode(const NodeId& nodeid)

    EXCLUSIVE_LOCKS_REQUIRED(m_mutex)

{

    AssertLockHeld(m_mutex);

    for (auto& [tx, state] : m_transactions) {

        for (auto& send_status : state.send_statuses) {

            if (send_status.nodeid == nodeid) {

                return TxAndSendStatusForNode{.tx = tx, .send_status = send_status};

            }

        }

    }

    return std::nullopt;

}