#include "data/LedgerCache.hpp"

#include "data/Types.hpp"
#include "data/impl/LedgerCacheFile.hpp"
#include "etl/Models.hpp"
#include "util/Assert.hpp"

#include <xrpl/basics/base_uint.h>

#include <cstddef>
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <map>
#include <mutex>
#include <optional>
#include <shared_mutex>
#include <string>
#include <utility>
#include <vector>

namespace data {

uint32_t
LedgerCache::latestLedgerSequence() const
{
    std::shared_lock const lck{mtx_};
    return latestSeq_;
}

void
LedgerCache::waitUntilCacheContainsSeq(uint32_t seq)
{
    if (disabled_)
        return;

    std::unique_lock lock(mtx_);
    cv_.wait(lock, [this, seq] { return latestSeq_ >= seq; });
    return;
}

void
LedgerCache::update(std::vector<LedgerObject> const& objs, uint32_t seq, bool isBackground)
{
    if (disabled_)
        return;

    {
        std::scoped_lock const lck{mtx_};
        if (seq > latestSeq_) {
            ASSERT(
                seq == latestSeq_ + 1 || latestSeq_ == 0,
                "New sequence must be either next or first. seq = {}, latestSeq_ = {}",
                seq,
                latestSeq_
            );
            latestSeq_ = seq;
        }
        for (auto const& obj : objs) {
            if (!obj.blob.empty()) {
                if (isBackground && deletes_.contains(obj.key))
                    continue;

                auto& e = map_[obj.key];
                if (seq > e.seq) {
                    e = {.seq = seq, .blob = obj.blob};
                }
            } else {
                map_.erase(obj.key);
                if (!full_ && !isBackground)
                    deletes_.insert(obj.key);
            }
        }
        cv_.notify_all();
    }
}

void
LedgerCache::update(std::vector<etl::model::Object> const& objs, uint32_t seq)
{
    if (disabled_)
        return;

    std::scoped_lock const lck{mtx_};
    if (seq > latestSeq_) {
        ASSERT(
            seq == latestSeq_ + 1 || latestSeq_ == 0,
            "New sequence must be either next or first. seq = {}, latestSeq_ = {}",
            seq,
            latestSeq_
        );
        latestSeq_ = seq;
    }

    deleted_.clear();  // previous update's deletes no longer needed

    for (auto const& obj : objs) {
        if (!obj.data.empty()) {
            auto& e = map_[obj.key];
            if (seq > e.seq)
                e = {.seq = seq, .blob = obj.data};
        } else {
            if (map_.contains(obj.key))
                deleted_[obj.key] = map_[obj.key];

            map_.erase(obj.key);
            if (!full_)
                deletes_.insert(obj.key);
        }
    }
    cv_.notify_all();
}

std::optional<LedgerObject>
LedgerCache::getSuccessor(ripple::uint256 const& key, uint32_t seq) const
{
    if (disabled_ or not full_)
        return {};

    std::shared_lock const lck{mtx_};
    ++successorReqCounter_.get();
    if (seq != latestSeq_)
        return {};
    auto e = map_.upper_bound(key);
    if (e == map_.end())
        return {};
    ++successorHitCounter_.get();
    return {{.key = e->first, .blob = e->second.blob}};
}

std::optional<LedgerObject>
LedgerCache::getPredecessor(ripple::uint256 const& key, uint32_t seq) const
{
    if (disabled_ or not full_)
        return {};

    std::shared_lock const lck{mtx_};
    if (seq != latestSeq_)
        return {};
    auto e = map_.lower_bound(key);
    if (e == map_.begin())
        return {};
    --e;
    return {{.key = e->first, .blob = e->second.blob}};
}

std::optional<Blob>
LedgerCache::get(ripple::uint256 const& key, uint32_t seq) const
{
    if (disabled_)
        return {};

    std::shared_lock const lck{mtx_};
    if (seq > latestSeq_)
        return {};
    ++objectReqCounter_.get();
    auto e = map_.find(key);
    if (e == map_.end())
        return {};
    if (seq < e->second.seq)
        return {};
    ++objectHitCounter_.get();
    return {e->second.blob};
}

std::optional<Blob>
LedgerCache::getDeleted(ripple::uint256 const& key, uint32_t seq) const
{
    if (disabled_)
        return std::nullopt;

    std::shared_lock const lck{mtx_};
    if (seq > latestSeq_)
        return std::nullopt;

    ++objectReqCounter_.get();

    auto e = deleted_.find(key);
    if (e == deleted_.end())
        return std::nullopt;

    if (seq < e->second.seq)
        return std::nullopt;

    ++objectHitCounter_.get();
    return {e->second.blob};
}

void
LedgerCache::setDisabled()
{
    disabled_ = true;
}

bool
LedgerCache::isDisabled() const
{
    return disabled_;
}

void
LedgerCache::setFull()
{
    if (disabled_)
        return;

    full_ = true;
    isCurrentlyLoading_ = false;
    std::scoped_lock const lck{mtx_};
    deletes_.clear();
}

bool
LedgerCache::isFull() const
{
    return full_;
}

size_t
LedgerCache::size() const
{
    std::shared_lock const lck{mtx_};
    return map_.size();
}

float
LedgerCache::getObjectHitRate() const
{
    if (objectReqCounter_.get().value() == 0u)
        return 1;
    return static_cast<float>(objectHitCounter_.get().value()) / objectReqCounter_.get().value();
}

float
LedgerCache::getSuccessorHitRate() const
{
    if (successorReqCounter_.get().value() == 0u)
        return 1;
    return static_cast<float>(successorHitCounter_.get().value()) /
        successorReqCounter_.get().value();
}

std::expected<void, std::string>
LedgerCache::saveToFile(std::string const& path) const
{
    if (not isFull()) {
        return std::unexpected{"Ledger cache is not full"};
    }

    impl::LedgerCacheFile file{path};
    std::shared_lock const lock{mtx_};
    impl::LedgerCacheFile::DataView const data{
        .latestSeq = latestSeq_, .map = map_, .deleted = deleted_
    };
    return file.write(data);
}

std::expected<void, std::string>
LedgerCache::loadFromFile(std::string const& path, uint32_t minLatestSequence)
{
    impl::LedgerCacheFile file{path};
    auto data = file.read(minLatestSequence);
    if (not data.has_value()) {
        return std::unexpected(std::move(data).error());
    }
    auto [latestSeq, map, deleted] = std::move(data).value();
    std::unique_lock const lock{mtx_};
    latestSeq_ = latestSeq;
    map_ = std::move(map);
    deleted_ = std::move(deleted);
    full_ = true;
    return {};
}

void
LedgerCache::startLoading()
{
    isCurrentlyLoading_ = true;
}

bool
LedgerCache::isCurrentlyLoading() const
{
    return isCurrentlyLoading_;
}

}  // namespace data