/*
 *
 * Modified by ScyllaDB
 * Copyright (C) 2015-present ScyllaDB
 */

/*
 * SPDX-License-Identifier: (LicenseRef-ScyllaDB-Source-Available-1.0 and Apache-2.0)
 */

#include "dht/range_streamer.hh"
#include "replica/database.hh"
#include "gms/gossiper.hh"
#include "utils/log.hh"
#include "streaming/stream_plan.hh"
#include "db/config.hh"
#include <fmt/ranges.h>
#include <seastar/core/semaphore.hh>
#include <seastar/core/sleep.hh>
#include "utils/assert.hh"
#include "utils/stall_free.hh"

namespace dht {

static logging::logger logger("range_streamer");

using inet_address = gms::inet_address;

std::unordered_map<locator::host_id, dht::token_range_vector> range_streamer::get_range_fetch_map(
        const std::unordered_map<dht::token_range, std::vector<locator::host_id>>& ranges_with_sources,
        const std::unordered_set<std::unique_ptr<i_source_filter>>& source_filters, const sstring& keyspace) {
    std::unordered_map<locator::host_id, dht::token_range_vector> range_fetch_map_map;
    const auto& topo = _token_metadata_ptr->get_topology();
    for (const auto& x : ranges_with_sources) {
        const dht::token_range& range_ = x.first;
        const std::vector<locator::host_id>& addresses = x.second;
        bool found_source = false;
        for (const auto& address : addresses) {
            if (topo.is_me(address)) {
                // If localhost is a source, we have found one, but we don't add it to the map to avoid streaming locally
                found_source = true;
                continue;
            }

            auto filtered = false;
            for (const auto& filter : source_filters) {
                if (!filter->should_include(get_token_metadata().get_topology(), address)) {
                    filtered = true;
                    break;
                }
            }

            if (filtered) {
                logger.debug("In get_range_fetch_map, keyspace = {}, endpoint= {} is filtered", keyspace, address);
                continue;
            }

            range_fetch_map_map[address].push_back(range_);
            found_source = true;
            break; // ensure we only stream from one other node for each range
        }

        if (!found_source) {
            auto& ks = _db.local().find_keyspace(keyspace);
            auto rf = ks.get_static_effective_replication_map()->get_replication_factor();
            // When a replacing node replaces a dead node with keyspace of RF
            // 1, it is expected that replacing node could not find a peer node
            // that contains data to stream from.
            if (_reason == streaming::stream_reason::replace && rf == 1) {
                logger.warn("Unable to find sufficient sources to stream range {} for keyspace {} with RF = 1 for replace operation", range_, keyspace);
            } else {
                throw std::runtime_error(format("unable to find sufficient sources for streaming range {} in keyspace {}", range_, keyspace));
            }
        }
    }

    return range_fetch_map_map;
}

// Must be called from a seastar thread
std::unordered_map<dht::token_range, std::vector<locator::host_id>> range_streamer::get_all_ranges_with_sources_for(
        const sstring& keyspace_name, const locator::vnode_effective_replication_map* erm, dht::token_range_vector desired_ranges) {
    logger.debug("{} ks={}", __func__, keyspace_name);

    auto range_addresses = erm->get_range_host_ids().get();

    logger.debug("keyspace={}, desired_ranges.size={}, range_addresses.size={}", keyspace_name, desired_ranges.size(), range_addresses.size());

    std::unordered_map<dht::token_range, std::vector<locator::host_id>> range_sources;
    for (auto& desired_range : desired_ranges) {
        auto found = false;
        for (auto& x : range_addresses) {
            if (need_preempt()) {
                seastar::thread::yield();
            }
            const wrapping_interval<token>& src_range = x.first;
            if (src_range.contains(desired_range, dht::token_comparator{})) {
                host_id_vector_replica_set preferred(x.second.begin(), x.second.end());
                get_token_metadata().get_topology().sort_by_proximity(_address, preferred);
                for (locator::host_id& p : preferred) {
                    range_sources[desired_range].push_back(p);
                }
                found = true;
            }
        }

        if (!found) {
            throw std::runtime_error(format("No sources found for {}", desired_range));
        }
    }

    return range_sources;
}

// Must be called from a seastar thread
std::unordered_map<dht::token_range, std::vector<locator::host_id>> range_streamer::get_all_ranges_with_strict_sources_for(
        const sstring& keyspace_name, const locator::vnode_effective_replication_map* erm, dht::token_range_vector desired_ranges, gms::gossiper& gossiper) {
    logger.debug("{} ks={}", __func__, keyspace_name);
    SCYLLA_ASSERT(_tokens.empty() == false);

    auto& strat = erm->get_replication_strategy();

    // Active ranges
    auto metadata_clone = get_token_metadata().clone_only_token_map().get();
    auto range_addresses = strat.get_range_host_ids(metadata_clone).get();

    // Pending ranges
    metadata_clone.update_topology(_address, _dr);
    metadata_clone.update_normal_tokens(_tokens, _address).get();
    auto pending_range_addresses = strat.get_range_host_ids(metadata_clone).get();
    metadata_clone.clear_gently().get();

    // Collects the source that will have its range moved to the new node
    std::unordered_map<dht::token_range, std::vector<locator::host_id>> range_sources;

    logger.debug("keyspace={}, desired_ranges.size={}, range_addresses.size={}", keyspace_name, desired_ranges.size(), range_addresses.size());

    for (auto& desired_range : desired_ranges) {
        for (auto& x : range_addresses) {
            const wrapping_interval<token>& src_range = x.first;
            if (need_preempt()) {
                seastar::thread::yield();
            }
            if (src_range.contains(desired_range, dht::token_comparator{})) {
                std::vector<locator::host_id> old_endpoints(x.second.begin(), x.second.end());
                auto it = pending_range_addresses.find(desired_range);
                if (it == pending_range_addresses.end()) {
                    throw std::runtime_error(format("Can not find desired_range = {} in pending_range_addresses", desired_range));
                }

                std::unordered_set<locator::host_id> new_endpoints(it->second.begin(), it->second.end());
                // Due to CASSANDRA-5953 we can have a higher RF then we have endpoints.
                // So we need to be careful to only be strict when endpoints == RF
                if (old_endpoints.size() == erm->get_replication_factor()) {
                    std::erase_if(old_endpoints, [&new_endpoints](locator::host_id ep) {
                        return new_endpoints.contains(ep);
                    });
                    if (old_endpoints.size() != 1) {
                        throw std::runtime_error(format("Expected 1 endpoint but found {:d}", old_endpoints.size()));
                    }
                }
                range_sources[desired_range].push_back(old_endpoints.front());
            }
        }

        // Validate
        auto it = range_sources.find(desired_range);
        if (it == range_sources.end()) {
            throw std::runtime_error(format("No sources found for {}", desired_range));
        }

        if (it->second.size() != 1) {
            throw std::runtime_error(format("Multiple endpoints found for {}", desired_range));
        }

        locator::host_id source_id = it->second.front();

        if (gossiper.is_enabled() && !gossiper.is_alive(source_id)) {
            throw std::runtime_error(format("A node required to move the data consistently is down ({}).  If you wish to move the data from a potentially "
                                            "inconsistent replica, restart the node with consistent_rangemovement=false",
                    source_id));
        }
    }

    return range_sources;
}

bool range_streamer::use_strict_sources_for_ranges(const sstring& keyspace_name, const locator::effective_replication_map& erm) {
    auto rf = erm.get_replication_factor();
    auto nr_nodes_in_ring = get_token_metadata().get_normal_token_owners().size();
    bool everywhere_topology = erm.get_replication_strategy().get_type() == locator::replication_strategy_type::everywhere_topology;
    // Use strict when number of nodes in the ring is equal or more than RF
    auto strict = _db.local().get_config().consistent_rangemovement() && !_tokens.empty() && !everywhere_topology && nr_nodes_in_ring >= rf;
    logger.debug("use_strict_sources_for_ranges: ks={}, nr_nodes_in_ring={}, rf={}, strict={}", keyspace_name, nr_nodes_in_ring, rf, strict);
    return strict;
}

void range_streamer::add_tx_ranges(const sstring& keyspace_name, std::unordered_map<locator::host_id, dht::token_range_vector> ranges_per_endpoint) {
    if (_nr_rx_added) {
        throw std::runtime_error("Mixed sending and receiving is not supported");
    }
    _nr_tx_added++;
    _to_stream.emplace(keyspace_name, std::move(ranges_per_endpoint));
}

void range_streamer::add_rx_ranges(const sstring& keyspace_name, std::unordered_map<locator::host_id, dht::token_range_vector> ranges_per_endpoint) {
    if (_nr_tx_added) {
        throw std::runtime_error("Mixed sending and receiving is not supported");
    }
    _nr_rx_added++;
    _to_stream.emplace(keyspace_name, std::move(ranges_per_endpoint));
}

// TODO: This is the legacy range_streamer interface, it is add_rx_ranges which adds rx ranges.
future<> range_streamer::add_ranges(const sstring& keyspace_name, locator::static_effective_replication_map_ptr erm, dht::token_range_vector ranges,
        gms::gossiper& gossiper, bool is_replacing) {
    return seastar::async([this, keyspace_name, ermp = std::move(erm), ranges = std::move(ranges), &gossiper, is_replacing]() mutable {
        if (_nr_tx_added) {
            throw std::runtime_error("Mixed sending and receiving is not supported");
        }
        _nr_rx_added++;
        auto erm = ermp->maybe_as_vnode_effective_replication_map();
        SCYLLA_ASSERT(erm != nullptr);
        auto ranges_for_keyspace = !is_replacing && use_strict_sources_for_ranges(keyspace_name, *erm)
                                           ? get_all_ranges_with_strict_sources_for(keyspace_name, erm, std::move(ranges), gossiper)
                                           : get_all_ranges_with_sources_for(keyspace_name, erm, std::move(ranges));

        if (logger.is_enabled(logging::log_level::debug)) {
            for (auto& x : ranges_for_keyspace) {
                logger.debug("{} : keyspace {} range {} exists on {}", _description, keyspace_name, x.first, x.second);
            }
        }

        std::unordered_map<locator::host_id, dht::token_range_vector> range_fetch_map =
                get_range_fetch_map(ranges_for_keyspace, _source_filters, keyspace_name);
        utils::clear_gently(ranges_for_keyspace).get();

        if (logger.is_enabled(logging::log_level::debug)) {
            for (auto& x : range_fetch_map) {
                logger.debug("{} : keyspace={}, ranges={} from source={}, range_size={}", _description, keyspace_name, x.second, x.first, x.second.size());
            }
        }
        _to_stream.emplace(keyspace_name, std::move(range_fetch_map));
    });
}

future<> range_streamer::stream_async() {
    _nr_ranges_remaining = nr_ranges_to_stream();
    _nr_total_ranges = _nr_ranges_remaining;
    _token_metadata_ptr = nullptr;
    logger.info("{} starts, nr_ranges_remaining={}", _description, _nr_ranges_remaining);
    auto start = lowres_clock::now();
    return do_for_each(_to_stream, [this, description = _description](auto& stream) {
        const auto& keyspace = stream.first;
        auto& ip_range_vec = stream.second;
        auto ips = ip_range_vec | std::views::keys | std::ranges::to<std::list>();
        // Fetch from or send to peer node in parallel
        logger.info("{} with {} for keyspace={} started, nodes_to_stream={}", description, ips, keyspace, ip_range_vec.size());
        return parallel_for_each(ip_range_vec, [this, description, keyspace](auto& ip_range) {
            auto& source = ip_range.first;
            auto& range_vec = ip_range.second;
            return seastar::with_semaphore(_limiter, 1, [this, description, keyspace, source, &range_vec]() mutable {
                return seastar::async([this, description, keyspace, source, &range_vec]() mutable {
                    // TODO: It is better to use fiber instead of thread here because
                    // creating a thread per peer can be some memory in a large cluster.
                    auto start_time = lowres_clock::now();
                    unsigned sp_index = 0;
                    unsigned nr_ranges_streamed = 0;
                    size_t nr_ranges_total = range_vec.size();
                    auto do_streaming = [&](dht::token_range_vector&& ranges_to_stream) {
                        auto sp = stream_plan(_stream_manager.local(), format("{}-{}-index-{:d}", description, keyspace, sp_index++), _reason, _topo_guard);
                        auto abort_listener = _abort_source.subscribe([&]() noexcept {
                            sp.abort();
                        });
                        _abort_source.check();
                        logger.info("{} with {} for keyspace={}, streaming [{}, {}) out of {} ranges", description, source, keyspace, nr_ranges_streamed,
                                nr_ranges_streamed + ranges_to_stream.size(), nr_ranges_total);
                        auto ranges_streamed = ranges_to_stream.size();
                        if (_nr_rx_added) {
                            sp.request_ranges(source, keyspace, std::move(ranges_to_stream), _tables);
                        } else if (_nr_tx_added) {
                            sp.transfer_ranges(source, keyspace, std::move(ranges_to_stream), _tables);
                        }
                        sp.execute().discard_result().get();
                        // Update finished percentage
                        nr_ranges_streamed += ranges_streamed;
                        _nr_ranges_remaining -= ranges_streamed;
                        float percentage = _nr_total_ranges == 0 ? 1 : (_nr_total_ranges - _nr_ranges_remaining) / (float)_nr_total_ranges;
                        _stream_manager.local().update_finished_percentage(_reason, percentage);
                        logger.info("Finished {} out of {} ranges for {}, finished percentage={}", _nr_total_ranges - _nr_ranges_remaining, _nr_total_ranges,
                                _reason, percentage);
                    };
                    dht::token_range_vector ranges_to_stream;
                    try {
                        for (auto it = range_vec.begin(); it < range_vec.end();) {
                            ranges_to_stream.push_back(*it);
                            ++it;
                            auto fraction = _db.local().get_config().stream_plan_ranges_fraction();
                            size_t nr_ranges_per_stream_plan = nr_ranges_total * fraction;
                            if (ranges_to_stream.size() < nr_ranges_per_stream_plan) {
                                continue;
                            } else {
                                do_streaming(std::exchange(ranges_to_stream, {}));
                                it = range_vec.erase(range_vec.begin(), it);
                            }
                        }
                        if (ranges_to_stream.size() > 0) {
                            do_streaming(std::exchange(ranges_to_stream, {}));
                            range_vec.clear();
                        }
                    } catch (...) {
                        auto t = std::chrono::duration_cast<std::chrono::duration<float>>(lowres_clock::now() - start_time).count();
                        logger.warn("{} with {} for keyspace={} failed, took {} seconds: {}", description, source, keyspace, t, std::current_exception());
                        throw;
                    }
                    auto t = std::chrono::duration_cast<std::chrono::duration<float>>(lowres_clock::now() - start_time).count();
                    logger.info("{} with {} for keyspace={} succeeded, took {} seconds", description, source, keyspace, t);
                });
            });
        });
    }).finally([this, start] {
        auto t = std::chrono::duration_cast<std::chrono::seconds>(lowres_clock::now() - start).count();
        auto nr_ranges_remaining = nr_ranges_to_stream();
        if (nr_ranges_remaining) {
            logger.warn("{} failed, took {} seconds, nr_ranges_remaining={}", _description, t, nr_ranges_remaining);
        } else {
            logger.info("{} succeeded, took {} seconds, nr_ranges_remaining={}", _description, t, nr_ranges_remaining);
        }
    });
}

size_t range_streamer::nr_ranges_to_stream() {
    size_t nr_ranges_remaining = 0;
    for (auto& fetch : _to_stream) {
        const auto& keyspace = fetch.first;
        auto& ip_range_vec = fetch.second;
        for (auto& ip_range : ip_range_vec) {
            auto& source = ip_range.first;
            auto& range_vec = ip_range.second;
            nr_ranges_remaining += range_vec.size();
            logger.debug("Remaining: keyspace={}, source={}, ranges={}", keyspace, source, range_vec);
        }
    }
    return nr_ranges_remaining;
}

} // namespace dht