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

/*
 * SPDX-License-Identifier: AGPL-3.0-or-later
 */

#pragma once

#include <boost/icl/interval.hpp>
#include <boost/icl/interval_map.hpp>

#include <seastar/core/semaphore.hh>
#include <seastar/core/sstring.hh>
#include <seastar/core/shared_ptr.hh>
#include <seastar/core/gate.hh>
#include <seastar/core/shared_future.hh>
#include <seastar/core/rwlock.hh>
#include <seastar/core/metrics_registration.hh>
#include <seastar/core/scheduling.hh>
#include <seastar/core/abort_source.hh>
#include <seastar/core/condition-variable.hh>
#include "log.hh"
#include "utils/exponential_backoff_retry.hh"
#include "utils/updateable_value.hh"
#include "utils/serialized_action.hh"
#include <vector>
#include <list>
#include <functional>
#include <algorithm>
#include "compaction.hh"
#include "compaction_weight_registration.hh"
#include "compaction_backlog_manager.hh"
#include "strategy_control.hh"
#include "backlog_controller.hh"
#include "seastarx.hh"
#include "sstables/exceptions.hh"
#include "tombstone_gc.hh"

namespace db {
class system_keyspace;
}

class compacting_sstable_registration;

class repair_history_map {
public:
    boost::icl::interval_map<dht::token, gc_clock::time_point, boost::icl::partial_absorber, std::less, boost::icl::inplace_max> map;
};

// Compaction manager provides facilities to submit and track compaction jobs on
// behalf of existing tables.
class compaction_manager {
public:
    using compaction_stats_opt = std::optional<sstables::compaction_stats>;
    struct stats {
        int64_t pending_tasks = 0;
        int64_t completed_tasks = 0;
        uint64_t active_tasks = 0; // Number of compaction going on.
        int64_t errors = 0;
    };
    using scheduling_group = backlog_controller::scheduling_group;
    struct config {
        scheduling_group compaction_sched_group;
        scheduling_group maintenance_sched_group;
        size_t available_memory = 0;
        utils::updateable_value<float> static_shares = utils::updateable_value<float>(0);
        utils::updateable_value<uint32_t> throughput_mb_per_sec = utils::updateable_value<uint32_t>(0);
    };
private:
    struct compaction_state {
        // Used both by compaction tasks that refer to the compaction_state
        // and by any function running under run_with_compaction_disabled().
        seastar::gate gate;

        // Prevents table from running major and minor compaction at the same time.
        rwlock lock;

        // Raised by any function running under run_with_compaction_disabled();
        long compaction_disabled_counter = 0;

        // Signaled whenever a compaction task completes.
        condition_variable compaction_done;

        compaction_backlog_tracker backlog_tracker;

        explicit compaction_state(table_state& t);
        compaction_state(compaction_state&&) = default;
        ~compaction_state();

        bool compaction_disabled() const noexcept {
            return compaction_disabled_counter > 0;
        }
    };

public:
    class can_purge_tombstones_tag;
    using can_purge_tombstones = bool_class<can_purge_tombstones_tag>;

    class task {
    public:
        enum class state {
            none,       // initial and final state
            pending,    // task is blocked on a lock, may alternate with active
                        // counted in compaction_manager::stats::pending_tasks
            active,     // task initiated active compaction, may alternate with pending
                        // counted in compaction_manager::stats::active_tasks
            done,       // task completed successfully (may transition only to state::none)
                        // counted in compaction_manager::stats::completed_tasks
            postponed,  // task was postponed (may transition only to state::none)
                        // represented by the postponed_compactions metric
            failed,     // task failed (may transition only to state::none)
                        // counted in compaction_manager::stats::errors
        };
        static std::string_view to_string(state);
    protected:
        compaction_manager& _cm;
        compaction::table_state* _compacting_table = nullptr;
        compaction_state& _compaction_state;
        sstables::compaction_data _compaction_data;
        state _state = state::none;

    private:
        shared_future<compaction_stats_opt> _compaction_done = make_ready_future<compaction_stats_opt>();
        exponential_backoff_retry _compaction_retry = exponential_backoff_retry(std::chrono::seconds(5), std::chrono::seconds(300));
        sstables::compaction_type _type;
        sstables::run_id _output_run_identifier;
        gate::holder _gate_holder;
        sstring _description;

    public:
        explicit task(compaction_manager& mgr, compaction::table_state* t, sstables::compaction_type type, sstring desc);

        task(task&&) = delete;
        task(const task&) = delete;

        virtual ~task();

    protected:
        virtual future<compaction_stats_opt> do_run() = 0;

        using throw_if_stopping = bool_class<struct throw_if_stopping_tag>;

        state switch_state(state new_state);

        future<semaphore_units<named_semaphore_exception_factory>> acquire_semaphore(named_semaphore& sem, size_t units = 1);

        // Return true if the task isn't stopped
        // and the compaction manager allows proceeding.
        inline bool can_proceed(throw_if_stopping do_throw_if_stopping = throw_if_stopping::no) const;
        void setup_new_compaction(sstables::run_id output_run_id = sstables::run_id::create_null_id());
        void finish_compaction(state finish_state = state::done) noexcept;

        // Compaction manager stop itself if it finds an storage I/O error which results in
        // stop of transportation services. It cannot make progress anyway.
        // Returns exception if error is judged fatal, and compaction task must be stopped,
        // otherwise, returns stop_iteration::no after sleep for exponential retry.
        future<stop_iteration> maybe_retry(std::exception_ptr err, bool throw_on_abort = false);

        // Compacts set of SSTables according to the descriptor.
        using release_exhausted_func_t = std::function<void(const std::vector<sstables::shared_sstable>& exhausted_sstables)>;
        future<sstables::compaction_result> compact_sstables_and_update_history(sstables::compaction_descriptor descriptor, sstables::compaction_data& cdata, release_exhausted_func_t release_exhausted,
                                  can_purge_tombstones can_purge = can_purge_tombstones::yes);
        future<sstables::compaction_result> compact_sstables(sstables::compaction_descriptor descriptor, sstables::compaction_data& cdata, release_exhausted_func_t release_exhausted,
                                  can_purge_tombstones can_purge = can_purge_tombstones::yes);
        future<> update_history(compaction::table_state& t, const sstables::compaction_result& res, const sstables::compaction_data& cdata);
        bool should_update_history(sstables::compaction_type ct) {
            return ct == sstables::compaction_type::Compaction;
        }
    public:
        future<compaction_stats_opt> run() noexcept;

        const compaction::table_state* compacting_table() const noexcept {
            return _compacting_table;
        }

        sstables::compaction_type type() const noexcept {
            return _type;
        }

        bool compaction_running() const noexcept {
            return _state == state::active;
        }

        const sstables::compaction_data& compaction_data() const noexcept {
            return _compaction_data;
        }

        sstables::compaction_data& compaction_data() noexcept {
            return _compaction_data;
        }

        bool generating_output_run() const noexcept {
            return compaction_running() && _output_run_identifier;
        }
        const sstables::run_id& output_run_id() const noexcept {
            return _output_run_identifier;
        }

        const sstring& description() const noexcept {
            return _description;
        }

        future<compaction_stats_opt> compaction_done() noexcept {
            return _compaction_done.get_future();
        }

        bool stopping() const noexcept {
            return _compaction_data.abort.abort_requested();
        }

        void stop(sstring reason) noexcept;

        sstables::compaction_stopped_exception make_compaction_stopped_exception() const;

        std::string describe() const;
    };

    class sstables_task : public task {
    protected:
        std::vector<sstables::shared_sstable> _sstables;

        void set_sstables(std::vector<sstables::shared_sstable> new_sstables);
        sstables::shared_sstable consume_sstable();

    public:
        explicit sstables_task(compaction_manager& mgr, compaction::table_state* t, sstables::compaction_type compaction_type, sstring desc, std::vector<sstables::shared_sstable> sstables)
            : task(mgr, t, compaction_type, std::move(desc))
        {
            set_sstables(std::move(sstables));
        }

        virtual ~sstables_task();
    };

    class major_compaction_task;
    class custom_compaction_task;
    class regular_compaction_task;
    class offstrategy_compaction_task;
    class rewrite_sstables_compaction_task;
    class cleanup_sstables_compaction_task;
    class validate_sstables_compaction_task;
    class compaction_manager_test_task;

private:
    // compaction manager may have N fibers to allow parallel compaction per shard.
    std::list<shared_ptr<task>> _tasks;

    // Possible states in which the compaction manager can be found.
    //
    // none: started, but not yet enabled. Once the compaction manager moves out of "none", it can
    //       never legally move back
    // stopped: stop() was called. The compaction_manager will never be enabled or disabled again
    //          and can no longer be used (although it is possible to still grab metrics, stats,
    //          etc)
    // enabled: accepting compactions
    // disabled: not accepting compactions
    //
    // Moving the compaction manager to and from enabled and disable states is legal, as many times
    // as necessary.
    enum class state { none, stopped, disabled, enabled };
    state _state = state::none;

    std::optional<future<>> _stop_future;

    stats _stats;
    seastar::metrics::metric_groups _metrics;
    double _last_backlog = 0.0f;

    // Store sstables that are being compacted at the moment. That's needed to prevent
    // a sstable from being compacted twice.
    std::unordered_set<sstables::shared_sstable> _compacting_sstables;

    future<> _waiting_reevalution = make_ready_future<>();
    condition_variable _postponed_reevaluation;
    // tables that wait for compaction but had its submission postponed due to ongoing compaction.
    std::unordered_set<compaction::table_state*> _postponed;
    // tracks taken weights of ongoing compactions, only one compaction per weight is allowed.
    // weight is value assigned to a compaction job that is log base N of total size of all input sstables.
    std::unordered_set<int> _weight_tracker;

    std::unordered_map<compaction::table_state*, compaction_state> _compaction_state;

    // Purpose is to serialize all maintenance (non regular) compaction activity to reduce aggressiveness and space requirement.
    // If the operation must be serialized with regular, then the per-table write lock must be taken.
    seastar::named_semaphore _maintenance_ops_sem = {1, named_semaphore_exception_factory{"maintenance operation"}};

    // This semaphore ensures that off-strategy compaction will be serialized for
    // all tables, to limit space requirement and protect against candidates
    // being picked more than once.
    seastar::named_semaphore _off_strategy_sem = {1, named_semaphore_exception_factory{"off-strategy compaction"}};

    seastar::shared_ptr<db::system_keyspace> _sys_ks;

    std::function<void()> compaction_submission_callback();
    // all registered tables are reevaluated at a constant interval.
    // Submission is a NO-OP when there's nothing to do, so it's fine to call it regularly.
    timer<lowres_clock> _compaction_submission_timer = timer<lowres_clock>(compaction_submission_callback());
    static constexpr std::chrono::seconds periodic_compaction_submission_interval() { return std::chrono::seconds(3600); }

    config _cfg;
    compaction_controller _compaction_controller;
    compaction_backlog_manager _backlog_manager;
    optimized_optional<abort_source::subscription> _early_abort_subscription;
    serialized_action _throughput_updater;
    std::optional<utils::observer<uint32_t>> _throughput_option_observer;
    serialized_action _update_compaction_static_shares_action;
    utils::observer<float> _compaction_static_shares_observer;
    uint64_t _validation_errors = 0;

    class strategy_control;
    std::unique_ptr<strategy_control> _strategy_control;

    per_table_history_maps _repair_history_maps;
    tombstone_gc_state _tombstone_gc_state;
private:
    future<compaction_stats_opt> perform_task(shared_ptr<task>);

    future<> stop_tasks(std::vector<shared_ptr<task>> tasks, sstring reason);
    future<> update_throughput(uint32_t value_mbs);

    // Return the largest fan-in of currently running compactions
    unsigned current_compaction_fan_in_threshold() const;

    // Return true if compaction can be initiated
    bool can_register_compaction(compaction::table_state& t, int weight, unsigned fan_in) const;
    // Register weight for a table. Do that only if can_register_weight()
    // returned true.
    void register_weight(int weight);
    // Deregister weight for a table.
    void deregister_weight(int weight);

    // Get candidates for compaction strategy, which are all sstables but the ones being compacted.
    std::vector<sstables::shared_sstable> get_candidates(compaction::table_state& t);

    template <typename Iterator, typename Sentinel>
    requires std::same_as<Sentinel, Iterator> || std::sentinel_for<Sentinel, Iterator>
    void register_compacting_sstables(Iterator first, Sentinel last);

    template <typename Iterator, typename Sentinel>
    requires std::same_as<Sentinel, Iterator> || std::sentinel_for<Sentinel, Iterator>
    void deregister_compacting_sstables(Iterator first, Sentinel last);

    // gets the table's compaction state
    // throws std::out_of_range exception if not found.
    compaction_state& get_compaction_state(compaction::table_state* t);

    // Return true if compaction manager is enabled and
    // table still exists and compaction is not disabled for the table.
    inline bool can_proceed(compaction::table_state* t) const;

    void postponed_compactions_reevaluation();
    void reevaluate_postponed_compactions() noexcept;
    // Postpone compaction for a table that couldn't be executed due to ongoing
    // similar-sized compaction.
    void postpone_compaction_for_table(compaction::table_state* t);

    future<compaction_stats_opt> perform_sstable_scrub_validate_mode(compaction::table_state& t);
    future<> update_static_shares(float shares);

    using get_candidates_func = std::function<future<std::vector<sstables::shared_sstable>>()>;

    // Guarantees that a maintenance task, e.g. cleanup, will be performed on all files available at the time
    // by retrieving set of candidates only after all compactions for table T were stopped, if any.
    template<typename TaskType, typename... Args>
    requires std::derived_from<TaskType, task>
    future<compaction_stats_opt> perform_task_on_all_files(compaction::table_state& t, sstables::compaction_type_options options, get_candidates_func, Args... args);

    future<compaction_stats_opt> rewrite_sstables(compaction::table_state& t, sstables::compaction_type_options options, get_candidates_func, can_purge_tombstones can_purge = can_purge_tombstones::yes);

    // Stop all fibers, without waiting. Safe to be called multiple times.
    void do_stop() noexcept;
    future<> really_do_stop();

    // Propagate replacement of sstables to all ongoing compaction of a given table
    void propagate_replacement(compaction::table_state& t, const std::vector<sstables::shared_sstable>& removed, const std::vector<sstables::shared_sstable>& added);

    // This constructor is suposed to only be used for testing so lets be more explicit
    // about invoking it. Ref #10146
    compaction_manager();
public:
    compaction_manager(config cfg, abort_source& as);
    ~compaction_manager();
    class for_testing_tag{};
    // An inline constructor for testing
    compaction_manager(for_testing_tag) : compaction_manager() {}

    const scheduling_group& compaction_sg() const noexcept {
        return _cfg.compaction_sched_group;
    }

    const scheduling_group& maintenance_sg() const noexcept {
        return _cfg.maintenance_sched_group;
    }

    size_t available_memory() const noexcept {
        return _cfg.available_memory;
    }

    float static_shares() const noexcept {
        return _cfg.static_shares.get();
    }

    uint32_t throughput_mbs() const noexcept {
        return _cfg.throughput_mb_per_sec.get();
    }

    void register_metrics();

    // enable the compaction manager.
    void enable();

    // Stop all fibers. Ongoing compactions will be waited. Should only be called
    // once, from main teardown path.
    future<> stop();

    // cancels all running compactions and moves the compaction manager into disabled state.
    // The compaction manager is still alive after drain but it will not accept new compactions
    // unless it is moved back to enabled state.
    future<> drain();

    // Submit a table to be compacted.
    void submit(compaction::table_state& t);

    // Can regular compaction be performed in the given table
    bool can_perform_regular_compaction(compaction::table_state& t);

    // Maybe wait before adding more sstables
    // if there are too many sstables.
    future<> maybe_wait_for_sstable_count_reduction(compaction::table_state& t);

    // Submit a table to be off-strategy compacted.
    // Returns true iff off-strategy compaction was required and performed.
    future<bool> perform_offstrategy(compaction::table_state& t);

    // Submit a table to be cleaned up and wait for its termination.
    //
    // Performs a cleanup on each sstable of the table, excluding
    // those ones that are irrelevant to this node or being compacted.
    // Cleanup is about discarding keys that are no longer relevant for a
    // given sstable, e.g. after node loses part of its token range because
    // of a newly added node.
    future<> perform_cleanup(owned_ranges_ptr sorted_owned_ranges, compaction::table_state& t);

    // Submit a table to be upgraded and wait for its termination.
    future<> perform_sstable_upgrade(owned_ranges_ptr sorted_owned_ranges, compaction::table_state& t, bool exclude_current_version);

    // Submit a table to be scrubbed and wait for its termination.
    future<compaction_stats_opt> perform_sstable_scrub(compaction::table_state& t, sstables::compaction_type_options::scrub opts);

    // Submit a table for major compaction.
    future<> perform_major_compaction(compaction::table_state& t);


    // Run a custom job for a given table, defined by a function
    // it completes when future returned by job is ready or returns immediately
    // if manager was asked to stop.
    //
    // parameter type is the compaction type the operation can most closely be
    //      associated with, use compaction_type::Compaction, if none apply.
    // parameter job is a function that will carry the operation
    future<> run_custom_job(compaction::table_state& s, sstables::compaction_type type, const char *desc, noncopyable_function<future<>(sstables::compaction_data&)> job);

    class compaction_reenabler {
        compaction_manager& _cm;
        compaction::table_state* _table;
        compaction_manager::compaction_state& _compaction_state;
        gate::holder _holder;

    public:
        compaction_reenabler(compaction_manager&, compaction::table_state&);
        compaction_reenabler(compaction_reenabler&&) noexcept;

        ~compaction_reenabler();

        compaction::table_state* compacting_table() const noexcept {
            return _table;
        }

        const compaction_manager::compaction_state& compaction_state() const noexcept {
            return _compaction_state;
        }
    };

    // Disable compaction temporarily for a table t.
    // Caller should call the compaction_reenabler::reenable
    future<compaction_reenabler> stop_and_disable_compaction(compaction::table_state& t);

    // Run a function with compaction temporarily disabled for a table T.
    future<> run_with_compaction_disabled(compaction::table_state& t, std::function<future<> ()> func);

    void plug_system_keyspace(db::system_keyspace& sys_ks) noexcept;
    void unplug_system_keyspace() noexcept;

    // Adds a table to the compaction manager.
    // Creates a compaction_state structure that can be used for submitting
    // compaction jobs of all types.
    void add(compaction::table_state& t);

    // Remove a table from the compaction manager.
    // Cancel requests on table and wait for possible ongoing compactions.
    future<> remove(compaction::table_state& t) noexcept;

    const stats& get_stats() const {
        return _stats;
    }

    const std::vector<sstables::compaction_info> get_compactions(compaction::table_state* t = nullptr) const;

    // Returns true if table has an ongoing compaction, running on its behalf
    bool has_table_ongoing_compaction(const compaction::table_state& t) const;

    bool compaction_disabled(compaction::table_state& t) const;

    // Stops ongoing compaction of a given type.
    future<> stop_compaction(sstring type, compaction::table_state* table = nullptr);

    // Stops ongoing compaction of a given table and/or compaction_type.
    future<> stop_ongoing_compactions(sstring reason, compaction::table_state* t = nullptr, std::optional<sstables::compaction_type> type_opt = {}) noexcept;

    double backlog() {
        return _backlog_manager.backlog();
    }

    void register_backlog_tracker(compaction_backlog_tracker& backlog_tracker) {
        _backlog_manager.register_backlog_tracker(backlog_tracker);
    }
    void register_backlog_tracker(compaction::table_state& t, compaction_backlog_tracker new_backlog_tracker);

    compaction_backlog_tracker& get_backlog_tracker(compaction::table_state& t);

    static sstables::compaction_data create_compaction_data();

    compaction::strategy_control& get_strategy_control() const noexcept;

    tombstone_gc_state& get_tombstone_gc_state() noexcept {
        return _tombstone_gc_state;
    };

    const tombstone_gc_state& get_tombstone_gc_state() const noexcept {
        return _tombstone_gc_state;
    };

    friend class compacting_sstable_registration;
    friend class compaction_weight_registration;
    friend class compaction_manager_test;
};

bool needs_cleanup(const sstables::shared_sstable& sst, const dht::token_range_vector& owned_ranges, schema_ptr s);

// Return all sstables but those that are off-strategy like the ones in maintenance set and staging dir.
std::vector<sstables::shared_sstable> in_strategy_sstables(compaction::table_state& table_s);

std::ostream& operator<<(std::ostream& os, compaction_manager::task::state s);
std::ostream& operator<<(std::ostream& os, const compaction_manager::task& task);