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

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

#pragma once

#include "service/migration_listener.hh"
#include "gms/endpoint_state.hh"
#include <seastar/core/abort_source.hh>
#include <seastar/core/gate.hh>
#include "gms/inet_address.hh"
#include "gms/feature.hh"
#include "gms/i_endpoint_state_change_subscriber.hh"
#include "schema/schema_fwd.hh"
#include "service/storage_service.hh"
#include "utils/pluggable.hh"
#include "utils/serialized_action.hh"
#include "service/raft/raft_group_registry.hh"
#include "service/raft/raft_group0_client.hh"
#include "db/timeout_clock.hh"

#include <vector>

class canonical_mutation;
class frozen_mutation;
namespace cql3 {
namespace functions { class user_function; class user_aggregate; }
}
namespace netw { class messaging_service; }

namespace gms {

class gossiper;
enum class application_state;
class versioned_value;

}

namespace db {
class system_keyspace;
}

namespace service {

class storage_proxy;

class migration_manager : public seastar::async_sharded_service<migration_manager>,
                            public gms::i_endpoint_state_change_subscriber,
                            public seastar::peering_sharded_service<migration_manager> {
private:
    migration_notifier& _notifier;

    std::unordered_map<locator::host_id, serialized_action> _schema_pulls;
    serialized_action _group0_barrier;
    std::vector<gms::feature::listener_registration> _feature_listeners;
    seastar::named_gate _background_tasks;
    static const std::chrono::milliseconds migration_delay;
    gms::feature_service& _feat;
    netw::messaging_service& _messaging;
    service::storage_proxy& _storage_proxy;
    utils::pluggable<storage_service> _ss;
    gms::gossiper& _gossiper;
    seastar::abort_source _as;
    service::raft_group0_client& _group0_client;
    sharded<db::system_keyspace>& _sys_ks;
    serialized_action _schema_push;
    table_schema_version _schema_version_to_publish;

    // If `false`, schema is synchronized only through Raft.
    // Here are the conditions when we should enable/disable schema pulls:
    // - If a node is bootstrapping in non-Raft mode, schema pulls must remain
    //   enabled.
    // - If a node is bootstrapping in Raft mode, it should never perform a
    //   schema pull.
    // - If a bootstrapped node is restarting in non-Raft mode but with Raft
    //   feature enabled (which means we should start upgrading to use Raft),
    //   or restarting in the middle of Raft upgrade procedure, schema pulls must
    //   remain enabled until the Raft upgrade procedure finishes.
    //   This is also the case of restarting after RECOVERY.
    // - If a bootstrapped node is restarting in Raft mode, it should never
    //   perform a schema pull.
    bool _enable_schema_pulls{true};

    friend class group0_state_machine; // needed for access to _messaging
    size_t _concurrent_ddl_retries;
public:
    migration_manager(migration_notifier&, gms::feature_service&, netw::messaging_service& ms, service::storage_proxy&, gms::gossiper& gossiper, service::raft_group0_client& group0_client, sharded<db::system_keyspace>& sysks);
    void plug_storage_service(service::storage_service& ss);
    future<> unplug_storage_service();

    migration_notifier& get_notifier() { return _notifier; }
    const migration_notifier& get_notifier() const { return _notifier; }
    service::storage_proxy& get_storage_proxy() { return _storage_proxy; }
    const service::storage_proxy& get_storage_proxy() const { return _storage_proxy; }
    const service::raft_group0_client& get_group0_client() const { return _group0_client; }
    abort_source& get_abort_source() noexcept { return _as; }
    const abort_source& get_abort_source() const noexcept { return _as; }
    serialized_action& get_group0_barrier() noexcept { return _group0_barrier; }
    const serialized_action& get_group0_barrier() const noexcept { return _group0_barrier; }
    bool use_raft() const noexcept { return !_enable_schema_pulls; }

    // Disable schema pulls when Raft group 0 is fully responsible for managing schema.
    future<> disable_schema_pulls();

    future<> submit_migration_task(locator::host_id endpoint, bool can_ignore_down_node = true);

    // Makes sure that this node knows about all schema changes known by "nodes" that were made prior to this call.
    future<> sync_schema(const replica::database& db, const std::vector<locator::host_id>& nodes);

    // Fetches schema from remote node and applies it locally.
    // Differs from submit_migration_task() in that all errors are propagated.
    // Coalesces requests.
    future<> merge_schema_from(locator::host_id);
    future<> do_merge_schema_from(locator::host_id);
    future<> reload_schema();

    // Merge mutations received from src.
    // Keep mutations alive around whole async operation.
    future<> merge_schema_from(locator::host_id src, const utils::chunked_vector<canonical_mutation>& mutations);
    // Incremented each time the function above is called. Needed by tests.
    size_t canonical_mutation_merge_count = 0;

    bool should_pull_schema_from(const locator::host_id& endpoint);
    bool has_compatible_schema_tables_version(const locator::host_id& endpoint);

    // The function needs to be called if the user wants to read most up-to-date group 0 state (including schema state)
    // (the function ensures that all previously finished group0 operations are visible on this node) or to write it.
    //
    // Call this *before* reading group 0 state (e.g. when performing a schema change, call this before validation).
    // Use `group0_guard::write_timestamp()` when creating mutations which modify group 0 (e.g. schema tables mutations).
    //
    // Call ONLY on shard 0.
    // Requires a quorum of nodes to be available in order to finish.
    // Parameters:
    //   timeout -- Optional. If set, this timeout is used for the group0.read_barrier operation.
    //              If the timeout is reached and there is no Raft quorum, an exception is thrown.
    //              The exception will include information about the current set of alive and
    //              unavailable voters.
    //              If not set, the default timeout is used (from the Scylla config parameter
    //              `group0_raft_op_timeout_in_ms`, which defaults to one minute).
    future<group0_guard> start_group0_operation(std::optional<raft_timeout> timeout = std::nullopt);

    // Apply a group 0 change.
    // The future resolves after the change is applied locally.
    // Parameters:
    //   timeout -- Optional. Applies only if raft is used (group0_guard.with_raft returns true).
    //              If set, this timeout is used for the group0.add_entry operation.
    //              If the timeout is reached and there is no Raft quorum, an exception is thrown.
    //              The exception will include information about the current set of alive and
    //              unavailable voters, which 
    //              If not set, the default timeout is used (from the Scylla config parameter
    //              `group0_raft_op_timeout_in_ms`, which defaults to one minute).
    template<typename mutation_type = schema_change>
    future<> announce(utils::chunked_vector<mutation> schema, group0_guard, std::string_view description, std::optional<raft_timeout> timeout = std::nullopt);

    void passive_announce(table_schema_version version);

    future<> drain();
    future<> stop();

    /**
     * Known peers in the cluster have the same schema version as us.
     */
    bool have_schema_agreement();
    future<> wait_for_schema_agreement(const replica::database& db, db::timeout_clock::time_point deadline, seastar::abort_source* as);

    // Maximum number of retries one should attempt when trying to perform
    // a DDL statement and getting `group0_concurrent_modification` exception.
    size_t get_concurrent_ddl_retries() const { return _concurrent_ddl_retries; }
private:
    void init_messaging_service();
    future<> uninit_messaging_service();

    future<> push_schema_mutation(locator::host_id endpoint, const utils::chunked_vector<mutation>& schema);

    future<> passive_announce();

    void schedule_schema_pull(locator::host_id endpoint, const gms::endpoint_state& state);

    future<> maybe_schedule_schema_pull(const table_schema_version& their_version, locator::host_id endpoint);

    template<typename mutation_type = schema_change>
    future<> announce_with_raft(utils::chunked_vector<mutation> schema, group0_guard, std::string_view description, std::optional<raft_timeout> timeout);
    future<> announce_without_raft(utils::chunked_vector<mutation> schema, group0_guard);

public:
    void register_feature_listeners();

    future<> maybe_sync(const schema_ptr& s, locator::host_id endpoint);

    // Returns schema of given version, either from cache or from remote node identified by 'from'.
    // The returned schema may not be synchronized. See schema::is_synced().
    // Intended to be used in the read path.
    future<schema_ptr> get_schema_for_read(table_schema_version, locator::host_id from, unsigned shard, netw::messaging_service& ms, abort_source& as);

    // Returns schema of given version, either from cache or from remote node identified by 'from'.
    // Ensures that this node is synchronized with the returned schema. See schema::is_synced().
    // Intended to be used in the write path, which relies on synchronized schema.
    future<schema_ptr> get_schema_for_write(table_schema_version, locator::host_id from, unsigned shard, netw::messaging_service& ms, abort_source& as);

private:
    virtual future<> on_join(gms::inet_address endpoint,locator::host_id id,  gms::endpoint_state_ptr ep_state, gms::permit_id) override;
    virtual future<> on_change(gms::inet_address endpoint, locator::host_id id, const gms::application_state_map& states, gms::permit_id) override;
    virtual future<> on_alive(gms::inet_address endpoint, locator::host_id id, gms::endpoint_state_ptr state, gms::permit_id) override;

public:
    // For tests only.
    void set_concurrent_ddl_retries(size_t);
};

extern template
future<> migration_manager::announce_with_raft<schema_change>(utils::chunked_vector<mutation> schema, group0_guard, std::string_view description, std::optional<raft_timeout> timeout);
extern template
future<> migration_manager::announce_with_raft<topology_change>(utils::chunked_vector<mutation> schema, group0_guard, std::string_view description, std::optional<raft_timeout> timeout);

extern template
future<> migration_manager::announce<schema_change>(utils::chunked_vector<mutation> schema, group0_guard, std::string_view description, std::optional<raft_timeout> timeout = std::nullopt);
extern template
future<> migration_manager::announce<topology_change>(utils::chunked_vector<mutation> schema, group0_guard, std::string_view description, std::optional<raft_timeout> timeout = std::nullopt);


future<column_mapping> get_column_mapping(db::system_keyspace& sys_ks, table_id, table_schema_version v);

utils::chunked_vector<mutation> prepare_keyspace_update_announcement(replica::database& db, lw_shared_ptr<keyspace_metadata> ksm, api::timestamp_type ts);

utils::chunked_vector<mutation> prepare_new_keyspace_announcement(replica::database& db, lw_shared_ptr<keyspace_metadata> ksm, api::timestamp_type timestamp);

// The timestamp parameter can be used to ensure that all nodes update their internal tables' schemas
// with identical timestamps, which can prevent an undeeded schema exchange
future<utils::chunked_vector<mutation>> prepare_column_family_update_announcement(storage_proxy& sp,
        schema_ptr cfm, std::vector<view_ptr> view_updates, api::timestamp_type ts);

future<utils::chunked_vector<mutation>> prepare_new_column_family_announcement(storage_proxy& sp, schema_ptr cfm, api::timestamp_type timestamp);
// The ksm parameter can describe a keyspace that hasn't been created yet.
// This function allows announcing a new keyspace together with its tables at once.
future<> prepare_new_column_family_announcement(utils::chunked_vector<mutation>& mutations,
        storage_proxy& sp, const keyspace_metadata& ksm, schema_ptr cfm, api::timestamp_type timestamp);
// Announce multiple tables in one operation
future<> prepare_new_column_families_announcement(utils::chunked_vector<mutation>& mutations,
        storage_proxy& sp, const keyspace_metadata& ksm, std::vector<schema_ptr> cfms, api::timestamp_type timestamp);

future<utils::chunked_vector<mutation>> prepare_new_type_announcement(storage_proxy& sp, user_type new_type, api::timestamp_type ts);

future<utils::chunked_vector<mutation>> prepare_new_function_announcement(storage_proxy& sp, shared_ptr<cql3::functions::user_function> func, api::timestamp_type ts);

future<utils::chunked_vector<mutation>> prepare_new_aggregate_announcement(storage_proxy& sp, shared_ptr<cql3::functions::user_aggregate> aggregate, api::timestamp_type ts);

future<utils::chunked_vector<mutation>> prepare_function_drop_announcement(storage_proxy& sp, shared_ptr<cql3::functions::user_function> func, api::timestamp_type ts);

future<utils::chunked_vector<mutation>> prepare_aggregate_drop_announcement(storage_proxy& sp, shared_ptr<cql3::functions::user_aggregate> aggregate, api::timestamp_type ts);

future<utils::chunked_vector<mutation>> prepare_update_type_announcement(storage_proxy& sp, user_type updated_type, api::timestamp_type ts);

future<utils::chunked_vector<mutation>> prepare_keyspace_drop_announcement(storage_proxy& sp, const sstring& ks_name, api::timestamp_type ts);

class drop_views_tag;
using drop_views = bool_class<drop_views_tag>;
future<utils::chunked_vector<mutation>> prepare_column_family_drop_announcement(storage_proxy& sp,
        const sstring& ks_name, const sstring& cf_name, api::timestamp_type ts, drop_views drop_views = drop_views::no);

future<utils::chunked_vector<mutation>> prepare_type_drop_announcement(storage_proxy& sp, user_type dropped_type, api::timestamp_type ts);

future<utils::chunked_vector<mutation>> prepare_new_view_announcement(storage_proxy& sp, view_ptr view, api::timestamp_type ts);

future<utils::chunked_vector<mutation>> prepare_view_update_announcement(storage_proxy& sp, view_ptr view, api::timestamp_type ts);

future<utils::chunked_vector<mutation>> prepare_view_drop_announcement(storage_proxy& sp, const sstring& ks_name, const sstring& cf_name, api::timestamp_type ts);

}