// Licensed to the Apache Software Foundation (ASF) under one

// or more contributor license agreements.  See the NOTICE file

// distributed with this work for additional information

// regarding copyright ownership.  The ASF licenses this file

// to you under the Apache License, Version 2.0 (the

// "License"); you may not use this file except in compliance

// with the License.  You may obtain a copy of the License at

//

//   http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing,

// software distributed under the License is distributed on an

// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

// KIND, either express or implied.  See the License for the

// specific language governing permissions and limitations

// under the License.

#pragma once

#include <bthread/types.h>

#include <stdint.h>

#include <atomic>

#include <cstdint>

#include <list>

#include <memory>

#include <mutex>

#include <stack>

#include <string>

#include <utility>

#include <vector>

#include "common/config.h"

#include "common/factory_creator.h"

#include "common/metrics/doris_metrics.h"

#include "common/status.h"

#include "concurrentqueue.h"

#include "core/block/block.h"

#include "exec/common/memory.h"

#include "exec/scan/scanner.h"

#include "exec/scan/task_executor/split_runner.h"

#include "runtime/runtime_profile.h"

namespace doris {

class ResourceContext;

class RuntimeState;

class TupleDescriptor;

class WorkloadGroup;

class ScanLocalStateBase;

class Dependency;

class Scanner;

class ScannerDelegate;

class ScannerScheduler;

class TaskExecutor;

class TaskHandle;

// Adaptive processor for dynamic scanner concurrency adjustment

struct ScannerAdaptiveProcessor {

    ENABLE_FACTORY_CREATOR(ScannerAdaptiveProcessor)

    ScannerAdaptiveProcessor() = default;

    ~ScannerAdaptiveProcessor() = default;

    // Expected scanners in this cycle

    int expected_scanners = 0;

    // Timing metrics

    // int64_t context_start_time = 0;

    // int64_t scanner_total_halt_time = 0;

    // int64_t scanner_gen_blocks_time = 0;

    // std::atomic_int64_t scanner_total_io_time = 0;

    // std::atomic_int64_t scanner_total_running_time = 0;

    // std::atomic_int64_t scanner_total_scan_bytes = 0;

    // Timestamps

    // std::atomic_int64_t last_scanner_finish_timestamp = 0;

    // int64_t check_all_scanners_last_timestamp = 0;

    // int64_t last_driver_output_full_timestamp = 0;

    int64_t adjust_scanners_last_timestamp = 0;

    // Adjustment strategy fields

    // bool try_add_scanners = false;

    // double expected_speedup_ratio = 0;

    // double last_scanner_scan_speed = 0;

    // int64_t last_scanner_total_scan_bytes = 0;

    // int try_add_scanners_fail_count = 0;

    // int check_slow_io = 0;

    // int32_t slow_io_latency_ms = 100; // Default from config

};

class ScanTask {

public:

    enum class State : int {

        PENDING,   // not scheduled yet

        IN_FLIGHT, // scheduled and running

        COMPLETED, // finished with result or error, waiting to be collected by scan node

        EOS,       // finished and no more data, waiting to be collected by scan node

    };

    ScanTask(std::weak_ptr<ScannerDelegate> delegate_scanner);

    ~ScanTask();

private:

    // whether current scanner is finished

    Status status = Status::OK();

    std::shared_ptr<ResourceContext> _resource_ctx;

    State _state = State::PENDING;

public:

    std::weak_ptr<ScannerDelegate> scanner;

    BlockUPtr cached_block = nullptr;

    bool is_first_schedule = true;

    // Use weak_ptr to avoid circular references and potential memory leaks with SplitRunner.

    // ScannerContext only needs to observe the lifetime of SplitRunner without owning it.

    // When SplitRunner is destroyed, split_runner.lock() will return nullptr, ensuring safe access.

    std::weak_ptr<SplitRunner> split_runner;

    void set_status(Status _status) {

        if (_status.is<ErrorCode::END_OF_FILE>()) {

            // set `eos` if `END_OF_FILE`, don't take `END_OF_FILE` as error

            _state = State::EOS;

        }

        status = _status;

    }

    Status get_status() const { return status; }

    bool status_ok() { return status.ok() || status.is<ErrorCode::END_OF_FILE>(); }

    bool is_eos() const { return _state == State::EOS; }

    void set_state(State state) {

        switch (state) {

        case State::PENDING:

            // A task returns to PENDING after the operator consumes its non-EOS cached block.

            // For example, one scanner may produce several blocks, so COMPLETED is not terminal.

            DCHECK(_state == State::PENDING || _state == State::IN_FLIGHT ||

                   _state == State::COMPLETED)

                    << (int)_state;

            DCHECK(cached_block == nullptr);

            break;

        case State::IN_FLIGHT:

            DCHECK(_state == State::COMPLETED || _state == State::PENDING ||

                   _state == State::IN_FLIGHT)

                    << (int)_state;

            DCHECK(cached_block == nullptr);

            break;

        case State::COMPLETED:

            DCHECK(_state == State::IN_FLIGHT) << (int)_state;

            DCHECK(cached_block != nullptr);

            break;

        case State::EOS:

            DCHECK(_state == State::IN_FLIGHT || status.is<ErrorCode::END_OF_FILE>())

                    << (int)_state;

            break;

        default:

            break;

        }

        _state = state;

    }

};

// ScannerContext is responsible for recording the execution status

// of a group of Scanners corresponding to a ScanNode.

// Including how many scanners are being scheduled, and maintaining

// a producer-consumer blocks queue between scanners and scan nodes.

//

// ScannerContext is also the scheduling unit of ScannerScheduler.

// ScannerScheduler schedules a ScannerContext at a time,

// and submits the Scanners to the scanner thread pool for data scanning.

class ScannerContext : public std::enable_shared_from_this<ScannerContext>,

                       public HasTaskExecutionCtx {

    ENABLE_FACTORY_CREATOR(ScannerContext);

    friend class ScannerScheduler;

public:

    ScannerContext(RuntimeState* state, ScanLocalStateBase* local_state,

                   const TupleDescriptor* output_tuple_desc, bool has_projection,

                   const std::list<std::shared_ptr<ScannerDelegate>>& scanners, int64_t limit_,

                   std::shared_ptr<Dependency> dependency, std::atomic<int64_t>* shared_scan_limit,

                   std::shared_ptr<MemShareArbitrator> arb, std::shared_ptr<MemLimiter> limiter,

                   int ins_idx, bool enable_adaptive_scan

#ifdef BE_TEST

                   ,

                   int num_parallel_instances

#endif

    );

    ~ScannerContext() override;

    Status init();

    // TODO(gabriel): we can also consider to return a list of blocks to reduce the scheduling overhead, but it may cause larger memory usage and more complex logic of block management.

    BlockUPtr get_free_block(bool force);

    void return_free_block(BlockUPtr block);

    void clear_free_blocks();

    inline void inc_block_usage(size_t usage) { _block_memory_usage += usage; }

    int64_t block_memory_usage() { return _block_memory_usage; }

    // Caller should make sure the pipeline task is still running when calling this function

    void update_peak_running_scanner(int num);

    void reestimated_block_mem_bytes(int64_t num);

    // Get next block from blocks queue. Called by ScanNode/ScanOperator

    // Set eos to true if there is no more data to read.

    Status get_block_from_queue(RuntimeState* state, Block* block, bool* eos, int id);

    [[nodiscard]] Status validate_block_schema(Block* block);

    // submit the running scanner to thread pool in `ScannerScheduler`

    // set the next scanned block to `ScanTask::current_block`

    // set the error state to `ScanTask::status`

    // set the `eos` to `ScanTask::eos` if there is no more data in current scanner

    Status submit_scan_task(std::shared_ptr<ScanTask> scan_task, std::unique_lock<std::mutex>&);

    // Publish a task whose current scan attempt has completed. The operator consumes its cached

    // block and returns a non-EOS task to PENDING for its next scan attempt.

    void push_completed_scan_task(std::shared_ptr<ScanTask> scan_task);

    // Return true if this ScannerContext need no more process

    bool done() const { return _is_finished || _should_stop; }

    std::string debug_string();

    std::shared_ptr<TaskHandle> task_handle() const { return _task_handle; }

    std::shared_ptr<ResourceContext> resource_ctx() const { return _resource_ctx; }

    RuntimeState* state() { return _state; }

    void stop_scanners(RuntimeState* state);

    int batch_size() const { return _batch_size; }

    // During low memory mode, there will be at most 4 scanners running and every scanner will

    // cache at most 1MB data. So that every instance will keep 8MB buffer.

    bool low_memory_mode() const;

    // TODO(yiguolei) add this as session variable

    int32_t low_memory_mode_scan_bytes_per_scanner() const {

        return 1 * 1024 * 1024; // 1MB

    }

    int32_t low_memory_mode_scanners() const { return 4; }

    ScanLocalStateBase* local_state() const { return _local_state; }

    // the unique id of this context

    std::string ctx_id;

    TUniqueId _query_id;

    bool _should_reset_thread_name = true;

    int32_t num_scheduled_scanners() {

        std::lock_guard<std::mutex> l(_transfer_lock);

        return _in_flight_tasks_num;

    }

    Status schedule_scan_task(std::shared_ptr<ScanTask> current_scan_task,

                              std::unique_lock<std::mutex>& transfer_lock,

                              std::unique_lock<std::shared_mutex>& scheduler_lock);

    // Context scheduling and operator consumption share this lock so queue-state changes and task

    // admission form one atomic decision. For example, two worker callbacks cannot both admit the

    // last available concurrency slot.

    std::mutex& transfer_lock() { return _transfer_lock; }

    // One Context submission represents many pending scanners in the ThreadPool scheduler.

    // Keeping this separate from scanner execution prevents duplicate runnables from accumulating.

    bool is_context_queued(const std::unique_lock<std::mutex>& transfer_lock) const;

    // Transition the Context runnable's queue state. The caller must hold _transfer_lock.

    void set_context_queued(bool queued, const std::unique_lock<std::mutex>& transfer_lock);

    // Publish a scheduler failure and make the Context terminal. The caller must hold

    // _transfer_lock so a retained ThreadPool callback cannot admit another scanner concurrently.

    void set_context_failure(const Status& failure,

                             const std::unique_lock<std::mutex>& transfer_lock);

    // Return a scanner to the admission queue after its block is consumed. It may not own a cached

    // block and may not be EOS: EOS scanners are terminal and must not run again.

    void push_pending_scan_task(std::shared_ptr<ScanTask> scan_task,

                                const std::unique_lock<std::mutex>& transfer_lock);

    // Return whether a Context worker can currently admit one pending scanner. This check has no

    // side effects, so the scheduler can avoid submitting a runnable that would immediately exit.

    // It always admits one scanner when nothing is progressing so the operator can be woken, and it

    // holds the Context at max(1, _min_scan_concurrency) while the scheduler pool has no slack,

    // like _get_margin() on the TaskExecutor path. The caller must hold _transfer_lock.

    bool can_admit_scan_task(const std::unique_lock<std::mutex>& transfer_lock) const;

    // Atomically check whether this context can start another scan task, move one task from

    // pending to in-flight, and return it. The caller must hold _transfer_lock.

    std::shared_ptr<ScanTask> try_get_next_scan_task(

            const std::unique_lock<std::mutex>& transfer_lock);

protected:

    /// Four criteria to determine whether to increase the parallelism of the scanners

    /// 1. It ran for at least `SCALE_UP_DURATION` ms after last scale up

    /// 2. Half(`WAIT_BLOCK_DURATION_RATIO`) of the duration is waiting to get blocks

    /// 3. `_free_blocks_memory_usage` < `_max_bytes_in_queue`, remains enough memory to scale up

    /// 4. At most scale up `MAX_SCALE_UP_RATIO` times to `_max_thread_num`

    void _set_scanner_done();

    bool _is_shared_scan_limit_exhausted() const;

    RuntimeState* _state = nullptr;

    ScanLocalStateBase* _local_state = nullptr;

    // the comment of same fields in VScanNode

    const TupleDescriptor* _output_tuple_desc = nullptr;

    Status _process_status = Status::OK();

    std::atomic_bool _should_stop = false;

    std::atomic_bool _is_finished = false;

    // Lazy-allocated blocks for all scanners to share, for memory reuse.

    moodycamel::ConcurrentQueue<BlockUPtr> _free_blocks;

    int _batch_size;

    // The limit from SQL's limit clause

    int64_t limit;

    // Points to the shared remaining limit on ScanOperatorX, shared across all

    // parallel instances and their scanners. -1 means no limit.

    std::atomic<int64_t>* _shared_scan_limit = nullptr;

    int64_t _max_bytes_in_queue = 0;

    // _transfer_lock protects _completed_tasks, _pending_tasks, and all other shared state

    // accessed by both the scanner thread pool and the operator (get_block_from_queue).

    std::mutex _transfer_lock;

    // Together, _completed_tasks and _in_flight_tasks_num represent all "occupied" concurrency

    // slots.  The scheduler uses their sum as the current concurrency:

    //

    //   current_concurrency = _completed_tasks.size() + _in_flight_tasks_num

    //

    // Lifecycle of a ScanTask:

    //   _pending_tasks  --(submit_scan_task on the TaskExecutor path,

    //                      try_get_next_scan_task on the ThreadPool path)--> [thread pool]

    //   --(push_completed_scan_task)--> _completed_tasks  --(get_block_from_queue)--> operator

    //   After consumption: non-EOS task goes back to _pending_tasks; EOS increments

    //   _num_finished_scanners.

    // Completed scan tasks whose cached_block is ready for the operator to consume.

    // Protected by _transfer_lock.  Written by push_completed_scan_task() (scanner thread),

    // read/popped by get_block_from_queue() (operator thread).

    std::list<std::shared_ptr<ScanTask>> _completed_tasks;

    // Scanners waiting to be admitted for execution. Stored as a stack (LIFO) so that

    // recently-used scanners are re-scheduled first, which is more likely to be cache-friendly.

    // Protected by _transfer_lock. Populated in the constructor and when an operator returns a

    // non-EOS task; drained by try_get_next_scan_task() or the TaskExecutor scheduler.

    std::stack<std::shared_ptr<ScanTask>> _pending_tasks;

    // True from the start of one Context submission until its runnable starts. The marker may

    // remain true when no runnable was retained: a failed submission makes the Context terminal,

    // and a submission that threw inside _run_context() publishes the error through the task that

    // was already admitted. In both cases the operator observes _process_status, so no further

    // submission is attempted. It does not describe scanners executing on workers. Protected by

    // _transfer_lock.

    bool _is_context_queued = false;

    // Number of scan tasks currently submitted to the scanner scheduler thread pool

    // (i.e. in-flight). Incremented before a task is submitted or directly admitted for

    // thread-pool execution, and decremented by push_completed_scan_task() when the worker

    // returns it.

    // Declared atomic so it can be read without _transfer_lock in non-critical paths,

    // but must be read under _transfer_lock whenever combined with _completed_tasks.size()

    // to form a consistent concurrency snapshot.

    std::atomic_int _in_flight_tasks_num = 0;

    // Scanner that is eos or error.

    int32_t _num_finished_scanners = 0;

    // weak pointer for _scanners, used in stop function

    std::vector<std::weak_ptr<ScannerDelegate>> _all_scanners;

    std::shared_ptr<RuntimeProfile> _scanner_profile;

    // This counter refers to scan operator's local state

    RuntimeProfile::Counter* _scanner_memory_used_counter = nullptr;

    RuntimeProfile::Counter* _newly_create_free_blocks_num = nullptr;

    RuntimeProfile::Counter* _scale_up_scanners_counter = nullptr;

    std::shared_ptr<ResourceContext> _resource_ctx;

    std::shared_ptr<Dependency> _dependency = nullptr;

    std::shared_ptr<doris::TaskHandle> _task_handle;

    std::weak_ptr<doris::TaskExecutor> _task_executor;

    std::atomic<int64_t> _block_memory_usage = 0;

    // adaptive scan concurrency related

    ScannerScheduler* _scanner_scheduler = nullptr;

    MOCK_REMOVE(const) int32_t _min_scan_concurrency_of_scan_scheduler = 0;

    // The overall target of our system is to make full utilization of the resources.

    // At the same time, we dont want too many tasks are queued by scheduler, that is not necessary.

    // Each scan operator can submit _max_scan_concurrency scanner to scheduelr if scheduler has enough resource.

    // So that for a single query, we can make sure it could make full utilization of the resource.

    int32_t _max_scan_concurrency = 0;

    MOCK_REMOVE(const) int32_t _min_scan_concurrency = 1;

    std::shared_ptr<ScanTask> _pull_next_scan_task(std::shared_ptr<ScanTask> current_scan_task,

                                                   int32_t current_concurrency);

    int32_t _get_margin(std::unique_lock<std::mutex>& transfer_lock,

                        std::unique_lock<std::shared_mutex>& scheduler_lock);

    // Memory-aware adaptive scheduling

    std::shared_ptr<MemLimiter> _scanner_mem_limiter = nullptr;

    std::shared_ptr<MemShareArbitrator> _mem_share_arb = nullptr;

    std::shared_ptr<ScannerAdaptiveProcessor> _adaptive_processor = nullptr;

    const int _ins_idx;

    const bool _enable_adaptive_scanners = false;

    // Adjust scan memory limit based on arbitrator feedback

    void _adjust_scan_mem_limit(int64_t old_scanner_mem_bytes, int64_t new_scanner_mem_bytes);

    // Calculate available scanner count for adaptive scheduling

    int _available_pickup_scanner_count();

    // TODO: Add implementation of runtime_info_feed_back

    // adaptive scan concurrency related end

};

} // namespace doris