// 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 <atomic>

#include <chrono>

#include <condition_variable>

#include <memory>

#include <mutex>

#include <thread>

#include <unordered_map>

#include <vector>

#include "common/status.h"

#include "runtime/memory/mem_tracker.h"

#include "udf/python/python_udf_meta.h"

#include "udf/python/python_udf_runtime.h"

namespace doris {

class PythonServerManager {

public:

    PythonServerManager() = default;

    ~PythonServerManager() { shutdown(); }

    static PythonServerManager& instance() {

        static PythonServerManager instance;

        return instance;

    }

    template <typename T>

    Status get_client(const PythonUDFMeta& func_meta, const PythonVersion& version,

                      std::shared_ptr<T>* client,

                      const std::shared_ptr<arrow::Schema>& data_schema = nullptr);

    static Status fork(const PythonVersion& version, ProcessPtr* process);

    // Clear Python module cache for a specific UDF location across all processes

    Status clear_module_cache(const std::string& location);

    // Clear Python UDAF runtime state after DROP FUNCTION

    void clear_udaf_state_cache(int64_t function_id);

    void shutdown();

#ifdef BE_TEST

    // For unit testing only.

    void check_and_recreate_processes_for_test() { _check_and_recreate_processes(); }

    void set_process_pool_for_test(const PythonVersion& version, std::vector<ProcessPtr> processes,

                                   bool initialized = true);

    std::vector<ProcessPtr> process_pool_snapshot_for_test(const PythonVersion& version);

    bool process_pool_is_initializing_for_test(const PythonVersion& version);

    bool process_pool_is_initialized_for_test(const PythonVersion& version);

    Status broadcast_action_to_processes_for_test(const std::string& action_type,

                                                  const std::string& body,

                                                  const std::string& log_name) {

        return _broadcast_action_to_processes(action_type, body, log_name);

    }

#endif

private:

    enum class PoolState {

        UNINITIALIZED,

        INITIALIZING,

        // `Initialized` means:

        // 1. All process slots have attempted initialization.

        // 2. At least one live process is available for requests.

        // 3. The health-check thread has been started.

        INITIALIZED,

        // Prevent the pool from being incorrectly reused after `shutdown()`

        STOPPED,

    };

    struct VersionedProcessPool {

        std::mutex mutex;

        // Coordinates initialization and repair workers with foreground requests.

        std::condition_variable cv;

        std::vector<ProcessPtr> processes;

        PoolState state = PoolState::UNINITIALIZED;

        // True when at least one process in the pool can serve requests.

        bool has_available_process = false;

        // True while a background repair is recreating dead or missing processes.

        bool repairing = false;

    };

    /** 

     * Lazily initialize and return the process pool for specific Python version. 

     */

    Result<std::shared_ptr<VersionedProcessPool>> _ensure_pool_initialized(

            const PythonVersion& version);

    /**

     * Pick an available process from specific pool, recreating one on demand if needed.

     */

    Status _get_process(const PythonVersion& version,

                        const std::shared_ptr<VersionedProcessPool>& versioned_pool,

                        ProcessPtr* process);

    /**

     * Start health check background thread (called once by ensure_pool_initialized)

     * Thread periodically checks process health and refreshes memory stats

     */

    void _start_health_check_thread();

    /**

     * Check process health and recreate dead processes

     */

    void _check_and_recreate_processes();

#ifdef BE_TEST

    static constexpr std::chrono::milliseconds PROCESS_START_TIMEOUT {500};

    static constexpr std::chrono::milliseconds PROCESS_TERMINATE_TIMEOUT {100};

    static constexpr std::chrono::milliseconds PROCESS_POOL_INIT_TIMEOUT {1000};

    static constexpr std::chrono::milliseconds PROCESS_REPAIR_WAIT_TIMEOUT {200};

#else

    static constexpr std::chrono::milliseconds PROCESS_START_TIMEOUT {5000};

    static constexpr std::chrono::milliseconds PROCESS_TERMINATE_TIMEOUT {1000};

    // FE's default send-fragments RPC timeout is 30s. Keep BE's Python pool wait below it so the

    // caller sees SERVICE_UNAVAILABLE with Python context instead of a generic RPC deadline error.

    static constexpr std::chrono::milliseconds PROCESS_POOL_INIT_TIMEOUT {20000};

    static constexpr std::chrono::milliseconds PROCESS_REPAIR_WAIT_TIMEOUT {1000};

#endif

    static int _repair_process_pool(const PythonVersion& version,

                                    const std::shared_ptr<VersionedProcessPool>& versioned_pool);

    /**

     * Read resident set size (RSS) for a single process from /proc/{pid}/statm

     */

    Status _read_process_memory(pid_t pid, size_t* rss_bytes);

    /**

     * Refresh memory statistics for all Python processes

     */

    void _refresh_memory_stats();

    Result<std::shared_ptr<VersionedProcessPool>> _get_or_create_process_pool(

            const PythonVersion& version);

    std::vector<std::pair<PythonVersion, std::shared_ptr<VersionedProcessPool>>>

    _snapshot_process_pools();

    Status _broadcast_action_to_processes(const std::string& action_type, const std::string& body,

                                          const std::string& log_name);

    static bool _select_alive_process_from_pool(const std::vector<ProcessPtr>& pool,

                                                ProcessPtr* process);

    std::unordered_map<PythonVersion, std::shared_ptr<VersionedProcessPool>> _process_pools;

    // Protects the version -> pool handle map only. Per-version process operations are guarded

    // by VersionedProcessPool::mutex.

    std::mutex _pools_mutex;

    // Health check background thread

    std::unique_ptr<std::thread> _health_check_thread;

    std::atomic<bool> _shutdown_flag {false};

    std::condition_variable _health_check_cv;

    std::mutex _health_check_mutex;

    MemTracker _mem_tracker {"PythonUDFProcesses"};

};

} // namespace doris