// 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 {

struct UserFunctionCacheEntry;

class PythonUDFPoolLease;

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,

                      std::shared_ptr<UserFunctionCacheEntry> package_cache_entry = nullptr);

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

    // Stop accepting new clients. Health check removes the pool after its last client closes.

    void drop_function(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 PythonUDFMeta& meta, const PythonVersion& version,

                                   std::vector<ProcessPtr> processes, bool initialized = true);

    std::vector<ProcessPtr> process_pool_snapshot_for_test(int64_t function_id);

    bool process_pool_is_initialized_for_test(int64_t function_id);

    bool wait_for_process_pool_initialized_for_test(int64_t function_id,

                                                    std::chrono::milliseconds timeout);

    bool wait_for_process_pool_initialization_finished_for_test(int64_t function_id,

                                                                std::chrono::milliseconds timeout);

#endif

private:

    friend class PythonUDFPoolLease;

    enum class PoolState {

        UNINITIALIZED,

        INITIALIZING,

        // `Initialized` means:

        // 1. All process slots have attempted initialization.

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

        INITIALIZED,

        // Reject new clients and late fork publication after DROP, shutdown or idle reclamation.

        STOPPED,

    };

    // Includes processes held by clients after DROP, without extending their lifetime.

    struct ProcessRegistry {

        void add(const ProcessPtr& process);

        std::vector<ProcessPtr> snapshot();

        std::mutex mutex;

        std::vector<std::weak_ptr<PythonUDFProcess>> processes;

    };

    struct FunctionProcessPool {

        // Interpreter information needed to replace dead processes in this function pool.

        PythonVersion version;

        // Detached fork/repair workers can outlive the manager.

        std::shared_ptr<ProcessRegistry> process_registry;

        int64_t function_id = 0;

        int32_t pool_size = 3;

        int64_t auto_suspend = PythonUDFMeta::DEFAULT_AUTO_SUSPEND_SECONDS;

        size_t active_clients = 0;

        std::chrono::steady_clock::time_point idle_since = std::chrono::steady_clock::now();

        std::shared_ptr<UserFunctionCacheEntry> package_cache_entry;

        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 function.

     */

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

            const PythonUDFMeta& meta, const PythonVersion& version,

            std::shared_ptr<UserFunctionCacheEntry> package_cache_entry = nullptr,

            std::shared_ptr<PythonUDFPoolLease>* lease = nullptr);

    /**

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

     */

    static void _start_pool_initialization(

            const std::shared_ptr<FunctionProcessPool>& function_pool, const PythonVersion& version,

            std::chrono::milliseconds process_pool_init_timeout);

    static void _start_pool_repair(const PythonVersion& version,

                                   const std::shared_ptr<FunctionProcessPool>& function_pool);

    Status _get_process(const PythonVersion& version,

                        const std::shared_ptr<FunctionProcessPool>& function_pool,

                        ProcessPtr* process);

    /**

     * Start health check background thread when the first function pool is created

     * Thread periodically reclaims pools, checks process health and refreshes memory stats.

     */

    void _start_health_check_thread();

    // Only reclaim pools with no active clients: STOPPED pools on the next scan; other pools

    // after auto_suspend seconds without a client (-1 disables idle reclamation).

    void _reclaim_idle_pools(std::chrono::steady_clock::time_point now);

    /**

     * 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<FunctionProcessPool>& function_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<FunctionProcessPool>> _get_or_create_process_pool(

            const PythonUDFMeta& meta, const PythonVersion& version,

            std::shared_ptr<UserFunctionCacheEntry> package_cache_entry,

            std::shared_ptr<PythonUDFPoolLease>* lease = nullptr);

    std::vector<std::shared_ptr<FunctionProcessPool>> _snapshot_process_pools();

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

                                                ProcessPtr* process);

    // Weak references keep dropped-but-active processes visible without keeping them alive.

    std::shared_ptr<ProcessRegistry> _process_registry = std::make_shared<ProcessRegistry>();

    // function_id -> process_pool

    std::unordered_map<int64_t, std::shared_ptr<FunctionProcessPool>> _process_pools;

    // Protects the function id -> pool map. DROP also stops the pool under this lock;

    // when taking both locks, acquire this before FunctionProcessPool::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