// Copyright (C) 2019-2020 Zilliz. All rights reserved.
//
// Licensed 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 <assert.h>
#include <condition_variable>
#include <iostream>
#include <queue>
#include <vector>

namespace milvus {

template <typename T>
class BlockingQueue {
 public:
    BlockingQueue() : mtx(), full_(), empty_() {
    }

    virtual ~BlockingQueue() {
    }

    BlockingQueue(const BlockingQueue& rhs) = delete;

    BlockingQueue&
    operator=(const BlockingQueue& rhs) = delete;

    void
    Put(const T& task) {
        std::unique_lock<std::mutex> lock(mtx);
        full_.wait(lock, [this] { return (queue_.size() < capacity_); });
        queue_.push(task);
        empty_.notify_all();
    }

    T
    Take() {
        std::unique_lock<std::mutex> lock(mtx);
        empty_.wait(lock, [this] { return !queue_.empty(); });
        T front(queue_.front());
        queue_.pop();
        full_.notify_all();
        return front;
    }

    T
    Front() {
        std::unique_lock<std::mutex> lock(mtx);
        empty_.wait(lock, [this] { return !queue_.empty(); });
        T front(queue_.front());
        return front;
    }

    T
    Back() {
        std::unique_lock<std::mutex> lock(mtx);
        empty_.wait(lock, [this] { return !queue_.empty(); });
        T back(queue_.back());
        return back;
    }

    size_t
    Size() const {
        std::lock_guard<std::mutex> lock(mtx);
        return queue_.size();
    }

    bool
    Empty() const {
        std::unique_lock<std::mutex> lock(mtx);
        return queue_.empty();
    }

    void
    SetCapacity(const size_t capacity) {
        capacity_ = (capacity > 0 ? capacity : capacity_);
    }

 protected:
    mutable std::mutex mtx;
    std::condition_variable full_;
    std::condition_variable empty_;
    std::queue<T> queue_;
    size_t capacity_ = 32;
};

}  // namespace milvus