/*
Copyright (c) 2025 WuJingrun（吴京润）

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.
 */
package f_concurrent

/**
 * 滑动窗口限流器
 */
public class SlidingWindowRateLimiter<T> <: RateLimiter<T> {
    private let queue: ArrayBlockingQueue<Mono>
    private let prev = AtomicOptionReference<Mono>()
    private let unfinishedTasks = AtomicInt64(1)
    /**
     * @param timeout 时间窗口
     * @param limit 时间窗口内最大任务数
     */
    public init(window!: Duration, timeout!: Duration, limit!: Int64) {
        super(timeout)
        if (window <= Duration.Zero || limit <= 0) {
            throw RateLimiterException('all parameters must be larger than zero')
        }
        queue = ArrayBlockingQueue<Mono>(limit)
        let timer = Timer.after(Duration.Zero) {
            if (let Some(out) <- this.prev.load() && !out.finished) {
                Console.writeln(
                    'SlidingWindowRateLimiter: ${unfinishedTasks.fetchAdd(1)} tasks are timeout in SlidingWindowRateLimiter for ${TypeInfo.of<T>()}.')
            }
            let mono = queue.remove()
            prev.store(mono)
            mono.time + window - MonoTime.now()
        }
        atExit(timer.cancel)
    }
    public func exec(default: ?T, task: () -> ?T): ?T {
        let mono = Mono()
        func exec() {
            try {
                task()
            } finally {
                mono.finished = true
            }
        }
        if (queue.add(mono, timeout)) {
            mono.time = MonoTime.now()
            if (let Some(x) <- exec()) {
                x
            } else {
                default
            }
        } else {
            default
        }
    }
}

private class Mono {
    private var _time = AtomicOptionReference<Box<MonoTime>>()
    private let _finished = AtomicBool(false)

    mut prop time: MonoTime {
        get() {
            while (_time.load().isNone()) {}
            _time.load().getOrThrow().value
        }
        set(value) {
            _time.store(Box<MonoTime>(value))
        }
    }
    mut prop finished: Bool {
        get() {
            _finished.load()
        }
        set(value) {
            _finished.store(value)
        }
    }
}