// Copyright (c) 2020, Compiler Explorer Authors
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
//     * Redistributions of source code must retain the above copyright notice,
//       this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above copyright
//       notice, this list of conditions and the following disclaimer in the
//       documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.

import {executionAsyncId} from 'async_hooks';

import {default as Queue} from 'p-queue';

export class CompilationQueue {
    constructor(concurrency, timeout) {
        this._running = new Set();
        this._queue = new Queue({
            concurrency,
            timeout,
            throwOnTimeout: true,
        });
    }

    static fromProps(ceProps) {
        return new CompilationQueue(
            ceProps('maxConcurrentCompiles', 1),
            ceProps('compilationEnvTimeoutMs'));
    }

    enqueue(job) {
        const enqueueAsyncId = executionAsyncId();
        // If we're asked to enqueue a job when we're already in a async queued job context, just run it.
        // This prevents a deadlock.
        if (this._running.has(enqueueAsyncId))
            return job();
        return this._queue.add(() => {
            const jobAsyncId = executionAsyncId();
            if (this._running.has(jobAsyncId))
                throw new Error('somehow we entered the context twice');
            try {
                this._running.add(jobAsyncId);
                return job();
            } finally {
                this._running.delete(jobAsyncId);
            }
        });
    }

    status() {
        const pending = this._queue.pending;
        const size = this._queue.size;
        return {
            busy: pending > 0 || size > 0,
            pending,
            size,
        };
    }
}