'use strict'

class AsyncLock { 
    constructor() {
        this.queue = []
        this.locked = false
    }
    
    acquire(){
        return new Promise((resolve) => {
            if (!this.locked) {
                // No contention, acquire lock immediately
                this.locked = true
                resolve()
            } else {
                // Add to queue when lock is busy
                this.queue.push(resolve)
            }
        })
    }

    release(){
        if (this.queue.length > 0) {
            // Resolve the next queued promise
            const nextResolve = this.queue.shift()
            nextResolve()
            // Keep locked status as true since we're passing the lock to the next waiter
        } else {
            // No waiters, unlock
            this.locked = false
        }
    }
}

module.exports = AsyncLock