Baileys/src/WAConnection/Mutex.ts

/**
 * A simple mutex that can be used as a decorator. For examples, see Tests.Mutex.ts
 * @param keyGetter if you want to lock functions based on certain arguments, specify the key for the function based on the arguments
 */
export function Mutex (keyGetter?: (...args: any[]) => string) {
    let tasks: { [k: string]: Promise<void> } = {}
    return function (_, __, descriptor: PropertyDescriptor) {
        const originalMethod = descriptor.value
        descriptor.value = function (this: Object, ...args) {
            const key = (keyGetter && keyGetter.call(this, ...args)) || 'undefined'

            tasks[key] = (async () => {
                try {
                    tasks[key] && await tasks[key]
                } catch {

                }
                const result = await originalMethod.call(this, ...args)
                return result
            })()
            return tasks[key]
        }
    }
}