class ClassWatcher {

    constructor(targetNode, classToWatch, classAddedCallback, classRemovedCallback) {
        this.targetNode = targetNode
        this.classToWatch = classToWatch
        this.classAddedCallback = classAddedCallback
        this.classRemovedCallback = classRemovedCallback
        this.observer = null
        this.lastClassState = targetNode.classList.contains(this.classToWatch)

        this.init()
    }

    init() {
        this.observer = new MutationObserver(this.mutationCallback.bind(this))
        this.observe()
    }

    observe() {
        this.observer.observe(this.targetNode, { attributes: true })
    }

    disconnect() {
        this.observer.disconnect()
    }

    mutationCallback(mutationsList) {
        for (let mutation of mutationsList) {
            if (mutation.type === 'attributes' && mutation.attributeName === 'class') {
                let currentClassState = mutation.target.classList.contains(this.classToWatch)
                if (this.lastClassState !== currentClassState) {
                    this.lastClassState = currentClassState
                    if (currentClassState) {
                        this.classAddedCallback()
                    } else {
                        this.classRemovedCallback()
                    }
                }
            }
        }
    }
}

function getEventHandlerName(target)
{
    return Object.keys(target).find(
        prop => prop.startsWith('__reactEventHandlers')
    )
}

const targetNode = $('.reaction-time-test')
const callbackNull = () => {}
const callbackReation = () => {
    const handlerName = getEventHandlerName(targetNode)

    if (targetNode[handlerName] && targetNode[handlerName].onMouseDown) {
        targetNode[handlerName].onMouseDown()
        console.log('Click!')
    } else {
        console.log('Click handler not found.')
    }
}

const classWatcher = new ClassWatcher($('.reaction-time-test'), 'view-go', callbackReation, callbackNull)