Drop_facts.ts

    // ignore 
    if (event.dataTransfer === null
        || event.target === null
        || !(event.target instanceof HTMLElement)) {
        console.log("Ignored illegal DragEvent")
        return
    }
    event.preventDefault()
    console.log("dropHandler", event)

    const data = event.dataTransfer.getData("application/json")
    //const data = event.dataTransfer.getData("text/plain")
    console.log(`Dropped data: '${event.dataTransfer.types}'`, event.dataTransfer.types)

    const fact: Fact = JSON.parse(data)
    console.warn(`Dropped Fact '${fact.label}':`, fact)

    const target: HTMLElement = event.target

    if (target.dataset.allowedTypes !== undefined) {
        //const allowedTypesStr = element.dataset["allowed-types"]
        const allowedTypesStr = target.dataset.allowedTypes
        const allowedTypes = allowedTypesStr.split(" ")

        if (!allowedTypes.includes(fact.type)) {
            console.warn(`The drop target is of type '${fact.type}' is not a member of the allowed types: ${allowedTypesStr}`)
            return
        }
    }

    //element.fact = fact
    target.dataset.factId = fact.uri
    $(target).trigger("FactAssigned", fact)

    // Mathmind belongs into Unity. 
    // const mathMind = document.querySelector('#math-mind-canvas')
    // if(mathMind instanceof HTMLCanvasElement)
    // {
    //     if (fact instanceof Point_Fact) {
    //         mathMind.dispatchEvent(new CustomEvent("PointAssigned", {detail: fact}))
    //         }
    // }

}

/** @param {MouseEvent} event  */
function clickHandler(event: MouseEvent) {
    // ignore 
    if (event.target == null
        || !(event.target instanceof HTMLElement)) {
        console.warn("Ignored illegal DragEvent")
        return
    }
    event.preventDefault()
    console.log("clickHandler")
    console.log("clickHandler", event)
    const target: HTMLElement = event.target
    switch (event.button) {
        case 0:
            console.log("Left button clicked")
            target.dataset.factId = undefined
            target.dispatchEvent(new Event("factUnassigned"))
            break
        case 1:
            console.log("Middle button clicked")
            break
        case 2:
            console.log("Right button clicked")
            if (target.dataset.slotId) {
                getHint(target.dataset.slotId)