var spinner = {};

spinner.Spinner =
function Spinner(element)
{
    this.show = function(delay)
    {
        clearTimeout(this.delayed_showing_timeout);
        this.delayed_showing_timeout = null;

        if (delay)
        {
            this.delayed_showing_timeout = setTimeout(function(thisthis){thisthis.show()}, delay, this);
        }
        else
        {
            this.element.classList.remove("hidden");
        }
    }

    this.hide = function()
    {
        clearTimeout(this.delayed_showing_timeout);
        this.delayed_showing_timeout = null;

        this.element.classList.add("hidden");
    }

    this.delayed_showing_timeout = null;
    this.element = element;
}

spinner.spinner_button_index = 0;
spinner.button_spinner_groups = {};
// When a group member is closing, it will call the closer on all other members
// in the group. Of course, this would recurse forever without some kind of
// flagging, so this dict will hold group_id:true if a close is in progress,
// and be empty otherwise.
spinner.spinner_group_closing = {};

spinner.add_to_spinner_group =
function add_to_spinner_group(group_id, button)
{
    if (!(group_id in spinner.button_spinner_groups))
    {
        spinner.button_spinner_groups[group_id] = [];
    }
    spinner.button_spinner_groups[group_id].push(button);
}

spinner.close_grouped_spinners =
function close_grouped_spinners(group_id)
{
    if (group_id && !(spinner.spinner_group_closing[group_id]))
    {
        spinner.spinner_group_closing[group_id] = true;
        for (let button of spinner.button_spinner_groups[group_id])
        {
            window[button.dataset.spinnerCloser]();
        }
        delete spinner.spinner_group_closing[group_id];
    }
}

spinner.open_grouped_spinners =
function open_grouped_spinners(group_id)
{
    for (let button of spinner.button_spinner_groups[group_id])
    {
        window[button.dataset.spinnerOpener]();
    }
}

spinner.init_button_with_spinner =
function init_button_with_spinner()
{
    /*
    To create a button that has a spinner, and cannot be clicked again while
    the action is running, assign it the class "button_with_spinner".
    When you're ready for the spinner to disappear, call
    window[button.dataset.spinnerCloser]().

    Optional:
        data-spinner-id: If you want to use your own element as the spinner,
            give its ID here. Otherwise a new one will be created.

        data-spinner-delay: The number of milliseconds to wait before the
            spinner appears. For tasks that you expect to run very quickly,
            this helps prevent a pointlessly short spinner. Note that the button
            always becomes disabled immediately, and this delay only affects
            the separate spinner element.

        data-holder-class: CSS class for the new span that holds the menu.

        data-spinner-group: An opaque string. All button_with_spinner that have
            the same group will go into spinner mode when any of them is
            clicked. Useful if you want to have two copies of a button on the
            page, or two buttons which do opposite things and you only want one
            to run at a time.
    */
    let buttons = Array.from(document.getElementsByClassName("button_with_spinner"));
    for (const button of buttons)
    {
        button.classList.remove("button_with_spinner");
        button.innerHTML = button.innerHTML.trim();

        let holder = document.createElement("span");
        holder.classList.add("spinner_holder");
        holder.classList.add(button.dataset.holderClass || "spinner_holder");
        button.parentElement.insertBefore(holder, button);
        holder.appendChild(button);

        let spinner_element;
        if (button.dataset.spinnerId)
        {
            spinner_element = document.getElementById(button.dataset.spinnerId);
        }
        else
        {
            spinner_element = document.createElement("span");
            spinner_element.innerText = "Working...";
            spinner_element.classList.add("hidden");
            holder.appendChild(spinner_element);
        }

        if (button.dataset.spinnerGroup)
        {
            spinner.add_to_spinner_group(button.dataset.spinnerGroup, button);
        }

        let spin = new spinner.Spinner(spinner_element);
        let spin_delay = parseFloat(button.dataset.spinnerDelay) || 0;

        button.dataset.spinnerOpener = "spinner_opener_" + spinner.spinner_button_index;
        window[button.dataset.spinnerOpener] = function spinner_opener()
        {
            spin.show(spin_delay);
            button.disabled = true;
        }
        // It is expected that the function referenced by onclick will call
        // window[button.dataset.spinnerCloser]() when appropriate, since from
        // our perspective we cannot be sure when to close the spinner.
        button.dataset.spinnerCloser = "spinner_closer_" + spinner.spinner_button_index;
        window[button.dataset.spinnerCloser] = function spinner_closer()
        {
            spinner.close_grouped_spinners(button.dataset.spinnerGroup);
            spin.hide();
            button.disabled = false;
        }

        let wrapped_onclick = button.onclick;
        button.removeAttribute('onclick');
        button.onclick = function()
        {
            if (button.dataset.spinnerGroup)
            {
                spinner.open_grouped_spinners(button.dataset.spinnerGroup);
            }
            else
            {
                window[button.dataset.spinnerOpener]();
            }
            return wrapped_onclick();
        }

        spinner.spinner_button_index += 1;
    }
}

spinner.on_pageload =
function on_pageload()
{
    spinner.init_button_with_spinner();
}
document.addEventListener("DOMContentLoaded", spinner.on_pageload);