/**
 * An overlay displayed in HTML.
 */
export class Overlay {
    private readonly overlay: HTMLDivElement;
    private readonly submitForm: HTMLFormElement | undefined;
    private readonly cancelForm: HTMLFormElement | undefined;


    /**
     * Constructs a new overlay.
     *
     * @param overlay the overlay element to show and hide
     * @param submitForm the form that invokes `onSubmit` and closes the overlay when submitted
     * @param cancelForm the form that closes the overlay when submitted
     * @param onSubmit the callback to invoke when the form is submit
     */
    constructor(
        overlay: HTMLDivElement,
        submitForm: HTMLFormElement | undefined,
        cancelForm: HTMLFormElement | undefined,
        onSubmit: (() => void) | undefined = undefined
    ) {
        this.overlay = overlay;
        overlay.addEventListener(
            "mousedown",
            event => {
                if (event.target === overlay)
                    this.hide();
            }
        );
        document.addEventListener(
            "keydown",
            event => {
                if (event.key === "Escape" && this.isVisible())
                    this.hide();
            }
        );

        this.submitForm = submitForm;
        submitForm?.addEventListener(
            "submit",
            event => {
                event.preventDefault();

                this.hide();
                onSubmit?.();
            }
        );

        this.cancelForm = cancelForm;
        cancelForm?.addEventListener(
            "submit",
            event => {
                event.preventDefault();

                this.hide();
            }
        );
    }


    /**
     * Shows the overlay.
     */
    show(): void {
        this.overlay.style.visibility = "unset";
    }

    /**
     * Hides the overlay.
     */
    hide(): void {
        this.overlay.style.visibility = "hidden";
    }

    /**
     * Returns `true` if and only if this overlay is currently visible.
     */
    isVisible(): boolean {
        return this.overlay.style.visibility !== "hidden";
    }
}