(function () {
    var backdrop = null;
    var modal = null;
    var titleEl = null;
    var bodyEl = null;
    var cancelBtn = null;
    var confirmBtn = null;
    var footerEl = null;
    var prevFocus = null;
    var currentOpts = null;
    var onKeydown = null;

    function build() {
        backdrop = document.createElement('div');
        backdrop.className = 'modal-backdrop';

        modal = document.createElement('div');
        modal.className = 'modal';
        modal.setAttribute('role', 'dialog');
        modal.setAttribute('aria-modal', 'true');

        var header = document.createElement('div');
        header.className = 'modal-header';
        titleEl = document.createElement('span');
        header.appendChild(titleEl);

        bodyEl = document.createElement('div');
        bodyEl.className = 'modal-body';

        footerEl = document.createElement('div');
        footerEl.className = 'modal-footer';

        cancelBtn = document.createElement('button');
        cancelBtn.type = 'button';
        confirmBtn = document.createElement('button');
        confirmBtn.type = 'button';

        modal.appendChild(header);
        modal.appendChild(bodyEl);
        modal.appendChild(footerEl);
        backdrop.appendChild(modal);

        backdrop.addEventListener('mousedown', function (e) {
            if (e.target === backdrop) close();
        });
        cancelBtn.addEventListener('click', close);
        confirmBtn.addEventListener('click', function () {
            if (confirmBtn.disabled) return;
            if (currentOpts && currentOpts.confirm && currentOpts.confirm.onConfirm) {
                currentOpts.confirm.onConfirm();
            }
        });
    }

    function open(opts) {
        if (backdrop && backdrop.parentNode) close();
        if (!backdrop) build();

        currentOpts = opts;
        prevFocus = document.activeElement;

        titleEl.textContent = opts.title || '';

        bodyEl.textContent = '';
        if (opts.body instanceof Node) {
            bodyEl.appendChild(opts.body);
        } else if (typeof opts.body === 'string') {
            bodyEl.textContent = opts.body;
        }

        var confirmOpts = opts.confirm || {};
        var cancelOpts = opts.cancel || {};

        confirmBtn.textContent = confirmOpts.label || 'OK';
        confirmBtn.className = 'btn' + (confirmOpts.danger ? ' danger' : '');
        confirmBtn.disabled = !!confirmOpts.initiallyDisabled;

        cancelBtn.textContent = cancelOpts.label || 'CANCEL';
        cancelBtn.className = 'btn';

        footerEl.textContent = '';
        if (opts.swapButtons) {
            footerEl.appendChild(confirmBtn);
            footerEl.appendChild(cancelBtn);
        } else {
            footerEl.appendChild(cancelBtn);
            footerEl.appendChild(confirmBtn);
        }

        document.body.appendChild(backdrop);

        setTimeout(function () {
            if (cancelOpts.autofocus) {
                cancelBtn.focus();
                return;
            }
            var firstInput = bodyEl.querySelector('input, textarea, select');
            if (firstInput) {
                firstInput.focus();
                if (firstInput.select) firstInput.select();
            } else {
                confirmBtn.focus();
            }
        }, 0);

        var enterConfirms = confirmOpts.enterConfirms !== false;
        onKeydown = function (e) {
            if (e.key === 'Escape') {
                e.preventDefault();
                close();
                return;
            }
            if (e.key === 'Enter' && enterConfirms) {
                var tag = (e.target && e.target.tagName) || '';
                if (tag === 'TEXTAREA') return;
                e.preventDefault();
                if (!confirmBtn.disabled) confirmBtn.click();
            }
        };
        document.addEventListener('keydown', onKeydown);

        return {
            close: close,
            setConfirmDisabled: function (d) { confirmBtn.disabled = !!d; },
            confirmButton: confirmBtn
        };
    }

    function close() {
        if (!backdrop || !backdrop.parentNode) return;
        if (onKeydown) {
            document.removeEventListener('keydown', onKeydown);
            onKeydown = null;
        }
        backdrop.parentNode.removeChild(backdrop);
        currentOpts = null;
        var toRestore = prevFocus;
        prevFocus = null;
        if (toRestore && toRestore.focus) {
            try { toRestore.focus(); } catch (e) {}
        }
    }

    window.openModal = open;
    window.closeModal = close;
})();