function debouncer(interval, callback) {
    let currentTimeout = null;

    function trigger() {
        currentTimeout = null;
        callback();
    }

    return function () {
        clearTimeout(currentTimeout);
        currentTimeout = setTimeout(trigger, interval);
    };
}

(function () {
    const form = document.querySelector('form.search');
    const input = form.querySelector('input');
    const results = form.querySelector('.live-results');
    const resultPrototype = document.getElementById('search-result-prototype').firstChild;

    function clearChildren(element) {
        while (element.lastChild) {
            element.removeChild(results.lastChild);
        }
    }

    let ongoing = false;
    function submit() {
        if (input.value === "") {
            results.classList.remove("show");
            clearChildren(results);
            return;
        }

        if (ongoing) return;
        ongoing = true;

        const query = input.value;
        fetch(
            "_search?snippet_size=14&limit=4&q=" + encodeURIComponent(query),
            {
                headers: {
                    "Accept": "application/json",
                },
                credentials: "same-origin",
            }
        ).then(response => {
            if (!response.ok) throw new Error("Unexpected status code (" + response.status + ")");

            return response.json();
        }).then(result => {
            clearChildren(results);

            result.hits.forEach((hit, index) => {
                const item = resultPrototype.cloneNode(true);
                item.querySelector('.link').href = hit.slug || ".";
                item.querySelector('.link').setAttribute("data-focusindex", index + 1);
                item.querySelector('.title').textContent = hit.title;
                item.querySelector('.snippet').innerHTML = hit.snippet;
                results.appendChild(item);
            })

            if (result.next) {
                const item = resultPrototype.cloneNode(true);
                item.querySelector('.link').href = "_search?q=" + encodeURIComponent(query);
                item.querySelector('.link').setAttribute("data-focusindex", result.hits.length + 1);
                item.querySelector('.link').innerHTML = "See more results\u2026";
                results.appendChild(item);
            }

            results.classList.add("show");

            if (input.value !== query) submitter();

            ongoing = false;
        }).catch(err => {
            console.error(err);

            clearChildren(results);
            results.classList.add("show");

            const item = document.createElement("li");
            item.classList.add("search-result");
            item.classList.add("error");
            item.textContent = "Live search unavailable";
            results.appendChild(item);

            ongoing = false;
        });
    }
    const submitter = debouncer(300, submit);

    input.addEventListener('input', submitter);

    form.addEventListener('focusin', () => form.classList.add("focus"));
    form.addEventListener('focusout', function (ev) {
        for (let ancestor = ev.relatedTarget; ancestor; ancestor = ancestor.parentElement) {
            if (ancestor === form) return;
        }

        // We are now actually losing focus from the form:
        form.classList.remove("focus");
    });

    function moveFocus(element, delta) {
        const focusIndexText = document.activeElement.getAttribute("data-focusindex");
        const nextIndex = focusIndexText ? parseInt(focusIndexText, 10) + delta : 0;

        const candidate = element.querySelector("[data-focusindex=\"" + nextIndex + "\"]");
        if (candidate) candidate.focus();
    }

    function focusControl(element, ev) {
        if (ev.key === 'ArrowUp') {
            ev.preventDefault();
            ev.stopPropagation();
            moveFocus(element, -1);
        } else if (ev.key === 'ArrowDown') {
            ev.preventDefault();
            ev.stopPropagation();
            moveFocus(element, 1);
        } else if (ev.key === 'Escape') {
            ev.preventDefault();
            ev.stopPropagation();
            document.activeElement && document.activeElement.blur();
        }
    }

    for (let element of document.querySelectorAll(".keyboard-focus-control")) {
        const captureElement = element;
        element.addEventListener('keydown', ev => focusControl(captureElement, ev));
    }

    const defaultKeyboardFocusControl = document.querySelector(".default-keyboard-focus-control");
    if (defaultKeyboardFocusControl) {
        document.addEventListener('keydown', ev => {
            focusControl(defaultKeyboardFocusControl, ev);
        });
    }
})();