1 files changed, 272 insertions, 0 deletions

diff --git a/src/scripts/lib/keyboardNav.ts b/src/scripts/lib/keyboardNav.ts
new file mode 100644
index 0000000..4c79a08
--- /dev/null
+++ b/src/scripts/lib/keyboardNav.ts
@@ -0,0 +1,272 @@
+import { getVerticalNeighbor } from "./dom.ts";
+
+function focusPrev(
+        owner: HTMLElement,
+        itemSelector: string,
+        wrap: boolean,
+        stateful: boolean,
+        current: HTMLElement,
+) {
+        const items = [...owner.querySelectorAll<HTMLElement>(itemSelector)];
+        const i = items.indexOf(current);
+
+        const prev = i > 0 ? items[i - 1] : wrap ? items.at(-1) : undefined;
+
+        if (!prev || prev === current) {
+                return false;
+        }
+
+        if (stateful) {
+                current.setAttribute("tabindex", "-1");
+                prev.removeAttribute("tabindex");
+        }
+        prev.focus();
+        return true;
+}
+
+function focusNext(
+        owner: HTMLElement,
+        itemSelector: string,
+        wrap: boolean,
+        stateful: boolean,
+        current: HTMLElement,
+) {
+        const items = [...owner.querySelectorAll<HTMLElement>(itemSelector)];
+        const i = items.indexOf(current);
+
+        const next = i < items.length - 1 ? items[i + 1] : wrap ? items[0] : undefined;
+
+        if (!next || next === current) {
+                return false;
+        }
+
+        if (stateful) {
+                current.setAttribute("tabindex", "-1");
+                next.removeAttribute("tabindex");
+        }
+        next.focus();
+        return true;
+}
+
+function focusUp(
+        owner: HTMLElement,
+        itemSelector: string,
+        wrap: boolean,
+        stateful: boolean,
+        current: HTMLElement,
+) {
+        const items = [...owner.querySelectorAll<HTMLElement>(itemSelector)];
+        let neighbor: HTMLElement | undefined = getVerticalNeighbor(-1, items, current);
+
+        if (!neighbor && wrap) {
+                neighbor = items.at(-1);
+        }
+
+        if (!neighbor || neighbor === current) {
+                return false;
+        }
+
+        if (stateful) {
+                current.setAttribute("tabindex", "-1");
+                neighbor.removeAttribute("tabindex");
+        }
+        neighbor.focus();
+        return true;
+}
+
+function focusDown(
+        owner: HTMLElement,
+        itemSelector: string,
+        wrap: boolean,
+        stateful: boolean,
+        current: HTMLElement,
+) {
+        const items = owner.querySelectorAll<HTMLElement>(itemSelector);
+        let neighbor = getVerticalNeighbor(1, items, current);
+
+        if (!neighbor && wrap) {
+                neighbor = items[0];
+        }
+
+        if (!neighbor || neighbor === current) {
+                return false;
+        }
+
+        if (stateful) {
+                current.setAttribute("tabindex", "-1");
+                neighbor.removeAttribute("tabindex");
+        }
+        neighbor.focus();
+        return true;
+}
+
+function focusFirst(
+        owner: HTMLElement,
+        itemSelector: string,
+        stateful: boolean,
+        current: HTMLElement,
+) {
+        const cards = [...owner.querySelectorAll<HTMLElement>(itemSelector)];
+        const first = cards[0];
+
+        if (!first || first === current) {
+                return false;
+        }
+
+        if (stateful) {
+                current.setAttribute("tabindex", "-1");
+                first.removeAttribute("tabindex");
+        }
+        first.focus();
+        return true;
+}
+
+function focusLast(
+        owner: HTMLElement,
+        itemSelector: string,
+        stateful: boolean,
+        current: HTMLElement,
+) {
+        const cards = [...owner.querySelectorAll<HTMLElement>(itemSelector)];
+        const last = cards.at(-1);
+
+        if (!last || last === current) {
+                return false;
+        }
+
+        if (stateful) {
+                current.setAttribute("tabindex", "-1");
+                last.removeAttribute("tabindex");
+        }
+        last.focus();
+        return true;
+}
+
+function onKeyDown(
+        owner: HTMLElement,
+        itemSelector: string,
+        horizontal: boolean,
+        vertical: boolean,
+        wrap: boolean,
+        stateful: boolean,
+        e: KeyboardEvent,
+) {
+        let handled = false;
+
+        if (!e.currentTarget) {
+                return;
+        }
+
+        switch (e.key) {
+                case "ArrowLeft": {
+                        if (horizontal) {
+                                handled = focusPrev(owner, itemSelector, wrap, stateful, e.currentTarget as HTMLElement);
+                        }
+                        break;
+                }
+
+                case "ArrowRight": {
+                        if (horizontal) {
+                                handled = focusNext(owner, itemSelector, wrap, stateful, e.currentTarget as HTMLElement);
+                        }
+                        break;
+                }
+
+                case "ArrowUp": {
+                        if (vertical) {
+                                handled = focusUp(owner, itemSelector, wrap, stateful, e.currentTarget as HTMLElement);
+                        }
+                        break;
+                }
+
+                case "ArrowDown": {
+                        if (vertical) {
+                                handled = focusDown(owner, itemSelector, wrap, stateful, e.currentTarget as HTMLElement);
+                        }
+                        break;
+                }
+
+                case "Home": {
+                        handled = focusFirst(owner, itemSelector, stateful, e.currentTarget as HTMLElement);
+                        break;
+                }
+
+                case "End": {
+                        handled = focusLast(owner, itemSelector, stateful, e.currentTarget as HTMLElement);
+                        break;
+                }
+        }
+
+        if (handled) {
+                e.stopPropagation();
+                e.preventDefault();
+        }
+}
+
+export function mountKeyboardNav() {
+        const keyboardNavEls = document.querySelectorAll<HTMLElement>(".js-keyboard-nav");
+
+        for (const keyboardNavEl of keyboardNavEls) {
+                const itemSelector = keyboardNavEl.dataset.keyboardNavItem ?? "";
+
+                if (!itemSelector) {
+                        console.error("Keyboard nav: No item class provided");
+                        continue;
+                }
+
+                let horizontal = false,
+                        vertical = false,
+                        wrap = false,
+                        stateful = false;
+
+                switch (keyboardNavEl.dataset.keyboardNavMode) {
+                        case "grid": {
+                                horizontal = true;
+                                vertical = true;
+                                stateful = true;
+                                break;
+                        }
+
+                        case "nav": {
+                                horizontal = true;
+                                wrap = true;
+                                break;
+                        }
+
+                        case "menu": {
+                                vertical = true;
+                                wrap = true;
+                                break;
+                        }
+
+                        case "list": {
+                                vertical = true;
+                                wrap = true;
+                                stateful = true;
+                                break;
+                        }
+                }
+
+                const onKeyDown_ = (e: KeyboardEvent) => {
+                        onKeyDown(keyboardNavEl, itemSelector, horizontal, vertical, wrap, stateful, e);
+                };
+
+                const itemEls = [...keyboardNavEl.querySelectorAll<HTMLElement>(itemSelector)].filter((el) =>
+                        el.matches("a, button, input"),
+                );
+                let focused = false;
+
+                for (const itemEl of itemEls) {
+                        itemEl.addEventListener("keydown", onKeyDown_);
+                        if (!itemEl.classList.contains("is-selected")) {
+                                itemEl.setAttribute("tabindex", "-1");
+                        } else {
+                                focused = true;
+                        }
+                }
+
+                if (!focused) {
+                        itemEls[0]?.removeAttribute("tabindex");
+                }
+        }
+}