(() => {
  const ROOT = "data-slhx-root";
  const HID = "data-hid";
  const SID = "data-sid";
  const runtimeAbiVersion = 1;
  const FINGERPRINT = "data-slhx-fp";
  const STATE = "data-slhx-st";
  const pending = new WeakMap();
  const queues = new WeakMap();
  const timers = new WeakMap();
  const atomStores = new WeakMap();

  function roots() {
    return Array.from(document.querySelectorAll(`[${ROOT}]`));
  }

  function rootOf(node) {
    return node && node.closest ? node.closest(`[${ROOT}]`) : null;
  }

  function closestInRoot(start, root, selector) {
    for (let node = start; node && node !== root.parentNode; node = node.parentNode) {
      if (node.matches && node.matches(selector)) return node;
      if (node === root) break;
    }
    return null;
  }

  function handleId(el) {
    const raw = el && el.getAttribute(HID);
    return raw && /^\d+$/.test(raw) ? raw : null;
  }

  function requestPolicy(el, eventName) {
    const policy = el.getAttribute("data-slhx-policy");
    if (policy) return policy;
    if (el.hasAttribute("data-slhx-debounce") || eventName === "input") return "latest";
    if (el.tagName === "FORM") return "drop";
    return "parallel";
  }

  function showPending(el, on) {
    const klass = el.getAttribute("data-slhx-pending-class");
    if (klass) el.classList.toggle(klass, on);
    const root = rootOf(el) || document;
    root.querySelectorAll("[data-slhx-indicator]").forEach((i) => { i.hidden = !on; });
    if (el.hasAttribute("data-slhx-disable-while-pending")) {
      const controls = el.matches("button,input,select,textarea") ? [el] : el.querySelectorAll("button,input,select,textarea");
      controls.forEach((c) => { c.disabled = on; });
    }
  }

  function formDataFor(el) {
    const form = el.tagName === "FORM" ? el : el.closest("form");
    const data = form ? new FormData(form) : new FormData();
    const id = handleId(el) || (form && handleId(form));
    if (id && !data.has("__h")) data.set("__h", id);
    for (const { name, value } of Array.from(el.attributes || [])) {
      if (name.startsWith("data-") && !name.startsWith("data-slhx-") && name !== HID && name !== SID) {
        data.set(name.slice(5).replace(/-/g, "_"), value);
      }
    }
    return { form, data, multipart: form && String(form.enctype).toLowerCase() === "multipart/form-data" };
  }

  function urlEncoded(data) {
    const encoded = new URLSearchParams();
    for (const [name, value] of data.entries()) {
      if (value instanceof File) continue;
      encoded.append(name, value);
    }
    return encoded;
  }

  function requestBody(data, multipart) {
    return multipart ? data : urlEncoded(data);
  }

  function requestUrl(form, data, method) {
    const url = new URL((form && form.action) || location.href, location.href);
    if (method === "GET") url.search = urlEncoded(data).toString();
    return url.href;
  }

  async function send(el, eventName) {
    if (el.getAttribute("data-slhx-confirm") && !confirm(el.getAttribute("data-slhx-confirm"))) return;
    const { form, data, multipart } = formDataFor(el);
    const target = form || el;
    const policy = requestPolicy(target, eventName);
    const active = pending.get(target);
    if (active && policy === "drop") return;
    if (active && policy === "latest") active.abort.abort();
    if (active && policy === "queue") {
      const base = queues.get(target) || active.done;
      let queued;
      const next = base.then(() => send(el, eventName));
      queued = next.catch(() => {}).finally(() => {
        if (queues.get(target) === queued) queues.delete(target);
      });
      queues.set(target, queued);
      return;
    }

    const abort = new AbortController();
    let finish;
    const done = new Promise((resolve) => { finish = resolve; });
    const method = String((form && form.method) || "POST").toUpperCase();
    const body = method === "GET" || method === "HEAD" ? undefined : requestBody(data, multipart);
    const headers = { "X-SLHX-Partial": "1", "Accept": "application/slhx, text/html" };
    if (body instanceof URLSearchParams) headers["Content-Type"] = "application/x-www-form-urlencoded;charset=UTF-8";
    pending.set(target, { abort, done });
    showPending(target, true);
    try {
      const response = await fetch(requestUrl(form, data, method), {
        method,
        body,
        headers,
        signal: abort.signal,
      });
      if (pending.get(target)?.abort !== abort && policy === "latest") return;
      await applyResponse(response, rootOf(target));
    } catch (error) {
      if (error.name !== "AbortError") emit(rootOf(target), "slhx:error", String(error));
    } finally {
      if (pending.get(target)?.abort === abort) {
        pending.delete(target);
        showPending(target, false);
      }
      finish();
    }
  }

  async function navigate(anchor, mode = "push") {
    const href = anchor.href;
    const root = rootOf(anchor);
    showPending(anchor, true);
    try {
      await navigateUrl(href, root, mode);
    } finally {
      showPending(anchor, false);
    }
  }

  async function navigateUrl(href, root, mode = "replace") {
    const response = await fetch(href, { headers: { "X-SLHX-Partial": "1", "Accept": "text/html" } });
    await applyResponse(response, root);
    if (mode === "push") history.pushState({ slhx: true }, "", href);
    else if (mode === "replace") history.replaceState({ slhx: true }, "", href);
  }

  async function applyResponse(response, root) {
    if (response.redirected) {
      location.href = response.url;
      return;
    }
    if (!compatibleFingerprint(response, root)) {
      location.reload();
      return;
    }
    const type = response.headers.get("content-type") || "";
    if (type.includes("text/html")) applyHtml(await response.text(), root, response.headers.get("x-slhx-title"));
    else if (type.includes("application/slhx")) applyBatch(await response.arrayBuffer(), root);
  }

  function compatibleFingerprint(response, root) {
    const received = response.headers.get("x-slhx-fingerprint");
    const expected = root && root.getAttribute(FINGERPRINT);
    return !received || !expected || received === expected;
  }

  function applyBatch(buffer, root) {
    const batch = decodeBatch(buffer);
    if (batch.abiVersion !== runtimeAbiVersion) {
      location.reload();
      return;
    }
    const expected = root && root.getAttribute(FINGERPRINT);
    if (expected && String(batch.fingerprint) !== expected) {
      location.reload();
      return;
    }
    const scope = root || document;
    const missingTarget = batch.ops.map((op) => canApplyOp(scope, op)).find(Boolean);
    if (missingTarget) {
      missing(scope, missingTarget);
      return;
    }
    for (const op of batch.ops) applyOp(scope, op);
  }

  function canApplyOp(scope, op) {
    if (op.kind === "put" && isAtom(op.target)) return null;
    if (op.kind === "put" || op.kind === "focus") return targetFor(scope, op.target) ? null : op.target;
    if (op.kind === "insert" || op.kind === "prepend") return targetFor(scope, op.target) ? null : op.target;
    if (op.kind === "remove") return (op.key ? keyedTarget(scope, op.target.resource.id, op.key) : targetFor(scope, op.target)) ? null : op.target;
    if (op.kind === "move") return targetFor(scope, op.target) && keyedTarget(scope, op.target.resource.id, op.key) ? null : op.target;
    if (op.kind === "navigate" && op.scroll && op.scroll.kind === "element") return targetFor(scope, op.scroll.target) ? null : op.scroll.target;
    return null;
  }

  function applyOp(scope, op) {
    if (op.kind === "put") {
      if (isAtom(op.target)) {
        atomStore(scope).set(String(op.target.resource.id), op.payload.value);
        return true;
      }
      const target = targetFor(scope, op.target);
      if (!target) return missing(scope, op.target);
      putPayload(target, op.payload);
    } else if (op.kind === "insert" || op.kind === "prepend") {
      const target = targetFor(scope, op.target);
      if (!target) return missing(scope, op.target);
      const nodes = fragmentNodes(op.payload, op.key);
      target[op.kind === "prepend" ? "prepend" : "append"](...nodes);
    } else if (op.kind === "remove") {
      const target = op.key ? keyedTarget(scope, op.target.resource.id, op.key) : targetFor(scope, op.target);
      if (!target) return missing(scope, op.target);
      target.remove();
    } else if (op.kind === "move") {
      const target = targetFor(scope, op.target);
      const item = keyedTarget(scope, op.target.resource.id, op.key);
      if (!target || !item) return missing(scope, op.target);
      const before = op.before && keyedTarget(scope, op.target.resource.id, op.before);
      target.insertBefore(item, before || null);
    } else if (op.kind === "focus") {
      const target = targetFor(scope, op.target);
      if (target && target.focus) target.focus();
      else return missing(scope, op.target);
    } else if (op.kind === "navigate") {
      if (op.mode === "redirect") location.href = op.url;
      else {
        history[op.mode === "replace" ? "replaceState" : "pushState"]({ slhx: true }, "", op.url);
        if (op.scroll === "top") scrollTo(0, 0);
        else if (op.scroll && op.scroll.kind === "element") {
          const target = targetFor(scope, op.scroll.target);
          if (target) target.scrollIntoView();
        }
        if (op.title) document.title = op.title;
      }
    } else if (op.kind === "emit") {
      handleRuntimeEvent(scope, op.name, op.payload);
      emit(scope, op.name, op.payload);
    }
    return true;
  }

  function targetFor(scope, ref) {
    if (isAtom(ref)) return null;
    if (ref.scope && ref.scope.kind === "key") return keyedTarget(scope, ref.resource.id, ref.scope.value);
    if (ref.scope && ref.scope.kind === "field") return fieldTarget(scope, ref.resource.id, ref.scope.value);
    return scope.querySelector(`[data-sid="${ref.resource.id}"], [data-slot-id="${ref.resource.id}"]`);
  }

  function isAtom(ref) {
    return ref && ref.resource && ref.resource.kind === "atom";
  }

  function atomStore(root) {
    const owner = root && root.nodeType === 1 ? root : document.documentElement;
    let store = atomStores.get(owner);
    if (!store) {
      store = new Map();
      atomStores.set(owner, store);
    }
    return store;
  }

  function atomValue(root, id) {
    return atomStore(rootOf(root) || root || roots()[0]).get(String(id));
  }

  function keyedTarget(scope, id, key) {
    const escapedKey = cssEscape(key);
    return scope.querySelector(`[data-sid="${id}"][data-key="${escapedKey}"], [data-sid="${id}"] [data-key="${escapedKey}"], [data-slot-id="${id}"][data-key="${escapedKey}"], [data-slot-id="${id}"] [data-key="${escapedKey}"]`);
  }

  function fieldTarget(scope, id, field) {
    const escapedField = cssEscape(field);
    return scope.querySelector(`[data-fid="${id}"] [name="${escapedField}"], [data-form-id="${id}"] [name="${escapedField}"]`);
  }

  function formErrorTarget(scope, id, field) {
    const escapedField = cssEscape(field);
    return scope.querySelector(`[data-fid="${id}"] [data-slhx-error-for="${escapedField}"], [data-form-id="${id}"] [data-slhx-error-for="${escapedField}"]`) ||
      scope.querySelector(`[data-fid="${id}"] [name="${escapedField}"], [data-form-id="${id}"] [name="${escapedField}"]`);
  }

  function putFormError(target, message) {
    if (target.matches && target.matches("input,textarea,select")) target.setCustomValidity(message);
    else target.textContent = message;
  }

  function putPayload(target, payload) {
    if (payload.kind === "html") target.innerHTML = payload.value;
    else if (target.matches && target.matches("input,textarea,select")) target.value = payload.value;
    else target.textContent = payload.value;
  }

  function fragmentNodes(payload, key) {
    const template = document.createElement("template");
    if (payload.kind === "html") template.innerHTML = payload.value;
    else template.textContent = payload.value;
    const nodes = Array.from(template.content.childNodes);
    const firstElement = nodes.find((node) => node.nodeType === 1);
    if (firstElement && key != null && !firstElement.hasAttribute("data-key")) firstElement.setAttribute("data-key", key);
    return nodes;
  }

  function handleRuntimeEvent(scope, name, payload) {
    if (name === "slhx:form-reset") {
      const form = scope.querySelector(`[data-fid="${payload}"], [data-form-id="${payload}"]`);
      if (form && form.reset) form.reset();
    } else if (name === "slhx:form-error") {
      const [id, field, message] = String(payload).split("\u001f");
      const target = formErrorTarget(scope, id, field);
      if (target) putFormError(target, message || "");
    } else if (name === "slhx:form-disable-while-pending") {
      const form = scope.querySelector(`[data-fid="${payload}"], [data-form-id="${payload}"]`);
      if (form) form.setAttribute("data-slhx-disable-while-pending", "");
    }
  }

  function missing(root, target) {
    emit(root, "slhx:missing-target", target);
    return false;
  }

  function cssEscape(value) {
    return String(value).replace(/\\/g, "\\\\").replace(/"/g, "\\\"");
  }

  function applyHtml(html, root, title) {
    const scope = root || document;
    const doc = new DOMParser().parseFromString(html, "text/html");
    const template = doc.querySelector("template[data-slhx]");
    if (!replaceSlot(scope, doc, "content", template ? template.innerHTML : html)) {
      location.reload();
      return;
    }
    replaceSlot(scope, doc, "nav");
    const nextTitle = title || (doc.querySelector("title") && doc.querySelector("title").textContent);
    if (nextTitle) document.title = nextTitle;
  }

  function replaceSlot(scope, doc, name, fallback) {
    const target = scope.querySelector(`[data-slhx-slot="${name}"], [data-slot="${name}"]`);
    if (!target) return false;
    const source = doc.querySelector(`[data-slhx-slot="${name}"], [data-slot="${name}"]`);
    if (!source && fallback === undefined) return false;
    target.innerHTML = source ? source.innerHTML : fallback;
    return true;
  }

  function emit(root, name, detail) {
    (root || document).dispatchEvent(new CustomEvent(name, { bubbles: true, detail }));
  }

  function defaultEvent(el) {
    if (el.getAttribute("data-slhx-on")) return el.getAttribute("data-slhx-on");
    if (el.tagName === "FORM") return "submit";
    return "click";
  }

  function bindRoot(root) {
    ["click", "submit", "input", "change"].forEach((name) => {
      root.addEventListener(name, (event) => {
        const nav = closestInRoot(event.target, root, "a[data-slhx-nav], [data-slhx-boost] a[href]");
        if (name === "click" && nav && sameOriginNav(event, nav)) {
          event.preventDefault();
          navigate(nav);
          return;
        }
        const el = closestInRoot(event.target, root, `[${HID}], [data-slhx-boost] form`);
        if (!el || defaultEvent(el) !== name) return;
        event.preventDefault();
        schedule(el, name);
      });
    });
    bindPolling(root);
  }

  function schedule(el, eventName) {
    const debounce = duration(el.getAttribute("data-slhx-debounce"));
    const throttle = duration(el.getAttribute("data-slhx-throttle"));
    if (debounce) {
      clearTimeout(timers.get(el));
      timers.set(el, setTimeout(() => send(el, eventName), debounce));
    } else if (throttle) {
      if (timers.get(el)) return;
      send(el, eventName).finally(() => setTimeout(() => timers.delete(el), throttle));
    } else {
      send(el, eventName);
    }
  }

  function bindPolling(root) {
    root.querySelectorAll("[data-slhx-every]").forEach((el) => {
      if (timers.has(el)) return;
      const ms = duration(el.getAttribute("data-slhx-every"));
      if (!ms) return;
      timers.set(el, setInterval(() => document.contains(el) ? send(el, "every") : clearInterval(timers.get(el)), ms));
    });
  }

  function duration(value) {
    if (!value) return 0;
    const match = String(value).trim().match(/^(\d+)(ms|s)?$/);
    if (!match) return 0;
    return Number(match[1]) * (match[2] === "s" ? 1000 : 1);
  }

  function bootstrapState(root) {
    const encoded = root.getAttribute(STATE);
    if (!encoded) return;
    const store = atomStore(root);
    for (const atom of decodeAtomState(encoded)) store.set(String(atom.id), atom.bytes);
  }

  function decodeAtomState(encoded) {
    const bytes = base64UrlBytes(encoded);
    const d = postcardDecoder(bytes);
    const atoms = d.vec(() => ({ id: d.varint(), bytes: d.bytes() }));
    if (!d.done()) throw new Error("trailing slhx state bytes");
    return atoms;
  }

  function base64UrlBytes(encoded) {
    const normalized = String(encoded).replace(/-/g, "+").replace(/_/g, "/");
    const padded = normalized + "=".repeat((4 - normalized.length % 4) % 4);
    return Uint8Array.from(atob(padded), (ch) => ch.charCodeAt(0));
  }

  function postcardDecoder(bytes) {
    let offset = 0;
    const need = (len) => {
      const end = offset + len;
      if (end > bytes.length) throw new Error("truncated slhx state");
      const slice = bytes.subarray(offset, end);
      offset = end;
      return slice;
    };
    const varint = () => {
      let shift = 0;
      let value = 0;
      for (;;) {
        const byte = need(1)[0];
        value |= (byte & 0x7f) << shift;
        if ((byte & 0x80) === 0) return value >>> 0;
        shift += 7;
      }
    };
    const bytesField = () => need(varint());
    const vec = (read) => Array.from({ length: varint() }, read);
    return { varint, bytes: bytesField, vec, done: () => offset === bytes.length };
  }

  function decoder(buffer) {
    const bytes = new Uint8Array(buffer);
    let offset = 0;
    const need = (len) => {
      const end = offset + len;
      if (end > bytes.length) throw new Error("truncated slhx batch");
      const slice = bytes.subarray(offset, end);
      offset = end;
      return slice;
    };
    const u8 = () => need(1)[0];
    const u32 = () => {
      const b = need(4);
      return (b[0] | (b[1] << 8) | (b[2] << 16) | (b[3] << 24)) >>> 0;
    };
    const u64 = () => {
      const lo = BigInt(u32());
      const hi = BigInt(u32());
      return lo | (hi << 32n);
    };
    const str = () => new TextDecoder().decode(need(u32()));
    const option = (read) => u8() === 0 ? null : read();
    const resource = () => ({ kind: ["slot", "atom", "handle", "form"][u8()], id: u32() });
    const scope = () => {
      const kind = u8();
      if (kind === 0) return null;
      return { kind: kind === 1 ? "key" : "field", value: str() };
    };
    const ref = () => ({ resource: resource(), scope: scope() });
    const payload = () => ({ kind: u8() === 0 ? "text" : "html", value: str() });
    const scroll = () => {
      const kind = u8();
      if (kind === 0) return "preserve";
      if (kind === 1) return "top";
      return { kind: "element", target: ref() };
    };
    const effect = () => {
      const kind = u8();
      if (kind === 0) return { kind: "put", target: ref(), payload: payload() };
      if (kind === 1) return { kind: "insert", target: ref(), key: str(), payload: payload() };
      if (kind === 2) return { kind: "prepend", target: ref(), key: str(), payload: payload() };
      if (kind === 3) return { kind: "remove", target: ref(), key: option(str) };
      if (kind === 4) return { kind: "move", target: ref(), key: str(), before: option(str) };
      if (kind === 5) return { kind: "focus", target: ref() };
      if (kind === 6) return { kind: "navigate", url: str(), mode: ["push", "replace", "redirect"][u8()], scroll: scroll(), title: option(str) };
      if (kind === 7) return { kind: "emit", name: str(), payload: str() };
      throw new Error(`unknown slhx effect ${kind}`);
    };
    const vec = (read) => Array.from({ length: u32() }, read);
    return { u8, u32, u64, vec, effect, done: () => offset === bytes.length };
  }

  function decodeBatch(buffer) {
    const d = decoder(buffer);
    if (String.fromCharCode(d.u8(), d.u8(), d.u8(), d.u8()) !== "SLHX") throw new Error("bad slhx batch magic");
    const batch = { abiVersion: d.u32(), fingerprint: d.u64(), ops: d.vec(d.effect) };
    if (!d.done()) throw new Error("trailing slhx batch bytes");
    return batch;
  }

  function sameOriginNav(event, anchor) {
    return !event.defaultPrevented && event.button === 0 && !event.metaKey && !event.ctrlKey && !event.shiftKey && !event.altKey &&
      anchor.origin === location.origin && !anchor.download && anchor.target !== "_blank";
  }

  function start() {
    roots().forEach((root) => {
      bootstrapState(root);
      bindRoot(root);
    });
    history.replaceState(history.state || { slhx: true }, "", location.href);
  }

  addEventListener("popstate", () => {
    const root = roots()[0];
    if (root) navigateUrl(location.href, root, "none").catch((error) => emit(root, "slhx:error", String(error)));
  });

  if (document.readyState === "loading") document.addEventListener("DOMContentLoaded", start);
  else start();

  window.slhx = Object.freeze({ runtimeAbiVersion, roots, rootOf, applyHtml, applyBatch, decodeBatch, atomValue, decodeAtomState });
})();