const SOURCE_ORDER = Object.freeze(["automatic", "imported", "system"]);
const SOURCE_LABELS = Object.freeze({
  automatic: "自动字体",
  imported: "已导入字体",
  system: "系统字体",
});

export function normalizeFontItems(items) {
  const seen = new Set();
  const normalized = [];
  for (const raw of Array.isArray(items) ? items : []) {
    if (!raw || typeof raw.id !== "string" || !raw.id || seen.has(raw.id)) continue;
    if (!SOURCE_ORDER.includes(raw.source)) continue;
    seen.add(raw.id);
    const family = String(raw.family || "未命名字体").trim() || "未命名字体";
    const style = String(raw.style || "Regular").trim() || "Regular";
    normalized.push(Object.freeze({
      id: raw.id,
      label: String(raw.label || family).trim() || family,
      family,
      style,
      source: raw.source,
    }));
  }
  return normalized;
}

export function filterFontItems(items, query = "") {
  const needle = String(query).trim().toLocaleLowerCase("zh-CN");
  if (!needle) return [...items];
  return items.filter((item) => (
    `${item.label} ${item.family} ${item.style}`.toLocaleLowerCase("zh-CN").includes(needle)
  ));
}

export function groupFontItems(items) {
  return SOURCE_ORDER
    .map((source) => ({
      source,
      label: SOURCE_LABELS[source],
      items: items.filter((item) => item.source === source),
    }))
    .filter((group) => group.items.length);
}

export function createFontPicker({ input, listbox, onCommit }) {
  let items = [];
  let selectedId = "default";
  let visibleItems = [];
  let activeIndex = -1;
  let enabled = false;
  let closeTimer = null;

  function selectedItem() {
    return items.find((item) => item.id === selectedId) || null;
  }

  function selectedLabel() {
    return selectedItem()?.label || "当前字体不可用，将自动回退";
  }

  function restoreLabel() {
    input.value = selectedLabel();
    input.classList.toggle("font-reference-missing", !selectedItem());
  }

  function close({ restore = true } = {}) {
    window.clearTimeout(closeTimer);
    listbox.hidden = true;
    input.setAttribute("aria-expanded", "false");
    input.removeAttribute("aria-activedescendant");
    activeIndex = -1;
    if (restore) restoreLabel();
  }

  function optionId(index) {
    return `${listbox.id}-option-${index}`;
  }

  function setActive(index) {
    if (!visibleItems.length) {
      activeIndex = -1;
      input.removeAttribute("aria-activedescendant");
      return;
    }
    activeIndex = Math.max(0, Math.min(index, visibleItems.length - 1));
    input.setAttribute("aria-activedescendant", optionId(activeIndex));
    listbox.querySelectorAll('[role="option"]').forEach((option, optionIndex) => {
      const active = optionIndex === activeIndex;
      option.classList.toggle("active", active);
      if (active) option.scrollIntoView({ block: "nearest" });
    });
  }

  function commit(item) {
    if (!item) return;
    selectedId = item.id;
    restoreLabel();
    close({ restore: false });
    onCommit?.(item);
  }

  function render(query = "") {
    visibleItems = filterFontItems(items, query);
    const groups = groupFontItems(visibleItems);
    const nodes = [];
    let optionIndex = 0;
    for (const group of groups) {
      const heading = document.createElement("div");
      heading.className = "font-option-group";
      heading.textContent = group.label;
      heading.setAttribute("role", "presentation");
      nodes.push(heading);
      for (const item of group.items) {
        const option = document.createElement("div");
        option.id = optionId(optionIndex);
        option.className = "font-option";
        option.setAttribute("role", "option");
        option.setAttribute("aria-selected", String(item.id === selectedId));
        option.setAttribute("aria-label", item.label);
        option.dataset.fontId = item.id;
        const label = document.createElement("span");
        label.textContent = item.family;
        const source = document.createElement("small");
        source.textContent = item.style;
        source.setAttribute("aria-hidden", "true");
        option.append(label, source);
        option.addEventListener("pointerdown", (event) => event.preventDefault());
        option.addEventListener("click", () => commit(item));
        nodes.push(option);
        optionIndex += 1;
      }
    }
    if (!visibleItems.length) {
      const empty = document.createElement("div");
      empty.className = "font-options-empty";
      empty.textContent = "没有匹配的字体";
      nodes.push(empty);
    }
    listbox.replaceChildren(...nodes);
    activeIndex = visibleItems.findIndex((item) => item.id === selectedId);
    if (activeIndex < 0 && visibleItems.length) activeIndex = 0;
    setActive(activeIndex);
  }

  function open(query = "") {
    if (!enabled) return;
    render(query);
    listbox.hidden = false;
    input.setAttribute("aria-expanded", "true");
  }

  input.addEventListener("focus", () => {
    if (!enabled) return;
    input.select();
    open();
  });
  input.addEventListener("click", () => open());
  input.addEventListener("input", (event) => {
    event.stopPropagation();
    open(input.value);
  });
  input.addEventListener("keydown", (event) => {
    if (!enabled) return;
    if (event.key === "ArrowDown" || event.key === "ArrowUp") {
      event.preventDefault();
      if (listbox.hidden) open();
      setActive(activeIndex + (event.key === "ArrowDown" ? 1 : -1));
    } else if (event.key === "Home" || event.key === "End") {
      event.preventDefault();
      if (listbox.hidden) open();
      setActive(event.key === "Home" ? 0 : visibleItems.length - 1);
    } else if (event.key === "Enter" && !listbox.hidden) {
      event.preventDefault();
      commit(visibleItems[activeIndex]);
    } else if (event.key === "Escape") {
      event.preventDefault();
      close();
    }
  });
  input.addEventListener("blur", () => {
    closeTimer = window.setTimeout(() => close(), 0);
  });

  restoreLabel();
  return Object.freeze({
    setItems(nextItems) {
      items = normalizeFontItems(nextItems);
      restoreLabel();
      if (!listbox.hidden) render();
    },
    setValue(identifier) {
      selectedId = typeof identifier === "string" && identifier ? identifier : "default";
      restoreLabel();
    },
    getValue() {
      return selectedId;
    },
    setEnabled(value) {
      enabled = Boolean(value);
      input.readOnly = !enabled;
      if (!enabled) close();
    },
    open,
    close,
  });
}