const STORAGE_KEY = "toyota-kanban-tasks-v1";

const STATUSES = [
  { id: "backlog", label: "\u30d0\u30c3\u30af\u30ed\u30b0", hint: "\u69cb\u60f3\u4e2d" },
  { id: "ready", label: "\u6e96\u5099", hint: "\u6e96\u5099\u4e2d" },
  { id: "inprogress", label: "\u4f5c\u696d", hint: "\u9032\u884c\u4e2d" },
  { id: "waiting", label: "\u5f85\u6a5f", hint: "\u505c\u6b62\u4e2d" },
  { id: "done", label: "\u5b8c\u4e86", hint: "\u5b8c\u4e86" }
];

const state = {
  tasks: [],
  filters: {
    search: "",
    searchRaw: "",
    selectedTags: [],
    dateFrom: "",
    dateTo: "",
    parentId: "",
    parentSearch: ""
  },
  selectionMode: false,
  selectedIds: new Set(),
  showParentView: false,
  highlightParentId: "",
  activeStatus: STATUSES[0].id,
  parentViewSearch: ""
};

const dom = {};
let initialized = false;

function init() {
  if (initialized) return;
  initialized = true;
  cacheDom();
  bindGlobalEvents();
  hydrateStaticUi();
  loadTasks();
  renderAll();
}

function cacheDom() {
  dom.board = document.getElementById("board");
  dom.statusDock = document.getElementById("status-dock");
  dom.parentView = document.getElementById("parent-view");
  dom.parentClusters = document.getElementById("parent-clusters");
  dom.selectionToolbar = document.getElementById("selection-toolbar");
  dom.selectionCount = document.getElementById("selection-count");
  dom.bulkStatusButtons = document.getElementById("bulk-status-buttons");
  dom.filterReset = document.getElementById("filter-reset-button");
  dom.parentFilter = document.getElementById("parent-filter-select");
  dom.parentFilterSearch = document.getElementById("parent-filter-search");
  dom.tagToggleContainer = document.getElementById("tag-toggle-container");
  dom.parentViewSearch = document.getElementById("parent-view-search");
  dom.parentViewClear = document.getElementById("parent-view-clear");
  dom.searchInput = document.getElementById("search-input");
  dom.dateFrom = document.getElementById("date-from");
  dom.dateTo = document.getElementById("date-to");
  dom.toggleGroupBtn = document.getElementById("btn-toggle-group");
  dom.toggleSelectionBtn = document.getElementById("btn-toggle-selection");
  dom.newTaskBtn = document.getElementById("btn-new-task");
  dom.bulkDeleteBtn = document.getElementById("btn-bulk-delete");
  dom.selectAllBtn = document.getElementById("btn-select-all");
  dom.clearSelectionBtn = document.getElementById("btn-clear-selection");
  dom.dialog = document.getElementById("task-dialog");
  dom.dialogTitle = document.getElementById("dialog-title");
  dom.dialogClose = document.getElementById("dialog-close");
  dom.taskForm = document.getElementById("task-form");
  dom.taskDeleteBtn = document.getElementById("task-delete-button");
  dom.taskStatusSelect = document.getElementById("task-status");
  dom.taskParentSelect = document.getElementById("task-parent");
  dom.taskCardTemplate = document.getElementById("task-card-template");
}

function bindGlobalEvents() {
  dom.newTaskBtn.addEventListener("click", () => openTaskDialog());
  dom.dialogClose.addEventListener("click", closeDialog);
  dom.taskForm.addEventListener("submit", handleTaskSubmit);
  dom.taskDeleteBtn.addEventListener("click", handleDialogDelete);
  dom.toggleGroupBtn.addEventListener("click", toggleParentView);
  dom.toggleSelectionBtn.addEventListener("click", toggleSelectionMode);
  dom.bulkDeleteBtn.addEventListener("click", handleBulkDelete);
  dom.selectAllBtn.addEventListener("click", handleSelectAll);
  dom.clearSelectionBtn.addEventListener("click", () => {
    state.selectedIds.clear();
    updateBulkActions();
    renderAll();
  });
  dom.searchInput.addEventListener("input", (event) => {
    const raw = event.target.value.trim();
    state.filters.searchRaw = raw;
    state.filters.search = raw.toLowerCase();
    renderAll();
  });
  dom.dateFrom.addEventListener("change", (event) => {
    state.filters.dateFrom = event.target.value;
    renderAll();
  });
  dom.dateTo.addEventListener("change", (event) => {
    state.filters.dateTo = event.target.value;
    renderAll();
  });
  dom.parentFilter.addEventListener("change", (event) => {
    state.filters.parentId = event.target.value;
    renderAll();
  });
  if (dom.filterReset) {
    dom.filterReset.addEventListener("click", resetFilters);
  }
  if (dom.parentFilterSearch) {
    dom.parentFilterSearch.addEventListener("input", (event) => {
      state.filters.parentSearch = event.target.value.trim();
      renderParentFilterOptions();
    });
  }
  if (dom.parentViewSearch) {
    dom.parentViewSearch.addEventListener("input", (event) => {
      state.parentViewSearch = event.target.value.trim();
      renderParentClusters();
    });
  }
  if (dom.parentViewClear) {
    dom.parentViewClear.addEventListener("click", () => {
      state.parentViewSearch = "";
      state.highlightParentId = "";
      state.filters.parentId = "";
      if (dom.parentViewSearch) dom.parentViewSearch.value = "";
      renderAll();
    });
  }
  dom.dialog.addEventListener("close", () => {
    dom.taskForm.reset();
    dom.taskDeleteBtn.hidden = true;
    dom.taskForm.dataset.editingId = "";
  });
}

function hydrateStaticUi() {
  STATUSES.forEach((status) => {
    const option = document.createElement("option");
    option.value = status.id;
    option.textContent = status.label;
    dom.taskStatusSelect.appendChild(option);
  });
  renderBulkStatusButtons();
}

function loadTasks() {
  try {
    const raw = localStorage.getItem(STORAGE_KEY);
    if (raw) {
      const parsed = JSON.parse(raw);
      if (Array.isArray(parsed)) {
        state.tasks = parsed;
        return;
      }
    }
  } catch (error) {
    console.error("Failed to parse storage", error);
  }
  state.tasks = createSampleTasks();
  saveTasks();
}

function saveTasks() {
  localStorage.setItem(STORAGE_KEY, JSON.stringify(state.tasks));
}

function renderAll() {
  document.body.classList.toggle("selection-mode", state.selectionMode);
  document.body.classList.toggle("parent-view-mode", state.showParentView);
  dom.parentView.classList.toggle("active", state.showParentView);
  dom.toggleGroupBtn.classList.toggle("active", state.showParentView);
  dom.toggleSelectionBtn.classList.toggle("active", state.selectionMode);

  if (dom.searchInput) dom.searchInput.value = state.filters.searchRaw;
  if (dom.dateFrom) dom.dateFrom.value = state.filters.dateFrom;
  if (dom.dateTo) dom.dateTo.value = state.filters.dateTo;
  if (dom.parentViewSearch) dom.parentViewSearch.value = state.parentViewSearch;

  const tagScopedTasks = getFilteredTasks({ includeTagFilter: false });
  renderTagToggles(tagScopedTasks);

  const filteredTasks = getFilteredTasks();
  const groupedByStatus = groupByStatus(filteredTasks);

  renderStatusDock(groupedByStatus);
  renderBoard(groupedByStatus);
  renderParentOptions();
  renderParentFilterOptions();
  renderParentClusters();
  updateBulkActions();
}

function renderBoard(groupedTasks) {
  dom.board.innerHTML = "";
  const status = STATUSES.find((item) => item.id === state.activeStatus) ?? STATUSES[0];
  const tasks = groupedTasks[status.id] ?? [];

  const column = document.createElement("section");
  column.className = "column";
  column.dataset.status = status.id;

  const header = document.createElement("header");
  header.className = "column-header";
  header.innerHTML = `<span>${status.label}</span><span class="column-count">${tasks.length}</span>`;

  const body = document.createElement("div");
  body.className = "column-body";
  if (tasks.length === 0) {
    body.classList.add("empty");
  } else {
    tasks.forEach((task) => body.appendChild(createTaskCard(task)));
  }

  column.append(header, body);
  dom.board.appendChild(column);
}

function renderParentOptions(currentId = "") {
  dom.taskParentSelect.innerHTML = "";
  const noneOption = document.createElement("option");
  noneOption.value = "";
  noneOption.textContent = "\u306a\u3057";
  dom.taskParentSelect.appendChild(noneOption);

  state.tasks
    .filter((task) => task.id !== currentId && !isDescendant(task.id, currentId))
    .sort((a, b) => a.title.localeCompare(b.title, "ja"))
    .forEach((task) => {
      const option = document.createElement("option");
      option.value = task.id;
      option.textContent = task.title;
      dom.taskParentSelect.appendChild(option);
    });
}

function renderParentFilterOptions() {
  const previous = state.filters.parentId || "";
  const searchTerm = state.filters.parentSearch.trim().toLowerCase();
  dom.parentFilter.innerHTML = "";
  const allOption = document.createElement("option");
  allOption.value = "";
  allOption.textContent = "\u3059\u3079\u3066";
  dom.parentFilter.appendChild(allOption);

  const allParents = state.tasks
    .filter((task) => !task.parentId)
    .sort((a, b) => a.title.localeCompare(b.title, "ja"));

  const filtered = [];
  allParents.forEach((task) => {
    if (!searchTerm || task.title.toLowerCase().includes(searchTerm)) {
      filtered.push(task);
    }
  });

  if (previous && !filtered.some((task) => task.id === previous)) {
    const selected = allParents.find((task) => task.id === previous);
    if (selected) {
      filtered.unshift(selected);
    }
  }

  filtered.forEach((task) => {
    const option = document.createElement("option");
    option.value = task.id;
    option.textContent = task.title;
    dom.parentFilter.appendChild(option);
  });

  const hasSelection = previous && allParents.some((task) => task.id === previous);
  dom.parentFilter.value = hasSelection ? previous : "";
  if (!hasSelection) {
    state.filters.parentId = "";
  }
  if (dom.parentFilterSearch) {
    dom.parentFilterSearch.value = state.filters.parentSearch;
  }
}

function renderStatusDock(groupedTasks) {
  dom.statusDock.innerHTML = "";
  STATUSES.forEach((status) => {
    const button = document.createElement("button");
    button.type = "button";
    button.className = "status-chip";
    button.dataset.status = status.id;
    if (status.id === state.activeStatus) {
      button.classList.add("active");
    }
    const count = groupedTasks[status.id]?.length ?? 0;
    button.innerHTML = `
      <div class="status-chip-text">
        <strong>${status.label}</strong>
        <span>${status.hint}</span>
      </div>
      <span class="status-chip-count">${count}</span>
    `;
    button.addEventListener("click", () => {
      if (state.activeStatus !== status.id) {
        state.activeStatus = status.id;
        renderAll();
      }
    });
    dom.statusDock.appendChild(button);
  });
}

function renderBulkStatusButtons() {
  dom.bulkStatusButtons.innerHTML = "";
  STATUSES.forEach((status) => {
    const button = document.createElement("button");
    button.type = "button";
    button.className = "btn subtle";
    button.textContent = status.label;
    button.addEventListener("click", () => handleBulkMove(status.id));
    dom.bulkStatusButtons.appendChild(button);
  });
}

function renderTagToggles(tasks = []) {
  const container = dom.tagToggleContainer;
  if (!container) return;
  container.innerHTML = "";

  const tagSet = new Set();
  tasks.forEach((task) => (task.tags ?? []).forEach((tag) => tagSet.add(tag)));
  const sortedTags = [...tagSet].sort((a, b) => a.localeCompare(b, "ja"));

  const available = new Set(sortedTags);
  state.filters.selectedTags = state.filters.selectedTags.filter((tag) => available.has(tag));

  if (!sortedTags.length) {
    const placeholder = document.createElement("span");
    placeholder.className = "tag-toggle-empty";
    placeholder.textContent = "\u30bf\u30b0\u306f\u672a\u767b\u9332\u3067\u3059";
    container.appendChild(placeholder);
    return;
  }

  sortedTags.forEach((tag) => {
    const button = document.createElement("button");
    button.type = "button";
    button.className = "tag-toggle";
    button.textContent = tag;
    const isActive = state.filters.selectedTags.includes(tag);
    button.setAttribute("aria-pressed", isActive ? "true" : "false");
    button.classList.toggle("active", isActive);
    button.addEventListener("click", () => toggleTagFilter(tag));
    container.appendChild(button);
  });
}

function toggleTagFilter(tag) {
  const list = state.filters.selectedTags;
  const index = list.indexOf(tag);
  if (index >= 0) {
    list.splice(index, 1);
  } else {
    list.push(tag);
  }
  renderAll();
}

function createTaskCard(task) {
  const card = dom.taskCardTemplate.content.firstElementChild.cloneNode(true);
  card.dataset.id = task.id;
  card.dataset.status = task.status;

  if (state.highlightParentId && (state.highlightParentId === task.id || state.highlightParentId === task.parentId)) {
    card.classList.add("highlighted");
  }

  const checkbox = card.querySelector(".task-select");
  checkbox.checked = state.selectedIds.has(task.id);
  checkbox.style.display = state.selectionMode ? "block" : "none";
  checkbox.addEventListener("change", (event) => {
    if (event.target.checked) {
      state.selectedIds.add(task.id);
    } else {
      state.selectedIds.delete(task.id);
    }
    updateBulkActions();
  });

  card.querySelector(".task-title").textContent = task.title;
  card.querySelector(".assignee").textContent = task.assignee ? `\u62c5\u5f53: ${task.assignee}` : "\u62c5\u5f53: \u672a\u5b9a";
  card.querySelector(".due-date").textContent = task.dueDate ? `\u671f\u9650: ${formatDate(task.dueDate)}` : "\u671f\u9650: \u672a\u8a2d\u5b9a";
  card.querySelector(".progress").textContent = task.progress || "\u9032\u6357\u30e1\u30e2\u306a\u3057";
  card.querySelector(".notes").textContent = task.notes || "\u5099\u8003\u306a\u3057";

  const linkEl = card.querySelector(".resource-link");
  if (task.link) {
    linkEl.href = task.link;
    linkEl.textContent = task.link;
    linkEl.style.display = "block";
  } else {
    linkEl.style.display = "none";
  }

  const tagContainer = card.querySelector(".task-tags");
  tagContainer.innerHTML = "";
  (task.tags || []).forEach((tag) => {
    const tagEl = document.createElement("span");
    tagEl.className = "task-tag";
    tagEl.textContent = tag;
    tagContainer.appendChild(tagEl);
  });

  const childrenContainer = card.querySelector(".task-children");
  const children = state.tasks.filter((item) => item.parentId === task.id);
  if (children.length) {
    children.forEach((child) => {
      const row = document.createElement("div");
      row.className = "task-child";
      const statusLabel = STATUSES.find((status) => status.id === child.status)?.label ?? "";
      row.innerHTML = `<span>${child.title}</span><span>${statusLabel}</span>`;
      childrenContainer.appendChild(row);
    });
  } else {
    childrenContainer.style.display = "none";
  }

  const quickButtons = card.querySelector(".status-quick-buttons");
  quickButtons.innerHTML = "";
  STATUSES.forEach((status) => {
    if (status.id === task.status) return;
    const button = document.createElement("button");
    button.type = "button";
    button.textContent = status.label;
    button.addEventListener("click", () => {
      updateTask(task.id, { status: status.id }, { skipRender: true });
      renderAll();
    });
    quickButtons.appendChild(button);
  });

  card.querySelector('[data-action="edit"]').addEventListener("click", () => openTaskDialog(task.id));
  card.querySelector('[data-action="delete"]').addEventListener("click", () => {
    if (confirm("\u3053\u306e\u30bf\u30b9\u30af\u3092\u524a\u9664\u3057\u307e\u3059\u304b\uff1f\u5b50\u30bf\u30b9\u30af\u3082\u524a\u9664\u3055\u308c\u307e\u3059\u3002")) {
      deleteTask(task.id);
      renderAll();
    }
  });

  return card;
}

function openTaskDialog(taskId = "") {
  const editing = Boolean(taskId);
  dom.dialogTitle.textContent = editing ? "\u30bf\u30b9\u30af\u3092\u7de8\u96c6" : "\u30bf\u30b9\u30af\u3092\u8ffd\u52a0";
  dom.taskDeleteBtn.hidden = !editing;
  dom.taskForm.dataset.editingId = editing ? taskId : "";
  populateTaskForm(editing ? getTask(taskId) : null);
  dom.dialog.showModal();
}

function closeDialog() {
  dom.dialog.close();
}

function populateTaskForm(task) {
  dom.taskForm.reset();
  renderParentOptions(task?.id ?? "");
  dom.taskForm.elements.title.value = task?.title ?? "";
  dom.taskForm.elements.assignee.value = task?.assignee ?? "";
  dom.taskForm.elements.dueDate.value = task?.dueDate ?? "";
  dom.taskForm.elements.link.value = task?.link ?? "";
  dom.taskForm.elements.tags.value = (task?.tags ?? []).join(", ");
  dom.taskForm.elements.progress.value = task?.progress ?? "";
  dom.taskForm.elements.notes.value = task?.notes ?? "";
  dom.taskForm.elements.parentId.value = task?.parentId ?? "";
  dom.taskForm.elements.status.value = task?.status ?? STATUSES[0].id;
}

function handleTaskSubmit(event) {
  event.preventDefault();
  const formData = new FormData(dom.taskForm);
  const payload = {
    title: formData.get("title").trim(),
    assignee: formData.get("assignee").trim(),
    dueDate: formData.get("dueDate") || "",
    link: formData.get("link").trim(),
    tags: formData
      .get("tags")
      .split(",")
      .map((tag) => tag.trim())
      .filter(Boolean),
    progress: formData.get("progress").trim(),
    notes: formData.get("notes").trim(),
    parentId: formData.get("parentId") || "",
    status: formData.get("status")
  };

  const editingId = dom.taskForm.dataset.editingId;
  if (editingId) {
    updateTask(editingId, payload, { skipRender: true, skipPersist: true });
    saveTasks();
  } else {
    const newTask = {
      id: generateId(),
      createdAt: Date.now(),
      updatedAt: Date.now(),
      ...payload
    };
    state.tasks.push(newTask);
    saveTasks();
  }

  renderAll();
  closeDialog();
}

function handleDialogDelete() {
  const editingId = dom.taskForm.dataset.editingId;
  if (!editingId) return;
  if (!confirm("\u3053\u306e\u30bf\u30b9\u30af\u3092\u524a\u9664\u3057\u307e\u3059\u304b\uff1f\u5b50\u30bf\u30b9\u30af\u3082\u524a\u9664\u3055\u308c\u307e\u3059\u3002")) return;
  deleteTask(editingId);
  renderAll();
  closeDialog();
}

function resetFilters() {
  state.filters.search = "";
  state.filters.searchRaw = "";
  state.filters.selectedTags = [];
  state.filters.dateFrom = "";
  state.filters.dateTo = "";
  state.filters.parentId = "";
  state.filters.parentSearch = "";
  state.parentViewSearch = "";
  state.parentViewSearch = "";
  state.highlightParentId = "";
  state.selectedIds.clear();
  state.selectionMode = false;
  state.showParentView = false;
  state.activeStatus = STATUSES[0].id;
  if (dom.searchInput) dom.searchInput.value = "";
  if (dom.dateFrom) dom.dateFrom.value = "";
  if (dom.dateTo) dom.dateTo.value = "";
  if (dom.parentFilterSearch) dom.parentFilterSearch.value = "";
  if (dom.parentViewSearch) dom.parentViewSearch.value = "";
  if (dom.parentViewClear) dom.parentViewClear.disabled = true;
  renderAll();
}

function handleBulkDelete() {
  if (!state.selectedIds.size) return;
  if (!confirm("\u9078\u629e\u3057\u305f\u30bf\u30b9\u30af\u3092\u307e\u3068\u3081\u3066\u524a\u9664\u3057\u307e\u3059\u304b\uff1f\u5b50\u30bf\u30b9\u30af\u3082\u524a\u9664\u3055\u308c\u307e\u3059\u3002")) {
    return;
  }
  [...state.selectedIds].forEach((taskId) => deleteTask(taskId));
  state.selectedIds.clear();
  updateBulkActions();
  renderAll();
}

function handleBulkMove(statusId) {
  if (!state.selectedIds.size) return;
  state.selectedIds.forEach((taskId) => updateTask(taskId, { status: statusId }, { skipRender: true, skipPersist: true }));
  saveTasks();
  renderAll();
}

function handleSelectAll() {
  const filtered = getFilteredTasks();
  filtered.forEach((task) => state.selectedIds.add(task.id));
  updateBulkActions();
  renderAll();
}

function focusParentTasks(parentId) {
  const parentTask = getTask(parentId);
  state.filters.search = "";
  state.filters.searchRaw = "";
  state.filters.selectedTags = [];
  state.filters.dateFrom = "";
  state.filters.dateTo = "";
  state.filters.parentId = parentId;
  state.highlightParentId = parentId;
  state.showParentView = false;
  state.selectionMode = false;
  state.selectedIds.clear();
  state.filters.parentSearch = "";
  state.parentViewSearch = "";
  if (parentTask) {
    state.activeStatus = parentTask.status;
  }
  renderAll();
}

function toggleParentView() {
  state.showParentView = !state.showParentView;
  if (state.showParentView) {
    state.selectionMode = false;
    state.selectedIds.clear();
    state.parentViewSearch = "";
  } else {
    state.highlightParentId = "";
  }
  renderAll();
}

function toggleSelectionMode() {
  state.selectionMode = !state.selectionMode;
  if (!state.selectionMode) {
    state.selectedIds.clear();
  }
  renderAll();
}

function renderParentClusters() {
  dom.parentClusters.innerHTML = "";
  if (!state.showParentView) return;

  if (dom.parentViewSearch) {
    dom.parentViewSearch.value = state.parentViewSearch;
  }
  if (dom.parentViewClear) {
    dom.parentViewClear.disabled = !state.highlightParentId;
  }

  const searchTerm = state.parentViewSearch.trim().toLowerCase();

  const parents = state.tasks
    .filter((task) => !task.parentId)
    .filter((parent) => {
      const matchesParent = matchesTaskFilters(parent);
      const childMatches = state.tasks.some((child) => child.parentId === parent.id && matchesTaskFilters(child));
      if (!(matchesParent || childMatches)) {
        return false;
      }

      if (!searchTerm) {
        return true;
      }

      const parentHaystack = [
        parent.title,
        parent.assignee,
        parent.progress,
        parent.notes,
        parent.link,
        ...(parent.tags ?? [])
      ]
        .filter(Boolean)
        .join(" ")
        .toLowerCase();
      if (parentHaystack.includes(searchTerm)) {
        return true;
      }

      return state.tasks.some((child) => {
        if (child.parentId !== parent.id) return false;
        const childHaystack = [
          child.title,
          child.assignee,
          child.progress,
          child.notes,
          child.link,
          ...(child.tags ?? [])
        ]
          .filter(Boolean)
          .join(" ")
          .toLowerCase();
        return childHaystack.includes(searchTerm);
      });
    })
    .sort((a, b) => a.title.localeCompare(b.title, "ja"));

  if (!parents.length) {
    const empty = document.createElement("div");
    empty.className = "parent-empty";
    empty.textContent = "条件に一致する親タスクがありません。";
    dom.parentClusters.appendChild(empty);
    return;
  }

  parents.forEach((parent) => {
    const children = state.tasks.filter((task) => task.parentId === parent.id);
    const isHighlighted = state.highlightParentId === parent.id;
    let expanded = isHighlighted;

    const cluster = document.createElement("div");
    cluster.className = "parent-cluster";
    if (isHighlighted) {
      cluster.classList.add("highlighted");
      cluster.classList.add("expanded");
    }

    const header = document.createElement("div");
    header.className = "cluster-header";

    const titleBox = document.createElement("div");
    titleBox.className = "cluster-title";

    const title = document.createElement("h4");
    title.textContent = parent.title;

    const meta = document.createElement("div");
    meta.className = "cluster-meta";
    const metaParts = [];
    if (parent.assignee) metaParts.push(`担当: ${parent.assignee}`);
    if (parent.dueDate) metaParts.push(`期限: ${formatDate(parent.dueDate)}`);
    metaParts.push(`子タスク ${children.length} 件`);
    meta.textContent = metaParts.join(" / ");

    titleBox.append(title, meta);

    const statusStrip = document.createElement("div");
    statusStrip.className = "cluster-status";
    STATUSES.forEach((status) => {
      const count = children.filter((child) => child.status === status.id).length;
      const pill = document.createElement("span");
      pill.className = "status-pill";
      pill.textContent = `${status.label} ${count}`;
      statusStrip.appendChild(pill);
    });

    const actions = document.createElement("div");
    actions.className = "cluster-actions";

    const toggleButton = document.createElement("button");
    toggleButton.type = "button";
    toggleButton.className = "btn tiny ghost";
    toggleButton.textContent = expanded ? "折りたたむ" : "展開";

    const focusButton = document.createElement("button");
    focusButton.type = "button";
    focusButton.className = "btn tiny subtle";
    focusButton.textContent = "ボードで表示";

    actions.append(toggleButton, focusButton);
    header.append(titleBox, statusStrip, actions);

    const body = document.createElement("div");
    body.className = "cluster-body";
    body.hidden = !expanded;

    if (children.length) {
      children
        .sort((a, b) => a.title.localeCompare(b.title, "ja"))
        .forEach((child) => {
          const row = document.createElement("div");
          row.className = "cluster-child-row";
          const statusLabel = STATUSES.find((status) => status.id === child.status)?.label ?? "";
          row.innerHTML = `<span class="child-title">${child.title}</span><span class="child-status">${statusLabel}</span>`;
          row.addEventListener("click", (event) => {
            event.stopPropagation();
            focusParentTasks(parent.id);
          });
          body.appendChild(row);
        });
    } else {
      const emptyChild = document.createElement("div");
      emptyChild.className = "cluster-child-empty";
      emptyChild.textContent = "子タスクはまだありません。";
      body.appendChild(emptyChild);
    }

    toggleButton.addEventListener("click", (event) => {
      event.stopPropagation();
      expanded = !expanded;
      body.hidden = !expanded;
      cluster.classList.toggle("expanded", expanded);
      toggleButton.textContent = expanded ? "折りたたむ" : "展開";
    });

    focusButton.addEventListener("click", (event) => {
      event.stopPropagation();
      focusParentTasks(parent.id);
    });

    header.addEventListener("click", (event) => {
      if (event.target.closest("button")) return;
      focusParentTasks(parent.id);
    });

    cluster.append(header, body);
    dom.parentClusters.appendChild(cluster);
  });
}

function matchesTaskFilters(task, options = {}) {
  const { includeTags = true } = options;
  const search = state.filters.search;
  const selectedTags = state.filters.selectedTags;
  const from = state.filters.dateFrom;
  const to = state.filters.dateTo;

  if (search) {
    const haystack = [
      task.title,
      task.assignee,
      task.progress,
      task.notes,
      task.link,
      ...(task.tags ?? [])
    ]
      .filter(Boolean)
      .join(" ")
      .toLowerCase();
    if (!haystack.includes(search)) {
      return false;
    }
  }

  if (includeTags && selectedTags.length) {
    const lowerTags = (task.tags ?? []).map((tag) => tag.toLowerCase());
    const matchesAll = selectedTags.every((tag) => lowerTags.includes(tag.toLowerCase()));
    if (!matchesAll) return false;
  }

  if (from && task.dueDate && task.dueDate < from) return false;
  if (to && task.dueDate && task.dueDate > to) return false;

  return true;
}

function getFilteredTasks(options = {}) {
  const { includeTagFilter = true } = options;
  const parentId = state.filters.parentId;
  const highlight = state.highlightParentId;

  return state.tasks.filter((task) => {
    if (!matchesTaskFilters(task, { includeTags: includeTagFilter })) {
      return false;
    }

    if (parentId && !(task.id === parentId || task.parentId === parentId)) {
      return false;
    }

    if (highlight && !(task.id === highlight || task.parentId === highlight)) {
      return false;
    }

    return true;
  });
}

function groupByStatus(tasks) {
  return tasks.reduce((acc, task) => {
    if (!acc[task.status]) acc[task.status] = [];
    acc[task.status].push(task);
    return acc;
  }, {});
}

function updateTask(taskId, patch, options = {}) {
  const task = getTask(taskId);
  if (!task) return;
  const { skipRender = false, skipPersist = false } = options;
  Object.assign(task, patch, { updatedAt: Date.now() });
  if (!skipPersist) {
    saveTasks();
  }
  if (!skipRender) {
    renderAll();
  }
}

function deleteTask(taskId) {
  const childIds = state.tasks.filter((task) => task.parentId === taskId).map((task) => task.id);
  state.tasks = state.tasks.filter((task) => task.id !== taskId);
  childIds.forEach((childId) => deleteTask(childId));
  state.selectedIds.delete(taskId);
  saveTasks();
}

function getTask(taskId) {
  return state.tasks.find((task) => task.id === taskId);
}

function isDescendant(candidateId, targetId) {
  if (!candidateId || !targetId) return false;
  let cursor = state.tasks.find((task) => task.id === candidateId)?.parentId;
  while (cursor) {
    if (cursor === targetId) return true;
    cursor = state.tasks.find((task) => task.id === cursor)?.parentId;
  }
  return false;
}

function updateBulkActions() {
  const visible = state.selectionMode;
  const count = state.selectedIds.size;
  if (dom.selectionToolbar) {
    dom.selectionToolbar.classList.toggle("active", visible);
  }
  if (dom.selectionCount) {
    dom.selectionCount.textContent = `${count}\u4EF6\u9078\u629E\u4E2D`;
  }
  dom.bulkDeleteBtn.disabled = count === 0;
  dom.clearSelectionBtn.disabled = count === 0;
  dom.bulkStatusButtons.querySelectorAll("button").forEach((button) => {
    button.disabled = count === 0;
  });
}

if (document.readyState === "loading") {
  document.addEventListener("DOMContentLoaded", init, { once: true });
} else {
  init();
}

function formatDate(isoDate) {
  if (!isoDate) return "";
  const [year, month, day] = isoDate.split("-");
  return `${year}/${month}/${day}`;
}

function generateId() {
  if (crypto?.randomUUID) return crypto.randomUUID();
  return `task-${Date.now()}-${Math.random().toString(16).slice(2)}`;
}

function createSampleTasks() {
  const now = new Date();
  const iso = (offset) => {
    const base = new Date(now);
    base.setDate(base.getDate() + offset);
    return base.toISOString().slice(0, 10);
  };

  const projectId = generateId();
  return [
    {
      id: projectId,
      title: "\u30e9\u30a4\u30f3\u6539\u5584\u306e\u5168\u4f53\u8a2d\u8a08",
      assignee: "\u7530\u4e2d",
      dueDate: iso(7),
      link: "https://www.toyota.co.jp/",
      tags: ["\u5de5\u7a0b\u7ba1\u7406", "\u512a\u5148"],
      progress: "\u73fe\u72b6\u5206\u6790\u3092\u5b8c\u4e86\u3002\u6539\u5584\u6848\u306e\u521d\u7a3f\u3092\u4f5c\u6210\u6e08\u307f\u3002",
      notes: "\u30b3\u30b9\u30c8\u8a66\u7b97\u3092\u8ffd\u52a0\u3059\u308b\u5fc5\u8981\u3042\u308a\u3002",
      parentId: "",
      status: "ready",
      createdAt: Date.now(),
      updatedAt: Date.now()
    },
    {
      id: generateId(),
      title: "\u6f5c\u5728\u30dc\u30c8\u30eb\u30cd\u30c3\u30af\u306e\u8abf\u67fb",
      assignee: "\u4f50\u85e4",
      dueDate: iso(3),
      link: "",
      tags: ["\u5de5\u7a0b\u7ba1\u7406", "\u8abf\u67fb"],
      progress: "\u30e9\u30a4\u30f3\u505c\u6b62\u30ed\u30b0\u304b\u30895\u4ef6\u306e\u5019\u88dc\u3092\u62bd\u51fa\u3002",
      notes: "\u73fe\u5834\u30d2\u30a2\u30ea\u30f3\u30b0\u3092\u4e88\u5b9a\u3002",
      parentId: projectId,
      status: "inprogress",
      createdAt: Date.now(),
      updatedAt: Date.now()
    },
    {
      id: generateId(),
      title: "\u5b89\u5168\u6559\u80b2\u30b3\u30f3\u30c6\u30f3\u30c4\u306e\u898b\u76f4\u3057",
      assignee: "\u4e2d\u6751",
      dueDate: iso(12),
      link: "file:///\\\\server\\docs\\safety",
      tags: ["\u6559\u80b2", "\u5b89\u5168"],
      progress: "\u65e2\u5b58\u6559\u6750\u306e\u68da\u5378\u3057\u5b8c\u4e86\u3002",
      notes: "\u65b0\u5165\u793e\u54e1\u5411\u3051\u306e\u8ffd\u52a0\u30d1\u30fc\u30c8\u304c\u5fc5\u8981\u3002",
      parentId: "",
      status: "backlog",
      createdAt: Date.now(),
      updatedAt: Date.now()
    },
    {
      id: generateId(),
      title: "AI\u5224\u5b9a\u30e2\u30c7\u30eb\u306e\u7cbe\u5ea6\u691c\u8a3c",
      assignee: "\u9234\u6728",
      dueDate: iso(-2),
      link: "",
      tags: ["AI", "\u54c1\u8cea"],
      progress: "\u30c6\u30b9\u30c8\u30c7\u30fc\u30bf\u306795%\u7cbe\u5ea6\u3002",
      notes: "\u73fe\u5834\u5c0e\u5165\u524d\u306b\u6700\u7d42\u78ba\u8a8d\u304c\u5fc5\u9808\u3002",
      parentId: "",
      status: "waiting",
      createdAt: Date.now(),
      updatedAt: Date.now()
    },
    {
      id: generateId(),
      title: "\u6539\u5584\u6848\u30ec\u30d3\u30e5\u30fc\u4f1a\u8b70",
      assignee: "\u7530\u4e2d",
      dueDate: iso(1),
      link: "https://teams.microsoft.com/",
      tags: ["\u4f1a\u8b70", "\u512a\u5148"],
      progress: "\u30a2\u30b8\u30a7\u30f3\u30c0\u4f5c\u6210\u6e08\u307f\u3002",
      notes: "\u53c2\u52a0\u8005\u3078\u306e\u8cc7\u6599\u914d\u5e03\u3092\u5b8c\u4e86\u3002",
      parentId: projectId,
      status: "ready",
      createdAt: Date.now(),
      updatedAt: Date.now()
    }
  ];
}