import { writable, get } from "svelte/store";
import type { BreadcrumbEntry, NodeDetail } from "./types.js";

const STORAGE_KEY = "filelib.browser";

interface PersistedState {
  expanded: string[];
  currentNodeId: string | null;
  tab: string | null;
  selectedFilePath: string | null;
}

function loadPersisted(): PersistedState {
  try {
    const raw = sessionStorage.getItem(STORAGE_KEY);
    if (raw) return JSON.parse(raw) as PersistedState;
  } catch { /* ignore */ }
  return { expanded: [], currentNodeId: null, tab: null, selectedFilePath: null };
}

function savePersisted(): void {
  try {
    const state: PersistedState = {
      expanded: [...get(expanded)],
      currentNodeId: get(currentNode)?.id ?? null,
      tab: get(activeTab),
      selectedFilePath: get(selectedFilePath),
    };
    sessionStorage.setItem(STORAGE_KEY, JSON.stringify(state));
  } catch { /* sessionStorage 不可用时静默忽略 */ }
}

const persisted = loadPersisted();

/** 树展开集合 / 当前选中节点 / 面包屑 / 树刷新计数。 */
export const expanded = writable<Set<string>>(new Set(persisted.expanded));
export const currentNode = writable<NodeDetail | null>(null);
export const breadcrumb = writable<BreadcrumbEntry[]>([]);
export const treeVersion = writable(0);

/** 刷新后需要恢复的节点 ID;LibraryView onMount 消费后清空。 */
export const restoreNodeId = persisted.currentNodeId;
/** 刷新后需要恢复的 tab;NodeDetailPanel 消费。 */
export const restoreTab = persisted.tab;

/** 右侧预览栏:当前选中文件路径(项目内);切换节点时清空。 */
export const selectedFilePath = writable<string | null>(persisted.selectedFilePath);
/** 文件列表刷新计数(编辑器保存/删除后 bump,列表随之重载)。 */
export const filesVersion = writable(0);

/** 当前激活的 tab(由 NodeDetailPanel 写入,持久化用)。 */
export const activeTab = writable<string | null>(persisted.tab);

// 订阅需要持久化的 store,变化时写 sessionStorage。
expanded.subscribe(() => savePersisted());
currentNode.subscribe(() => savePersisted());
selectedFilePath.subscribe(() => savePersisted());
activeTab.subscribe(() => savePersisted());

export function bumpTree(): void {
  treeVersion.update((v) => v + 1);
}

export function bumpFiles(): void {
  filesVersion.update((v) => v + 1);
}

export function clearSelectedFile(): void {
  selectedFilePath.set(null);
}

export function toggleExpanded(id: string): void {
  expanded.update((set) => {
    const next = new Set(set);
    if (next.has(id)) next.delete(id);
    else next.add(id);
    return next;
  });
}