import { useEffect, useState } from "react";

const TAB_IDS = ["overview", "department", "region", "customer"] as const;
const SECTION_IDS = ["inventory", "models", "flow"] as const;

export type AssetTab = (typeof TAB_IDS)[number];
export type AssetSection = (typeof SECTION_IDS)[number];

interface AssetHashState {
  tab: AssetTab;
  section: AssetSection;
}

const DEFAULT_STATE: AssetHashState = { tab: "overview", section: "inventory" };

const isTab = (value: string | undefined): value is AssetTab =>
  Boolean(value) && (TAB_IDS as readonly string[]).includes(value as string);
const isSection = (value: string | undefined): value is AssetSection =>
  Boolean(value) && (SECTION_IDS as readonly string[]).includes(value as string);

function parseHash(): AssetHashState {
  const [first, second, third] = window.location.hash.slice(1).split("/");
  if (first !== "assets") return DEFAULT_STATE;
  return {
    tab: isTab(second) ? second : "overview",
    section: isSection(third) ? third : "inventory",
  };
}

function writeHash(tab: AssetTab, section: AssetSection) {
  const parts = ["assets", tab];
  // 默认子页签不写入，保持 `#assets/<tab>` 简洁。
  if (tab === "overview" && section !== "inventory") parts.push(section);
  const hash = `#${parts.join("/")}`;
  window.history.replaceState(
    null,
    "",
    `${window.location.pathname}${window.location.search}${hash}`,
  );
}

/**
 * 资产模块页签状态 ↔ URL hash 二级/三级段（`#assets/<tab>[/<section>]`）。
 * 默认值不写入 hash，刷新可恢复，链接可分享；与 Shell 的一级模块段兼容。
 */
export function useAssetHash() {
  const [state, setState] = useState<AssetHashState>(parseHash);

  useEffect(() => {
    const onChange = () => setState(parseHash());
    window.addEventListener("hashchange", onChange);
    return () => window.removeEventListener("hashchange", onChange);
  }, []);

  const update = (next: Partial<AssetHashState>) => {
    const merged = { ...state, ...next };
    writeHash(merged.tab, merged.section);
    setState(merged);
  };

  return [state, update] as const;
}