import { isTauriRuntime } from "./platform";

export const DESKTOP_SERVER_URL_KEY = "ctms_desktop_server_url";
export const DESKTOP_SERVER_URL_CHANGED_EVENT = "ctms:desktop-server-url-changed";

export type DesktopServerUrlValidationResult =
  | { ok: true; url: string }
  | { ok: false; reason: string };

const LOCAL_HTTP_HOSTS = new Set(["localhost", "127.0.0.1", "::1", "[::1]"]);

const getStorage = (): Storage | null => {
  if (typeof window === "undefined") return null;
  try {
    return window.localStorage;
  } catch {
    return null;
  }
};

const emitServerUrlChanged = (previous: string | null, current: string | null): void => {
  if (typeof window === "undefined") return;
  window.dispatchEvent(
    new CustomEvent(DESKTOP_SERVER_URL_CHANGED_EVENT, {
      detail: { previous, current },
    }),
  );
};

export const normalizeDesktopServerUrl = (value: string): DesktopServerUrlValidationResult => {
  const raw = value.trim();
  if (!raw) return { ok: false, reason: "请输入服务器地址" };

  let parsed: URL;
  try {
    parsed = new URL(raw);
  } catch {
    return { ok: false, reason: "服务器地址格式不正确" };
  }

  if (parsed.username || parsed.password) {
    return { ok: false, reason: "服务器地址不能包含用户名或密码" };
  }

  const isHttps = parsed.protocol === "https:";
  const isLocalHttp = parsed.protocol === "http:" && LOCAL_HTTP_HOSTS.has(parsed.hostname);
  if (!isHttps && !isLocalHttp) {
    return { ok: false, reason: "非本地服务必须使用 HTTPS" };
  }

  return { ok: true, url: `${parsed.origin}/` };
};

export const getDesktopServerUrl = (): string | null => {
  const stored = getStorage()?.getItem(DESKTOP_SERVER_URL_KEY);
  if (!stored) return null;
  const result = normalizeDesktopServerUrl(stored);
  return result.ok ? result.url : null;
};

export const hasDesktopServerUrl = (): boolean => Boolean(getDesktopServerUrl());

export const setDesktopServerUrl = (value: string): DesktopServerUrlValidationResult => {
  const result = normalizeDesktopServerUrl(value);
  if (!result.ok) return result;
  const storage = getStorage();
  if (!storage) return { ok: false, reason: "当前环境无法保存服务器地址" };
  const previous = getDesktopServerUrl();
  storage.setItem(DESKTOP_SERVER_URL_KEY, result.url);
  emitServerUrlChanged(previous, result.url);
  return result;
};

export const clearDesktopServerUrl = (): void => {
  const previous = getDesktopServerUrl();
  getStorage()?.removeItem(DESKTOP_SERVER_URL_KEY);
  emitServerUrlChanged(previous, null);
};

export const shouldRequireDesktopServerUrl = (): boolean => isTauriRuntime() && !hasDesktopServerUrl();