"use client";

const APP_HISTORY_KEY = "boss.app.history.v1";
const NATIVE_SESSION_KEY = "boss.native.session.v1";
const MAX_HISTORY_ENTRIES = 48;

export type NativeSessionSnapshot = {
  restoreToken: string;
  account: string;
  displayName: string;
  expiresAt: string;
  lastSyncedAt: string;
};

export type AppBackAction =
  | { mode: "history" }
  | { mode: "replace"; target: string }
  | { mode: "noop" };

function isBrowser() {
  return typeof window !== "undefined";
}

function readJsonStorage<T>(key: string, storage: Storage): T | null {
  try {
    const raw = storage.getItem(key);
    return raw ? (JSON.parse(raw) as T) : null;
  } catch {
    return null;
  }
}

function writeJsonStorage(key: string, value: unknown, storage: Storage) {
  try {
    storage.setItem(key, JSON.stringify(value));
  } catch {
    // Ignore storage write failures in constrained webviews.
  }
}

function basePathFor(input: string) {
  return input.split("#")[0]?.split("?")[0] || "/";
}

function fallbackForPath(input: string) {
  const pathname = basePathFor(input);
  if (pathname === "/auth/login") return null;
  if (pathname.startsWith("/auth/")) return "/auth/login";
  if (pathname === "/conversations") return null;
  if (pathname.startsWith("/conversations/")) return "/conversations";
  if (pathname === "/devices") {
    return input.includes("?") ? "/devices" : "/conversations";
  }
  if (pathname.startsWith("/devices/")) return "/devices";
  if (pathname === "/me") return "/conversations";
  if (pathname.startsWith("/me/")) return "/me";
  return "/conversations";
}

export function currentAppLocation() {
  if (!isBrowser()) return "/";
  return `${window.location.pathname}${window.location.search}${window.location.hash}`;
}

export function pushAppHistoryEntry(path: string) {
  if (!isBrowser()) return;
  const current = readJsonStorage<string[]>(APP_HISTORY_KEY, window.sessionStorage) ?? [];
  const normalized = path || "/";
  const next = current.filter((entry) => entry !== normalized);
  next.push(normalized);
  writeJsonStorage(APP_HISTORY_KEY, next.slice(-MAX_HISTORY_ENTRIES), window.sessionStorage);
}

export function popAppHistoryEntry(expectedPath?: string) {
  if (!isBrowser()) return;
  const current = readJsonStorage<string[]>(APP_HISTORY_KEY, window.sessionStorage) ?? [];
  if (!current.length) return;
  if (expectedPath && current[current.length - 1] !== expectedPath) {
    writeJsonStorage(
      APP_HISTORY_KEY,
      current.filter((entry) => entry !== expectedPath),
      window.sessionStorage,
    );
    return;
  }
  current.pop();
  writeJsonStorage(APP_HISTORY_KEY, current, window.sessionStorage);
}

export function resolveAppBackAction(currentPath: string, explicitFallback?: string): AppBackAction {
  if (!isBrowser()) {
    return explicitFallback ? { mode: "replace", target: explicitFallback } : { mode: "noop" };
  }

  const history = readJsonStorage<string[]>(APP_HISTORY_KEY, window.sessionStorage) ?? [];
  const previous = [...history].reverse().find((entry) => entry !== currentPath);
  if (previous) {
    return { mode: "history" };
  }

  const fallback = explicitFallback ?? fallbackForPath(currentPath);
  if (fallback && fallback !== currentPath) {
    return { mode: "replace", target: fallback };
  }

  return { mode: "noop" };
}

export async function isNativeBossApp() {
  if (!isBrowser()) return false;
  const { Capacitor } = await import("@capacitor/core");
  return Capacitor.getPlatform() !== "web";
}

async function preferencesApi() {
  if (!(await isNativeBossApp())) return null;
  const { Preferences } = await import("@capacitor/preferences");
  return Preferences;
}

export async function persistNativeSessionSnapshot(snapshot: NativeSessionSnapshot) {
  const serialized = JSON.stringify(snapshot);
  const preferences = await preferencesApi();
  if (preferences) {
    await preferences.set({ key: NATIVE_SESSION_KEY, value: serialized });
    return;
  }
  if (isBrowser()) {
    window.localStorage.setItem(NATIVE_SESSION_KEY, serialized);
  }
}

export async function readNativeSessionSnapshot() {
  const preferences = await preferencesApi();
  if (preferences) {
    const result = await preferences.get({ key: NATIVE_SESSION_KEY });
    return result.value ? (JSON.parse(result.value) as NativeSessionSnapshot) : null;
  }
  if (!isBrowser()) return null;
  return readJsonStorage<NativeSessionSnapshot>(NATIVE_SESSION_KEY, window.localStorage);
}

export async function clearNativeSessionSnapshot() {
  const preferences = await preferencesApi();
  if (preferences) {
    await preferences.remove({ key: NATIVE_SESSION_KEY });
    return;
  }
  if (isBrowser()) {
    window.localStorage.removeItem(NATIVE_SESSION_KEY);
  }
}