import type { FunnelAnswers } from "./types";

/**
 * Структура данных для хранения состояния воронки
 */
export interface FunnelRuntimeState {
  answers: FunnelAnswers;
  history: string[];
  version: number;
  timestamp?: number; // Для отслеживания времени последнего обновления
}

/**
 * Префикс для ключей в localStorage
 */
const STORAGE_PREFIX = "funnel_state_";

/**
 * Время жизни данных в localStorage (7 дней)
 */
const STORAGE_TTL = 7 * 24 * 60 * 60 * 1000;

/**
 * Проверяет доступность localStorage
 */
function isLocalStorageAvailable(): boolean {
  try {
    const testKey = "__storage_test__";
    localStorage.setItem(testKey, "test");
    localStorage.removeItem(testKey);
    return true;
  } catch {
    return false;
  }
}

/**
 * Получает ключ для localStorage по ID воронки
 */
function getStorageKey(funnelId: string): string {
  return `${STORAGE_PREFIX}${funnelId}`;
}

/**
 * Сохраняет состояние воронки в localStorage
 */
export function saveFunnelState(
  funnelId: string,
  state: FunnelRuntimeState
): void {
  if (!isLocalStorageAvailable()) {
    return;
  }

  try {
    const dataToSave: FunnelRuntimeState = {
      ...state,
      timestamp: Date.now(),
    };

    localStorage.setItem(getStorageKey(funnelId), JSON.stringify(dataToSave));
  } catch (error) {
    console.warn("Failed to save funnel state to localStorage:", error);
  }
}

/**
 * Загружает состояние воронки из localStorage
 */
export function loadFunnelState(funnelId: string): FunnelRuntimeState | null {
  if (!isLocalStorageAvailable()) {
    return null;
  }

  try {
    const stored = localStorage.getItem(getStorageKey(funnelId));
    if (!stored) {
      return null;
    }

    const data = JSON.parse(stored) as FunnelRuntimeState;

    // Проверяем TTL
    if (data.timestamp) {
      const age = Date.now() - data.timestamp;
      if (age > STORAGE_TTL) {
        // Данные устарели, удаляем
        clearFunnelState(funnelId);
        return null;
      }
    }

    return data;
  } catch (error) {
    console.warn("Failed to load funnel state from localStorage:", error);
    return null;
  }
}

/**
 * Очищает состояние воронки из localStorage
 */
export function clearFunnelState(funnelId: string): void {
  if (!isLocalStorageAvailable()) {
    return;
  }

  try {
    localStorage.removeItem(getStorageKey(funnelId));
  } catch (error) {
    console.warn("Failed to clear funnel state from localStorage:", error);
  }
}

/**
 * Очищает все устаревшие состояния воронок
 */
export function clearExpiredFunnelStates(): void {
  if (!isLocalStorageAvailable()) {
    return;
  }

  try {
    const now = Date.now();
    const keysToRemove: string[] = [];

    // Проходим по всем ключам в localStorage
    for (let i = 0; i < localStorage.length; i++) {
      const key = localStorage.key(i);
      if (!key?.startsWith(STORAGE_PREFIX)) {
        continue;
      }

      const value = localStorage.getItem(key);
      if (!value) {
        continue;
      }

      try {
        const data = JSON.parse(value) as FunnelRuntimeState;
        if (data.timestamp && now - data.timestamp > STORAGE_TTL) {
          keysToRemove.push(key);
        }
      } catch {
        // Если не удалось распарсить - удаляем
        keysToRemove.push(key);
      }
    }

    // Удаляем устаревшие ключи
    for (const key of keysToRemove) {
      localStorage.removeItem(key);
    }
  } catch (error) {
    console.warn("Failed to clear expired funnel states:", error);
  }
}