/**
 * 本地缓存模块 - localStorage 封装，按 integrateId 隔离
 */
import { ChatMessage, CacheData } from './types';
import { logger } from './logger';

const STORAGE_PREFIX = 'csk_history_';
const MAX_MESSAGES = 200;
const TRIM_COUNT = 50;

/** 生成存储 key */
function storageKey(integrateId: string): string {
  return `${STORAGE_PREFIX}${integrateId}`;
}

/**
 * 保存消息到 localStorage
 */
export function saveMessages(integrateId: string, messages: ChatMessage[]): void {
  try {
    // 消息上限裁剪：保留最新 200 条，超出裁剪最早 50 条
    let trimmed = messages;
    if (trimmed.length > MAX_MESSAGES) {
      trimmed = trimmed.slice(TRIM_COUNT);
      logger.warn(`消息数量达到上限，已裁剪最早 ${TRIM_COUNT} 条，当前 ${trimmed.length} 条`);
    }

    const data: CacheData = {
      messages: trimmed,
      updatedAt: Date.now(),
    };
    localStorage.setItem(storageKey(integrateId), JSON.stringify(data));
  } catch (e) {
    if (e instanceof Error && e.name === 'QuotaExceededError') {
      logger.error('localStorage 空间不足，会话历史保存失败。建议清空历史记录。');
    } else {
      logger.error('保存会话历史失败', e);
    }
  }
}

/**
 * 从 localStorage 加载消息
 */
export function loadMessages(integrateId: string): ChatMessage[] {
  try {
    const raw = localStorage.getItem(storageKey(integrateId));
    if (!raw) {
      return [];
    }
    const data: CacheData = JSON.parse(raw);
    if (!data || !Array.isArray(data.messages)) {
      return [];
    }
    logger.info(`加载历史消息 integrateId=${integrateId} count=${data.messages.length}`);
    return data.messages;
  } catch (e) {
    logger.warn('加载会话历史失败', e);
    return [];
  }
}

/**
 * 清空指定 integrateId 的本地缓存
 */
export function clearMessages(integrateId: string): void {
  try {
    localStorage.removeItem(storageKey(integrateId));
  } catch (e) {
    logger.warn('清空会话历史失败', e);
  }
}