import { Injectable } from "@nestjs/common";
import { getRedis } from "../../config/redis.js";
import { cacheMetrics } from "../observability/metrics.js";

const CACHE_TTL_SECONDS = 300; // 5 分钟

/**
 * config-service Redis 缓存服务。
 *
 * 缓存策略：
 * - Plugin registry: `config:plugin:{pluginId}` → JSON PluginRegistryItem
 * - User layout override: `config:user-layout:{userId}` → JSON UserLayoutOverride
 * - TTL: 5 分钟，超时自动失效重新从 DB 加载
 * - 失效：admin 修改配置或用户更新布局时主动 del
 *
 * 使用 ioredis 单例（config/redis.ts 管理），不重复创建连接。
 */
@Injectable()
export class ConfigCacheService {
  private static buildPluginKey(pluginId: string): string {
    return `config:plugin:${pluginId}`;
  }

  private static buildUserLayoutKey(userId: string): string {
    return `config:user-layout:${userId}`;
  }

  // ============ Plugin Registry ============

  async getPlugin(pluginId: string): Promise<string | null> {
    const redis = getRedis();
    const raw = await redis.get(ConfigCacheService.buildPluginKey(pluginId));
    if (!raw) {
      cacheMetrics.recordMiss("plugin");
      return null;
    }
    cacheMetrics.recordHit("plugin");
    return raw;
  }

  async setPlugin(pluginId: string, json: string): Promise<void> {
    const redis = getRedis();
    await redis.set(
      ConfigCacheService.buildPluginKey(pluginId),
      json,
      "EX",
      CACHE_TTL_SECONDS,
    );
  }

  async invalidatePlugin(pluginId: string, reason = "manual"): Promise<void> {
    const redis = getRedis();
    await redis.del(ConfigCacheService.buildPluginKey(pluginId));
    cacheMetrics.recordInvalidation("plugin", reason);
  }

  /**
   * 批量失效所有 plugin 缓存（admin 全量更新时调用）。
   * 通过 SCAN 匹配 config:plugin:* 模式删除。
   */
  async invalidateAllPlugins(reason = "admin-update"): Promise<void> {
    const redis = getRedis();
    let cursor = "0";
    do {
      const [next, keys] = await redis.scan(
        cursor,
        "MATCH",
        "config:plugin:*",
        "COUNT",
        100,
      );
      cursor = next;
      if (keys.length > 0) {
        await redis.del(...keys);
      }
    } while (cursor !== "0");
    cacheMetrics.recordInvalidation("plugin", reason);
  }

  // ============ User Layout Override ============

  async getUserLayout(userId: string): Promise<string | null> {
    const redis = getRedis();
    const raw = await redis.get(ConfigCacheService.buildUserLayoutKey(userId));
    if (!raw) {
      cacheMetrics.recordMiss("user-layout");
      return null;
    }
    cacheMetrics.recordHit("user-layout");
    return raw;
  }

  async setUserLayout(userId: string, json: string): Promise<void> {
    const redis = getRedis();
    await redis.set(
      ConfigCacheService.buildUserLayoutKey(userId),
      json,
      "EX",
      CACHE_TTL_SECONDS,
    );
  }

  async invalidateUserLayout(userId: string, reason = "manual"): Promise<void> {
    const redis = getRedis();
    await redis.del(ConfigCacheService.buildUserLayoutKey(userId));
    cacheMetrics.recordInvalidation("user-layout", reason);
  }
}