import Redis from "ioredis";
import { cacheHits, cacheMisses } from "../monitoring/metrics.js";
import { logCacheHit, logCacheMiss } from "../monitoring/logger.js";
import { logger } from "../monitoring/logger.js";

/**
 * Redis-basierter Cache mit Fallback auf In-Memory
 */
export class RedisCache<T> {
  private redis: Redis | null = null;
  private memoryCache: Map<string, { data: T; expiresAt: number }> = new Map();
  private defaultTTL: number;
  private cacheType: string;
  private useRedis: boolean;

  constructor(defaultTTL: number, cacheType: string) {
    this.defaultTTL = defaultTTL;
    this.cacheType = cacheType;
    this.useRedis = process.env["REDIS_ENABLED"] === "true";

    if (this.useRedis) {
      this.initRedis();
    } else {
      logger.info(
        `Redis Cache deaktiviert für ${cacheType}, verwende In-Memory Cache`
      );
    }
  }

  private async initRedis() {
    try {
      this.redis = new Redis({
        host: process.env["REDIS_HOST"] || "localhost",
        port: parseInt(process.env["REDIS_PORT"] || "6379"),
        password: process.env["REDIS_PASSWORD"],
        retryStrategy: (times) => {
          // Bei Fehler: Fallback auf In-Memory nach 3 Versuchen
          if (times > 3) {
            logger.warn(
              "Redis-Verbindung fehlgeschlagen, verwende In-Memory Cache"
            );
            this.useRedis = false;
            return null; // Stoppe Retry
          }
          return Math.min(times * 50, 2000);
        },
        maxRetriesPerRequest: 3,
      });

      this.redis.on("error", (error) => {
        logger.error("Redis-Fehler", { error, cacheType: this.cacheType });
        // Fallback auf In-Memory bei Fehler
        this.useRedis = false;
      });

      this.redis.on("connect", () => {
        logger.info(`Redis verbunden für ${this.cacheType}`);
      });

      // Test-Verbindung
      await this.redis.ping();
      logger.info(`Redis Cache aktiviert für ${this.cacheType}`);
    } catch (error) {
      logger.warn(
        "Redis-Initialisierung fehlgeschlagen, verwende In-Memory Cache",
        {
          error,
          cacheType: this.cacheType,
        }
      );
      this.useRedis = false;
    }
  }

  async set(key: string, data: T, ttl?: number): Promise<void> {
    const ttlMs = ttl || this.defaultTTL;
    const serialized = JSON.stringify(data);

    if (this.useRedis && this.redis) {
      try {
        // Redis TTL in Sekunden
        const ttlSeconds = Math.ceil(ttlMs / 1000);
        await this.redis.setex(key, ttlSeconds, serialized);
        return;
      } catch (error) {
        logger.warn("Redis set fehlgeschlagen, verwende In-Memory", {
          error,
          key,
        });
        this.useRedis = false;
      }
    }

    // Fallback: In-Memory
    const expiresAt = Date.now() + ttlMs;
    this.memoryCache.set(key, { data, expiresAt });
  }

  async get(key: string): Promise<T | null> {
    if (this.useRedis && this.redis) {
      try {
        const value = await this.redis.get(key);
        if (value) {
          // Cache Hit
          cacheHits.inc({ cache_type: this.cacheType });
          logCacheHit(key, this.cacheType);
          return JSON.parse(value) as T;
        }
        // Cache Miss
        cacheMisses.inc({ cache_type: this.cacheType });
        logCacheMiss(key, this.cacheType);
        return null;
      } catch (error) {
        logger.warn("Redis get fehlgeschlagen, verwende In-Memory", {
          error,
          key,
        });
        this.useRedis = false;
      }
    }

    // Fallback: In-Memory
    const entry = this.memoryCache.get(key);
    if (!entry) {
      cacheMisses.inc({ cache_type: this.cacheType });
      logCacheMiss(key, this.cacheType);
      return null;
    }

    if (Date.now() > entry.expiresAt) {
      this.memoryCache.delete(key);
      cacheMisses.inc({ cache_type: this.cacheType });
      logCacheMiss(key, this.cacheType);
      return null;
    }

    cacheHits.inc({ cache_type: this.cacheType });
    logCacheHit(key, this.cacheType);
    return entry.data;
  }

  async clear(): Promise<void> {
    if (this.useRedis && this.redis) {
      try {
        // Lösche alle Keys mit unserem Prefix
        const keys = await this.redis.keys(`${this.cacheType}:*`);
        if (keys.length > 0) {
          await this.redis.del(...keys);
        }
      } catch (error) {
        logger.warn("Redis clear fehlgeschlagen", { error });
      }
    }
    this.memoryCache.clear();
  }

  async delete(key: string): Promise<void> {
    if (this.useRedis && this.redis) {
      try {
        await this.redis.del(key);
        return;
      } catch (error) {
        logger.warn("Redis delete fehlgeschlagen", { error, key });
      }
    }
    this.memoryCache.delete(key);
  }

  async disconnect(): Promise<void> {
    if (this.redis) {
      await this.redis.quit();
      this.redis = null;
    }
  }
}