import { PrismaClient } from "@prisma/client";
import { logger } from "../utils/logger";
import {
  BatchLookupRequest,
  BatchLookupResponse,
} from "../types/tableManagement";

const prisma = new PrismaClient();

/**
 * 참조 테이블 데이터 캐싱 서비스
 * 작은 참조 테이블의 성능 최적화를 위한 메모리 캐시
 */
export class ReferenceCacheService {
  private cache = new Map<string, Map<string, any>>();
  private cacheStats = new Map<
    string,
    { hits: number; misses: number; lastUpdated: Date }
  >();
  private readonly MAX_CACHE_SIZE = 1000; // 테이블당 최대 캐시 크기
  private readonly CACHE_TTL = 5 * 60 * 1000; // 5분 TTL

  /**
   * 작은 참조 테이블 전체 캐싱
   */
  async preloadReferenceTable(
    tableName: string,
    keyColumn: string,
    displayColumn: string
  ): Promise<void> {
    try {
      logger.info(`참조 테이블 캐싱 시작: ${tableName}`);

      // 테이블 크기 확인
      const countResult = (await prisma.$queryRawUnsafe(`
        SELECT COUNT(*) as count FROM ${tableName}
      `)) as Array<{ count: bigint }>;

      const count = Number(countResult[0]?.count || 0);

      if (count > this.MAX_CACHE_SIZE) {
        logger.warn(`테이블이 너무 큼, 캐싱 건너뜀: ${tableName} (${count}건)`);
        return;
      }

      // 데이터 조회 및 캐싱
      const data = (await prisma.$queryRawUnsafe(`
        SELECT ${keyColumn} as key, ${displayColumn} as value 
        FROM ${tableName}
        WHERE ${keyColumn} IS NOT NULL 
        AND ${displayColumn} IS NOT NULL
      `)) as Array<{ key: any; value: any }>;

      const tableCache = new Map<string, any>();

      for (const row of data) {
        tableCache.set(String(row.key), row.value);
      }

      // 캐시 저장
      const cacheKey = `${tableName}.${keyColumn}.${displayColumn}`;
      this.cache.set(cacheKey, tableCache);

      // 통계 초기화
      this.cacheStats.set(cacheKey, {
        hits: 0,
        misses: 0,
        lastUpdated: new Date(),
      });

      logger.info(`참조 테이블 캐싱 완료: ${tableName} (${data.length}건)`);
    } catch (error) {
      logger.error(`참조 테이블 캐싱 실패: ${tableName}`, error);
    }
  }

  /**
   * 캐시에서 참조 값 조회
   */
  getLookupValue(
    table: string,
    keyColumn: string,
    displayColumn: string,
    key: string
  ): any | null {
    const cacheKey = `${table}.${keyColumn}.${displayColumn}`;
    const tableCache = this.cache.get(cacheKey);

    if (!tableCache) {
      this.updateCacheStats(cacheKey, false);
      return null;
    }

    // TTL 확인
    const stats = this.cacheStats.get(cacheKey);
    if (stats && Date.now() - stats.lastUpdated.getTime() > this.CACHE_TTL) {
      logger.debug(`캐시 TTL 만료: ${cacheKey}`);
      this.cache.delete(cacheKey);
      this.cacheStats.delete(cacheKey);
      this.updateCacheStats(cacheKey, false);
      return null;
    }

    const value = tableCache.get(String(key));
    this.updateCacheStats(cacheKey, value !== undefined);

    return value || null;
  }

  /**
   * 배치 룩업 (성능 최적화)
   */
  async batchLookup(
    requests: BatchLookupRequest[]
  ): Promise<BatchLookupResponse[]> {
    const responses: BatchLookupResponse[] = [];
    const missingLookups = new Map<string, BatchLookupRequest[]>();

    // 캐시에서 먼저 조회
    for (const request of requests) {
      const cacheKey = `${request.table}.${request.key}.${request.displayColumn}`;
      const value = this.getLookupValue(
        request.table,
        request.key,
        request.displayColumn,
        request.key
      );

      if (value !== null) {
        responses.push({ key: request.key, value });
      } else {
        // 캐시 미스 - DB 조회 필요
        if (!missingLookups.has(request.table)) {
          missingLookups.set(request.table, []);
        }
        missingLookups.get(request.table)!.push(request);
      }
    }

    // 캐시 미스된 항목들 DB에서 조회
    for (const [tableName, missingRequests] of missingLookups) {
      try {
        const keys = missingRequests.map((req) => req.key);
        const displayColumn = missingRequests[0].displayColumn; // 같은 테이블이므로 동일

        const data = (await prisma.$queryRaw`
          SELECT key_column as key, ${displayColumn} as value 
          FROM ${tableName}
          WHERE key_column = ANY(${keys})
        `) as Array<{ key: any; value: any }>;

        // 결과를 응답에 추가
        for (const row of data) {
          responses.push({ key: String(row.key), value: row.value });
        }

        // 없는 키들은 null로 응답
        const foundKeys = new Set(data.map((row) => String(row.key)));
        for (const req of missingRequests) {
          if (!foundKeys.has(req.key)) {
            responses.push({ key: req.key, value: null });
          }
        }
      } catch (error) {
        logger.error(`배치 룩업 실패: ${tableName}`, error);

        // 에러 발생 시 null로 응답
        for (const req of missingRequests) {
          responses.push({ key: req.key, value: null });
        }
      }
    }

    return responses;
  }

  /**
   * 캐시 통계 업데이트
   */
  private updateCacheStats(cacheKey: string, isHit: boolean): void {
    let stats = this.cacheStats.get(cacheKey);
    if (!stats) {
      stats = { hits: 0, misses: 0, lastUpdated: new Date() };
      this.cacheStats.set(cacheKey, stats);
    }

    if (isHit) {
      stats.hits++;
    } else {
      stats.misses++;
    }
  }

  /**
   * 캐시 적중률 조회
   */
  getCacheHitRate(
    table: string,
    keyColumn: string,
    displayColumn: string
  ): number {
    const cacheKey = `${table}.${keyColumn}.${displayColumn}`;
    const stats = this.cacheStats.get(cacheKey);

    if (!stats || stats.hits + stats.misses === 0) {
      return 0;
    }

    return stats.hits / (stats.hits + stats.misses);
  }

  /**
   * 전체 캐시 적중률 조회
   */
  getOverallCacheHitRate(): number {
    let totalHits = 0;
    let totalRequests = 0;

    for (const stats of this.cacheStats.values()) {
      totalHits += stats.hits;
      totalRequests += stats.hits + stats.misses;
    }

    return totalRequests > 0 ? totalHits / totalRequests : 0;
  }

  /**
   * 캐시 무효화
   */
  invalidateCache(
    table?: string,
    keyColumn?: string,
    displayColumn?: string
  ): void {
    if (table && keyColumn && displayColumn) {
      const cacheKey = `${table}.${keyColumn}.${displayColumn}`;
      this.cache.delete(cacheKey);
      this.cacheStats.delete(cacheKey);
      logger.info(`캐시 무효화: ${cacheKey}`);
    } else {
      // 전체 캐시 무효화
      this.cache.clear();
      this.cacheStats.clear();
      logger.info("전체 캐시 무효화");
    }
  }

  /**
   * 캐시 상태 조회
   */
  getCacheInfo(): Array<{
    cacheKey: string;
    size: number;
    hitRate: number;
    lastUpdated: Date;
  }> {
    const info: Array<{
      cacheKey: string;
      size: number;
      hitRate: number;
      lastUpdated: Date;
    }> = [];

    for (const [cacheKey, tableCache] of this.cache) {
      const stats = this.cacheStats.get(cacheKey);
      const hitRate = stats
        ? stats.hits + stats.misses > 0
          ? stats.hits / (stats.hits + stats.misses)
          : 0
        : 0;

      info.push({
        cacheKey,
        size: tableCache.size,
        hitRate,
        lastUpdated: stats?.lastUpdated || new Date(),
      });
    }

    return info;
  }

  /**
   * 자주 사용되는 참조 테이블들 자동 캐싱
   */
  async autoPreloadCommonTables(): Promise<void> {
    try {
      logger.info("공통 참조 테이블 자동 캐싱 시작");

      // 일반적인 참조 테이블들
      const commonTables = [
        { table: "user_info", key: "user_id", display: "user_name" },
        { table: "comm_code", key: "code_id", display: "code_name" },
        { table: "dept_info", key: "dept_code", display: "dept_name" },
        { table: "companies", key: "company_code", display: "company_name" },
      ];

      for (const { table, key, display } of commonTables) {
        try {
          await this.preloadReferenceTable(table, key, display);
        } catch (error) {
          logger.warn(`공통 테이블 캐싱 실패 (무시함): ${table}`, error);
        }
      }

      logger.info("공통 참조 테이블 자동 캐싱 완료");
    } catch (error) {
      logger.error("공통 참조 테이블 자동 캐싱 실패", error);
    }
  }
}

export const referenceCacheService = new ReferenceCacheService();