export interface CDNConfig {
  provider: "cloudflare" | "aws-cloudfront" | "google-cloud-cdn" | "azure-cdn";
  endpoint: string;
  customDomain?: string;
  accessKey?: string;
  secretKey?: string;
  distributionId?: string;
  zone?: string;
  enabled: boolean;
  cacheSettings: {
    [mimeType: string]: {
      maxAge: number; // 초 단위
      staleWhileRevalidate: number;
      staleIfError: number;
    };
  };
}

export interface CDNProvider {
  upload(file: Buffer, key: string, mimeType: string): Promise<string>;
  delete(key: string): Promise<void>;
  invalidate(keys: string[]): Promise<void>;
  getUrl(key: string): string;
  getCacheHeaders(mimeType: string): Record<string, string>;
}

// 기본 캐시 설정
export const DEFAULT_CACHE_SETTINGS = {
  // 이미지
  "image/jpeg": {
    maxAge: 31536000,
    staleWhileRevalidate: 86400,
    staleIfError: 604800,
  },
  "image/png": {
    maxAge: 31536000,
    staleWhileRevalidate: 86400,
    staleIfError: 604800,
  },
  "image/gif": {
    maxAge: 31536000,
    staleWhileRevalidate: 86400,
    staleIfError: 604800,
  },
  "image/webp": {
    maxAge: 31536000,
    staleWhileRevalidate: 86400,
    staleIfError: 604800,
  },
  "image/avif": {
    maxAge: 31536000,
    staleWhileRevalidate: 86400,
    staleIfError: 604800,
  },

  // 비디오
  "video/mp4": {
    maxAge: 31536000,
    staleWhileRevalidate: 86400,
    staleIfError: 604800,
  },
  "video/webm": {
    maxAge: 31536000,
    staleWhileRevalidate: 86400,
    staleIfError: 604800,
  },

  // 오디오
  "audio/mp3": {
    maxAge: 31536000,
    staleWhileRevalidate: 86400,
    staleIfError: 604800,
  },
  "audio/wav": {
    maxAge: 31536000,
    staleWhileRevalidate: 86400,
    staleIfError: 604800,
  },
  "audio/ogg": {
    maxAge: 31536000,
    staleWhileRevalidate: 86400,
    staleIfError: 604800,
  },

  // 문서
  "application/pdf": {
    maxAge: 86400,
    staleWhileRevalidate: 3600,
    staleIfError: 86400,
  },
  "application/msword": {
    maxAge: 86400,
    staleWhileRevalidate: 3600,
    staleIfError: 86400,
  },
  "text/plain": {
    maxAge: 86400,
    staleWhileRevalidate: 3600,
    staleIfError: 86400,
  },

  // 기본값
  default: { maxAge: 3600, staleWhileRevalidate: 300, staleIfError: 3600 },
};

// 환경변수에서 CDN 설정 로드
export function loadCDNConfig(): CDNConfig {
  return {
    provider:
      (process.env.CDN_PROVIDER as CDNConfig["provider"]) || "cloudflare",
    endpoint: process.env.CDN_ENDPOINT || "",
    customDomain: process.env.CDN_CUSTOM_DOMAIN,
    accessKey: process.env.CDN_ACCESS_KEY,
    secretKey: process.env.CDN_SECRET_KEY,
    distributionId: process.env.CDN_DISTRIBUTION_ID,
    zone: process.env.CDN_ZONE,
    enabled: process.env.CDN_ENABLED === "true",
    cacheSettings: {
      ...DEFAULT_CACHE_SETTINGS,
      // 환경별 오버라이드 가능
    },
  };
}

// 파일 키 생성 (CDN에서 사용할 경로)
export function generateCDNKey(fileName: string, uploadId?: string): string {
  const timestamp = Date.now();
  const randomString = Math.random().toString(36).substring(2, 8);

  if (uploadId) {
    return `media/${uploadId}/${fileName}`;
  }

  return `media/${timestamp}-${randomString}/${fileName}`;
}

// MIME 타입으로 적절한 캐시 설정 가져오기
export function getCacheSettingsForMimeType(mimeType: string) {
  return (
    DEFAULT_CACHE_SETTINGS[mimeType as keyof typeof DEFAULT_CACHE_SETTINGS] ||
    DEFAULT_CACHE_SETTINGS.default
  );
}

// CDN URL 검증
export function isValidCDNUrl(url: string, config: CDNConfig): boolean {
  if (!config.enabled) return false;

  const validDomains = [config.endpoint];
  if (config.customDomain) {
    validDomains.push(config.customDomain);
  }

  try {
    const urlObj = new URL(url);
    return validDomains.some(
      (domain) =>
        urlObj.hostname === domain || urlObj.hostname.endsWith(`.${domain}`)
    );
  } catch {
    return false;
  }
}

// CDN 상태 확인
export async function checkCDNHealth(config: CDNConfig): Promise<{
  healthy: boolean;
  latency?: number;
  error?: string;
}> {
  if (!config.enabled) {
    return { healthy: false, error: "CDN disabled" };
  }

  const startTime = Date.now();

  try {
    const testUrl = config.customDomain
      ? `https://${config.customDomain}/health-check`
      : `${config.endpoint}/health-check`;

    const response = await fetch(testUrl, {
      method: "HEAD",
      signal: AbortSignal.timeout(5000),
    });

    const latency = Date.now() - startTime;

    return {
      healthy: response.ok,
      latency,
      error: response.ok ? undefined : `HTTP ${response.status}`,
    };
  } catch (error) {
    return {
      healthy: false,
      latency: Date.now() - startTime,
      error: error instanceof Error ? error.message : "Unknown error",
    };
  }
}

// CDN 통계
export interface CDNStats {
  totalRequests: number;
  cacheHitRate: number;
  bandwidthUsed: number; // bytes
  averageLatency: number; // ms
  errorRate: number;
  lastUpdated: Date;
}

// 모의 CDN 통계 (실제 구현에서는 각 프로바이더 API 사용)
export function getMockCDNStats(): CDNStats {
  return {
    totalRequests: 150000,
    cacheHitRate: 0.94,
    bandwidthUsed: 2.5 * 1024 * 1024 * 1024, // 2.5GB
    averageLatency: 45,
    errorRate: 0.002,
    lastUpdated: new Date(),
  };
}