/**
 * JST (Asia/Tokyo) タイムゾーンでISO 8601形式のタイムスタンプを生成
 */
function getJSTTimestamp(): string {
  const now = new Date();
  // JSTタイムゾーンで時刻を取得してISO形式に変換
  return new Date(now.toLocaleString('en-US', { timeZone: 'Asia/Tokyo' })).toISOString();
}

export enum SegmentationErrorCode {
  INITIALIZATION_FAILED = 'INITIALIZATION_FAILED',
  MODEL_NOT_INITIALIZED = 'MODEL_NOT_INITIALIZED',
  INVALID_IMAGE_DATA = 'INVALID_IMAGE_DATA',
  SEGMENTATION_FAILED = 'SEGMENTATION_FAILED',
  MASK_GENERATION_FAILED = 'MASK_GENERATION_FAILED',
  INVALID_MASK_DATA = 'INVALID_MASK_DATA',
  MEMORY_LIMIT_EXCEEDED = 'MEMORY_LIMIT_EXCEEDED',
  PROCESSING_TIMEOUT = 'PROCESSING_TIMEOUT',
  BACKGROUND_INPAINTING_FAILED = 'BACKGROUND_INPAINTING_FAILED',
  OBJECT_REGENERATION_FAILED = 'OBJECT_REGENERATION_FAILED',
  COPY_REPLACEMENT_FAILED = 'COPY_REPLACEMENT_FAILED',
  HEADER_COMPOSITION_FAILED = 'HEADER_COMPOSITION_FAILED',
  PROMPT_GENERATION_FAILED = 'PROMPT_GENERATION_FAILED',
  TEXT_GENERATION_FAILED = 'TEXT_GENERATION_FAILED',
}

export class SegmentationError extends Error {
  constructor(
    message: string,
    public code: SegmentationErrorCode,
    public details?: any,
  ) {
    super(message);
    this.name = 'SegmentationError';
  }
}

export class ValidationError extends Error {
  constructor(
    message: string,
    public field: string,
    public value?: any,
  ) {
    super(message);
    this.name = 'ValidationError';
  }
}

export interface ErrorResponse {
  error: {
    code: string;
    message: string;
    details?: any;
  };
  timestamp: string;
  requestId?: string;
}

export function createErrorResponse(error: Error, requestId?: string): ErrorResponse {
  if (error instanceof SegmentationError) {
    return {
      error: {
        code: error.code,
        message: error.message,
        details: error.details,
      },
      timestamp: getJSTTimestamp(),
      requestId,
    };
  }

  if (error instanceof ValidationError) {
    return {
      error: {
        code: 'VALIDATION_ERROR',
        message: error.message,
        details: {
          field: error.field,
          value: error.value,
        },
      },
      timestamp: getJSTTimestamp(),
      requestId,
    };
  }

  // 一般的なエラー
  return {
    error: {
      code: 'INTERNAL_ERROR',
      message: 'An unexpected error occurred',
      details: process.env.NODE_ENV === 'development' ? error.message : undefined,
    },
    timestamp: getJSTTimestamp(),
    requestId,
  };
}

// メモリ使用量をチェック
export function checkMemoryUsage(threshold: number = 0.9): void {
  const usage = process.memoryUsage();
  const heapUsed = usage.heapUsed;
  const heapTotal = usage.heapTotal;
  const ratio = heapUsed / heapTotal;

  if (ratio > threshold) {
    throw new SegmentationError(`Memory usage too high: ${Math.round(ratio * 100)}%`, SegmentationErrorCode.MEMORY_LIMIT_EXCEEDED, {
      heapUsed,
      heapTotal,
      ratio,
    });
  }
}

// タイムアウト付き処理実行
export async function withTimeout<T>(promise: Promise<T>, timeoutMs: number, operation: string): Promise<T> {
  const timeoutPromise = new Promise<never>((_, reject) => {
    setTimeout(() => {
      reject(
        new SegmentationError(`Operation '${operation}' timed out after ${timeoutMs}ms`, SegmentationErrorCode.PROCESSING_TIMEOUT, {
          operation,
          timeoutMs,
        }),
      );
    }, timeoutMs);
  });

  return Promise.race([promise, timeoutPromise]);
}

// リトライ機能付き処理実行
export async function withRetry<T>(
  fn: () => Promise<T>,
  options: {
    maxRetries?: number;
    delay?: number;
    backoff?: number;
    onRetry?: (error: Error, attempt: number) => void;
  } = {},
): Promise<T> {
  const { maxRetries = 3, delay = 1000, backoff = 2, onRetry } = options;

  let lastError: Error;

  for (let attempt = 1; attempt <= maxRetries; attempt++) {
    try {
      return await fn();
    } catch (error) {
      lastError = error as Error;

      if (attempt === maxRetries) {
        throw lastError;
      }

      if (onRetry) {
        onRetry(lastError, attempt);
      }

      const waitTime = delay * Math.pow(backoff, attempt - 1);
      await new Promise((resolve) => setTimeout(resolve, waitTime));
    }
  }

  throw lastError!;
}