src/utils/idGenerator.ts

/**
 * OpenAI-compatible ID generator utility
 *
 * OpenAI ID patterns:
 * - Chat completions: chatcmpl-{29 alphanumeric chars}
 * - Tool calls: call_{24 alphanumeric chars}
 *
 * Total lengths:
 * - chatcmpl- prefix (8 chars) + 29 = 37 characters
 * - call_ prefix (5 chars) + 24 = 29 characters
 */

// Default sizes matching OpenAI's observed patterns
export const OPENAI_ID_DEFAULTS = {
  CHAT_COMPLETION_LENGTH: 29,
  TOOL_CALL_LENGTH: 24,
  BATCH_ID_LENGTH: 24,
  FILE_ID_LENGTH: 24,
};

// Prefixes used by OpenAI
export const OPENAI_ID_PREFIXES = {
  CHAT_COMPLETION: 'chatcmpl-',
  TOOL_CALL: 'call_',
  BATCH: 'batch_',
  FILE: 'file-',
};

const ALPHANUMERIC_CHARS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';

/**
 * Generates a random alphanumeric string of specified length
 * @param length - The length of the random string to generate
 * @returns Random alphanumeric string
 */
export function generateRandomAlphanumeric(length: number): string {
  const array = new Uint8Array(length);
  crypto.getRandomValues(array);

  let result = '';
  for (let i = 0; i < length; i++) {
    result += ALPHANUMERIC_CHARS[array[i] % ALPHANUMERIC_CHARS.length];
  }
  return result;
}

/**
 * Validates if an ID matches OpenAI's expected format
 * @param id - The ID to validate
 * @param prefix - Expected prefix
 * @param minLength - Minimum length of the random part (optional)
 * @param maxLength - Maximum length of the random part (optional)
 * @returns boolean indicating if the ID is valid
 */
export type IdType = 'chatCompletion' | 'toolCall' | 'batch' | 'file' | 'rerank' | 'custom';

interface GenerateIdOptions {
  type: IdType;
  customPrefix?: string;
  length?: number;
}

/**
 * Generates an OpenAI-compatible ID
 * @param options - Configuration options for ID generation
 * @returns Generated ID string
 */
export function generateOpenAICompatibleId(options: GenerateIdOptions): string {
  const { type, customPrefix, length } = options;

  let prefix: string;
  let randomLength: number;

  switch (type) {
    case 'chatCompletion':
      prefix = OPENAI_ID_PREFIXES.CHAT_COMPLETION;
      randomLength = length ?? OPENAI_ID_DEFAULTS.CHAT_COMPLETION_LENGTH;
      break;
    case 'toolCall':
      prefix = OPENAI_ID_PREFIXES.TOOL_CALL;
      randomLength = length ?? OPENAI_ID_DEFAULTS.TOOL_CALL_LENGTH;
      break;
    case 'batch':
      prefix = OPENAI_ID_PREFIXES.BATCH;
      randomLength = length ?? OPENAI_ID_DEFAULTS.BATCH_ID_LENGTH;
      break;
    case 'file':
      prefix = OPENAI_ID_PREFIXES.FILE;
      randomLength = length ?? OPENAI_ID_DEFAULTS.FILE_ID_LENGTH;
      break;
    case 'rerank':
      prefix = 'rerank_';
      randomLength = length ?? OPENAI_ID_DEFAULTS.CHAT_COMPLETION_LENGTH;
      break;
    case 'custom':
      prefix = customPrefix ?? '';
      randomLength = length ?? OPENAI_ID_DEFAULTS.CHAT_COMPLETION_LENGTH;
      break;
    default:
      prefix = OPENAI_ID_PREFIXES.CHAT_COMPLETION;
      randomLength = OPENAI_ID_DEFAULTS.CHAT_COMPLETION_LENGTH;
  }

  return prefix + generateRandomAlphanumeric(randomLength);
}

/**
 * Gets an ID, honoring user-provided or upstream ID if valid, otherwise generates a new one
 * @param providedId - User-provided or upstream ID (optional)
 * @param type - Type of ID for generation/validation
 * @param options - Additional options
 * @returns Valid ID (provided or generated)
 */
export function getOrGenerateId(
  providedId: string | undefined | null,
  type: IdType,
  options?: {
    customPrefix?: string;
    length?: number;
  },
): string {
  const { customPrefix, length } = options ?? {};

  if (providedId && typeof providedId === 'string' && providedId.trim() !== '') {
    return providedId;
  }

  return generateOpenAICompatibleId({ type, customPrefix, length });
}