Recursive Dynamic Update DynamoDB (WIP)

dynamicUpdate.ts

import { NativeAttributeValue } from '@aws-sdk/util-dynamodb/src/models';
import { AttributeValue } from '@aws-sdk/client-dynamodb';
import { marshall } from '@aws-sdk/util-dynamodb';

interface DynamoUpdateParams {
  UpdateExpression: string;
  ExpressionAttributeNames: Record<string, string>;
  ExpressionAttributeValues: Record<string, AttributeValue>;
}

const attributeExtractor = (item: Record<string, unknown>) => Object.entries(item).reduce((previous, [key, value]): Record<string, string> =>
    ({
      ...previous,
      ...{ [`#${key}`]: key },
      ...(typeof value === 'object' && value !== null && Object.keys(item).length > 0) && attributeExtractor(value as Record<string, unknown>)
    }),
  {});

const valueExtractor = (item: Record<string, NativeAttributeValue>) => Object.entries(item).reduce((previous, [key, value]): Record<string, string> =>
    ({
      ...previous,
      ...(typeof value !== 'object') && marshall({ [`:${key}`]: value }),
      ...(typeof value === 'object' && value !== null && Object.keys(item).length > 0) && valueExtractor(value as Record<string, unknown>)
    }),
  {});

const expressionCreator = (item: Record<string, unknown>, prefix: string|null) =>
  Object.entries(item).reduce<string>((carry, [key, value]): string => {
    const prefixedKey = prefix ? `${prefix}.#${key}` : `#${key}`;

    if (typeof value === 'object' && value !== null && Object.keys(item).length > 0) {
      return `${carry}${expressionCreator(value as Record<string, unknown>, prefixedKey)}`;
    }

    return `${carry} ${prefixedKey} = :${key},`;
  }, '');
export const dynamicUpdateExpressionFromObject = <T extends { [K in keyof T]: NativeAttributeValue }>(item: T): DynamoUpdateParams => {
  const ExpressionAttributeNames: Record<string, string> = attributeExtractor(item);
  const ExpressionAttributeValues: Record<string, AttributeValue> = valueExtractor(item);
  const UpdateExpression = `SET${expressionCreator(item, null).slice(0, -1)}`;

  return {
    UpdateExpression,
    ExpressionAttributeNames,
    ExpressionAttributeValues,
  };
};