Feature request: Provide a helper function to decode a base64 encoded payload

[sdangol]

Use case

When working with Kinesis data streams, I want to extend my schema and decode a base64 encoded payload. Currently, I have to do this manually.

import { KinesisDataStreamRecordPayload } from '@aws-lambda-powertools/parser/schemas/kinesis';
import { fromBase64 } from '@aws-lambda-powertools/commons/utils/base64';
import { gunzipSync } from 'node:zlib';
import { z } from 'zod';

const decoder = new TextDecoder();
const decompress = (data: string): string => {
try {
  return JSON.parse(gunzipSync(fromBase64(data, 'base64')).toString('utf8'));
} catch {
  return data;
}
};

const extendedSchema = KinesisDataStreamRecordPayload.extend({ 
  data: z.string().transform((data) => {
  const decompressed = decompress(data);
  const decoded = decoder.decode(fromBase64(data, 'base64'));
  try {
    // If data was not compressed, try to parse it as JSON otherwise it must be string
    return decompressed === data ? JSON.parse(decoded) : decompressed;
  } catch {
    return decoded;
  }
})
});
type _ExtendedKinesisDataStream = z.infer<typeof extendedSchema>;

Solution/User Experience

It would be easier to do this if there was a helper function similar to the JSONStringified helper. So that, the experience would be

import { Base64Encoded } from '@aws-lambda-powertools/parser/helpers';
import { KinesisDataStreamRecordPayload } from '@aws-lambda-powertools/parser/schemas/kinesis';
import { z } from 'zod';

const extendedSchema = KinesisDataStreamRecordPayload.extend({ 
  data: Base64Encoded(z.string())
});
type _ExtendedKinesisDataStream = z.infer<typeof extendedSchema>;

Alternative solutions

Acknowledgment

• This feature request meets Powertools for AWS Lambda (TypeScript) Tenets
• Should this be considered in other Powertools for AWS Lambda languages? i.e. Python, Java, and .NET

Future readers

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[powertools-for-aws-oss-automation]

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