TS pagination cursor class

pagination.ts

import { createCipheriv, createDecipheriv, randomBytes } from 'crypto'
import process from 'node:process'
import { CustomError } from 'ts-custom-error'
import { z } from 'zod'

export const environment = z
  .object({
    PAGINATION_SECRET_KEY: z.string().min(1)
  })
  .parse(process.env)

export class FeedCursorParsingError extends CustomError {}

export class FeedCursor<T extends z.ZodTypeAny> {
  private readonly key: Buffer
  private readonly algorithm = 'chacha20-poly1305'
  private readonly nonceLength = 12
  private readonly authTagLength = 16

  constructor(private readonly schema: T) {
    this.key = Buffer.alloc(32, environment.PAGINATION_SECRET_KEY)
  }

  encrypt(cursor: z.infer<T>): string {
    const nonce = randomBytes(this.nonceLength)
    const cipher = createCipheriv(this.algorithm, this.key, nonce, { authTagLength: this.authTagLength })

    const serializedData = Buffer.from(JSON.stringify(cursor))
    const ciphertext = Buffer.concat([cipher.update(serializedData), cipher.final()])
    const authTag = cipher.getAuthTag()

    return Buffer.concat([nonce, ciphertext, authTag]).toString('base64')
  }

  decrypt(cursor: string): z.infer<T> | FeedCursorParsingError {
    const encryptedBuffer = Buffer.from(cursor, 'base64')

    const nonce = encryptedBuffer.slice(0, this.nonceLength)
    const authTag = encryptedBuffer.slice(-16)
    const ciphertext = encryptedBuffer.slice(this.nonceLength, -16)

    const decipher = createDecipheriv(this.algorithm, this.key, nonce, { authTagLength: this.authTagLength })
    decipher.setAuthTag(authTag)

    const decryptedData = Buffer.concat([decipher.update(ciphertext), decipher.final()])
    try {
      return this.schema.parse(JSON.parse(decryptedData.toString()))
    } catch (cause: unknown) {
      return new FeedCursorParsingError('', { cause })
    }
  }
}