Statement SDK

The Statement Store primitive is an off-chain data store for signed messages (known as statements) accessible via RPC.

Getting Started

Install the Statement SDK using your package manager:

pnpm i @polkadot-api/sdk-statement

The function createStatementSdk takes a simple request-response function, which is expected to implement the Statement JSON-RPC API.

The actual interface of the function is

type RequestFn = (method: string, params: Array<any>) => Promise<any>

The property _request of a client can be used for this matter.

import { createClient } from "polkadot-api"
import { getWsProvider } from "polkadot-api/ws-provider"
 
const client = createClient(
  getWsProvider("wss://paseo-people-next-rpc.polkadot.io"),
)
 
import { createStatementSdk } from "@polkadot-api/sdk-statement"
 
const statementSdk = createStatementSdk(client._request)

Get Statements

Get Complete Store (`dump`)

The function dump will get all statements from the provider's store. Note that this endpoint might be rate-limited in some cases.

// all currently available statements of that node.
const statements = await statementSdk.dump()

Get Filtered Statements (`getStatements`)

This function will query for filtered statements by topic and/or dest key (find meaning in Statement Store docs.

Parameters

dest: Binary for specific dest key. null for no dest key. undefined to disable filtering by dest
topics: Array of up to 4 topics to filter by.

import { stringToTopic } from "@polkadot-api/sdk-statement"
 
// statements with specific topics and specific decryptionkey.
const statements = await statementSdk.getStatements({
  topics: [stringToTopic("pop"), stringToTopic("chat"), stringToTopic("v1")],
  dest: Binary.fromHex(
    "0xf0673d30606ee26672707e4fd2bc8b58d3becb7aba2d5f60add64abb5fea4710",
  ),
})

Submit Statements

Create Statement Signer

In order to sign a Statement, we need to create a signer. This can be done with the helper getStatementSigner, taking:

publicKey: Pubkey of the signer
type: ed25519, sr25519, ecdsa signature type.
signFn: (payload: Uint8Array) => Uint8Array | Promise<Uint8Array> Cryptographic signing function.

As one can notice, this is very similar to the PolkadotSigner interface. Check those docs to learn more!

import { getStatementSigner } from "@polkadot-api/sdk-statement"
import { ed25519 } from "@noble/curves/ed25519.js"
 
const SECRET_KEY = new Uint8Array() // get your key
 
const signer = getStatementSigner(
  ed25519.getPublicKey(SECRET_KEY),
  "ed25519",
  (i) => ed25519.sign(i, SECRET_KEY),
)

Create Statement

In order to create a statement, it is as simple as creating an UnsignedStatement object.

import { Binary } from "polkadot-api"
import type { UnsignedStatement } from "@polkadot-api/sdk-statement"
 
const statement: UnsignedStatement = {
  data: Binary.fromHex("0xDEADBEEF"),
  priority: 1,
}

Submit Statement

Once we have the signer and the statement, we can go to sign and submit it to the store!

const signer = getStatementSigner(
  ed25519.getPublicKey(SECRET_KEY),
  "ed25519",
  (i) => ed25519.sign(i, SECRET_KEY),
)
 
const statement: UnsignedStatement = {
  data: Binary.fromHex("0xDEADBEEF"),
  priority: 1,
}
 
const signed = await signer.sign(statement)
 
await statementSdk.submit(signed)