blend-sdk-js

Blend Protocol SDK for Javascript to assist in interacting with the Blend Protocol.

Getting Started

1. Install it using npm:

npm install @blend-capital/blend-sdk

Usage

Each Blend Protocol contract exports a contract class for interacting with the contract. Some contracts, like the Pool, include additional classes to help read ledger state.

NOTE: There is an outstanding issue passing XDR objects between packages. See the following issue for more details: https://github.com/stellar/js-stellar-base/issues/617

Both the blend-utils and blend-ui repositories make extensive use of this SDK for reference.

Supply an Asset to a Pool

The contract class creates an operation as a base64 XDR string that can be used with the @stellar/stellar-sdk TransactionBuilder class. When interacting with Soroban contracts, the invoker must populate the SorobanData portion of the transaction. The @stellar/stellar-sdk provides an easy way to do this by simulating the transaction against an RPC. For more details about how to submit a Soroban operation to the Stellar network, please see: https://developers.stellar.org/docs/build/guides/transactions/invoke-contract-tx-sdk

import { PoolContract, RequestType } from '@blend-capital/blend-sdk';
import { xdr } from '@stellar/stellar-sdk';

const asset: Address = // C... the Address of the asset to lend
const user: Address = // G... some Address
const to_lend: bigint = // ... the amount to lend as a bigint fixed point number with the tokens decimals 

const pool_contract = new PoolContract(poolId);
const supply_op = xdr.Operation.fromXDR(
    pool_contract.submit({
        from: user,
        spender: user,
        to: user,
        requests: [
            {
                amount: to_lend,
                request_type: RequestType.SupplyCollateral,
                address: asset,
            },
        ],
    }),
    'base64'
);

// build a transaction with the operation and submit it to the network

To submit other actions against the pool, you can modify the Requests array to contain the actions to take against the pool for from, spender, and to.

Read ledger data for a Pool and a User

Helper classes are included to help read ledger data for a pool from an RPC efficiently. The following code reads the ledger data for the pool, it's reserves, and the state of it's backstop.

import {
  Backstop,
  BackstopPool,
  BackstopPoolEst,
  BackstopPoolUser,
  BackstopPoolUserEst,
  Network,
  Pool,
  PoolEstimate,
  PoolOracle,
  PositionsEstimate,
} from '@blend-capital/blend-sdk';

const network: Network = {
  rpc: // rpc URL,
  passphrase: // Stellar network passphrase,
  // optional, allows you to connect to a local RPC instance
  opts: { allowHttp: true },
};

const backstop_id = // C... the address of the backstop contract
const pool_id = // C... the address of the pool contract
const user_id = // G... the address of a user that has taken a position in the pool

// Load the pool data from the ledger to check things like supported reserves, current interest rates
// and other pool specific information like emissions.
const pool = await Pool.load(network, pool_id);

// If price is needed, load the pool's oracle.
const pool_oracle = await pool.loadOracle();

// Additional estimates aggregate information using oracle prices. For example,
// the PoolEstimate class calculates things like total value supplied and borrowed.
const pool_est = PoolEstimate.build(pool.reserves, pool_oracle);

// The pool also allows you to directly load a user's position and emissions information.
const pool_user = await pool.loadUser(user_id);

// Additional estimates for their positions calculate things like borrow limit, net apr, ect.
const user_est = PositionsEstimate.build(pool, pool_oracle, pool_user.positions);

// Load the backstop data from the ledger to check things like the status of the backstop token and the
// configuration of the backstop
const backstop = await Backstop.load(network, backstop_id);

// Load a pool's backstop data to get information like backstop size, Q4W percentage, and more.
const backstop_pool = await BackstopPool.load(network, backstop_id, pool_id);

// Additional estimates calculate the total number of BLND/USDC tokens the backstop holds.
const backstop_pool_est = BackstopPoolEst.build(backstop.backstopToken, backstop_pool.poolBalance);

// Load a user's position in a pool's backstop
const backstop_pool_user = await BackstopPoolUser.load(network, backstop_id, pool_id, user_id);

// Additional estimates calcualte total number of BLND/USDC tokens the user holds the status
// of any queued withdrawals, and the unclaimed emissions.
const backstop_pool_user_est = BackstopPoolUserEst.build(backstop, backstop_pool, backstop_pool_user);