blend-sdk-js

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

Getting Started

1. Install it using npm:

``bash
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.

$3

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

`ts
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.

$3

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.

`ts
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);
``