Build on Writz

SPV=CBX23YKCCJMAMBMSCNP6YVKEXUIYK2CTKSR4TQ3RVBPAFYZFVCW7W4EO
READER=GB2BSYQS3FRJ5LZSSIDF3ZCSG5MKWJT5SZ3OZO4QRCAMCR357YAVPTWT   # any G... address

stellar contract invoke --id $SPV --network testnet --source-account $READER --send=no -- get_best_tip

{"chainwork":"1813841685","hash":"64460cd64bcb2b7b89262a51c5a913520670b55c00a590760848bdde12000000","height":327934}

TXID=eac0f95c531b4bd5307597f74bedd7379928539056b9a1467ea6d1159507e269
curl -s "https://api.testnet.writz.xyz/spv-proof/$TXID?confirmations=6" > proof.json
jq '.sorobanArgs | {block_hash, tx_index, proof_len: (.merkle_proof|length), min_confirmations}' proof.json

{
  "block_hash": "fe324a4450cea25959ed180d312172c8484e8e08837b75835d3ec48f02000000",
  "tx_index": 842,
  "proof_len": 10,
  "min_confirmations": 6
}

stellar contract invoke --id $SPV --network testnet --source-account $READER --send=no -- \
  verify_transaction \
  --block_hash "$(jq -r .sorobanArgs.block_hash proof.json)" \
  --merkle_proof "$(jq -c .sorobanArgs.merkle_proof proof.json)" \
  --tx_index "$(jq -r .sorobanArgs.tx_index proof.json)" \
  --raw_tx "$(jq -r .sorobanArgs.raw_tx proof.json)" \
  --min_confirmations 6

{"block_hash":"fe324a4450cea25959ed180d312172c8484e8e08837b75835d3ec48f02000000","block_height":327928,"confirmations":7,"txid":"69e2079515d1a67e46a1b9569053289937d7ed4bf7977530d54b1b535cf9c0ea"}

cd examples/verify-bitcoin-tx && bun install && bun run start

import { createWritzClient } from "@writz/sdk";

const writz = createWritzClient(); // testnet preset
const { result } = await writz.verifyBitcoinTx("eac0f95c531b4bd5307597f74bedd7379928539056b9a1467ea6d1159507e269");
// { txid, txidDisplay, blockHash, blockHeight: 327928, confirmations }

stellar contract bindings typescript --network testnet \
  --contract-id CBX23YKCCJMAMBMSCNP6YVKEXUIYK2CTKSR4TQ3RVBPAFYZFVCW7W4EO \
  --output-dir bitcoin-spv-client
cd bitcoin-spv-client && bun install && bun run build

import { Client, networks } from "./bitcoin-spv-client/dist/index.js";

const spv = new Client({ ...networks.testnet, rpcUrl: "https://soroban-testnet.stellar.org" });
const hex = (s: string) => Buffer.from(s, "hex");

const txid = "eac0f95c531b4bd5307597f74bedd7379928539056b9a1467ea6d1159507e269";
const { sorobanArgs: a } = await (
  await fetch(`https://api.testnet.writz.xyz/spv-proof/${txid}`)
).json();

const { result } = await spv.verify_transaction({
  block_hash: hex(a.block_hash),
  merkle_proof: a.merkle_proof.map(hex),
  tx_index: a.tx_index,
  raw_tx: hex(a.raw_tx),
  min_confirmations: 6,
});
console.log(result.isOk() ? result.unwrap() : result.unwrapErr());
// { block_hash: <Buffer fe 32 ...>, block_height: 327928, confirmations: 7, txid: <Buffer 69 e2 ...> }

use soroban_sdk::{contractclient, contracttype, Bytes, BytesN, Env, Vec};

#[contracttype]
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct SpvVerificationResult {
    pub txid: BytesN<32>,       // SHA256d(raw_tx), internal byte order
    pub block_hash: BytesN<32>, // internal byte order
    pub block_height: u32,
    pub confirmations: u32,     // depth below the light client's tip, tip = 1
}

#[contractclient(name = "BitcoinSpvClient")]
pub trait BitcoinSpv {
    fn verify_transaction(
        env: Env,
        block_hash: BytesN<32>,
        merkle_proof: Vec<BytesN<32>>,
        tx_index: u32,
        raw_tx: Bytes,
        min_confirmations: u32,
    ) -> SpvVerificationResult;
}

// Inside a contract function (spv: Address is the bitcoin-spv contract ID):
let proof = match BitcoinSpvClient::new(&env, &spv)
    .try_verify_transaction(&block_hash, &merkle_proof, &tx_index, &raw_tx, &6)
{
    Ok(Ok(result)) => result,
    _ => return Err(Error::ProofRejected), // your own contract error
};

[dependencies]
soroban-sdk = "26"
spv-types = { git = "https://github.com/WritzProtocol/writz", rev = "0a1065991ee0498ad2c54367e0ffa69ca4a59a9a" }

// Value in sats of the first output whose scriptPubKey equals `expected_spk`
// (works for any script type: P2WPKH, P2WSH, P2TR, ...). None if there is none.
let sats: Option<u64> = spv_types::btc_parser::find_p2wsh_output(&raw_tx, &expected_spk);

LEND=CABF7VK7F25ZGDLV6EWSAU3NYQYKDQNDSJIISDMDZAUASMSXUADSHZGG
stellar contract invoke --id $LEND --network testnet --source-account $READER --send=no -- get_protocol_state
stellar contract invoke --id $LEND --network testnet --source-account $READER --send=no -- get_borrow_rate_bp
stellar contract invoke --id $LEND --network testnet --source-account $READER --send=no -- get_supply_balance --lender $READER

{"borrow_index":"1000000000000000000","index_ledger":5352956,"last_keeper_heartbeat":1792788367,"reserve_usdc":"0","supply_index":"1000000000000000000","total_borrowed":"0","total_scaled_supply":"10000000000"}
"0"
"10000000000"

LEND=CABF7VK7F25ZGDLV6EWSAU3NYQYKDQNDSJIISDMDZAUASMSXUADSHZGG
stellar contract invoke --id $LEND --network testnet --source-account me --send=no -- get_supply_rate_bp
stellar contract invoke --id $LEND --network testnet --source-account me -- supply_usdc --supplier $(stellar keys address me) --amount 100000000
stellar contract invoke --id $LEND --network testnet --source-account me --send=no -- get_supply_balance --lender $(stellar keys address me)
stellar contract invoke --id $LEND --network testnet --source-account me -- withdraw_supply --supplier $(stellar keys address me) --amount 100000000