feat: add coinselect and basic wallet functionality to sdk

Signed-off-by: Gregory Hill <[email protected]>

sdk/package.json

@@ -30,6 +30,7 @@
     "yargs": "^17.5.1"
   },
   "dependencies": {
-    "bitcoinjs-lib": "^6.1.5"
+    "bitcoinjs-lib": "^6.1.5",
+    "coinselect": "^3.1.13"
   }
-}
+}

sdk/src/@types/coinselect/index.d.ts

@@ -0,0 +1,40 @@
+declare module "coinselect" {
+    interface Input {
+        txId: string,
+        vout: number,
+        value: number,
+        // For use with PSBT:
+        // not needed for coinSelect, but will be passed on to inputs later
+        nonWitnessUtxo?: Buffer,
+        // OR
+        // if your utxo is a segwit output, you can use witnessUtxo instead
+        witnessUtxo?: {
+            script: Buffer,
+            value: number,
+        }
+    }
+
+    interface Output {
+        address?: string,
+        value: number
+    }
+
+    /**
+    * Blackjack, with Accumulative fallback
+    * @param inputs The UTXOs to spend from.
+    * @param outputs The transaction outputs.
+    * @param feeRate The current Bitcoin fee rate.
+    * @returns The fee paid to the network.
+    */
+    function coinSelect(
+        inputs: Array<Input>,
+        outputs: Array<Output>,
+        feeRate: number // satoshis per byte
+    ): {
+        inputs?: Array<Input>,
+        outputs?: Array<Output>,
+        fee: number,
+    };
+
+    export = coinSelect;
+}

sdk/src/index.ts

@@ -2,3 +2,4 @@ export * from "./electrs";
 export * from "./relay";
 export * from "./utils";
 export * from "./ordinals";
+export * from "./wallet";

sdk/src/wallet.ts

@@ -0,0 +1,61 @@
+import { Psbt, Transaction, Network, TxOutput, address as addressUtils } from "bitcoinjs-lib";
+import { ElectrsClient } from "./electrs";
+
+import coinSelect = require('coinselect');
+
+export interface Wallet {
+    getAddress(): Promise<string>;
+    getChangeAddress(): Promise<string>;
+    signPsbt(psbt: Psbt): Promise<Psbt>;
+}
+
+export async function createAndFundTransaction(electrsClient: ElectrsClient, wallet: Wallet, network: Network, txOutputs: Array<TxOutput>): Promise<Transaction> {
+    const address = await wallet.getAddress();
+    const utxos = await electrsClient.getAddressUtxos(address);
+
+    const { inputs, outputs } = coinSelect(
+        utxos.map(utxo => {
+            return {
+                txId: utxo.txid,
+                vout: utxo.vout,
+                value: utxo.value,
+            }
+        }),
+        txOutputs.map(txOut => {
+            return {
+                address: addressUtils.fromOutputScript(txOut.script, network),
+                value: txOut.value,
+            }
+        }),
+        1
+    );
+
+    let psbt = new Psbt({ network })
+
+    inputs.forEach(input =>
+        psbt.addInput({
+            hash: input.txId,
+            index: input.vout,
+            // TODO: determine these from electrs utxos
+            nonWitnessUtxo: input.nonWitnessUtxo,
+            witnessUtxo: input.witnessUtxo,
+        })
+    );
+
+    const changeAddress = await wallet.getChangeAddress();
+    outputs.forEach(output => {
+        // watch out, outputs may have been added that you need to provide
+        // an output address/script for
+        if (!output.address) {
+            output.address = changeAddress;
+        }
+
+        psbt.addOutput({
+            address: output.address,
+            value: output.value,
+        })
+    });
+
+    await wallet.signPsbt(psbt);
+    return psbt.extractTransaction();
+}