feat(bitcoin): add taproot lock output method to Script

packages/bitcoin/__tests__/bitcoin/script.spec.ts

@@ -0,0 +1,36 @@
+import { expect } from 'chai';
+
+import { Script } from '../../lib/Script';
+
+describe('Script', () => {
+  it('outputs Taproot scriptPubKey', () => {
+    const pubkey =
+      'f1637044d08d5891cdf4c6b066667e75eebaae79a9de91c5f5eb5bcc682a502e';
+    const buffer = Buffer.from(pubkey, 'hex');
+
+    const expected = Buffer.concat([Buffer.from([34, 81, 32]), buffer]);
+
+    expect(Script.p2trLock(buffer).serialize()).to.be.eql(expected);
+  });
+
+  it('parses raw Taproot scriptPubKey bytes', () => {
+    const pubkey =
+      'f1637044d08d5891cdf4c6b066667e75eebaae79a9de91c5f5eb5bcc682a502e';
+    const script = Script.p2trLock(Buffer.from(pubkey, 'hex'));
+
+    expect(Script.fromRaw(script.serializeCmds()).serializeCmds()).to.be.eql(
+      script.serializeCmds(),
+    );
+  });
+
+  it('throws when parsing empty raw script bytes', () => {
+    expect(() => Script.fromRaw(Buffer.alloc(0))).to.throw(
+      'Cannot parse empty script',
+    );
+  });
+
+  it('throws on invalid length pubkey', () => {
+    const buffer = Buffer.from([0x00, 0x01, 0x02]);
+    expect(() => Script.p2trLock(buffer)).to.throw();
+  });
+});

packages/bitcoin/lib/Script.ts

@@ -144,11 +144,11 @@ export class Script implements ICloneable<Script> {
     }
 
     return new Script(
-            Script.number(m),
-            ...pubkeys,
-            Script.number(pubkeys.length),
-            OpCode.OP_CHECKMULTISIG,
-        ); // prettier-ignore
+      Script.number(m),
+      ...pubkeys,
+      Script.number(pubkeys.length),
+      OpCode.OP_CHECKMULTISIG,
+    ); // prettier-ignore
   }
 
   /**
@@ -170,9 +170,9 @@ export class Script implements ICloneable<Script> {
       asssertValidSig(sig);
     }
     return new Script(
-            OpCode.OP_0,
-            ...sigs
-        ); // prettier-ignore
+      OpCode.OP_0,
+      ...sigs
+    ); // prettier-ignore
   }
 
   /**
@@ -198,10 +198,10 @@ export class Script implements ICloneable<Script> {
     }
 
     return new Script(
-            OpCode.OP_HASH160,
-            scriptHash160,
-            OpCode.OP_EQUAL,
-        ); // prettier-ignore
+      OpCode.OP_HASH160,
+      scriptHash160,
+      OpCode.OP_EQUAL,
+    ); // prettier-ignore
   }
 
   /**
@@ -255,9 +255,9 @@ export class Script implements ICloneable<Script> {
     const hash160PubKey = value.length === 20 ? value : hash160(value);
 
     return new Script(
-            OpCode.OP_0,
-            hash160PubKey,
-        ); // prettier-ignore
+      OpCode.OP_0,
+      hash160PubKey,
+    ); // prettier-ignore
   }
 
   /**
@@ -274,9 +274,25 @@ export class Script implements ICloneable<Script> {
     }
 
     return new Script(
-            OpCode.OP_0,
-            sha256Script,
-        ); // prettier-ignore
+      OpCode.OP_0,
+      sha256Script,
+    ); // prettier-ignore
+  }
+
+  /**
+   * Create a standard Pay-to-Taproot scriptPubKey by accepting the
+   * sha256 of the Taproot as input. It is of the format:
+   *   OP_1 <x-only-tweaked-pubkey>
+   */
+  public static p2trLock(taproot: Buffer): Script {
+    if (taproot.length !== 32) {
+      throw new BitcoinError(BitcoinErrorCode.Hash256Invalid);
+    }
+
+    return new Script(
+      OpCode.OP_1,
+      taproot,
+    ); // prettier-ignore
   }
 
   /**
@@ -298,6 +314,17 @@ export class Script implements ICloneable<Script> {
     return new Script(...cmds);
   }
 
+  /**
+   * Parses raw script command bytes without a leading length prefix.
+   */
+  public static fromRaw(buf: Buffer): Script {
+    if (buf.length === 0) {
+      throw new Error('Cannot parse empty script');
+    }
+
+    return new Script(...Script.parseCmds(buf));
+  }
+
   /**
    * When supplied with a Buffer of cmds this method will parse the commands
    * into data blocks or op_codes depending on the meaning of the bytes
@@ -362,7 +389,7 @@ export class Script implements ICloneable<Script> {
 
   /**
    * Returns true if other script is an exact match of the current script.
-   * This requires all data element sto be exact matches and all operations
+   * This requires all data elements to be exact matches and all operations
    * to be exact matches.
    * @param other
    */

packages/core/__tests__/dlc/TxBuilder.spec.ts

@@ -1,4 +1,4 @@
-import { Value } from '@node-dlc/bitcoin';
+import { Script, Value } from '@node-dlc/bitcoin';
 import {
   DlcAcceptWithoutSigs,
   DlcOffer,
@@ -77,7 +77,13 @@ describe('TxBuilder', () => {
   const createTestDlcAccept = (
     acceptCollateral: bigint,
     fundingInputs: FundingInput[] = [],
+    scripts: { payoutSpk?: Buffer; changeSpk?: Buffer } = {},
   ): DlcAcceptWithoutSigs => {
+    const defaultSpk = Buffer.from(
+      '0014' + Buffer.alloc(20).toString('hex'),
+      'hex',
+    );
+
     return new DlcAcceptWithoutSigs(
       1, // protocolVersion
       Buffer.alloc(32), // temporaryContractId
@@ -87,10 +93,10 @@ describe('TxBuilder', () => {
         '02F9308A019258C31049344F85F89D5229B531C845836F99B08601F113BCE036F9',
         'hex',
       ),
-      Buffer.from('0014' + Buffer.alloc(20).toString('hex'), 'hex'), // payoutSpk
+      scripts.payoutSpk ?? defaultSpk,
       BigInt(4), // payoutSerialId
       fundingInputs,
-      Buffer.from('0014' + Buffer.alloc(20).toString('hex'), 'hex'), // changeSpk
+      scripts.changeSpk ?? defaultSpk,
       BigInt(5), // changeSerialId
     );
   };
@@ -294,6 +300,40 @@ describe('TxBuilder', () => {
         Number(DUST_LIMIT),
       );
     });
+
+    it('should preserve offer Taproot change scriptPubKey', () => {
+      const offerInput = createTestFundingInput(BigInt(1050000));
+      const offer = createTestDlcOffer(BigInt(1000000), [offerInput]);
+      const accept = createTestDlcAccept(BigInt(0), []);
+      const taprootSpk = Script.p2trLock(Buffer.alloc(32, 1)).serializeCmds();
+      offer.changeSpk = taprootSpk;
+
+      const builder = new BatchDlcTxBuilder([offer], [accept]);
+      const tx = builder.buildFundingTransaction();
+
+      const hasTaprootChange = tx.outputs.some((output) =>
+        output.scriptPubKey.serializeCmds().equals(taprootSpk),
+      );
+      expect(hasTaprootChange).to.equal(true);
+    });
+
+    it('should preserve accept Taproot change scriptPubKey', () => {
+      const offerInput = createTestFundingInput(BigInt(1000000));
+      const acceptInput = createTestFundingInput(BigInt(1050000), 2);
+      const offer = createTestDlcOffer(BigInt(500000), [offerInput]);
+      const taprootSpk = Script.p2trLock(Buffer.alloc(32, 2)).serializeCmds();
+      const accept = createTestDlcAccept(BigInt(500000), [acceptInput], {
+        changeSpk: taprootSpk,
+      });
+
+      const builder = new BatchDlcTxBuilder([offer], [accept]);
+      const tx = builder.buildFundingTransaction();
+
+      const hasTaprootChange = tx.outputs.some((output) =>
+        output.scriptPubKey.serializeCmds().equals(taprootSpk),
+      );
+      expect(hasTaprootChange).to.equal(true);
+    });
   });
 
   describe('BatchDlcTxBuilder.buildFundingTransaction - Error Handling', () => {

packages/core/lib/dlc/TxBuilder.ts

@@ -253,15 +253,15 @@ export class BatchDlcTxBuilder {
     if (offerChangeValue >= DUST_LIMIT) {
       outputs.push({
         value: Value.fromSats(Number(offerChangeValue)),
-        script: Script.p2wpkhLock(this.dlcOffers[0].changeSpk.slice(2)),
+        script: Script.fromRaw(this.dlcOffers[0].changeSpk),
         serialId: this.dlcOffers[0].changeSerialId,
       });
     }
 
     if (acceptChangeValue >= DUST_LIMIT) {
       outputs.push({
         value: Value.fromSats(Number(acceptChangeValue)),
-        script: Script.p2wpkhLock(this.dlcAccepts[0].changeSpk.slice(2)),
+        script: Script.fromRaw(this.dlcAccepts[0].changeSpk),
         serialId: this.dlcAccepts[0].changeSerialId,
       });
     }