feat: Implement DLC Input Splicing for Reusing Funding Outputs

[matthewjablack]

Summary

This PR implements DLC input splicing functionality, enabling DLC funding outputs to be reused as inputs in subsequent DLC transactions. This is essential for advanced DLC workflows like splicing, rolling contracts, and multi-party DLC chains.

Dependencies

This PR requires AtomicFinance/node-dlc#228 to be merged first, which adds the underlying DLC Input support for spliced contracts.

Key Features

DLC Input Splicing

• Reuse DLC funding outputs: Previous DLC funding outputs can now be used as inputs in new DLC transactions
• Mixed input support: Combine DLC inputs with regular wallet inputs in a single transaction
• Proper multisig handling: Automatic detection and signing of 2-of-2 multisig DLC inputs

Explicit Input Control

• InputSupplementationMode: Fine-grained control over input supplementation (None, Optional, Required)
• Fixed input support: Use exact inputs without automatic supplementation when needed
• Collateral calculation: Calculate maximum possible collateral with available inputs

Advanced Key Management

• Dynamic key derivation: Automatically find private keys for DLC funding pubkeys across wallet addresses
• Two-phase signing: Support offerer-first, acceptor-completion signing flow for DLC inputs
• Cross-wallet compatibility: Handle DLC inputs created by different wallet instances

Enhanced Transaction Creation

• Spliced transactions: Automatic detection and routing to CreateSplicedDlcTransactions when DLC inputs are present
• Backward compatibility: Regular DLC creation unchanged when no DLC inputs are used
• Proper witness construction: Correct P2WSH multisig witness handling for DLC inputs

Technical Implementation

Core Types

• InputSupplementationMode enum for explicit input control
• DlcInputInfo interface for DLC-specific input metadata
• Enhanced Input class with isDlcInput() and DLC input support

Key Methods Added

• calculateMaxCollateral() - Determine maximum funding with given inputs
• createDlcFundingInput() - Create DLC inputs from funding transactions
• findDlcFundingPrivateKey() - Derive keys across wallet addresses
• GetInputsForAmountWithMode() - Input supplementation with explicit control

CFD-DLC-JS Integration

• GetRawDlcFundingInputSignature - DLC-specific input signing
• SignDlcFundingInput - Complete DLC multisig input signing
• VerifyDlcFundingInputSignature - Verify DLC input signatures
• CreateSplicedDlcTransactions - Handle mixed input types

Testing

• Integration test covering full splicing workflow
• End-to-end test: single-funded DLC → spliced DLC with mixed inputs

Use Cases Enabled

• DLC Splicing: Add/remove collateral from existing DLCs
• DLC Chains: Create sequences of dependent DLCs
• Contract Rolling: Extend or modify existing DLC terms

Breaking Changes

None - all changes are backward compatible. Existing DLC creation flows work unchanged.

Migration Guide

Existing code requires no changes. New splicing functionality is opt-in through new parameters:

// Before: Regular DLC creation (unchanged)
const dlcOffer = await alice.dlc.createDlcOffer(contractInfo, collateral, feeRate, cetLocktime, refundLocktime);

// New: DLC splicing with explicit input control  
const dlcOffer = await alice.dlc.createDlcOffer(
  contractInfo, 
  collateral, 
  feeRate, 
  cetLocktime, 
  refundLocktime,
  [dlcFundingInput, regularInput], // Mix DLC and regular inputs
  InputSupplementationMode.None    // Explicit control
);

Test Results

• All existing tests pass
• New DLC splicing integration test passes
• Proper handling of DLC input signing and verification
• Mixed input types work correctly in single transaction

This implementation enables sophisticated DLC workflows while maintaining full backward compatibility with existing code.

Related Work

• Depends on: node-dlc#228 - Add DLC Input support for spliced contracts

[changeset-bot]

🦋 Changeset detected

Latest commit: aeb2027

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 17 packages

Name	Type
@atomicfinance/bitcoin-js-wallet-provider	Patch
@atomicfinance/bitcoin-wallet-provider	Patch
@atomicfinance/bitcoin-dlc-provider	Patch
@atomicfinance/client	Patch
@atomicfinance/types	Patch
@atomicfinance/bitcoin-cfd-provider	Patch
@atomicfinance/bitcoin-esplora-api-provider	Patch
@atomicfinance/bitcoin-esplora-batch-api-provider	Patch
@atomicfinance/bitcoin-node-wallet-provider	Patch
@atomicfinance/bitcoin-rpc-provider	Patch
@atomicfinance/bitcoin-utils	Patch
@atomicfinance/crypto	Patch
@atomicfinance/errors	Patch
@atomicfinance/jsonrpc-provider	Patch
@atomicfinance/node-provider	Patch
@atomicfinance/provider	Patch
@atomicfinance/utils	Patch

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