Refactor: Extract shared ECC utilities into dedicated module

[jamespepper81]

Description

This PR consolidates duplicated ECC validation, transaction size estimation, and address derivation logic into a new shared utility module (ecc-utils.ts). This eliminates code duplication across bitcoin-service.ts, cpfp-service.ts, and rbf-service.ts, improving maintainability and reducing the risk of inconsistencies.

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🎨 UI/UX improvement
• ♻️ Code refactoring (no functional changes)
• ⚡ Performance improvement
• 🔒 Security improvement
• 🧪 Test coverage improvement
• 🔧 Build/CI improvement

Changes Made

New Module: services/ecc-utils.ts

• ECC Validation Functions

  • validateECCLibrary(): Basic ECC functionality validation (private key validation, point generation)
  • validateECCLibraryFull(): Comprehensive validation including signing and verification
  • initializeBitcoinJsWithECC(): Centralized bitcoinjs-lib initialization with ECC

• Transaction Size Estimation

  • estimateTransactionSize(): Unified transaction size calculation for SegWit P2WPKH
  • Exported constants: P2WPKH_INPUT_SIZE, P2WPKH_OUTPUT_SIZE, TX_BASE_SIZE

• Address Derivation Utilities

  • deriveAddressIndexAndChainFromAddress(): Find BIP32 path (index + chain) for an address
  • deriveAddressIndexFromAddress(): Legacy function for external chain only
  • findNextUnusedAddressIndex(): Determine next available address index
  • generateChangeAddress(): Generate change address (chain 1)
  • generateCancellationAddress(): Generate address for RBF cancellation

• Cache Management

  • clearAddressIndexCache(): Clear cached address derivations
  • getAddressIndexCacheSize(): Query cache size for debugging

Updated Files

services/bitcoin-service.ts

• Removed duplicate estimateTransactionSize() function
• Removed duplicate generateChangeAddress() function
• Removed ~110 lines of ECC validation code from createTransaction()
• Replaced with imports from ecc-utils.ts
• Simplified ECC initialization to use validateECCLibraryFull()

services/cpfp-service.ts

• Removed duplicate estimateTransactionSize() function
• Removed duplicate generateChangeAddress() function
• Removed duplicate deriveAddressIndexAndChainFromAddress() function
• Removed duplicate deriveAddressIndexFromAddress() function
• Removed ~260 lines of duplicated code
• Replaced with imports from ecc-utils.ts
• Updated clearCPFPAddressIndexCache() to delegate to ecc-utils
• Simplified ECC initialization in createCPFPTransaction()

Benefits

1. DRY Principle: Eliminates ~370 lines of duplicated code
2. Consistency: Single source of truth for ECC validation and address derivation
3. Maintainability: Changes to ECC logic only need to be made in one place
4. Testability: Utilities can now be unit tested independently
5. Documentation: Comprehensive JSDoc comments explain each function's purpose and behavior
6. Performance: Shared caching mechanism benefits all services

Testing Performed

Manual Testing

• Verified transaction creation still works correctly
• Verified CPFP transaction creation still works correctly
• Verified address derivation produces consistent results

https://claude.ai/code/session_01ExDrbBrFwxPbWtZEumt1hD