Refactor: Consolidate EVM chain code and reduce duplication

[TaprootFreak]

Summary

This PR consolidates duplicate code across standard EVM chains (Ethereum, Sepolia, BSC, Optimism, Arbitrum, Polygon, Base, Gnosis) and introduces architectural improvements using factory and proxy patterns.

Impact:

• 38 files changed
• Net: +372 / -399 lines (~27 lines reduction)
• Actual duplicate code removed: ~573 lines
• Type safety improvements

---

Changes

1. Environment Configuration Consolidation

Problem: All EVM chains used identical private keys but required separate env variables.

Solution: Introduced fallback pattern for wallet private keys:

const getWalletPrivateKey = (chainSpecific: string | undefined): string | undefined => {
  return chainSpecific || process.env.STANDARD_EVM_WALLET_PRIVATE_KEY;
};

Benefit: Can use single STANDARD_EVM_WALLET_PRIVATE_KEY instead of 9 separate variables (while still supporting chain-specific overrides for non-standard chains like Citrea).

Files: src/config/config.ts

---

2. Asset Service Native Coin Consolidation

Before: 8 separate get*Coin() methods (getEthCoin, getBnbCoin, etc.)

After: Single getNativeCoin(blockchain) method with mapping:

private static readonly NATIVE_COIN_MAP: Partial<Record<Blockchain, string>> = {
  [Blockchain.ETHEREUM]: 'ETH',
  [Blockchain.BINANCE_SMART_CHAIN]: 'BNB',
  // ... etc
};

async getNativeCoin(blockchain: Blockchain): Promise<Asset> {
  const coinName = AssetService.NATIVE_COIN_MAP[blockchain];
  return this.getAssetByQuery({ name: coinName, blockchain, type: AssetType.COIN });
}

Benefit:

• Eliminates 8 duplicate methods
• Centralized mapping for all blockchains
• Used by 8 Payout Prepare Strategies

Files: src/shared/models/asset/asset.service.ts, src/subdomains/supporting/payout/strategies/prepare/impl/*.strategy.ts

---

3. PayIn Service Consolidation (Factory + Proxy Pattern)

Before: 9 nearly identical EVM PayIn services (~10 lines each, total ~90 lines)

After: Factory + Proxy pattern

New Architecture:

1. PayInEvmFactory: Manages service instantiation with lazy-loaded singleton pattern
2. PayInEvmProxyService: Abstract base class that delegates to factory
3. IPayInEvmService: Interface for type-safe dependency injection
4. Chain-specific services: Simplified to 3 lines each

// Before (~10 lines per service × 9 chains)
@Injectable()
export class PayInEthereumService extends PayInEvmService {
  constructor(ethereumService: EthereumService) {
    super(ethereumService);
  }
}

// After (3 lines per service × 9 chains)
@Injectable()
export class PayInEthereumService extends PayInEvmProxyService {
  protected readonly blockchain = Blockchain.ETHEREUM;
  constructor(factory: PayInEvmFactory) { super(factory); }
}

Benefit:

• Reduced boilerplate from ~90 lines to ~27 lines
• Centralized service instantiation logic
• Type-safe through interface
• Maintains backward compatibility (all services still exported)

Files:

• src/subdomains/supporting/payin/services/payin-evm.factory.ts (NEW)
• src/subdomains/supporting/payin/services/base/payin-evm-proxy.service.ts (NEW)
• src/subdomains/supporting/payin/services/base/payin-evm.interface.ts (NEW)
• src/subdomains/supporting/payin/services/payin-*.service.ts (9 files simplified)
• src/subdomains/supporting/payin/payin.module.ts

---

4. PayIn Strategy Webhook Consolidation

Before: 7 EVM strategies duplicated onModuleInit() with identical webhook setup (~17 lines each)

After: Moved to AlchemyStrategy base class

Benefit: Eliminated ~119 lines of duplicate webhook initialization code

Files:

• src/subdomains/supporting/payin/strategies/register/impl/base/alchemy.strategy.ts
• src/subdomains/supporting/payin/strategies/register/impl/*.strategy.ts (7 files)

---

5. Blockchain Registry Service Refactoring

Before: Large switch statements for service/client lookup (~84 lines)

After: Map-based lookups with explicit type safety

constructor(...) {
  const serviceEntries: Array<[Blockchain, BlockchainServiceType]> = [
    [Blockchain.ETHEREUM, this.ethereumService],
    // ... all services
  ];
  this.serviceMap = new Map(serviceEntries);
}

getService(blockchain: Blockchain): BlockchainServiceType {
  const service = this.serviceMap.get(blockchain);
  if (!service) throw new Error(`No service found for blockchain ${blockchain}`);
  return service;
}

Benefit:

• Reduced from 84 lines to ~35 lines
• Better type safety with explicit array typing
• More maintainable

Files: src/integration/blockchain/shared/services/blockchain-registry.service.ts

---

6. Crypto Service Switch Statement Consolidation

Before: Large switch statements checking every EVM chain individually

After: Use EvmBlockchains array with .includes() check

// Before
switch (blockchain) {
  case Blockchain.ETHEREUM:
  case Blockchain.SEPOLIA:
  // ... 9 cases
    return EvmUtil.getPaymentRequest(...);
}

// After
if (EvmBlockchains.includes(blockchain)) {
  return EvmUtil.getPaymentRequest(...);
}

Benefit: More maintainable, automatically includes new standard EVM chains

Files: src/integration/blockchain/shared/services/crypto.service.ts

---

7. Blockchain Util Consolidation

Before: Switch statements for asset/address paths

After: Array-based checks with EvmBlockchains.includes()

Benefit: Cleaner, more maintainable

Files: src/integration/blockchain/shared/util/blockchain.util.ts

---

Type Safety Improvements

• Used Partial<Record<Blockchain, T>> instead of Record<Blockchain, T | undefined>
• Explicit array typing for Map constructors to avoid type inference issues
• Interface-based dependency injection for better decoupling
• All TypeScript compilation errors resolved

---

Breaking Changes

None. All changes are internal refactorings. Public APIs remain unchanged.

---

Test Plan

• Verify TypeScript compilation: npm run build
• Run test suite: npm run test
• Run linter: npm run lint
• Manual testing of PayIn flows for EVM chains
• Manual testing of Payout flows for EVM chains
• Verify webhook registration still works
• Check that asset fetching works correctly

---

Performance

• Minimal impact: Factory uses singleton pattern with lazy loading
• Proxy getter overhead is negligible (factory returns cached instance)
• Overall: No measurable performance degradation expected

---

Migration Guide

For Developers

No code changes required. All refactorings are internal.

For DevOps

Optional: Can consolidate 9 EVM wallet private key env variables into single STANDARD_EVM_WALLET_PRIVATE_KEY variable (but chain-specific variables still work for backward compatibility).

Example:

# Before (still works)
ETH_WALLET_PRIVATE_KEY=xxx
SEPOLIA_WALLET_PRIVATE_KEY=xxx
BSC_WALLET_PRIVATE_KEY=xxx
# ... etc

# After (new, cleaner)
STANDARD_EVM_WALLET_PRIVATE_KEY=xxx
# Override for non-standard chains only:
CITREA_TESTNET_WALLET_PRIVATE_KEY=yyy