class ApiService {
  protected port: number;
  protected app: Express;
  protected server: Server | null;
  protected chainContexts: ChainContext[];

  static getInstance(port?: number): ApiService
  async start(): Promise<Server>
  async stop(): Promise<void>
  setChainContexts(chainContexts: ChainContext[]): void
  getChainContexts(): ChainContext[]
}

const api = ApiService.getInstance(8080);
await api.start();

// Set chain contexts after initialization
api.setChainContexts(chainContexts);

// Later, stop the server
await api.stop();

yarn cli run --disable-api

yarn cli run --api-port 3000

class ChainContext {
  readonly deploymentBlock: number;
  readonly pageSize: number;
  readonly dryRun: boolean;
  readonly watchdogTimeout: number;
  readonly addresses?: string[];
  readonly processEveryNumBlocks: number;

  provider: providers.Provider;
  chainId: SupportedChainId;
  registry: Registry;
  orderBookApi: OrderBookApi;
  filterPolicy: FilterPolicy | undefined;
  contract: ComposableCoW;
  multicall: Multicall3;

  static async init(options: ContextOptions, storage: DBService): Promise<ChainContext>
  async warmUp(oneShot?: boolean): Promise<void>
  get health(): ChainHealth
  static get health(): ChainWatcherHealth
}

const context = await ChainContext.init({
  rpc: 'https://eth-mainnet.g.alchemy.com/v2/...',
  deploymentBlock: 16842080,
  pageSize: 5000,
  dryRun: false,
  // ... other options
}, storage);

await context.warmUp();
// Now watching for new blocks

// Single chain health
const chainHealth = context.health;
// { sync: 'IN_SYNC', chainId: 1, lastProcessedBlock: {...}, isHealthy: true }

// All chains health
const overallHealth = ChainContext.health;
// { overallHealth: true, chains: { 1: {...}, 5: {...} } }

// WebSocket
rpc: 'wss://eth-mainnet.ws.alchemy.com/v2/...'

// HTTP
rpc: 'https://eth-mainnet.g.alchemy.com/v2/...'

class DBService {
  protected db: Level<string, string>;

  static getInstance(path?: string): DBService
  async open(): Promise<void>
  async close(): Promise<void>
  getDB(): Level<string, string>
}

const options: DatabaseOptions<string, string> = {
  valueEncoding: 'json',      // Store as JSON
  createIfMissing: true,      // Create if doesn't exist
  errorIfExists: false,       // Allow opening existing DB
};

// Get singleton instance
const storage = DBService.getInstance('./database');

// Open connection
await storage.open();

// Access underlying LevelDB
const db = storage.getDB();
await db.get('key');
await db.put('key', 'value');

// Batch operations
await db.batch()
  .put('key1', 'value1')
  .put('key2', 'value2')
  .write();

// Close connection
await storage.close();

yarn cli run --database-path /path/to/db

await Promise.allSettled([
  ApiService.getInstance().stop(),
  DBService.getInstance().close(),
]);