Initial commit: Arb Pulse monolith with CI and optional Fly deploy.

Real-time BTC cross-exchange arbitrage detection (Kraken, Bybit, OKX, Binance)
with React dashboard, GitHub Actions CI, and documented Fly.io deploy workflow.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/infrastructure/state/order-book-manager.ts

@@ -0,0 +1,53 @@
+import { config } from "../config/config.js";
+import {
+  EXCHANGE_IDS,
+  type BestQuote,
+  type ExchangeId,
+  type FeedStatus,
+  type OrderBook,
+} from "../../domain/entities/index.js";
+import type { IQuoteBook } from "../../domain/ports/ports.js";
+
+export class OrderBookManager implements IQuoteBook {
+  private books = new Map<ExchangeId, OrderBook>();
+
+  update(book: OrderBook): void {
+    this.books.set(book.exchange, book);
+  }
+
+  getBook(exchange: ExchangeId): OrderBook | undefined {
+    return this.books.get(exchange);
+  }
+
+  isFresh(exchange: ExchangeId, now: number): boolean {
+    const book = this.books.get(exchange);
+    if (!book) return false;
+    return now - book.recvTs <= config.staleMs;
+  }
+
+  private statusFor(book: OrderBook | undefined, now: number): FeedStatus {
+    if (!book) return "connecting";
+    const age = now - book.recvTs;
+    if (age > config.staleMs * 3) return "down";
+    if (age > config.staleMs) return "stale";
+    return "live";
+  }
+
+  bestQuotes(now: number): BestQuote[] {
+    return EXCHANGE_IDS.map((exchange) => {
+      const book = this.books.get(exchange);
+      const topBid = book?.bids[0];
+      const topAsk = book?.asks[0];
+      return {
+        exchange,
+        bid: topBid?.price ?? null,
+        bidQty: topBid?.qty ?? null,
+        ask: topAsk?.price ?? null,
+        askQty: topAsk?.qty ?? null,
+        recvTs: book?.recvTs ?? null,
+        status: this.statusFor(book, now),
+        ageMs: book ? now - book.recvTs : null,
+      };
+    });
+  }
+}