Add Binance REST client with OHLCV, ticker, and volume methods

Implements BinanceRestClient wrapping python-binance with get_top_coins,
get_ohlcv, get_all_prices, and get_24h_volume. Includes mocked unit tests
for all public methods.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

data/binance_rest.py

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+import pandas as pd
+from binance.client import Client
+import logging
+
+logger = logging.getLogger(__name__)
+
+class BinanceRestClient:
+    def __init__(self, api_key: str, api_secret: str):
+        self.client = Client(api_key, api_secret)
+
+    def get_top_coins(self, limit: int = 50) -> list[str]:
+        tickers = self.client.get_ticker()
+        usdt_pairs = [
+            t for t in tickers
+            if t["symbol"].endswith("USDT") and not t["symbol"].startswith("USDT")
+        ]
+        usdt_pairs.sort(key=lambda x: float(x["quoteVolume"]), reverse=True)
+        return [t["symbol"] for t in usdt_pairs[:limit]]
+
+    def get_ohlcv(self, symbol: str, interval: str = "1h", limit: int = 100) -> pd.DataFrame:
+        klines = self.client.get_klines(symbol=symbol, interval=interval, limit=limit)
+        df = pd.DataFrame(klines, columns=[
+            "timestamp", "open", "high", "low", "close", "volume",
+            "close_time", "quote_volume", "trades", "taker_buy_base",
+            "taker_buy_quote", "ignore",
+        ])
+        for col in ["open", "high", "low", "close", "volume", "quote_volume"]:
+            df[col] = df[col].astype(float)
+        df["timestamp"] = pd.to_datetime(df["timestamp"], unit="ms")
+        return df[["timestamp", "open", "high", "low", "close", "volume", "quote_volume"]]
+
+    def get_all_prices(self) -> dict[str, float]:
+        tickers = self.client.get_all_tickers()
+        return {t["symbol"]: float(t["price"]) for t in tickers}
+
+    def get_24h_volume(self, symbol: str) -> dict:
+        ticker = self.client.get_ticker(symbol=symbol)
+        return {
+            "volume": float(ticker["volume"]),
+            "quote_volume": float(ticker["quoteVolume"]),
+            "price_change_pct": float(ticker["priceChangePercent"]),
+        }

tests/test_binance_rest.py

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+import pytest
+from unittest.mock import patch, MagicMock
+from data.binance_rest import BinanceRestClient
+
+@pytest.fixture
+def client():
+    with patch("data.binance_rest.Client") as mock_client_cls:
+        mock_client_cls.return_value = MagicMock()
+        c = BinanceRestClient(api_key="test", api_secret="test")
+    return c
+
+def test_get_top_coins_returns_symbols(client):
+    mock_tickers = [
+        {"symbol": "BTCUSDT", "quoteVolume": "1000000"},
+        {"symbol": "ETHUSDT", "quoteVolume": "500000"},
+        {"symbol": "BTCETH", "quoteVolume": "200000"},
+    ]
+    with patch.object(client.client, "get_ticker", return_value=mock_tickers):
+        result = client.get_top_coins(limit=2)
+    assert "BTCUSDT" in result
+    assert "ETHUSDT" in result
+    assert "BTCETH" not in result
+
+def test_get_ohlcv_returns_dataframe(client):
+    mock_klines = [
+        [1700000000000, "40000", "41000", "39000", "40500", "100",
+         1700003599999, "4050000", 500, "50", "2025000", "0"]
+    ]
+    with patch.object(client.client, "get_klines", return_value=mock_klines):
+        df = client.get_ohlcv("BTCUSDT", interval="1h", limit=1)
+    assert len(df) == 1
+    assert "close" in df.columns
+    assert df.iloc[0]["close"] == 40500.0
+
+def test_get_all_tickers(client):
+    mock_prices = [
+        {"symbol": "BTCUSDT", "price": "40000.00"},
+        {"symbol": "ETHUSDT", "price": "3500.00"},
+    ]
+    with patch.object(client.client, "get_all_tickers", return_value=mock_prices):
+        result = client.get_all_prices()
+    assert result["BTCUSDT"] == 40000.0