feat(mcp-deribit): leverage_cap module with TDD

services/mcp-deribit/src/mcp_deribit/leverage_cap.py

@@ -0,0 +1,56 @@
+"""Leverage cap server-side per place_order.
+
+Cap letto dal secret JSON via campo `max_leverage`. Default 1 (cash) se assente.
+"""
+from __future__ import annotations
+
+from fastapi import HTTPException
+
+
+def get_max_leverage(creds: dict) -> int:
+    """Legge max_leverage dal secret. Default 1 se mancante."""
+    raw = creds.get("max_leverage", 1)
+    try:
+        value = int(raw)
+    except (TypeError, ValueError):
+        value = 1
+    return max(1, value)
+
+
+def enforce_leverage(
+    requested: int | float | None,
+    *,
+    creds: dict,
+    exchange: str,
+) -> int:
+    """Verifica e applica leverage cap. Ritorna leverage applicabile.
+
+    Solleva HTTPException(403, LEVERAGE_CAP_EXCEEDED) se requested > cap.
+    Se requested is None, applica il cap come default.
+    """
+    cap = get_max_leverage(creds)
+    if requested is None:
+        return cap
+    lev = int(requested)
+    if lev < 1:
+        raise HTTPException(
+            status_code=403,
+            detail={
+                "error": "LEVERAGE_CAP_EXCEEDED",
+                "exchange": exchange,
+                "requested": lev,
+                "max": cap,
+                "reason": "leverage must be >= 1",
+            },
+        )
+    if lev > cap:
+        raise HTTPException(
+            status_code=403,
+            detail={
+                "error": "LEVERAGE_CAP_EXCEEDED",
+                "exchange": exchange,
+                "requested": lev,
+                "max": cap,
+            },
+        )
+    return lev

services/mcp-deribit/tests/test_leverage_cap.py

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+from __future__ import annotations
+
+import pytest
+from fastapi import HTTPException
+
+from mcp_deribit.leverage_cap import enforce_leverage, get_max_leverage
+
+
+def test_get_max_leverage_returns_creds_value():
+    creds = {"max_leverage": 5}
+    assert get_max_leverage(creds) == 5
+
+
+def test_get_max_leverage_default_when_missing():
+    """Default 1 (cash) se il secret non ha max_leverage."""
+    assert get_max_leverage({}) == 1
+
+
+def test_enforce_leverage_pass_under_cap():
+    creds = {"max_leverage": 3}
+    enforce_leverage(2, creds=creds, exchange="deribit")  # no raise
+
+
+def test_enforce_leverage_pass_at_cap():
+    creds = {"max_leverage": 3}
+    enforce_leverage(3, creds=creds, exchange="deribit")  # no raise
+
+
+def test_enforce_leverage_reject_over_cap():
+    creds = {"max_leverage": 3}
+    with pytest.raises(HTTPException) as exc:
+        enforce_leverage(10, creds=creds, exchange="deribit")
+    assert exc.value.status_code == 403
+    assert exc.value.detail["error"] == "LEVERAGE_CAP_EXCEEDED"
+    assert exc.value.detail["exchange"] == "deribit"
+    assert exc.value.detail["requested"] == 10
+    assert exc.value.detail["max"] == 3
+
+
+def test_enforce_leverage_reject_when_below_one():
+    creds = {"max_leverage": 3}
+    with pytest.raises(HTTPException) as exc:
+        enforce_leverage(0, creds=creds, exchange="deribit")
+    assert exc.value.status_code == 403
+
+
+def test_enforce_leverage_default_when_none():
+    """Se requested è None, applica il cap come default."""
+    creds = {"max_leverage": 3}
+    result = enforce_leverage(None, creds=creds, exchange="deribit")
+    assert result == 3