feat: strategy builder

backend/routers/strategy_builder.py

@@ -146,6 +146,38 @@ def chain(
         raise HTTPException(status_code=404, detail=str(e))
 
 
+@router.get("/presets")
+def presets(
+    symbol: str = Query(...),
+    horizon_days: int = Query(8),
+    dte_min: Optional[int] = Query(None),
+    dte_max: Optional[int] = Query(None),
+):
+    """The full strategy catalog (services.backtest_strategies.STRATEGIES) built from the
+    REAL current chain instead of Backtest's synthetic grid — so a preset click here seeds
+    the leg editor with actually-quoted strikes/expiries, ready to price or replay as-is.
+    n_expiries=5 (vs. Strategy Builder's own default of 3) so calendar/diagonal presets,
+    which need two distinct expiries, reliably have a second one to draw from."""
+    from services.backtest_strategies import STRATEGIES, build_legs
+    try:
+        chain_slice = get_chain_slice(symbol, horizon_days, 5, dte_min=dte_min, dte_max=dte_max)
+    except ValueError as e:
+        raise HTTPException(status_code=404, detail=str(e))
+
+    expiries = chain_slice["expiries"]
+    if not expiries:
+        raise HTTPException(status_code=404, detail=f"Aucune échéance exploitable pour '{symbol}'.")
+    near, far = expiries[0], expiries[1] if len(expiries) > 1 else None
+
+    out = []
+    for key, label, n_legs in STRATEGIES:
+        legs = build_legs(key, chain_slice["spot"], 0.05, near, far)
+        if not legs:
+            continue  # e.g. calendar/diagonal with only one real expiry available right now
+        out.append({"key": key, "label": label, "n_legs": n_legs, "legs": legs})
+    return out
+
+
 @router.post("/price")
 def price(req: PriceRequest):
     if not req.legs: