Add Polaris FastAPI backend: models/schemas, pricing+scoring+order router, importer, Celery tasks, API routers, seed script

backend/app/engines/scoring.py

@@ -0,0 +1,70 @@
+"""Supplier scoring.
+
+Weighted score (0-100):
+    40% price       — cheaper supplier cost vs. the eligible pool
+    20% inventory   — stock sufficiency for the requested qty
+    15% speed       — shipping_time ('3-5 days' -> avg days)
+    10% fulfillment — supplier_performance.fulfillment_rate
+    10% returns     — inverse of supplier_performance.return_rate
+     5% history     — reliability_score blended with stock_accuracy
+"""
+import re
+
+
+def _num(value, default=0.0):
+    try:
+        return float(value or 0)
+    except (TypeError, ValueError):
+        return default
+
+
+def _shipping_days(sp):
+    text = (sp.shipping_time or "").strip()
+    numbers = re.findall(r"\d+", text)
+    if not numbers:
+        return 5.0
+    return float(sum(int(n) for n in numbers)) / len(numbers)
+
+
+def score_supplier(db, supplier, sp, qty, price_pool=None):
+    perf = supplier.performance
+
+    # 1) price (40%) — cheaper than pool average is better
+    cost = _num(sp.supplier_cost)
+    if price_pool and price_pool.get("avg_cost"):
+        avg = price_pool["avg_cost"]
+        price_score = max(0.0, 100.0 - (cost / avg - 1.0) * 100.0)
+    else:
+        price_score = 50.0
+
+    # 2) inventory (20%) — can we fill the quantity?
+    inventory = int(sp.supplier_inventory or 0)
+    inv_score = 100.0 if inventory >= qty else max(0.0, (inventory / qty) * 100.0)
+
+    # 3) speed (15%) — fewer shipping days is better
+    days = _shipping_days(sp)
+    speed_score = max(0.0, 100.0 - days * 12.0)
+
+    # 4) fulfillment (10%)
+    fulfillment = 100.0 if perf is None else _num(perf.fulfillment_rate, 100.0)
+
+    # 5) returns (10%) — 0% returns = 100 points, 20% returns = 0 points
+    return_rate = 0.0 if perf is None else _num(perf.return_rate, 0.0)
+    returns_score = max(0.0, 100.0 - return_rate * 5.0)
+
+    # 6) history (5%) — reliability blended with stock accuracy
+    reliability = _num(supplier.reliability_score, 50.0)
+    if perf is None:
+        history_score = reliability
+    else:
+        history_score = 0.5 * reliability + 0.5 * _num(perf.stock_accuracy, 100.0)
+
+    total = (
+        0.40 * price_score
+        + 0.20 * inv_score
+        + 0.15 * speed_score
+        + 0.10 * fulfillment
+        + 0.10 * returns_score
+        + 0.05 * history_score
+    )
+    return round(min(100.0, max(0.0, total)), 2)