fix: use equal weight sharing for remaining 15% and quantize min_rate floor comparison to 2 decimal places

backend/app/services/website_client.py

@@ -71,15 +71,9 @@ def calculate_target_rate(values: list[Any], percent: Any = 0, algorithm: str =
         if N == 1:
             base = rates_sorted[0]
         else:
-            base = Decimal("0")
-            remaining = Decimal("1.0")
-            for i in range(N):
-                if i == N - 1:
-                    weight = remaining
-                else:
-                    weight = remaining * Decimal("0.85")
-                    remaining -= weight
-                base += rates_sorted[i] * weight
+            w1 = Decimal("0.85")
+            w_others = Decimal("0.15") / Decimal(N - 1)
+            base = rates_sorted[0] * w1 + sum(rates_sorted[1:], Decimal("0")) * w_others
     else:
         raise WebsiteError(f"不支持的算法：{algorithm}")
     pct = Decimal(str(percent or 0))
@@ -87,9 +81,9 @@ def calculate_target_rate(values: list[Any], percent: Any = 0, algorithm: str =
         raise WebsiteError("百分比不能为负数")
     target_rate = (base * (Decimal("1") + pct / Decimal("100"))).quantize(Decimal("0.01"), rounding=ROUND_HALF_UP)
     if algorithm == "priority_weighted_plus_percent":
-        min_rate = min(rates)
-        if target_rate < min_rate:
-            target_rate = min_rate
+        min_rate_2d = min(rates).quantize(Decimal("0.01"), rounding=ROUND_HALF_UP)
+        if target_rate < min_rate_2d:
+            target_rate = min_rate_2d
     return target_rate
 
 

backend/test_website_client.py

@@ -406,8 +406,17 @@ def test_calculate_target_rate_priority_weighted():
     assert calculate_target_rate(["0.18", "0.25"], 50, "priority_weighted_plus_percent") == Decimal("0.29")
     # 单来源时等同于该来源倍率 + 百分比
     assert calculate_target_rate(["0.18"], 50, "priority_weighted_plus_percent") == Decimal("0.27")
-    # 多来源时权重按低倍率优先，最高倍率不会主导价格
-    assert calculate_target_rate(["0.18", "0.25", "0.38"], 50, "priority_weighted_plus_percent") == Decimal("0.29")
+    # 多来源时最低倍率占 85%，其余平分 15%：
+    # 0.18 * 0.85 + (0.25 + 0.38) * 0.075 = 0.20025 -> 0.20025 * 1.5 = 0.300375 -> 0.30
+    assert calculate_target_rate(["0.18", "0.25", "0.38"], 50, "priority_weighted_plus_percent") == Decimal("0.30")
+
+    # 4 个来源以锁定均分 15% 的权重语义：
+    # 0.18 * 0.85 + (0.24 + 0.30 + 0.36) * 0.05 = 0.198 -> 0.198 * 1.5 = 0.297 -> 0.30
+    assert calculate_target_rate(["0.18", "0.24", "0.30", "0.36"], 50, "priority_weighted_plus_percent") == Decimal("0.30")
+    assert calculate_target_rate(["0.18", "0.24", "0.30", "0.36"], 0, "priority_weighted_plus_percent") == Decimal("0.20")
+
+    # 验证保护线与精度保护：最低来源 0.124，应当四舍五入并返回两位小数
+    assert calculate_target_rate(["0.124"], 0, "priority_weighted_plus_percent") == Decimal("0.12")
 
     # 无可用正数倍率时报错
     with pytest.raises(WebsiteError, match="没有可用的正数上游倍率"):