修正

backend/app/payroll/settings/router.py

@@ -2,7 +2,7 @@
 給与設定・税率・保険料管理API (Settings Management API)
 """
 from fastapi import APIRouter, HTTPException, status, UploadFile, File
-from typing import List
+from typing import List, Optional
 from datetime import date
 import csv
 import io
@@ -17,10 +17,40 @@ from ...core.database import get_connection
 router = APIRouter(prefix="/payroll/settings", tags=["Payroll - Settings"])
 
 
+# ========================================
+# ヘルパー関数：年度フォールバック処理
+# ========================================
+def get_child_support_rate_with_fallback(target_year: int) -> Optional[dict]:
+    """子ども・子育て拠出金率を取得（指定年度がない場合は前年度を参照、最大3年遡る）"""
+    with get_connection() as conn:
+        with conn.cursor() as cur:
+            # まず指定年度を検索
+            cur.execute(
+                "SELECT * FROM child_support_contribution_rates WHERE rate_year = %s ORDER BY contribution_id DESC LIMIT 1",
+                (target_year,)
+            )
+            result = cur.fetchone()
+            
+            # 見つからない場合は前年度以前を検索
+            if not result:
+                for year_offset in range(1, 4):
+                    previous_year = target_year - year_offset
+                    cur.execute(
+                        "SELECT * FROM child_support_contribution_rates WHERE rate_year = %s ORDER BY contribution_id DESC LIMIT 1",
+                        (previous_year,)
+                    )
+                    result = cur.fetchone()
+                    if result:
+                        break
+            
+            return result
+
+
 # ========================================
 # 給与基本設定
 # ========================================
 
+
 @router.post("/salary", response_model=schemas.SalarySetting, status_code=status.HTTP_201_CREATED)
 def create_salary_setting(setting: schemas.SalarySettingCreate):
     """給与設定を作成"""
@@ -744,6 +774,7 @@ def calculate_income_tax(monthly_income: Decimal, dependents_count: int = 0, tar
     
     with get_connection() as conn:
         with conn.cursor() as cur:
+            # 月収がmonthly_income_from <= income < monthly_income_toの範囲に入るか検索
             cur.execute(
                 """
                 SELECT tax_amount FROM income_tax_table 
@@ -751,13 +782,29 @@ def calculate_income_tax(monthly_income: Decimal, dependents_count: int = 0, tar
                 AND (valid_to IS NULL OR valid_to >= %s)
                 AND dependents_count = %s
                 AND monthly_income_from <= %s
-                AND monthly_income_to >= %s
+                AND monthly_income_to > %s
                 LIMIT 1
                 """,
                 (target_date, target_date, dependents_count, monthly_income, monthly_income)
             )
             result = cur.fetchone()
             
+            # 見つからない場合は、Toが同値のケースも検索
+            if not result:
+                cur.execute(
+                    """
+                    SELECT tax_amount FROM income_tax_table 
+                    WHERE valid_from <= %s
+                    AND (valid_to IS NULL OR valid_to >= %s)
+                    AND dependents_count = %s
+                    AND monthly_income_from <= %s
+                    AND monthly_income_to = %s
+                    LIMIT 1
+                    """,
+                    (target_date, target_date, dependents_count, monthly_income, monthly_income)
+                )
+                result = cur.fetchone()
+            
             if not result:
                 return {"monthly_income": monthly_income, "dependents_count": dependents_count, "tax_amount": 0}