에러코드 누적 순위 차트 축 수정 — 에러코드 Y축, 충전기별 스택

- 기존: 충전기 Y축 + 에러코드별 스택 (충전기 중심)
- 변경: 에러코드 Y축 + 충전기별 스택 (에러코드 순위 중심)
- 어떤 에러코드가 가장 많이 발생했는지 + 어떤 충전기에서 발생했는지 한눈에 확인

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/main.py

@@ -543,63 +543,77 @@ def stats_top_chargers(limit: int = 10):
 
 
 @app.get("/api/stats/charger-error-codes")
-def stats_charger_error_codes(charger_limit: int = 10, code_limit: int = 6):
-    """충전기별 에러코드 누적 건수 Top N (에러코드 입력된 신고 기준)."""
+def stats_charger_error_codes(code_limit: int = 10, charger_limit: int = 5):
+    """에러코드별 누적 건수 Top N (어느 충전기에서 발생했는지 함께 반환)."""
     from database import SessionLocal
     from sqlalchemy import text
     from collections import defaultdict
     db = SessionLocal()
     try:
         rows = db.execute(text("""
-            SELECT rep.charger_id,
-                   COALESCE(c.station_name, rep.charger_id) AS station_name,
-                   COALESCE(c.name, '') AS charger_name,
-                   TRIM(rep.error_code) AS error_code,
-                   COUNT(*) AS cnt
+            SELECT TRIM(rep.error_code)                        AS error_code,
+                   rep.charger_id,
+                   COALESCE(c.station_name, rep.charger_id)   AS station_name,
+                   COALESCE(c.name, '')                        AS charger_name,
+                   COUNT(*)                                    AS cnt
             FROM reports rep
             LEFT JOIN chargers c ON c.id = rep.charger_id
             WHERE rep.error_code IS NOT NULL
               AND TRIM(rep.error_code) != ''
-            GROUP BY rep.charger_id, c.station_name, c.name, TRIM(rep.error_code)
+            GROUP BY TRIM(rep.error_code), rep.charger_id, c.station_name, c.name
         """)).fetchall()
 
         if not rows:
-            return {"chargers": [], "error_codes": []}
+            return {"error_codes": [], "charger_labels": {}}
 
+        # error_code → {total, chargers: {cid: cnt}}
+        code_info    = {}
+        # charger_id → label, total across all codes
         charger_info = {}
-        code_totals = defaultdict(int)
 
-        for row in rows:
-            cid, sname, cname, ecode, cnt = row
+        for ecode, cid, sname, cname, cnt in rows:
             cnt = int(cnt)
-            if cid not in charger_info:
-                charger_info[cid] = {"station_name": sname, "charger_name": cname,
-                                     "total": 0, "errors": {}}
-            charger_info[cid]["total"] += cnt
-            charger_info[cid]["errors"][ecode] = cnt
-            code_totals[ecode] += cnt
+            if ecode not in code_info:
+                code_info[ecode] = {"total": 0, "chargers": {}}
+            code_info[ecode]["total"]          += cnt
+            code_info[ecode]["chargers"][cid]   = cnt
 
-        top_chargers = sorted(charger_info.items(), key=lambda x: -x[1]["total"])[:charger_limit]
-        top_codes    = [c for c, _ in sorted(code_totals.items(), key=lambda x: -x[1])[:code_limit]]
+            if cid not in charger_info:
+                label = sname + (f" ({cname})" if cname else "")
+                if len(label) > 20: label = label[:18] + "…"
+                charger_info[cid] = {"label": label, "total": 0}
+            charger_info[cid]["total"] += cnt
+
+        # Top N error codes by total
+        top_codes = sorted(code_info.items(), key=lambda x: -x[1]["total"])[:code_limit]
+
+        # Top M chargers across all top codes
+        top_cids = [cid for cid, _ in
+                    sorted(charger_info.items(), key=lambda x: -x[1]["total"])[:charger_limit]]
 
         result = []
-        for cid, info in reversed(top_chargers):   # 역순: 차트에서 1위가 위에
-            label = info["station_name"]
-            if info["charger_name"]:
-                label += f" ({info['charger_name']})"
-            if len(label) > 22:
-                label = label[:20] + "…"
-            errors = info["errors"]
-            other  = sum(cnt for code, cnt in errors.items() if code not in top_codes)
-            entry  = {"charger_id": cid, "label": label, "total": info["total"]}
-            for code in top_codes:
-                entry[code] = errors.get(code, 0)
+        for ecode, info in reversed(top_codes):   # 역순: 차트에서 1위가 위에
+            entry = {"error_code": ecode, "total": info["total"]}
+            other = 0
+            for cid, cnt in info["chargers"].items():
+                if cid in top_cids:
+                    entry[cid] = cnt
+                else:
+                    other += cnt
             if other:
-                entry["기타"] = other
+                entry["__other__"] = other
             result.append(entry)
 
-        has_other = any(r.get("기타", 0) > 0 for r in result)
-        all_codes = top_codes + (["기타"] if has_other else [])
-        return {"chargers": result, "error_codes": all_codes}
+        has_other = any(r.get("__other__", 0) > 0 for r in result)
+        charger_labels = {cid: charger_info[cid]["label"] for cid in top_cids}
+        if has_other:
+            charger_labels["__other__"] = "기타"
+
+        dataset_keys = top_cids + (["__other__"] if has_other else [])
+        return {
+            "error_codes":    result,          # 에러코드별 집계 (역순)
+            "charger_labels": charger_labels,  # charger_id → 표시명
+            "dataset_keys":   dataset_keys,    # 차트 dataset 순서
+        }
     finally:
         db.close()