fix: merge

backend/app/rules/transit_rules.py

@@ -1,46 +1,49 @@
-"""Transit (self-transfer) detection rules.
-
-Identifies transactions that are internal transfers between the victim's
-own accounts (e.g. bank -> Alipay -> WeChat) and should NOT be counted
-as fraud loss.
-"""
+"""Transit (self-transfer) detection rules."""
 from datetime import datetime
 
 from app.models.transaction import TransactionRecord
 
-SELF_KEYWORDS = ["本人", "自己", "余额", "充值", "提现", "银行卡转入", "银行卡充值"]
+SELF_KEYWORDS = ("本人", "自己", "余额", "充值", "提现", "银行卡转入", "银行卡充值")
+APP_PATTERNS = ("支付宝", "微信", "银行卡", "数字钱包")
 FEE_TRANSIT_WINDOW_SECONDS = 120
 FEE_TOLERANCE_RATIO = 0.02
 
 
+def _normalize_text(value: str | None) -> str:
+    return (value or "").strip().lower()
+
+
+def _contains_any(text: str, patterns: tuple[str, ...]) -> bool:
+    return any(p in text for p in patterns)
+
+
+def _amount_ratio_diff(a: float, b: float) -> float:
+    base = max(a, b)
+    return 0 if base <= 0 else abs(a - b) / base
+
+
 def is_self_transfer(tx: TransactionRecord, known_self_accounts: list[str]) -> bool:
-    """Check if a transaction is an inter-account transfer by the victim."""
-    counterparty = (tx.counterparty_name or "").lower()
-    remark = (tx.remark or "").lower()
+    """Single-transaction heuristic for victim self-transfer."""
+    counterparty = _normalize_text(tx.counterparty_name)
+    remark = _normalize_text(tx.remark)
 
-    # Rule 1: counterparty matches known self accounts
-    for acct in known_self_accounts:
-        if acct and acct.lower() in counterparty:
+    # Rule 1: explicit known self account hit
+    if any(acct and _normalize_text(acct) in counterparty for acct in known_self_accounts):
         return True
 
-    # Rule 2: counterparty contains self-transfer keywords
-    for kw in SELF_KEYWORDS:
-        if kw in counterparty or kw in remark:
+    # Rule 2: self-transfer keywords
+    if _contains_any(counterparty, SELF_KEYWORDS) or _contains_any(remark, SELF_KEYWORDS):
         return True
 
-    # Rule 3: counterparty references another payment app owned by victim
-    app_keywords = ["支付宝", "微信", "银行卡", "数字钱包"]
-    victim_patterns = [f"{app}-" for app in app_keywords] + app_keywords
-    for pat in victim_patterns:
-        if pat in counterparty:
-            if tx.direction.value == "out":
+    # Rule 3: outflow to another own payment channel
+    if tx.direction.value == "out" and _contains_any(counterparty, APP_PATTERNS):
         return True
 
     return False
 
 
 def is_fee_tolerant_transit_pair(tx_a: TransactionRecord, tx_b: TransactionRecord) -> bool:
-    """Two-way transfer pattern: opposite direction, close time, similar amount."""
+    """Pair heuristic: opposite direction, close time, amount diff <= 2%."""
     if tx_a.direction.value == tx_b.direction.value:
         return False
 
@@ -48,16 +51,46 @@ def is_fee_tolerant_transit_pair(tx_a: TransactionRecord, tx_b: TransactionRecor
     amount_b = float(tx_b.amount or 0)
     if amount_a <= 0 or amount_b <= 0:
         return False
+    if _amount_ratio_diff(amount_a, amount_b) > FEE_TOLERANCE_RATIO:
+        return False
 
     time_a = tx_a.trade_time
     time_b = tx_b.trade_time
     if not isinstance(time_a, datetime) or not isinstance(time_b, datetime):
         return False
-    if abs((time_a - time_b).total_seconds()) > FEE_TRANSIT_WINDOW_SECONDS:
+    try:
+        return abs((time_a - time_b).total_seconds()) <= FEE_TRANSIT_WINDOW_SECONDS
+    except TypeError:
         return False
 
-    amount_base = max(amount_a, amount_b)
-    if amount_base <= 0:
-        return False
-    diff_ratio = abs(amount_a - amount_b) / amount_base
-    return diff_ratio <= FEE_TOLERANCE_RATIO
+
+def mark_transit_transactions(
+    transactions: list[TransactionRecord],
+    known_self_accounts: list[str],
+) -> None:
+    """Mark `is_transit` in-place using single-transaction + pair rules."""
+    candidates = [tx for tx in transactions if not tx.is_duplicate]
+    if not candidates:
+        return
+
+    # Pass 1: single transaction rules
+    for tx in candidates:
+        if is_self_transfer(tx, known_self_accounts):
+            tx.is_transit = True
+
+    # Pass 2: pair rules within 2-minute window
+    sorted_txs = sorted(candidates, key=lambda tx: tx.trade_time)
+    for i, tx_a in enumerate(sorted_txs):
+        j = i + 1
+        while j < len(sorted_txs):
+            tx_b = sorted_txs[j]
+            try:
+                seconds_gap = (tx_b.trade_time - tx_a.trade_time).total_seconds()
+            except TypeError:
+                break
+            if seconds_gap > FEE_TRANSIT_WINDOW_SECONDS:
+                break
+            if is_fee_tolerant_transit_pair(tx_a, tx_b):
+                tx_a.is_transit = True
+                tx_b.is_transit = True
+            j += 1

backend/app/services/matching_service.py

@@ -15,7 +15,7 @@ from app.models.transaction import TransactionRecord
 from app.models.transaction_cluster import TransactionCluster
 from app.repositories.transaction_repo import TransactionRepository
 from app.rules.dedup_rules import is_duplicate_pair
-from app.rules.transit_rules import is_self_transfer, is_fee_tolerant_transit_pair
+from app.rules.transit_rules import mark_transit_transactions
 
 
 async def run_matching(case_id: UUID, self_accounts: list[str], db: AsyncSession) -> None:
@@ -34,8 +34,6 @@ async def run_matching(case_id: UUID, self_accounts: list[str], db: AsyncSession
 
     # ── Layer 1 & 2: dedup ──
     matched: set[UUID] = set()
-    clusters: list[TransactionCluster] = []
-
     for i, tx_a in enumerate(transactions):
         if tx_a.id in matched:
             continue
@@ -61,23 +59,9 @@ async def run_matching(case_id: UUID, self_accounts: list[str], db: AsyncSession
                 tx.cluster_id = cluster.id
                 if tx.id != primary.id:
                     tx.is_duplicate = True
-            clusters.append(cluster)
 
     # ── Layer 3: transit detection ──
-    for tx in transactions:
-        if tx.is_duplicate:
-            continue
-        if is_self_transfer(tx, self_accounts):
-            tx.is_transit = True
-
-    # Rule extension: if an in/out pair occurs within 2 minutes and
-    # amount difference is within 2% (e.g. fee), mark both as transit.
-    non_duplicate = [tx for tx in transactions if not tx.is_duplicate]
-    for i, tx_a in enumerate(non_duplicate):
-        for tx_b in non_duplicate[i + 1 :]:
-            if is_fee_tolerant_transit_pair(tx_a, tx_b):
-                tx_a.is_transit = True
-                tx_b.is_transit = True
+    mark_transit_transactions(transactions, self_accounts)
 
     await db.flush()
 

backend/tests/test_rules.py

@@ -8,7 +8,11 @@ import pytest
 from app.models.transaction import Direction
 from app.models.evidence_image import SourceApp
 from app.rules.dedup_rules import is_duplicate_pair
-from app.rules.transit_rules import is_self_transfer, is_fee_tolerant_transit_pair
+from app.rules.transit_rules import (
+    is_self_transfer,
+    is_fee_tolerant_transit_pair,
+    mark_transit_transactions,
+)
 from app.rules.assessment_rules import classify_transaction
 
 
@@ -105,6 +109,36 @@ class TestTransitRules:
         )
         assert not is_fee_tolerant_transit_pair(out_tx, in_tx)
 
+    def test_wechat_recharge_in_then_out_marked_transit(self):
+        in_tx = _make_tx(
+            trade_time=datetime(2026, 3, 17, 21, 46, 0, tzinfo=timezone.utc),
+            amount=50,
+            direction=Direction.in_,
+            counterparty_name="零钱充值-来自工商银行(3893)",
+            counterparty_account="",
+            self_account_tail_no="3893",
+            order_no="",
+            remark="",
+            confidence=0.95,
+            is_transit=False,
+        )
+        out_tx = _make_tx(
+            trade_time=datetime(2026, 3, 17, 21, 46, 59, tzinfo=timezone.utc),
+            amount=50,
+            direction=Direction.out,
+            counterparty_name="童年",
+            counterparty_account="1154****0928",
+            self_account_tail_no="3893",
+            order_no="",
+            remark="充值",
+            confidence=0.98,
+            is_transit=False,
+        )
+        txs = [in_tx, out_tx]
+        mark_transit_transactions(txs, known_self_accounts=[])
+        assert in_tx.is_transit
+        assert out_tx.is_transit
+
 
 class TestAssessmentRules:
     def test_transit_classified_as_low(self):