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backend/app/services/analyzer.py

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+"""Fund flow analysis: build directed graph and summary from transactions."""
+
+from collections import defaultdict
+from decimal import Decimal
+
+import networkx as nx
+
+from app.schemas.analysis import (
+    AnalysisSummaryResponse,
+    AppSummary,
+    FlowGraphResponse,
+    FlowNode,
+    FlowEdge,
+)
+from app.schemas.transaction import TransactionResponse
+
+# Transaction types that mean money leaving victim's app (outflow)
+OUT_TYPES = {"转出", "消费", "付款", "提现"}
+# Transaction types that mean money entering victim's app (inflow)
+IN_TYPES = {"转入", "收款", "充值"}
+
+
+def _is_out(t: TransactionResponse) -> bool:
+    return t.transaction_type in OUT_TYPES or "转出" in (t.transaction_type or "") or "消费" in (t.transaction_type or "")
+
+
+def _is_in(t: TransactionResponse) -> bool:
+    return t.transaction_type in IN_TYPES or "转入" in (t.transaction_type or "") or "收款" in (t.transaction_type or "")
+
+
+def _node_id(app_or_counterparty: str, kind: str) -> str:
+    """Generate stable node id; kind in ('victim_app', 'counterparty')."""
+    import hashlib
+    safe = (app_or_counterparty or "").strip() or "unknown"
+    h = hashlib.sha256(f"{kind}:{safe}".encode()).hexdigest()[:12]
+    return f"{kind}_{h}"
+
+
+def build_flow_graph(transactions: list[TransactionResponse]) -> tuple[FlowGraphResponse, AnalysisSummaryResponse]:
+    """
+    Build directed graph and summary from transaction list.
+    Node: victim's app (app_source when outflow) or counterparty (counterparty_name or counterparty_account).
+    Edge: source -> target with total amount and count.
+    """
+    out_by_app: dict[str, Decimal] = defaultdict(Decimal)
+    in_by_app: dict[str, Decimal] = defaultdict(Decimal)
+    total_out = Decimal(0)
+    total_in = Decimal(0)
+    counterparties: set[str] = set()
+    # (source_id, target_id) -> (amount, count)
+    edges_agg: dict[tuple[str, str], tuple[Decimal, int]] = defaultdict(lambda: (Decimal(0), 0))
+    node_labels: dict[str, str] = {}
+    node_types: dict[str, str] = {}
+
+    for t in transactions:
+        amount = t.amount if isinstance(t.amount, Decimal) else Decimal(str(t.amount))
+        app = (t.app_source or "").strip() or "未知APP"
+        counterparty = (t.counterparty_name or t.counterparty_account or "未知对方").strip() or "未知对方"
+        counterparties.add(counterparty)
+
+        victim_node_id = _node_id(app, "victim_app")
+        node_labels[victim_node_id] = app
+        node_types[victim_node_id] = "victim_app"
+
+        cp_node_id = _node_id(counterparty, "counterparty")
+        node_labels[cp_node_id] = counterparty
+        node_types[cp_node_id] = "counterparty"
+
+        if _is_out(t):
+            out_by_app[app] += amount
+            total_out += amount
+            key = (victim_node_id, cp_node_id)
+            am, cnt = edges_agg[key]
+            edges_agg[key] = (am + amount, cnt + 1)
+        elif _is_in(t):
+            in_by_app[app] += amount
+            total_in += amount
+            key = (cp_node_id, victim_node_id)
+            am, cnt = edges_agg[key]
+            edges_agg[key] = (am + amount, cnt + 1)
+
+    all_apps = set(out_by_app.keys()) | set(in_by_app.keys())
+    by_app = {
+        app: AppSummary(
+            in_amount=in_by_app.get(app, Decimal(0)),
+            out_amount=out_by_app.get(app, Decimal(0)),
+        )
+        for app in all_apps
+    }
+    summary = AnalysisSummaryResponse(
+        total_out=total_out,
+        total_in=total_in,
+        net_loss=total_out - total_in,
+        by_app=by_app,
+        counterparty_count=len(counterparties),
+    )
+
+    nodes = [
+        FlowNode(id=nid, label=node_labels[nid], type=node_types.get(nid))
+        for nid in node_labels
+    ]
+    edges = [
+        FlowEdge(source=src, target=tgt, amount=am, count=cnt)
+        for (src, tgt), (am, cnt) in edges_agg.items()
+    ]
+    graph = FlowGraphResponse(nodes=nodes, edges=edges)
+    return graph, summary