feat(backend): complete modular monolith with ledger, fastapi and websocket

app/domains/trading/service.py

@@ -0,0 +1,75 @@
+import uuid
+from decimal import Decimal
+from typing import List, Optional
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy import select
+from app.models.entities import MarketModel, OrderModel, MarketStatus
+from app.domains.ledger.service import LedgerService
+
+class MarketService:
+    """预测市场领域服务"""
+
+    def __init__(self, session: AsyncSession):
+        self.session = session
+
+    async def list_markets(self, category: Optional[str] = None, status: Optional[str] = None) -> List[MarketModel]:
+        stmt = select(MarketModel)
+        if category:
+            stmt = stmt.where(MarketModel.category == category)
+        if status:
+            stmt = stmt.where(MarketModel.status == status)
+        stmt = stmt.order_by(MarketModel.created_at.desc())
+        result = await self.session.execute(stmt)
+        return list(result.scalars().all())
+
+    async def get_market(self, market_address: str) -> Optional[MarketModel]:
+        stmt = select(MarketModel).where(MarketModel.market_address == market_address.lower())
+        result = await self.session.execute(stmt)
+        return result.scalar_one_or_none()
+
+class TradingService:
+    """交易撮合与下单领域服务"""
+
+    def __init__(self, session: AsyncSession):
+        self.session = session
+        self.ledger_service = LedgerService(session)
+
+    async def place_order(
+        self,
+        user_address: str,
+        market_address: str,
+        outcome_index: int,
+        side: str,
+        amount: Decimal,
+        price: Optional[Decimal] = None
+    ) -> OrderModel:
+        """执行下单流程"""
+        order_id = str(uuid.uuid4())
+        fee = amount * Decimal("0.006") # 0.6% protocol fee
+
+        # 1. 记账并扣款/冻结
+        await self.ledger_service.record_trade(
+            address=user_address,
+            market_address=market_address,
+            order_id=order_id,
+            side=side,
+            amount=amount,
+            fee=fee
+        )
+
+        # 2. 生成订单记录
+        order = OrderModel(
+            order_id=order_id,
+            market_address=market_address.lower(),
+            user_address=user_address.lower(),
+            side=side,
+            outcome_index=outcome_index,
+            amount=amount,
+            price=price,
+            status="FILLED",
+            filled_amount=amount,
+            fee=fee
+        )
+        self.session.add(order)
+        await self.session.flush()
+        return order