feat: add portfolio detail API with calculated values

backend/app/api/portfolio.py

@@ -1,6 +1,7 @@
 """
 Portfolio management API endpoints.
 """
+from decimal import Decimal
 from typing import List
 
 from fastapi import APIRouter, Depends, HTTPException, status
@@ -12,7 +13,7 @@ from app.models.portfolio import Portfolio, PortfolioType, Target, Holding, Tran
 from app.schemas.portfolio import (
     PortfolioCreate, PortfolioUpdate, PortfolioResponse, PortfolioDetail,
     TargetCreate, TargetResponse,
-    HoldingCreate, HoldingResponse,
+    HoldingCreate, HoldingResponse, HoldingWithValue,
     TransactionCreate, TransactionResponse,
     RebalanceResponse, RebalanceSimulationRequest, RebalanceSimulationResponse,
 )
@@ -316,3 +317,63 @@ async def simulate_rebalance(
     portfolio = _get_portfolio(db, portfolio_id, current_user.id)
     service = RebalanceService(db)
     return service.calculate_rebalance(portfolio, additional_amount=data.additional_amount)
+
+
+@router.get("/{portfolio_id}/detail", response_model=PortfolioDetail)
+async def get_portfolio_detail(
+    portfolio_id: int,
+    current_user: CurrentUser,
+    db: Session = Depends(get_db),
+):
+    """Get portfolio with calculated values."""
+    portfolio = _get_portfolio(db, portfolio_id, current_user.id)
+
+    # Get current prices
+    tickers = [h.ticker for h in portfolio.holdings]
+    service = RebalanceService(db)
+    prices = service.get_current_prices(tickers)
+
+    # Calculate holding values
+    holdings_with_value = []
+    total_value = Decimal("0")
+    total_invested = Decimal("0")
+
+    for holding in portfolio.holdings:
+        current_price = prices.get(holding.ticker, Decimal("0"))
+        value = current_price * holding.quantity
+        invested = Decimal(str(holding.avg_price)) * holding.quantity
+        profit_loss = value - invested
+        profit_loss_ratio = (profit_loss / invested * 100) if invested > 0 else Decimal("0")
+
+        total_value += value
+        total_invested += invested
+
+        holdings_with_value.append(HoldingWithValue(
+            ticker=holding.ticker,
+            quantity=holding.quantity,
+            avg_price=Decimal(str(holding.avg_price)),
+            current_price=current_price,
+            value=value,
+            current_ratio=Decimal("0"),  # Will be calculated after total
+            profit_loss=profit_loss,
+            profit_loss_ratio=profit_loss_ratio.quantize(Decimal("0.01")),
+        ))
+
+    # Calculate current ratios
+    for h in holdings_with_value:
+        if total_value > 0:
+            h.current_ratio = (h.value / total_value * 100).quantize(Decimal("0.01"))
+
+    return PortfolioDetail(
+        id=portfolio.id,
+        user_id=portfolio.user_id,
+        name=portfolio.name,
+        portfolio_type=portfolio.portfolio_type.value,
+        created_at=portfolio.created_at,
+        updated_at=portfolio.updated_at,
+        targets=portfolio.targets,
+        holdings=holdings_with_value,
+        total_value=total_value,
+        total_invested=total_invested,
+        total_profit_loss=total_value - total_invested,
+    )