1 files changed, 62 insertions, 0 deletions
diff --git a/services/portfolio-manager/src/portfolio_manager/portfolio.py b/services/portfolio-manager/src/portfolio_manager/portfolio.py
new file mode 100644
index 0000000..59106bb
--- /dev/null
+++ b/services/portfolio-manager/src/portfolio_manager/portfolio.py
@@ -0,0 +1,62 @@
+"""Portfolio tracking for the portfolio manager service."""
+from decimal import Decimal
+
+from shared.models import Order, OrderSide, Position
+
+
+class _PositionState:
+    """Internal state for tracking a single symbol's position."""
+
+    def __init__(self) -> None:
+        self.quantity: Decimal = Decimal("0")
+        self.avg_entry: Decimal = Decimal("0")
+
+
+class PortfolioTracker:
+    """Tracks positions and updates them based on filled orders."""
+
+    def __init__(self) -> None:
+        self._positions: dict[str, _PositionState] = {}
+
+    def _get_or_create(self, symbol: str) -> _PositionState:
+        if symbol not in self._positions:
+            self._positions[symbol] = _PositionState()
+        return self._positions[symbol]
+
+    def apply_order(self, order: Order) -> None:
+        """Update internal position state based on a filled order."""
+        state = self._get_or_create(order.symbol)
+
+        if order.side == OrderSide.BUY:
+            # Weighted average entry price
+            total_cost = state.avg_entry * state.quantity + order.price * order.quantity
+            state.quantity += order.quantity
+            if state.quantity > Decimal("0"):
+                state.avg_entry = total_cost / state.quantity
+        elif order.side == OrderSide.SELL:
+            state.quantity -= order.quantity
+            # Keep avg_entry unchanged unless fully sold
+            if state.quantity <= Decimal("0"):
+                state.quantity = Decimal("0")
+                state.avg_entry = Decimal("0")
+
+    def get_position(self, symbol: str) -> Position | None:
+        """Return a Position model for the symbol, or None if no/zero position."""
+        state = self._positions.get(symbol)
+        if state is None or state.quantity <= Decimal("0"):
+            return None
+        return Position(
+            symbol=symbol,
+            quantity=state.quantity,
+            avg_entry_price=state.avg_entry,
+            current_price=state.avg_entry,  # No live price here; caller can update
+        )
+
+    def get_all_positions(self) -> list[Position]:
+        """Return all non-zero positions."""
+        positions = []
+        for symbol in self._positions:
+            pos = self.get_position(symbol)
+            if pos is not None:
+                positions.append(pos)
+        return positions