bootstrap

engine/forecast.py

@@ -0,0 +1,100 @@
+from copy import deepcopy
+
+from cashflow_model import Account, FinancialModel
+
+
+class ForecastError(Exception):
+    pass
+
+
+class ForecastService:
+    def __init__(self, model: FinancialModel):
+        self.model = deepcopy(model)
+
+    def forecast_cashflow(self, months: int = 12) -> list[dict]:
+        if months < 1:
+            raise ForecastError("months must be >= 1")
+
+        results = []
+        for account in self.model.accounts:
+            balance = account.balance
+            monthly = self._project_account(account, months)
+            for m in range(months):
+                balance = monthly[m]["balance"]
+                results.append({
+                    "account": account.name,
+                    "month": m + 1,
+                    "balance": round(balance, 2),
+                    "income": round(monthly[m]["income"], 2),
+                    "expenses": round(monthly[m]["expenses"], 2),
+                })
+        return results
+
+    def _project_account(self, account: Account, months: int) -> list[dict]:
+        balance = account.balance
+        monthly = []
+        for m in range(months):
+            income = 0.0
+            expenses = 0.0
+
+            for t in self.model.transactions:
+                if t.account == str(account.id):
+                    if t.amount > 0:
+                        income += t.amount
+                    else:
+                        expenses += abs(t.amount)
+
+            for r in self.model.recurring:
+                if r.category == "income":
+                    income += abs(r.amount)
+                else:
+                    expenses += abs(r.amount)
+
+            income += self._asset_income(account)
+            expenses += self._liability_cost(account)
+
+            balance += income - expenses
+
+            asset_growth = sum(
+                a.value * a.growth_rate / 12
+                for a in self.model.assets
+            )
+            balance += asset_growth
+
+            monthly.append({
+                "balance": balance,
+                "income": income,
+                "expenses": expenses,
+            })
+        return monthly
+
+    def _asset_income(self, account: Account) -> float:
+        return sum(
+            a.value * a.growth_rate / 12
+            for a in self.model.assets
+        )
+
+    def _liability_cost(self, account: Account) -> float:
+        total = 0.0
+        for liability in self.model.liabilities:
+            interest_cost = liability.balance * liability.interest / 100 / 12
+            total += interest_cost
+            liability.balance -= liability.payment - interest_cost
+            if liability.balance < 0:
+                liability.balance = 0
+        return total
+
+    def summary(self, months: int = 12) -> dict:
+        results = self.forecast_cashflow(months)
+        if not results:
+            return {"total_balance": 0, "total_income": 0, "total_expenses": 0, "months": months}
+
+        final = results[-1]
+        all_income = sum(r["income"] for r in results)
+        all_expenses = sum(r["expenses"] for r in results)
+        return {
+            "total_balance": final["balance"],
+            "total_income": round(all_income, 2),
+            "total_expenses": round(all_expenses, 2),
+            "months": months,
+        }