Refactor: extract shared code, add TransactionService, consolidate utilities

expense_tracker/app.py

@@ -6,7 +6,10 @@
 from expense_tracker.utils.migration import migrate_legacy_databases
 from expense_tracker.core.merchant_repository import MerchantCategoryRepository
 from expense_tracker.core.transaction_repository import TransactionRepository
+from expense_tracker.services.merchant import MerchantCategoryService
+from expense_tracker.services.transaction import TransactionService
 from expense_tracker.services.statistics import StatisticsService
+from expense_tracker.utils.merchant_normalizer import normalize_merchant
 
 def main():
     """Start the Expense Tracker application."""
@@ -24,6 +27,10 @@ def main():
     merchant_repo = MerchantCategoryRepository(
         str(get_database_path("merchant_categories.db"))
     )
+    merchant_service = MerchantCategoryService(
+        merchant_repo, transaction_repo, normalize_merchant
+    )
+    transaction_service = TransactionService(transaction_repo, merchant_service)
     statistics_service = StatisticsService(transaction_repo)
 
     root = Tk()
@@ -35,6 +42,6 @@ def main():
         tb.Style("darkly")
     except Exception:
         ttk.Style()
-    MainWindow(root, transaction_repo, merchant_repo, statistics_service)
+    MainWindow(root, transaction_repo, transaction_service, statistics_service)
     root.focus_force()
     root.mainloop()

expense_tracker/core/transaction_repository.py

@@ -234,28 +234,6 @@ def get_monthly_net_income(self, start_date: date, end_date: date) -> float:
         result = row.fetchone()
         return result["net_income"] if result["net_income"] is not None else 0.0
 
-    def get_top_spending_category(self, start_date: date, end_date: date) -> tuple[str, float] | None:
-        """
-        Returns the category with the highest spending (sum of negative amounts) for a specific month.
-        Returns tuple of (category_name, total_spending) or None if no expenses exist.
-        """
-        rows = self.conn.execute(
-            """
-            SELECT category, SUM(ABS(amount)) as total
-            FROM transactions
-            WHERE date >= ? AND date < ?
-              AND amount < 0
-            GROUP BY category
-            ORDER BY total DESC
-            LIMIT 1
-            """,
-            (start_date.isoformat(), end_date.isoformat()),
-        )
-        result = rows.fetchone()
-        if result is None:
-            return None
-        return (result["category"], result["total"])
-
     def get_transactions_for_date(self, target_date: date) -> list[Transaction]:
         """
         Query transactions matching exact date.
@@ -298,7 +276,7 @@ def get_latest_month_with_data(self) -> tuple[int, int]:
         return (result["year"], result["month"])
 
 
-    def get_all_months_with_data(self) -> list[tuple[int, int]]:
+    def get_all_months_with_data(self) -> set[tuple[int, int]]:
         """
         Returns a list of (year, month) tuples for all months that have transaction data.
         Ordered by year and month descending (most recent first).

expense_tracker/gui/dialogs/add_expense.py

@@ -1,66 +1,37 @@
 from datetime import date
 import tkinter as tk
-from tkinter import ttk, messagebox
+from tkinter import messagebox
 
 from expense_tracker.core.models import Transaction
-from expense_tracker.core.transaction_repository import TransactionRepository
+from expense_tracker.services.transaction import TransactionService
+from expense_tracker.gui.dialogs.expense_form import build_expense_form, validate_amount
 
 
 class AddExpenseDialog(tk.Toplevel):
-    def __init__(self, master, repo: TransactionRepository):
+    def __init__(self, master, transaction_service: TransactionService):
         super().__init__(master)
-        self.repo = repo
+        self.transaction_service = transaction_service
         self.title("Add Expense")
         self.resizable(False, False)
 
         self.amount_var = tk.StringVar()
         self.category_var = tk.StringVar()
         self.description_var = tk.StringVar()
 
-        self._build_form()
-
-    def _build_form(self):
-        frame = ttk.Frame(self)
-        frame.pack(fill="both", padx=10, pady=10)
-
-        # Amount
-        ttk.Label(frame, text="Amount (e.g. 12.50):").grid(row=0, column=0, sticky="w")
-        amount = ttk.Entry(frame, textvariable=self.amount_var, width=20)
-        amount.grid(row=1, column=0, sticky="w")
-
-        # Category
-        ttk.Label(frame, text="Category:").grid(row=2, column=0, sticky="w")
-        category = ttk.Entry(frame, textvariable=self.category_var, width=20)
-        category.grid(row=3, column=0, sticky="w")
-
-        # Description
-        ttk.Label(frame, text="Description:").grid(row=4, column=0, sticky="w")
-        description = ttk.Entry(frame, textvariable=self.description_var, width=20)
-        description.grid(row=5, column=0, sticky="w")
-
-        # Buttons
-        button_frame = ttk.Frame(frame)
-        button_frame.grid(row=6, column=0, pady=10, sticky="e")
-        ttk.Button(button_frame, text="Add", command=self._on_add).pack(
-            side="right", padx=5
+        build_expense_form(
+            self,
+            self.amount_var,
+            self.category_var,
+            self.description_var,
+            submit_text="Add",
+            on_submit=self._on_add,
+            on_cancel=self._on_cancel,
         )
-        ttk.Button(button_frame, text="Cancel", command=self._on_cancel).pack(
-            side="right"
-        )
-
-        # Keyboard bindings
         self.bind("<Escape>", lambda e: self._on_cancel())
 
     def _on_add(self):
-        raw = self.amount_var.get()
-        if not raw:
-            messagebox.showerror("Error", "Amount is required.")
-            return
-
-        try:
-            amount = float(raw)
-        except ValueError:
-            messagebox.showerror("Error", "Amount must be a valid number.")
+        amount = validate_amount(self.amount_var)
+        if amount is None:
             return
 
         try:
@@ -71,7 +42,7 @@ def _on_add(self):
                 category=self.category_var.get() or "Uncategorized",
                 description=self.description_var.get() or "",
             )
-            saved_transaction = self.repo.add_transaction(transaction)
+            saved_transaction = self.transaction_service.add_transaction(transaction)
             self.result = saved_transaction.id
             self.destroy()
             messagebox.showinfo(

expense_tracker/gui/dialogs/edit_expense.py

@@ -2,10 +2,8 @@
 import tkinter as tk
 from tkinter import ttk, messagebox
 
-from expense_tracker.core.transaction_repository import TransactionRepository
-from expense_tracker.core.merchant_repository import MerchantCategoryRepository
-from expense_tracker.services.merchant import MerchantCategoryService
-from expense_tracker.utils.merchant_normalizer import normalize_merchant
+from expense_tracker.services.transaction import TransactionService
+from expense_tracker.gui.dialogs.expense_form import build_expense_form, validate_amount
 
 logger = logging.getLogger(__name__)
 
@@ -14,17 +12,12 @@ class EditExpenseDialog(tk.Toplevel):
     def __init__(
         self,
         master,
-        repo: TransactionRepository,
-        merchant_repo: MerchantCategoryRepository,
+        transaction_service: TransactionService,
         transaction_id: int,
     ):
         super().__init__(master)
-        self.repo = repo
-        self.merchant_repo = merchant_repo
+        self.transaction_service = transaction_service
         self.transaction_id = transaction_id
-        self.merchant_service = MerchantCategoryService(
-            merchant_repo, repo, normalize_merchant
-        )
         self.title("Edit Expense")
         self.resizable(False, False)
 
@@ -40,66 +33,37 @@ def __init__(
 
         self.prev_data = None
 
-        self._build_form()
-        self._load_transaction_data()
-
-    def _build_form(self):
-        frame = ttk.Frame(self)
-        frame.pack(fill="both", padx=10, pady=10)
-
-        # Amount
-        ttk.Label(frame, text="Amount (e.g. 12.50):").grid(row=0, column=0, sticky="w")
-        amount = ttk.Entry(frame, textvariable=self.amount_var, width=20)
-        amount.grid(row=1, column=0, sticky="w")
-
-        # Category
-        ttk.Label(frame, text="Category:").grid(row=2, column=0, sticky="w")
-        category = ttk.Entry(frame, textvariable=self.category_var, width=20)
-        category.grid(row=3, column=0, sticky="w")
-
-        # Description
-        ttk.Label(frame, text="Description:").grid(row=4, column=0, sticky="w")
-        description = ttk.Entry(frame, textvariable=self.description_var, width=20)
-        description.grid(row=5, column=0, sticky="w")
-
-        # Buttons
-        button_frame = ttk.Frame(frame)
-        button_frame.grid(row=6, column=0, pady=10, sticky="e")
-        ttk.Button(button_frame, text="Save", command=self._on_save).pack(
-            side="right", padx=5
-        )
-        ttk.Button(button_frame, text="Cancel", command=self._on_cancel).pack(
-            side="right"
+        build_expense_form(
+            self,
+            self.amount_var,
+            self.category_var,
+            self.description_var,
+            submit_text="Save",
+            on_submit=self._on_save,
+            on_cancel=self._on_cancel,
         )
-
-        # Keyboard bindings
         self.bind("<Escape>", lambda e: self._on_cancel())
 
+        self._load_transaction_data()
+
     def _load_transaction_data(self):
-        self.prev_data = self.repo.get_transaction(self.transaction_id)
+        self.prev_data = self.transaction_service.get_transaction(self.transaction_id)
         if self.prev_data is not None:
             self.amount_var.set(str(self.prev_data.amount))
             self.category_var.set(self.prev_data.category)
             self.description_var.set(self.prev_data.description)
 
-            # Only suggest category if the current category is "Uncategorized"
+            # Suggest a better category if currently uncategorized
             if self.prev_data.category == "Uncategorized":
-                suggested_category = self.merchant_repo.get_category(
-                    normalize_merchant(self.prev_data.description)
+                suggested = self.transaction_service.suggest_category(
+                    self.prev_data.description, self.prev_data.amount
                 )
-                if suggested_category:
-                    self.category_var.set(suggested_category.category)
+                if suggested != "Uncategorized":
+                    self.category_var.set(suggested)
 
     def _on_save(self):
-        raw = self.amount_var.get()
-        if not raw:
-            messagebox.showerror("Error", "Amount is required.")
-            return
-
-        try:
-            amount = float(raw)
-        except ValueError:
-            messagebox.showerror("Error", "Amount must be a valid number.")
+        amount = validate_amount(self.amount_var)
+        if amount is None:
             return
 
         try:
@@ -108,34 +72,22 @@ def _on_save(self):
                 "category": self.category_var.get() or "Uncategorized",
                 "description": self.description_var.get() or "",
             }
-            self.repo.update_transaction(self.transaction_id, data)
-
-            # Check if we need to update merchant categories
-            if (
-                self.prev_data is not None
-                and self.prev_data.category != data["category"]
-            ):
-                try:
-                    self.merchant_service.update_category(
-                        self.prev_data.description, data["category"]
-                    )
-                    self.merchant_service.update_uncategorized_transactions()
-                    messagebox.showinfo(
-                        "Success",
-                        f"Transaction {self.transaction_id} updated and related transactions recategorized.",
-                    )
-                except Exception as e:
-                    messagebox.showerror(
-                        "Error", f"Failed to update related transactions: {e}"
-                    )
-                self.destroy()
+
+            categories_updated = self.transaction_service.update_transaction(
+                self.transaction_id, data
+            )
+
+            if categories_updated:
+                messagebox.showinfo(
+                    "Success",
+                    f"Transaction {self.transaction_id} updated and related transactions recategorized.",
+                )
             else:
-                # No category change, just close the dialog
                 self.result = self.transaction_id
                 messagebox.showinfo(
                     "Success", f"Transaction {self.transaction_id} updated."
                 )
-                self.destroy()
+            self.destroy()
 
         except Exception as e:
             messagebox.showerror("Error", f"Failed to update transaction: {e}")

expense_tracker/gui/dialogs/expense_form.py

@@ -0,0 +1,57 @@
+import tkinter as tk
+from tkinter import ttk, messagebox
+
+
+def build_expense_form(
+    parent: tk.Widget,
+    amount_var: tk.StringVar,
+    category_var: tk.StringVar,
+    description_var: tk.StringVar,
+    submit_text: str,
+    on_submit,
+    on_cancel,
+) -> ttk.Frame:
+    """Build the shared Amount/Category/Description form used by Add and Edit dialogs."""
+    frame = ttk.Frame(parent)
+    frame.pack(fill="both", padx=10, pady=10)
+
+    # Amount
+    ttk.Label(frame, text="Amount (e.g. 12.50):").grid(row=0, column=0, sticky="w")
+    ttk.Entry(frame, textvariable=amount_var, width=20).grid(
+        row=1, column=0, sticky="w"
+    )
+
+    # Category
+    ttk.Label(frame, text="Category:").grid(row=2, column=0, sticky="w")
+    ttk.Entry(frame, textvariable=category_var, width=20).grid(
+        row=3, column=0, sticky="w"
+    )
+
+    # Description
+    ttk.Label(frame, text="Description:").grid(row=4, column=0, sticky="w")
+    ttk.Entry(frame, textvariable=description_var, width=20).grid(
+        row=5, column=0, sticky="w"
+    )
+
+    # Buttons
+    button_frame = ttk.Frame(frame)
+    button_frame.grid(row=6, column=0, pady=10, sticky="e")
+    ttk.Button(button_frame, text=submit_text, command=on_submit).pack(
+        side="right", padx=5
+    )
+    ttk.Button(button_frame, text="Cancel", command=on_cancel).pack(side="right")
+
+    return frame
+
+
+def validate_amount(amount_var: tk.StringVar) -> float | None:
+    """Validate and parse the amount field. Shows error messagebox on failure."""
+    raw = amount_var.get()
+    if not raw:
+        messagebox.showerror("Error", "Amount is required.")
+        return None
+    try:
+        return float(raw)
+    except ValueError:
+        messagebox.showerror("Error", "Amount must be a valid number.")
+        return None