backend/expense_manager.py

import json
import os
from datetime import datetime
from typing import List, Dict, Any

DB_PATH = os.path.join(os.path.dirname(__file__), "database.json")

if not os.path.exists(DB_PATH):
    with open(DB_PATH, "w") as f:
        json.dump({"expenses": [], "reminders": []}, f, indent=4)

def _load_db() -> Dict[str, Any]:
    """Safely load JSON database."""
    try:
        with open(DB_PATH, "r") as f:
            return json.load(f)
    except Exception:
        return {"expenses": [], "reminders": []}

def _save_db(data: Dict[str, Any]):
    """Safely write JSON database."""
    with open(DB_PATH, "w") as f:
        json.dump(data, f, indent=4)

def today_iso() -> str:
    """Returns today's date in ISO format."""
    return datetime.now().strftime("%Y-%m-%d")

def add_expense(entry: Dict[str, Any]) -> None:
    """Add a new expense to database.json."""
    db = _load_db()
    if "expenses" not in db:
        db["expenses"] = []
    db["expenses"].append(entry)
    _save_db(db)

def list_expenses(user_id: str) -> List[Dict[str, Any]]:
    """Return all expenses for a user."""
    db = _load_db()
    expenses = db.get("expenses", [])
    return [e for e in expenses if e.get("user_id") == user_id]

def total_spent(user_id: str) -> float:
    """Compute total spent by user."""
    expenses = list_expenses(user_id)
    return sum([e.get("amount", 0) for e in expenses])

def expenses_by_category(user_id: str) -> Dict[str, float]:
    """Aggregate total amount per category."""
    result = {}
    for e in list_expenses(user_id):
        cat = e.get("category", "Uncategorized")
        result[cat] = result.get(cat, 0) + e.get("amount", 0)
    return result

def recent_expenses(user_id: str, limit: int = 5) -> List[Dict[str, Any]]:
    """Return N most recent expenses."""
    items = list_expenses(user_id)
    items_sorted = sorted(items, key=lambda x: x.get("date", ""), reverse=True)
    return items_sorted[:limit]