from datetime import timedelta
from peewee import fn
import database

def get_start_end_dates(period, date):
    if period == 'daily':
        start_date = date
        end_date = date + timedelta(days=1)
    elif period == 'weekly':
        start_date = date - timedelta(days=date.weekday())
        end_date = start_date + timedelta(days=7)
    elif period == 'monthly':
        start_date = date.replace(day=1)
        next_month = start_date + timedelta(days=32)
        end_date = next_month.replace(day=1)
    elif period == 'yearly':
        start_date = date.replace(day=1, month=1)
        end_date = start_date.replace(year=start_date.year + 1)
    else:
        raise ValueError("Invalid period specified")
    
    return start_date, end_date

def aggregate_transactions_by_category(user_id, start_date, end_date):
    query = (database.Transaction
                    .select(database.TransactionCategory.name, fn.SUM(database.Transaction.amount).alias('total'))
                    .join(database.TransactionCategory, on=(database.Transaction.subcategory == database.TransactionCategory.primary_key))
                    .where(
                        (database.Transaction.user == user_id) &
                        (database.Transaction.transaction_date >= start_date) &
                        (database.Transaction.transaction_date < end_date))
                    .group_by(database.TransactionCategory.name))
    return [{transaction.subcategory.name: transaction.total} for transaction in query]