import sqlite3
import os
from datetime import datetime

def connect_db():
    """
    Connects to the SQLite database file and returns the connection object.
    If the file does not exist, it prints an an error message.
    """
    db_file = 'time_tracker.db'
    if not os.path.exists(db_file):
        print(f"Error: Database file '{db_file}' not found. Please run the database creation script first.")
        return None
    return sqlite3.connect(db_file)

def unbilled_time_report():
    """
    Generates a report of unbilled time entries for a selected client.
    """
    conn = connect_db()
    if not conn:
        return

    try:
        cursor = conn.cursor()

        # Display active clients for selection
        cursor.execute('SELECT client_id, client_name FROM clients WHERE active = 1 ORDER BY client_name')
        active_clients = cursor.fetchall()

        if not active_clients:
            print("No active clients found to generate a report for.")
            return

        print("\n--- Select a Client for Unbilled Time Report ---")
        for client_id, client_name in active_clients:
            print(f"{client_id}: {client_name}")
        print("0: Exit")
        print("--------------------------------------------------\n")

        while True:
            try:
                choice = input("Enter the ID of the client (or 0 to exit): ")
                if choice == '0':
                    print("Exiting report generation.")
                    return

                client_id = int(choice)
                if any(c[0] == client_id for c in active_clients):
                    break
                else:
                    print("Invalid client ID. Please enter a valid ID from the list.")
            except ValueError:
                print("Invalid input. Please enter a number.")

        # Fetch client details and billing rate
        cursor.execute('SELECT client_name, billing_rate FROM clients WHERE client_id = ?', (client_id,))
        client_name, billing_rate = cursor.fetchone()

        # Fetch unbilled time entries for the selected client, including description
        cursor.execute('''
            SELECT date, hours, description, project
            FROM time_tracking
            WHERE client_id = ? AND invoiced = 0
            ORDER BY date
        ''', (client_id,))

        time_entries = cursor.fetchall()

        if not time_entries:
            print(f"\nNo unbilled time entries found for {client_name}.")
            return

        # Calculate daily summary, descriptions, and total cost
        daily_summary = {}
        grand_total_cost = 0.0

        for entry_date, hours, description, project in time_entries:
            if entry_date not in daily_summary:
                daily_summary[entry_date] = {'hours': 0.0, 'cost': 0.0, 'entries': []}
            
            daily_summary[entry_date]['hours'] += hours
            daily_summary[entry_date]['cost'] += hours * billing_rate
            daily_summary[entry_date]['entries'].append({'description': description, 'project': project})
            grand_total_cost += hours * billing_rate

        # Print the formatted report
        print(f"\n--- Unbilled Time Report for {client_name} ---")
        print(f"Total Unbilled Cost: ${grand_total_cost:.2f}\n")
        
        for daily_date, summary in daily_summary.items():
            print(f"Date: {daily_date} | Hours: {summary['hours']:.2f} | Cost: ${summary['cost']:.2f}")
            for entry in summary['entries']:
                print(f"  - Project: {entry['project']}, Description: {entry['description']}")
            print("-" * 32)
            
        print(f"\nReport generated on {datetime.now().strftime('%Y-%m-%d %H:%M:%S')}")

    except sqlite3.Error as e:
        print(f"An error occurred: {e}")
    finally:
        if conn:
            conn.close()

def main_menu():
    """
    Displays the main menu and handles user choices.
    """
    while True:
        print("\n--- Reports Menu ---")
        print("1: Unbilled Time")
        print("0: Exit")
        print("--------------------\n")
        choice = input("Enter your choice: ")

        if choice == '1':
            unbilled_time_report()
        elif choice == '0':
            print("Exiting reports script. Goodbye!")
            break
        else:
            print("Invalid choice. Please try again.")

if __name__ == "__main__":
    main_menu()