from datetime import datetime, timedelta, timezone

def calculate_next_review(box_level: int) -> datetime:
    intervals = {
        1: 1,
        2: 3,
        3: 7,
        4: 14,
        5: 30
    }
    days = intervals.get(box_level, 1)
    return datetime.now(timezone.utc) + timedelta(days=days)

def evaluate_new_box(current_box: int, rating: str) -> int:
    """
    rating: "Correct", "Mixed", "Incorrect"
    """
    if rating == "Correct":
        return min(current_box + 1, 5)
    elif rating == "Mixed":
        return current_box
    else: # Incorrect
        return 1

def lazy_check_streak(streak_data):
    """
    Evaluates streak on Login (lazy checking). 
    Resets to 0 if the user missed a day.
    """
    if not streak_data.get('last_active_date'):
        return streak_data

    now = datetime.now(timezone.utc)
    current_date = now.date()
    last_active_date = datetime.strptime(streak_data['last_active_date'], '%Y-%m-%d').date()
    
    delta = (current_date - last_active_date).days
    
    if delta > 1:
        streak_data['current_streak'] = 0
    return streak_data

def increment_streak(streak_data):
    """
    Updates the streak object when a practice session is completed.
    """
    now = datetime.now(timezone.utc)
    current_date = now.date()
    
    last_active = streak_data.get('last_active_date')
    if last_active:
        last_active_date = datetime.strptime(last_active, '%Y-%m-%d').date()
        delta = (current_date - last_active_date).days
    else:
        delta = 2 # force increment for first time
        
    if delta == 1 or last_active is None:
        streak_data['current_streak'] += 1
        streak_data['longest_streak'] = max(streak_data['longest_streak'], streak_data['current_streak'])
    elif delta > 1:
        # Restarting streak
        streak_data['current_streak'] = 1
        streak_data['longest_streak'] = max(streak_data['longest_streak'], streak_data['current_streak'])
    
    streak_data['last_active_date'] = current_date.isoformat()
    return streak_data