from datetime import date, timedelta


def get_date_range(period):
    """Return start date for period filter, or None for 'all'."""
    today = date.today()
    if period == "month":
        return today.replace(day=1)
    elif period == "3months":
        return today - timedelta(days=90)
    elif period == "year":
        return today.replace(month=1, day=1)
    return None


def get_template_leaderboard(template_id, period="all", limit=10):
    """Return top wrestlers by score_percent for a template."""
    from .models import LeistungstestResult

    qs = LeistungstestResult.objects.filter(template_id=template_id)

    start_date = get_date_range(period)
    if start_date:
        qs = qs.filter(completed_at__date__gte=start_date)

    qs = qs.select_related('wrestler')

    results = []
    all_results = list(qs)
    all_results.sort(key=lambda r: (-r.score_percent, r.total_time_seconds))
    for rank, result in enumerate(all_results[:limit], 1):
        results.append({
            'rank': rank,
            'wrestler_id': result.wrestler_id,
            'wrestler_name': str(result.wrestler),
            'score_percent': result.score_percent,
            'total_time_seconds': result.total_time_seconds,
            'completed_at': result.completed_at.date().isoformat() if result.completed_at else None,
        })
    return results


def get_exercise_leaderboard(exercise_id, period="all", limit=10):
    """Return top wrestlers by best time for an exercise."""
    from .models import LeistungstestResultItem, LeistungstestResult
    from django.db.models import Min

    start_date = get_date_range(period)

    qs = LeistungstestResultItem.objects.filter(exercise_id=exercise_id)
    if start_date:
        qs = qs.filter(result__completed_at__date__gte=start_date)

    # Get best time per wrestler
    best_times = qs.values('result__wrestler__id', 'result__wrestler__first_name', 'result__wrestler__last_name', 'result__completed_at__date')\
        .annotate(best_time=Min('elapsed_seconds'))\
        .order_by('best_time')

    results = []
    for rank, item in enumerate(best_times[:limit], 1):
        wrestler_name = f"{item['result__wrestler__first_name']} {item['result__wrestler__last_name']}"
        results.append({
            'rank': rank,
            'wrestler_id': item['result__wrestler__id'],
            'wrestler_name': wrestler_name.strip(),
            'best_time_seconds': item['best_time'],
            'completed_at': item['result__completed_at__date'].isoformat() if item['result__completed_at__date'] else None,
        })
    return results


def get_used_exercises():
    """Return all exercises that have been used in any Leistungstest result."""
    from .models import LeistungstestResultItem
    from exercises.models import Exercise

    exercise_ids = LeistungstestResultItem.objects.values_list('exercise_id', flat=True).distinct()
    return Exercise.objects.filter(id__in=exercise_ids).order_by('name')