"""Pagination utilities."""

from flask import request, current_app
from typing import Tuple


def get_pagination_params(req=None) -> Tuple[int, int]:
    """
    Extract pagination parameters from request.

    Returns:
        Tuple of (page, per_page)
    """
    if req is None:
        req = request

    default_size = current_app.config.get('DEFAULT_PAGE_SIZE', 20)
    max_size = current_app.config.get('MAX_PAGE_SIZE', 100)

    try:
        page = max(1, int(req.args.get('page', 1)))
    except (TypeError, ValueError):
        page = 1

    try:
        per_page = int(req.args.get('perpage', req.args.get('per_page', default_size)))
        per_page = max(1, min(per_page, max_size))
    except (TypeError, ValueError):
        per_page = default_size

    return page, per_page


def paginate_query(query, page: int, per_page: int):
    """
    Apply pagination to a SQLAlchemy query.

    Returns:
        Tuple of (items, total)
    """
    total = query.count()
    items = query.offset((page - 1) * per_page).limit(per_page).all()
    return items, total