from __future__ import annotations

from typing import List, Tuple

from PIL import ImageDraw

from .base import SelectableList
from .item import ListItem


class ListView(SelectableList):
    """Compact scrolling list – shows up to *max_visible* items at once.

    The visible window is kept centred on the selected item and scrolls
    as the selection moves.

    ``font_size`` is forwarded to :pymeth:`ListItem.render` so the
    underlying render function can use it (e.g. for PIL ``draw.text``).
    Pass ``None`` to let render functions use their own default.
    """

    def __init__(self, *args, font_size: int | None = None, **kwargs):
        super().__init__(*args, **kwargs)
        self.font_size = font_size

    def _get_visible_window(self) -> Tuple[List[ListItem], int]:
        """Return (visible_items, start_offset)."""
        total = len(self._items)
        if total <= self.max_visible:
            return self._items, 0

        start = max(0, self.selected_index - self.max_visible // 2)
        start = min(start, total - self.max_visible)
        end = start + self.max_visible
        return self._items[start:end], start

    def render(self, draw: ImageDraw.ImageDraw, y_start: int) -> None:
        if not self._items:
            return

        visible_items, start = self._get_visible_window()

        fs = self.font_size or 10
        kwargs = {} if self.font_size is None else {'font_size': self.font_size}

        for idx, item in enumerate(visible_items):
            actual_idx = start + idx
            y_pos = y_start + idx * self.item_height

            if actual_idx == self.selected_index:
                self._draw_highlight(draw, self.x_offset, y_pos + fs // 2, font_size=fs)
                item.render(draw, (self.x_offset, y_pos), fill='white', **kwargs)
            else:
                item.render(draw, (self.x_offset, y_pos), fill='black', **kwargs)