from __future__ import annotations

from PIL import ImageDraw

from .base import SelectableList


class CarouselView(SelectableList):
    """Single-item display – shows the selected item centred and larger.

    Position indicator dots at the bottom communicate how many items
    exist and which one is currently selected.  Uses
    :pymethod:`ListItem.render_large` so callers can optionally provide
    a more detailed rendering for carousel mode.

    ``large_font_size`` controls the font size passed to
    :pymethod:`ListItem.render_large` (default 30, roughly 3× PIL default).

    ``center_x`` sets the horizontal centre used when drawing the item text
    (default 84, the midpoint of a 168 px wide display).  PIL's ``anchor='mm'``
    is forwarded so the text is centred on that x coordinate.

    ``render_height`` is the total vertical space (in pixels) allocated to the
    carousel; dots are placed at the very bottom of this region.  Defaults to
    ``max_visible * item_height``.
    """

    def __init__(self, *args,
                 large_font_size: int = 30,
                 center_x: int = 84,
                 render_height: int | None = None,
                 **kwargs):
        super().__init__(*args, **kwargs)
        self.large_font_size = large_font_size
        self.center_x = center_x
        self.render_height = render_height

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

        item = self._items[self.selected_index]
        height = self.render_height or (self.max_visible * self.item_height)
        y_center = y_start + height // 2

        # Render selected item centred (large variant, no highlight)
        item.render_large(
            draw,
            (self.center_x, y_center),
            fill='black',
            font_size=self.large_font_size,
            anchor='mm',
        )

        total = len(self._items)

        # Position indicator dots at the top of the allocated area
        if total > 1:
            indicator_y = y_start
            dot_spacing = min(8, max(4, 80 // max(total - 1, 1)))
            total_width = (total - 1) * dot_spacing
            start_x = self.center_x - total_width // 2

            for i in range(total):
                x = start_x + i * dot_spacing
                r = 2 if i == self.selected_index else 1
                draw.circle((x, indicator_y), r, fill='black')