"""Exports one event's final board as a PNG.

Reads the live Redis canvas rather than replaying the history like gif.py -
once placement is over the canvas endpoint serves a wiped board, but Redis
still holds the real final one (see tasks.py).
"""

from io import BytesIO

from events.models import Event

from .canvas import read_canvas
from .gif import _render_frame
from .models import PlaceSettings


def build_final_png(event: Event) -> bytes:
    """Renders `event`'s current board as a PNG, upscaled like gif.py.

    Redis only pads up to the last written pixel, so a short canvas is
    padded with white (and a longer one, e.g. from before a shrink, cut)
    to the current grid dimensions."""
    place_settings = PlaceSettings.current(event)
    width, height = place_settings.width, place_settings.height
    size = width * height

    canvas = read_canvas(event.path, width, height)[:size].ljust(size, b"\0")

    buffer = BytesIO()
    _render_frame(bytearray(canvas), width, height).save(buffer, format="PNG")
    return buffer.getvalue()