// Selected-planet marker. When the SelectionStore holds a planet, the
// map draws one accent ring tight around it so the current selection is
// visible on the canvas itself (the inspector/sheet show the detail).
// Ship-group selection is intentionally not ringed here — groups are
// addressed by report index and have no single stable map coordinate.

import { DARK_THEME, type CirclePrim, type Theme } from "./world";

/** Planet marker radius in world units; mirrors `battle-markers.ts`. */
const PLANET_RADIUS_WORLD = 6;
/** The ring sits just outside the marker (and the bombing ring at +3). */
const SELECTION_RING_RADIUS = PLANET_RADIUS_WORLD + 4;

/** High-bit prefix so the ring id never collides with planet numbers,
 * route lines, reach rings (`0xb…`), or battle markers. */
export const SELECTION_RING_ID = 0xc0000000;
/** Below interactive primitives so it never wins a click. */
const SELECTION_RING_PRIORITY = 0;

/**
 * computeSelectionRing returns one ring primitive centred on the selected
 * planet, or `null` when nothing (or a non-planet) is selected or the
 * planet is absent from the current report. `theme` supplies the ring
 * colour and defaults to `DARK_THEME`.
 */
export function computeSelectionRing(
	planets: ReadonlyArray<{ number: number; x: number; y: number }>,
	selectedPlanetId: number | null,
	theme: Theme = DARK_THEME,
): CirclePrim | null {
	if (selectedPlanetId === null) return null;
	const planet = planets.find((p) => p.number === selectedPlanetId);
	if (planet === undefined) return null;
	return {
		kind: "circle",
		id: SELECTION_RING_ID,
		priority: SELECTION_RING_PRIORITY,
		hitSlopPx: 0,
		x: planet.x,
		y: planet.y,
		radius: SELECTION_RING_RADIUS,
		style: {
			strokeColor: theme.selectionRing,
			strokeAlpha: 0.95,
			strokeWidthPx: 1.5,
		},
	};
}