// Pure helpers for the lobby `games` submenu.
//
// Both the sidebar (`lib/screens/lobby-shell.svelte`) and the bare-`lobby`
// resolver (`lib/screens/lobby-screen.svelte`) need to agree on which
// sub-screen is the "first available" — the one auto-expanded in the
// sidebar and the redirect target when the user lands on the bare lobby
// alias. Centralising the predicates here keeps the two surfaces from
// drifting apart.
//
// The functions are intentionally pure: they take a resolved snapshot of
// lobby / account state, return the visible sub-screen list (in canonical
// order) and the first entry, and never touch stores or globals. Callers
// derive the state from `lobbyData` / `account` and the DEV-affordances
// flag.

export type GamesSubScreen =
	| "games-active-past"
	| "games-recruitment"
	| "games-invitations"
	| "games-private-games";

/**
 * LobbyNavState is the resolved snapshot of the lobby state the
 * games-submenu visibility rules depend on. Build it from the live
 * stores at the call site; the helpers below stay pure on top.
 */
export interface LobbyNavState {
	/** Player has at least one own / past game in `lobby.my-games.list`. */
	readonly hasMyGames: boolean;
	/** Player has at least one pending invite in `lobby.invites.list`. */
	readonly hasInvitations: boolean;
	/** Player is on a paid tier, or the build exposes DEV affordances. */
	readonly isPaidOrDev: boolean;
}

/**
 * visibleGamesSubScreens returns the games-submenu sub-screens that
 * are currently visible, in canonical display order:
 *
 *   1. `games-active-past` — only when the player has games.
 *   2. `games-recruitment` — always visible.
 *   3. `games-invitations` — only when the player has pending invites.
 *   4. `games-private-games` — only when paid-tier or DEV.
 *
 * `games-recruitment` is unconditional, so the returned array is
 * always non-empty.
 */
export function visibleGamesSubScreens(
	state: LobbyNavState,
): readonly GamesSubScreen[] {
	const out: GamesSubScreen[] = [];
	if (state.hasMyGames) out.push("games-active-past");
	out.push("games-recruitment");
	if (state.hasInvitations) out.push("games-invitations");
	if (state.isPaidOrDev) out.push("games-private-games");
	return out;
}

/**
 * firstVisibleGamesScreen returns the first entry from
 * `visibleGamesSubScreens(state)`. Since `games-recruitment` is
 * unconditional, the result is always defined.
 */
export function firstVisibleGamesScreen(state: LobbyNavState): GamesSubScreen {
	return visibleGamesSubScreens(state)[0]!;
}