import type { themes } from "./themes.ts";

export const USER_THEMES = ["light", "dark", "system"] as const;
export type UserTheme = (typeof USER_THEMES)[number];

// "reader" = fall through to the visitor's theme; "enforce" = override with the wiki's theme.
export type WikiThemeMode = "reader" | "enforce";

export type ThemeName = keyof typeof themes;

export function resolveUserTheme(
	cookieHeader: string | null | undefined,
): UserTheme {
	if (!cookieHeader) return "system";
	const match = cookieHeader.match(/(?:^|;\s*)theme=([^;]+)/);
	if (!match?.[1]) return "system";
	const val = match[1].trim();
	if ((USER_THEMES as readonly string[]).includes(val)) {
		return val as UserTheme;
	}
	return "system";
}