/* ============================================================================
   ROUTE HANDLE
   ----------------------------------------------------------------------------
   The shell reads a few presentation decisions off the deepest route's
   `handle`, so a page can flip the header or footer to the light surface
   without the root layout knowing anything about that page.

     export const handle = { navSurface: "light" } satisfies RouteHandle;
   ========================================================================= */

/** Which tier-2 surface a shell element paints. `:root` is the dark one. */
export type ShellSurface = "dark" | "light";

export interface RouteHandle {
  /** Surface for the sticky header. Default "dark". */
  readonly navSurface?: ShellSurface;
  /** Surface for the footer. Default "dark". */
  readonly footerSurface?: ShellSurface;
  /**
   * Override the canonical pathname the shell emits for this route - e.g. a
   * paginated listing that should point page 2 at page 1. Locale-prefixed.
   */
  readonly canonicalPath?: string;
  /**
   * "This page emits its own canonical + hreflang - do not add the shell's
   * prefix-swapped pair." Set by detail routes, whose Arabic counterpart has
   * its own Strapi slug, so swapping the locale prefix alone points the
   * alternate at a URL that does not exist.
   */
  readonly selfAlternates?: boolean;
  /** Anything a route wants to hang off its own handle. */
  readonly [key: string]: unknown;
}

function readSurface(value: unknown): ShellSurface | undefined {
  return value === "dark" || value === "light" ? value : undefined;
}

export function readNavSurface(handle: Record<string, unknown>): ShellSurface | undefined {
  return readSurface(handle.navSurface);
}

export function readFooterSurface(
  handle: Record<string, unknown>,
): ShellSurface | undefined {
  return readSurface(handle.footerSurface);
}

export function readCanonicalPath(
  handle: Record<string, unknown>,
): string | undefined {
  return typeof handle.canonicalPath === "string" ? handle.canonicalPath : undefined;
}

export function readSelfAlternates(
  handle: Record<string, unknown>,
): boolean | undefined {
  return handle.selfAlternates === true ? true : undefined;
}