/**
 * Shared logic and copy for the "last distance offered" figure.
 *
 * The primary and secondary admissions sections lay their metrics out
 * differently (a seamless tile grid vs. metric cards), so the markup is not
 * shared — but the words are. Every caveat below is doing a specific job, and
 * a figure that appeared on one template without them would be misleading in a
 * way the other template was not:
 *
 *   * The year, because a cut-off is the outcome of one particular admissions
 *     round and means nothing detached from it.
 *   * "not a fixed catchment", because that is the inference a parent will
 *     otherwise draw, and it is wrong — the distance moves every year.
 *   * The route count, because on a banded school the headline is the widest
 *     of several cut-offs and does not apply to every child.
 */

import type { SchoolAdmissionDistance } from '@/lib/types';
import { formatCutoffDistance, formatEntryYear } from '@/lib/utils';

export interface CutoffDisplay {
  /** Headline figure, e.g. "0.31 miles". */
  primary: string;
  /** Supporting conversion, e.g. "500 m". */
  secondary: string;
  /** Entry point the figure belongs to, e.g. "September 2025". */
  entryYear: string;
  /** Present only where several admission routes were collapsed into one figure. */
  routeNote: string | null;
}

/** What the cut-off measures, and what it does not. Identical on both templates. */
export const CUTOFF_NOTE =
  'The furthest home offered a place, after higher priorities such as siblings, ' +
  'faith and EHCP were applied. It is not a fixed catchment — it moves every year ' +
  'with the number of applications.';

/** Straight-line, because that is how councils measure it. */
export const CUTOFF_MEASUREMENT_NOTE = 'Measured in a straight line from the school.';

export function describeCutoff(
  distance: SchoolAdmissionDistance | null | undefined
): CutoffDisplay | null {
  if (!distance) return null;

  const figure = formatCutoffDistance(distance.distance_m);
  if (!figure) return null;

  const routes = distance.route_count ?? 1;

  return {
    primary: figure.primary,
    secondary: figure.secondary,
    entryYear: formatEntryYear(distance.year),
    routeNote:
      routes > 1
        ? `Furthest of ${routes} admission routes at this school — the one that ` +
          'applies to your child may have had a shorter cut-off.'
        : null,
  };
}