/**
 * The facts the school header and the search rows print, so a parent reads
 * the same words in the list and on the page.
 *
 * Every value comes from one register field. Nothing is inferred or explained
 * inline, and a missing field prints nothing.
 */

import type { School } from './types';
import { hasNurseryClasses, hasReligiousCharacter, isSelective, singleSexLabel } from './utils';

/** The search filter's type groups (backend/school_groups.py), without its
 *  parenthesised notes: fees have a flag of their own. */
const TYPE_GROUP_LABELS: Record<string, string> = {
  state: 'State school',
  independent: 'Independent school',
  special: 'Special school (SEND)',
  post16: 'Sixth form or college',
  alternative: 'Alternative provision',
};

/** The school's type in the search filter's terms, or the register's own name
 *  for a type in no group (secure units, online providers). */
export function schoolTypeLabel(school: Pick<School, 'type_group' | 'school_type'>): string | null {
  const grouped = school.type_group ? TYPE_GROUP_LABELS[school.type_group] : undefined;
  return grouped ?? (school.school_type?.trim() || null);
}

/** "condition": changes who can apply or what it costs.
 *  "provision": what the school offers. */
export type SchoolFlagKind = 'condition' | 'provision';

export interface SchoolFlag {
  label: string;
  kind: SchoolFlagKind;
}

type FlagFields = Pick<
  School,
  'type_group' | 'admissions_policy' | 'gender' | 'religious_denomination'
  | 'nursery_provision' | 'has_sixth_form' | 'phase'
>;

/**
 * Flags for what applies, in a fixed order: conditions first, then provision.
 *
 * Selective needs the exact value. The register files a partly selective
 * school as "Non-selective", so that value is never printed.
 */
export function schoolFlags(school: FlagFields): SchoolFlag[] {
  const flags: SchoolFlag[] = [];
  const condition = (label: string) => flags.push({ label, kind: 'condition' });
  const provision = (label: string) => flags.push({ label, kind: 'provision' });
  const phase = school.phase?.trim().toLowerCase();

  if (school.type_group === 'independent') condition('Fee-paying');
  if (isSelective(school.admissions_policy)) condition('Selective');
  const singleSex = singleSexLabel(school.gender);
  if (singleSex) condition(singleSex);
  if (hasReligiousCharacter(school.religious_denomination)) {
    condition(school.religious_denomination!.trim());
  }
  if (hasNurseryClasses(school.nursery_provision) && phase !== 'nursery') provision('Nursery class');
  if (school.has_sixth_form && phase !== '16 plus') provision('Sixth form');
  return flags;
}