import type { AdministrativeInfo, LocationAlternative } from './types';

/**
 * India Post office-type suffixes on locality names (e.g. "Hessarghatta Lake S.O").
 * These are post-office designations, not buyer-facing locality labels.
 */
const INDIA_POST_OFFICE_SUFFIX =
  /\s+(?:B\.?\s*O\.?|S\.?\s*O\.?|H\.?\s*O\.?|P\.?\s*O\.?|D\.?\s*S\.?\s*O\.?|S\.?\s*D\.?\s*O\.?|S\.?\s*B\.?\s*C\.?|C\.?\s*P\.?\s*C\.?|M\.?\s*D\.?\s*G\.?)\.?\s*$/i;

/** Remove trailing India Post office suffix from a locality name. */
export function stripIndiaPostOfficeSuffix(name: string): string {
  return name.replace(INDIA_POST_OFFICE_SUFFIX, '').replace(/\s+/g, ' ').trim();
}

/** Case-insensitive key for deduplicating locality names. */
export function localityDedupeKey(name: string): string {
  return stripIndiaPostOfficeSuffix(name).toLowerCase();
}

export interface ProcessedLocalityLookup {
  adminInfo: AdministrativeInfo;
  alternatives: LocationAlternative[];
  localityOptions: string[];
  selectedLocality: string;
}

/**
 * Normalize primary locality + alternatives from location lookup:
 * - strip S.O / H.O / B.O style suffixes for display
 * - merge duplicates that differ only by office suffix
 */
export function processLocalityLookup(
  adminInfo: AdministrativeInfo,
  alternatives: LocationAlternative[] = [],
): ProcessedLocalityLookup {
  const seen = new Set<string>();
  const localityOptions: string[] = [];

  const addUnique = (rawName: string) => {
    const key = localityDedupeKey(rawName);
    if (!key || seen.has(key)) return;
    seen.add(key);
    localityOptions.push(stripIndiaPostOfficeSuffix(rawName));
  };

  addUnique(adminInfo.locality);
  for (const alt of alternatives) {
    addUnique(alt.name);
  }

  const primaryClean = stripIndiaPostOfficeSuffix(adminInfo.locality);
  const primaryKey = localityDedupeKey(adminInfo.locality);

  const cleanedAlternatives = alternatives
    .map((alt) => ({
      ...alt,
      name: stripIndiaPostOfficeSuffix(alt.name),
    }))
    .filter((alt) => {
      const key = localityDedupeKey(alt.name);
      return key && key !== primaryKey;
    })
    .filter(
      (alt, idx, arr) =>
        arr.findIndex((a) => localityDedupeKey(a.name) === localityDedupeKey(alt.name)) === idx,
    );

  return {
    adminInfo: { ...adminInfo, locality: primaryClean },
    alternatives: cleanedAlternatives,
    localityOptions,
    selectedLocality: primaryClean,
  };
}