<?php
function has_cyrillic(string $s): bool {
  return (bool) preg_match('/\p{Cyrillic}/u', $s);
}

function norm_key(string $s): string {
  $s = mb_strtolower(trim($s), 'UTF-8');
  $s = str_replace(['ё'], ['е'], $s);                // homogénéiser RU
  $s = preg_replace('/[\'"’\-\s]+/u', '', $s);       // enlève tirets, espaces, quotes
  return $s;
}

// Translittération simple RU -> latin (fallback si intl n’est pas dispo)
function translit_ru_to_lat(string $s): string {
  if (class_exists('Transliterator')) {
    // "Russian-Latin/BGN" produit Parizh (Париж) -> "parizh"
    $t = \Transliterator::create('Russian-Latin/BGN; Lower();');
    if ($t) return $t->transliterate($s);
  }
  $map = [
    'а'=>'a','б'=>'b','в'=>'v','г'=>'g','д'=>'d','е'=>'e','ё'=>'e','ж'=>'zh','з'=>'z','и'=>'i','й'=>'i','к'=>'k',
    'л'=>'l','м'=>'m','н'=>'n','о'=>'o','п'=>'p','р'=>'r','с'=>'s','т'=>'t','у'=>'u','ф'=>'f','х'=>'kh','ц'=>'ts',
    'ч'=>'ch','ш'=>'sh','щ'=>'shch','ъ'=>'','ы'=>'y','ь'=>'','э'=>'e','ю'=>'yu','я'=>'ya',
  ];
  $s = mb_strtolower($s, 'UTF-8');
  return strtr($s, $map);
}

// Retourne une liste de candidats latins (pour LIKE) à partir d’une saisie q
function city_query_candidates(string $q): array {
  $q = trim($q);
  if ($q === '') return [];

  $cands = [];
  $cands[] = mb_strtolower($q, 'UTF-8'); // saisie brute (si déjà latine)

  // charger alias RU -> latin
  $aliases = @include __DIR__ . '/city_aliases_ru.php';
  if (!is_array($aliases)) $aliases = [];

  if (has_cyrillic($q)) {
    // 1) correspondance par préfixe dans les alias (ПАР → Paris)
    $key = norm_key($q);
    foreach ($aliases as $ru => $lat) {
      if (strpos(norm_key($ru), $key) === 0) {
        $cands[] = $lat;
      }
    }
    // 2) translittération simple (Париж -> parizh)
    $cands[] = translit_ru_to_lat($q);
  }

  // Normalisation légère des candidats (minuscules, accents retirés si possible)
  $res = [];
  foreach (array_unique($cands) as $c) {
    $lc = mb_strtolower($c, 'UTF-8');
    // enlever accents (si intl transliterator dispo)
    if (class_exists('Transliterator')) {
      $t = \Transliterator::create('Any-Latin; Latin-ASCII;');
      if ($t) $lc = $t->transliterate($lc);
    }
    $res[] = $lc;
  }
  return array_values(array_unique($res));
}