/// Auto-classification: infer the species a free-text variety label refers to,
/// so typing "Maíz de la abuela" can link *Zea mays* (and prefill the category)
/// without the grower opening the species picker.
///
/// Pure domain logic (no DB, no Flutter) so it is trivially unit-testable. The
/// repository feeds it the bundled catalog names; matching is done here.
library;

/// One catalog name that can identify a species: a common (vernacular) name or
/// the scientific name, paired with the species it belongs to. The matcher is
/// language-agnostic — it never assumes es/en — so the repository passes names
/// from every bundled locale at once.
class SpeciesNameEntry {
  const SpeciesNameEntry({required this.speciesId, required this.name});

  final String speciesId;
  final String name;
}

/// Detects the species a free-text variety [label] refers to by matching a
/// bundled [names] entry as a whole word inside the label — accent- and
/// case-insensitively. "Maíz de la abuela" → *Zea mays*; "Tomate cherry" →
/// *Solanum lycopersicum*.
///
/// Returns the matched species id, or null when nothing matches or the best
/// match is ambiguous. The rules keep it from mislabelling:
///   * **Whole-word (token) match only**, so "pea" never fires on "peach" nor
///     "haba" on "habanero" — a common name must appear as its own word(s).
///   * **Longest name wins** (most specific): "broad bean" beats "bean".
///   * **Ambiguous → null**: if the winning name maps to more than one species
///     (e.g. "calabaza" spanning several squashes), it is left for the grower
///     to disambiguate rather than guessed.
///
/// A light trailing-`s` fold lets a plural label word ("Tomates", "Habas")
/// still match a singular catalog name. It is an additive nudge for the many
/// languages that pluralise with `-s`, never an override of an exact match, and
/// it cannot introduce a match that a different word did not already carry.
String? matchSpeciesInLabel(String label, List<SpeciesNameEntry> names) {
  final haystack = _tokenize(label);
  if (haystack.isEmpty) return null;

  ({int tokens, int chars})? best;
  final winners = <String>{};
  for (final entry in names) {
    final needle = _tokenize(entry.name);
    if (!_containsSequence(haystack, needle)) continue;
    final chars = needle.fold<int>(0, (sum, t) => sum + t.length);
    final score = (tokens: needle.length, chars: chars);
    if (best == null || _isBetter(score, best)) {
      best = score;
      winners
        ..clear()
        ..add(entry.speciesId);
    } else if (score.tokens == best.tokens && score.chars == best.chars) {
      winners.add(entry.speciesId);
    }
  }

  // A single species behind the best-scoring name(s) → confident; otherwise the
  // name is shared across species, so leave it unclassified.
  return winners.length == 1 ? winners.first : null;
}

bool _isBetter(({int tokens, int chars}) a, ({int tokens, int chars}) b) =>
    a.tokens > b.tokens || (a.tokens == b.tokens && a.chars > b.chars);

/// Lowercases, splits on any non-letter/non-digit boundary (Unicode-aware, so
/// non-Latin scripts survive), and folds Latin diacritics on each token.
List<String> _tokenize(String s) => s
    .toLowerCase()
    .split(_wordBoundary)
    .where((t) => t.isNotEmpty)
    .map(_foldDiacritics)
    .toList(growable: false);

final RegExp _wordBoundary = RegExp(r'[^\p{L}\p{N}]+', unicode: true);

/// True when [needle] appears as a contiguous run of words inside [haystack].
bool _containsSequence(List<String> haystack, List<String> needle) {
  if (needle.isEmpty || needle.length > haystack.length) return false;
  for (var i = 0; i + needle.length <= haystack.length; i++) {
    var matched = true;
    for (var j = 0; j < needle.length; j++) {
      if (!_wordsEqual(haystack[i + j], needle[j])) {
        matched = false;
        break;
      }
    }
    if (matched) return true;
  }
  return false;
}

bool _wordsEqual(String a, String b) => a == b || _singular(a) == _singular(b);

/// Drops a single trailing `s` from words longer than three letters — a
/// deliberately crude plural fold (see [matchSpeciesInLabel]).
String _singular(String t) =>
    (t.length > 3 && t.endsWith('s')) ? t.substring(0, t.length - 1) : t;

/// Folds common Latin diacritics to their base letter so "Maiz" matches "Maíz".
/// Only Latin marks are folded; other scripts pass through untouched, keeping
/// the matcher usable for any language.
String _foldDiacritics(String token) {
  if (token.codeUnits.every((c) => c < 0x80)) return token; // fast path: ASCII
  final buffer = StringBuffer();
  for (final ch in token.split('')) {
    buffer.write(_diacriticFolds[ch] ?? ch);
  }
  return buffer.toString();
}

const Map<String, String> _diacriticFolds = {
  'á': 'a', 'à': 'a', 'ä': 'a', 'â': 'a', 'ã': 'a', 'å': 'a', 'ā': 'a',
  'ă': 'a', 'ą': 'a',
  'é': 'e', 'è': 'e', 'ë': 'e', 'ê': 'e', 'ē': 'e', 'ė': 'e', 'ę': 'e',
  'ě': 'e',
  'í': 'i', 'ì': 'i', 'ï': 'i', 'î': 'i', 'ī': 'i', 'į': 'i', 'ı': 'i',
  'ó': 'o', 'ò': 'o', 'ö': 'o', 'ô': 'o', 'õ': 'o', 'ø': 'o', 'ō': 'o',
  'ő': 'o',
  'ú': 'u', 'ù': 'u', 'ü': 'u', 'û': 'u', 'ū': 'u', 'ů': 'u', 'ű': 'u',
  'ñ': 'n', 'ń': 'n', 'ň': 'n',
  'ç': 'c', 'ć': 'c', 'č': 'c',
  'ş': 's', 'š': 's', 'ș': 's', 'ś': 's',
  'ž': 'z', 'ź': 'z', 'ż': 'z',
  'ý': 'y', 'ÿ': 'y',
  'ğ': 'g', 'ł': 'l', 'ð': 'd', 'þ': 'th', 'ß': 'ss', 'œ': 'oe', 'æ': 'ae',
};