class FrenchInflector

final class FrenchInflector implements InflectorInterface {
    
    /**
     * A list of all rules for pluralise.
     *
     * @see https://la-conjugaison.nouvelobs.com/regles/grammaire/le-pluriel-des-noms-121.php
     */
    private const PLURALIZE_REGEXP = [
        // First entry: regexp
        // Second entry: replacement
        // Words finishing with "s", "x" or "z" are invariables
        // Les mots finissant par "s", "x" ou "z" sont invariables
[
            '/(s|x|z)$/i',
            '\\1',
        ],
        // Words finishing with "eau" are pluralized with a "x"
        // Les mots finissant par "eau" prennent tous un "x" au pluriel
[
            '/(eau)$/i',
            '\\1x',
        ],
        // Words finishing with "au" are pluralized with a "x" excepted "landau"
        // Les mots finissant par "au" prennent un "x" au pluriel sauf "landau"
[
            '/^(landau)$/i',
            '\\1s',
        ],
        [
            '/(au)$/i',
            '\\1x',
        ],
        // Words finishing with "eu" are pluralized with a "x" excepted "pneu", "bleu", "émeu"
        // Les mots finissant en "eu" prennent un "x" au pluriel sauf "pneu", "bleu", "émeu"
[
            '/^(pneu|bleu|émeu)$/i',
            '\\1s',
        ],
        [
            '/(eu)$/i',
            '\\1x',
        ],
        // Words finishing with "al" are pluralized with a "aux" excepted
        // Les mots finissant en "al" se terminent en "aux" sauf
[
            '/^(bal|carnaval|caracal|chacal|choral|corral|étal|festival|récital|val)$/i',
            '\\1s',
        ],
        [
            '/al$/i',
            '\\1aux',
        ],
        // Aspirail, bail, corail, émail, fermail, soupirail, travail, vantail et vitrail font leur pluriel en -aux
[
            '/^(aspir|b|cor|ém|ferm|soupir|trav|vant|vitr)ail$/i',
            '\\1aux',
        ],
        // Bijou, caillou, chou, genou, hibou, joujou et pou qui prennent un x au pluriel
[
            '/^(bij|caill|ch|gen|hib|jouj|p)ou$/i',
            '\\1oux',
        ],
        // Invariable words
[
            '/^(cinquante|soixante|mille)$/i',
            '\\1',
        ],
        // French titles
[
            '/^(mon|ma)(sieur|dame|demoiselle|seigneur)$/',
            'mes\\2s',
        ],
        [
            '/^(Mon|Ma)(sieur|dame|demoiselle|seigneur)$/',
            'Mes\\2s',
        ],
    ];
    
    /**
     * A list of all rules for singularize.
     */
    private const SINGULARIZE_REGEXP = [
        // First entry: regexp
        // Second entry: replacement
        // Aspirail, bail, corail, émail, fermail, soupirail, travail, vantail et vitrail font leur pluriel en -aux
[
            '/((aspir|b|cor|ém|ferm|soupir|trav|vant|vitr))aux$/i',
            '\\1ail',
        ],
        // Words finishing with "eau" are pluralized with a "x"
        // Les mots finissant par "eau" prennent tous un "x" au pluriel
[
            '/(eau)x$/i',
            '\\1',
        ],
        // Words finishing with "al" are pluralized with a "aux" expected
        // Les mots finissant en "al" se terminent en "aux" sauf
[
            '/(amir|anim|arsen|boc|can|capit|capor|chev|crist|génér|hopit|hôpit|idé|journ|littor|loc|m|mét|minér|princip|radic|termin)aux$/i',
            '\\1al',
        ],
        // Words finishing with "au" are pluralized with a "x" excepted "landau"
        // Les mots finissant par "au" prennent un "x" au pluriel sauf "landau"
[
            '/(au)x$/i',
            '\\1',
        ],
        // Words finishing with "eu" are pluralized with a "x" excepted "pneu", "bleu", "émeu"
        // Les mots finissant en "eu" prennent un "x" au pluriel sauf "pneu", "bleu", "émeu"
[
            '/(eu)x$/i',
            '\\1',
        ],
        //  Words finishing with "ou" are pluralized with a "s" excepted bijou, caillou, chou, genou, hibou, joujou, pou
        // Les mots finissant par "ou" prennent un "s" sauf bijou, caillou, chou, genou, hibou, joujou, pou
[
            '/(bij|caill|ch|gen|hib|jouj|p)oux$/i',
            '\\1ou',
        ],
        // French titles
[
            '/^mes(dame|demoiselle)s$/',
            'ma\\1',
        ],
        [
            '/^Mes(dame|demoiselle)s$/',
            'Ma\\1',
        ],
        [
            '/^mes(sieur|seigneur)s$/',
            'mon\\1',
        ],
        [
            '/^Mes(sieur|seigneur)s$/',
            'Mon\\1',
        ],
        // Default rule
[
            '/s$/i',
            '',
        ],
    ];
    
    /**
     * A list of words which should not be inflected.
     * This list is only used by singularize.
     */
    private const UNINFLECTED = '/^(abcès|accès|abus|albatros|anchois|anglais|autobus|bois|brebis|carquois|cas|chas|colis|concours|corps|cours|cyprès|décès|devis|discours|dos|embarras|engrais|entrelacs|excès|fils|fois|gâchis|gars|glas|héros|intrus|jars|jus|kermès|lacis|legs|lilas|marais|mars|matelas|mépris|mets|mois|mors|obus|os|palais|paradis|parcours|pardessus|pays|plusieurs|poids|pois|pouls|printemps|processus|progrès|puits|pus|rabais|radis|recors|recours|refus|relais|remords|remous|rictus|rhinocéros|repas|rubis|sans|sas|secours|sens|souris|succès|talus|tapis|tas|taudis|temps|tiers|univers|velours|verglas|vernis|virus)$/i';
    public function singularize(string $plural) : array {
        if ($this->isInflectedWord($plural)) {
            return [
                $plural,
            ];
        }
        foreach (self::SINGULARIZE_REGEXP as $rule) {
            [
                $regexp,
                $replace,
            ] = $rule;
            if (1 === preg_match($regexp, $plural)) {
                return [
                    preg_replace($regexp, $replace, $plural),
                ];
            }
        }
        return [
            $plural,
        ];
    }
    public function pluralize(string $singular) : array {
        if ($this->isInflectedWord($singular)) {
            return [
                $singular,
            ];
        }
        foreach (self::PLURALIZE_REGEXP as $rule) {
            [
                $regexp,
                $replace,
            ] = $rule;
            if (1 === preg_match($regexp, $singular)) {
                return [
                    preg_replace($regexp, $replace, $singular),
                ];
            }
        }
        return [
            $singular . 's',
        ];
    }
    private function isInflectedWord(string $word) : bool {
        return 1 === preg_match(self::UNINFLECTED, $word);
    }

}