class SpanishInflector

final class SpanishInflector implements InflectorInterface {
    
    /**
     * A list of all rules for pluralise.
     *
     * @see https://www.spanishdict.com/guide/spanish-plural-noun-forms
     * @see https://www.rae.es/gram%C3%A1tica/morfolog%C3%ADa/la-formaci%C3%B3n-del-plural-plurales-en-s-y-plurales-en-es-reglas-generales
     */
    // First entry: regex
    // Second entry: replacement
    private const PLURALIZE_REGEXP = [
        // Specials sí, no
[
            '/(sí|no)$/i',
            '\\1es',
        ],
        // Words ending with vowel must use -s (RAE 3.2a, 3.2c)
[
            '/(a|e|i|o|u|á|é|í|ó|ú)$/i',
            '\\1s',
        ],
        // Word ending in s or x and the previous letter is accented (RAE 3.2n)
[
            '/ás$/i',
            'ases',
        ],
        [
            '/és$/i',
            'eses',
        ],
        [
            '/ís$/i',
            'ises',
        ],
        [
            '/ós$/i',
            'oses',
        ],
        [
            '/ús$/i',
            'uses',
        ],
        // Words ending in -ión must changed to -iones
[
            '/ión$/i',
            '\\1iones',
        ],
        // Words ending in some consonants must use -es (RAE 3.2k)
[
            '/(l|r|n|d|j|s|x|ch|y)$/i',
            '\\1es',
        ],
        // Word ending in z, must changed to ces
[
            '/(z)$/i',
            'ces',
        ],
    ];
    
    /**
     * A list of all rules for singularize.
     */
    private const SINGULARIZE_REGEXP = [
        // Specials sí, no
[
            '/(sí|no)es$/i',
            '\\1',
        ],
        // Words ending in -ión must changed to -iones
[
            '/iones$/i',
            '\\1ión',
        ],
        // Word ending in z, must changed to ces
[
            '/ces$/i',
            'z',
        ],
        // Word ending in s or x and the previous letter is accented (RAE 3.2n)
[
            '/(\\w)ases$/i',
            '\\1ás',
        ],
        [
            '/eses$/i',
            'és',
        ],
        [
            '/ises$/i',
            'ís',
        ],
        [
            '/(\\w{2,})oses$/i',
            '\\1ós',
        ],
        [
            '/(\\w)uses$/i',
            '\\1ús',
        ],
        // Words ending in some consonants and -es, must be the consonants
[
            '/(l|r|n|d|j|s|x|ch|y)e?s$/i',
            '\\1',
        ],
        // Words ended with vowel and s, must be vowel
[
            '/(a|e|i|o|u|á|é|ó|í|ú)s$/i',
            '\\1',
        ],
    ];
    private const UNINFLECTED_RULES = [
        // Words ending with pies (RAE 3.2n)
'/.*(piés)$/i',
    ];
    private const UNINFLECTED = '/^(lunes|martes|miércoles|jueves|viernes|análisis|torax|yo|pies)$/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 {
        foreach (self::UNINFLECTED_RULES as $rule) {
            if (1 === preg_match($rule, $word)) {
                return true;
            }
        }
        return 1 === preg_match(self::UNINFLECTED, $word);
    }

}