<?php

/**
 * Decides whether what a student typed is the name of a country.
 *
 * Names in tk_countries come in the style of "Congo, Democratic Republic of
 * the" and "Vatican City (Holy See)", which nobody types. So every country
 * name is expanded into the forms a student might reasonably use:
 *
 *  - capitals, accents, punctuation, HTML entities (e107 stores an apostrophe as
 *    &#039;), "&" / "and", "St" / "Saint" and a leading "the" are ignored
 *  - "Congo, Republic of the" also accepts "Republic of the Congo"
 *  - "Vatican City (Holy See)" also accepts "Vatican City" and "Holy See"
 *  - well-known alternative names are accepted (USA, Holland, Ivory Coast,
 *    Burma, Czech Republic ...): see $aliasGroups
 *  - one slipped letter is forgiven in names of 8 or more letters
 *    ("Kyrgystan"), but never when what was typed is exactly the name of a
 *    different country ("Dominica" for the Dominican Republic), or is just as
 *    close to a different country ("Sorth Korea")
 */
class CountryNames {

    private static $translit = [
        'à' => 'a', 'á' => 'a', 'â' => 'a', 'ã' => 'a', 'ä' => 'a', 'å' => 'a', 'ā' => 'a', 'ă' => 'a', 'ą' => 'a',
        'ç' => 'c', 'ć' => 'c', 'č' => 'c', 'ď' => 'd', 'đ' => 'd', 'ð' => 'd',
        'è' => 'e', 'é' => 'e', 'ê' => 'e', 'ë' => 'e', 'ē' => 'e', 'ė' => 'e', 'ę' => 'e', 'ě' => 'e',
        'ì' => 'i', 'í' => 'i', 'î' => 'i', 'ï' => 'i', 'ī' => 'i', 'ı' => 'i',
        'ł' => 'l', 'ñ' => 'n', 'ń' => 'n', 'ň' => 'n',
        'ò' => 'o', 'ó' => 'o', 'ô' => 'o', 'õ' => 'o', 'ö' => 'o', 'ø' => 'o', 'ō' => 'o', 'ő' => 'o',
        'ř' => 'r', 'ś' => 's', 'š' => 's', 'ş' => 's', 'ș' => 's', 'ť' => 't', 'ț' => 't',
        'ù' => 'u', 'ú' => 'u', 'û' => 'u', 'ü' => 'u', 'ū' => 'u', 'ů' => 'u', 'ű' => 'u',
        'ý' => 'y', 'ÿ' => 'y', 'ž' => 'z', 'ź' => 'z', 'ż' => 'z',
        'ß' => 'ss', 'æ' => 'ae', 'œ' => 'oe', 'þ' => 'th',
    ];

    /**
     * Alternative names, already in normalized form (see normalize()). If a
     * country's name is in a group, every name in the group is accepted.
     * Only names that belong to exactly one country belong here: "congo" and
     * "korea" are left out on purpose.
     */
    private static $aliasGroups = [
        ['united states of america', 'united states', 'usa', 'u s a', 'us', 'u s', 'america'],
        ['united kingdom', 'uk', 'u k', 'great britain', 'britain'],
        ['czechia', 'czech republic'],
        ['myanmar', 'burma'],
        ['timor leste', 'east timor'],
        ['cote d ivoire', 'ivory coast'],
        ['eswatini', 'swaziland'],
        ['north macedonia', 'macedonia'],
        ['cabo verde', 'cape verde'],
        ['turkey', 'turkiye'],
        ['netherlands', 'holland'],
        ['democratic republic of the congo', 'democratic republic of congo', 'dr congo', 'drc', 'congo kinshasa'],
        ['republic of the congo', 'republic of congo', 'congo brazzaville'],
        ['south korea', 'republic of korea', 'korea south'],
        ['north korea', 'democratic peoples republic of korea', 'korea north', 'dprk'],
        ['russia', 'russian federation'],
        ['vatican city', 'vatican', 'holy see', 'vatican city state'],
        ['micronesia', 'federated states of micronesia'],
        ['brunei', 'brunei darussalam'],
        ['laos', 'lao peoples democratic republic'],
        ['syria', 'syrian arab republic'],
        ['vietnam', 'viet nam'],
        ['iran', 'islamic republic of iran'],
        ['bolivia', 'plurinational state of bolivia'],
        ['venezuela', 'bolivarian republic of venezuela'],
        ['tanzania', 'united republic of tanzania'],
        ['moldova', 'republic of moldova'],
        ['palestine', 'state of palestine'],
        ['kosovo', 'republic of kosovo'],
        ['sao tome and principe', 'sao tome'],
        ['trinidad and tobago', 'trinidad'],
        ['antigua and barbuda', 'antigua'],
        ['bosnia and herzegovina', 'bosnia', 'herzegovina'],
        ['united arab emirates', 'uae'],
        ['saint kitts and nevis', 'saint kitts'],
        ['saint vincent and the grenadines', 'saint vincent'],
    ];

    /**
     * Lower case, accents removed, punctuation turned into single spaces.
     */
    public static function normalize($name) {
        // e107 stores an apostrophe as &#039; ("Cote d&#039;Ivoire"), so decode first.
        $s = html_entity_decode((string) $name, ENT_QUOTES | ENT_HTML5, 'UTF-8');
        $s = mb_strtolower($s, 'UTF-8');
        $s = strtr($s, self::$translit);
        $s = str_replace('&', ' and ', $s);
        $s = preg_replace('/[^a-z0-9]+/', ' ', $s);
        $s = trim(preg_replace('/\s+/', ' ', $s));
        $s = preg_replace('/^the /', '', $s);
        $s = preg_replace('/\bst\b/', 'saint', $s);
        return $s;
    }

    /**
     * Every normalized form accepted for a country name.
     *
     * @return string[]
     */
    public static function forms($name) {
        $name = (string) $name;

        $variants = [$name];
        if (preg_match('/^(.*?)\s*\((.*)\)\s*$/u', $name, $m)) {
            $variants[] = $m[1];
            $variants[] = $m[2];
        }
        foreach ($variants as $variant) {
            if (strpos($variant, ',') !== false) {
                $parts = array_map('trim', explode(',', $variant, 2));
                $variants[] = $parts[1] . ' ' . $parts[0]; // "Congo, Republic of the" -> "Republic of the Congo"
            }
        }

        $forms = [];
        foreach ($variants as $variant) {
            $form = self::normalize($variant);
            if ($form !== '') {
                $forms[$form] = true;
            }
        }

        foreach (array_keys($forms) as $form) {
            foreach (self::$aliasGroups as $group) {
                if (in_array((string) $form, $group, true)) {
                    foreach ($group as $member) {
                        $forms[$member] = true;
                    }
                }
            }
        }

        return array_map('strval', array_keys($forms));
    }

    /**
     * Is $typed a correct name for the country called $expected?
     *
     * @param string   $expected The country's name as stored (tk_countries.country).
     * @param string   $typed    What the student typed.
     * @param string[] $allNames Every country name, so another country's name is never accepted.
     * @return bool
     */
    public static function matches($expected, $typed, array $allNames = []) {
        $typedForm = self::normalize($typed);
        if ($typedForm === '' || strlen($typedForm) > 60) {
            return false;
        }

        $accepted = self::forms($expected);
        if (in_array($typedForm, $accepted, true)) {
            return true;
        }

        // The other countries (everything that isn't the same country as $expected).
        $others = [];
        foreach ($allNames as $other) {
            $otherForms = self::forms($other);
            if (array_intersect($accepted, $otherForms)) {
                continue; // the same country
            }
            $others[] = $otherForms;
        }

        foreach ($others as $otherForms) {
            if (in_array($typedForm, $otherForms, true)) {
                return false; // the name of a different country
            }
        }

        // One slipped letter in a long name is forgiven...
        $slip = false;
        foreach ($accepted as $form) {
            if (strlen($form) >= 8 && levenshtein($typedForm, $form) <= 1) {
                $slip = true;
                break;
            }
        }
        if (!$slip) {
            return false;
        }

        // ...unless it is just as close to a different country ("Sorth Korea").
        foreach ($others as $otherForms) {
            foreach ($otherForms as $form) {
                if (strlen($form) >= 8 && levenshtein($typedForm, $form) <= 1) {
                    return false;
                }
            }
        }

        return true;
    }
}