<?php

namespace App\Chat;

/**
 * The smileys of the 2002 applet (net.spray.chat.a.g::for), found in a segment of text:
 *
 * - composed faces: eyes + nose + mouth, ":-)", ";o)", "8-D"... (the nose is required: ":)" stays text); a digit
 *   after it colours the face (":-)2" pink), then "#c" / "#d" a left hand (thumb up / finger), and one more
 *   "c" / "d" a right hand (":-)#cd");
 * - "#00".."#14": drawn pictures (bomb, heart...); #02 #04 #13 #14 take a colour digit ("#135");
 * - "@00".."@59": the pictures of smiley.gif (3 rows of 20 cells of 32 x 20, assets/smileys/smiley.png), the ones
 *   of the applet's "Smileys" panel.
 */
final class Smileys
{
    public const EYES = ':;8\'<|[B>%]}{O(';
    public const NOSES = '*!&-#=>oO$<';
    public const MOUTHS = ')(D|OoXxpP/\\*!{}#[$';

    public const DEFAULT_COLOR = 10;
    /** The pictures of smiley.gif: 20 a row, 3 rows. */
    public const IMAGES = 60;
    public const BIG_COUNT = 15;

    /**
     * Cuts a text into pieces: strings, and smileys as arrays.
     *
     * @return list<string|array{kind: string, eyes?: int, nose?: int, mouth?: int, hands?: int, color?: int, n?: int, source: string}>
     */
    public static function parse(string $text, int $images = self::IMAGES): array
    {
        $out = [];
        $plain = '';
        $len = strlen($text);
        $i = 0;
        while ($i < $len) {
            $smiley = self::at($text, $i, $len, $images);
            if ($smiley === null) {
                $plain .= $text[$i];
                $i++;
                continue;
            }
            if ($plain !== '') {
                $out[] = $plain;
                $plain = '';
            }
            $out[] = $smiley;
            $i += strlen($smiley['source']);
        }
        if ($plain !== '') {
            $out[] = $plain;
        }
        return $out;
    }

    /** @return array{kind: string, eyes?: int, nose?: int, mouth?: int, hands?: int, color?: int, n?: int, source: string}|null */
    private static function at(string $s, int $i, int $len, int $images): ?array
    {
        if ($len - $i < 3) {
            return null;
        }
        $e = strpos(self::EYES, $s[$i]);
        if ($e !== false) {
            $n = strpos(self::NOSES, $s[$i + 1]);
            $m = strpos(self::MOUTHS, $s[$i + 2]);
            if ($n === false || $m === false) {
                return null;
            }
            $extra = 0;
            $color = self::DEFAULT_COLOR;
            if ($len - $i >= 4 && ctype_digit($s[$i + 3])) {
                $color = (int)$s[$i + 3];
                $extra = 1;
            }
            $hands = 0;
            if ($len - $i >= 5 + $extra && $s[$i + 3 + $extra] === '#' && in_array($s[$i + 4 + $extra], ['c', 'd'], true)) {
                $hands |= $s[$i + 4 + $extra] === 'd' ? 1 : 2;
                $extra += 2;
                if ($len - $i >= 4 + $extra && in_array($s[$i + 3 + $extra], ['c', 'd'], true)) {
                    $hands |= $s[$i + 3 + $extra] === 'd' ? 4 : 8;
                    $extra += 1;
                }
            }
            return ['kind' => 'face', 'eyes' => $e, 'nose' => $n, 'mouth' => $m, 'color' => $color, 'hands' => $hands,
                'source' => substr($s, $i, 3 + $extra)];
        }
        $c = $s[$i];
        if (($c !== '#' && $c !== '@') || !ctype_digit(substr($s, $i + 1, 2))) {
            return null;
        }
        $nn = (int)substr($s, $i + 1, 2);
        if ($c === '#' && $nn < self::BIG_COUNT) {
            $color = in_array($nn, [13, 14], true) ? 1 : self::DEFAULT_COLOR;
            $length = 3;
            if (in_array($nn, [2, 4, 13, 14], true) && $len - $i >= 4 && ctype_digit($s[$i + 3])) {
                $color = (int)$s[$i + 3];
                $length = 4;
            }
            return ['kind' => 'big', 'n' => $nn, 'color' => $color, 'source' => substr($s, $i, $length)];
        }
        if ($c === '@' && $nn < $images) {
            return ['kind' => 'image', 'n' => $nn, 'source' => substr($s, $i, 3)];
        }
        return null;
    }
}