ac-ms-url-shortener/src/QrBrandedRenderer.php

<?php
declare(strict_types=1);

/** Branded QR PNG: high error correction + centered app logo with white border. */
final class QrBrandedRenderer {
    private const LOGO_FRACTION = 0.24;
    private const BORDER_FRACTION = 0.05;

    private function __construct() {
    }

    public static function renderPng(string $text, int $size = 256): ?string {
        $text = trim($text);
        if ($text === '') {
            return null;
        }
        $raw = self::rawQrPng($text, $size);
        if ($raw === null) {
            return null;
        }
        $branded = self::overlayLogo($raw);
        return $branded ?? $raw;
    }

    public static function dataUri(string $text, int $size = 256): ?string {
        $png = self::renderPng($text, $size);
        if ($png === null) {
            return null;
        }
        return 'data:image/png;base64,' . base64_encode($png);
    }

    /** @return list<string> */
    private static function logoCandidates(): array {
        $paths = [];
        $env = getenv('AC_QR_LOGO_PATH');
        if (is_string($env) && $env !== '') {
            $paths[] = $env;
        }
        $paths[] = dirname(__DIR__) . '/assets/ac_qr_logo.png';
        $paths[] = __DIR__ . '/../assets/ac_qr_logo.png';
        $paths[] = dirname(__DIR__, 2) . '/ac-platform-php/assets/ac_qr_logo.png';
        $paths[] = dirname(__DIR__, 2) . '/ac-platform-php/public/assets/ac_qr_logo.png';
        return $paths;
    }

    /** @return \GdImage|false */
    private static function loadLogoImage(string $path) {
        $bytes = @file_get_contents($path);
        if (!is_string($bytes) || $bytes === '') {
            return false;
        }
        $img = @imagecreatefromstring($bytes);
        return $img !== false ? $img : false;
    }

    private static function logoPath(): ?string {
        foreach (self::logoCandidates() as $path) {
            if (is_readable($path)) {
                return $path;
            }
        }
        return null;
    }

    private static function rawQrPng(string $text, int $size): ?string {
        $qrencode = trim((string) shell_exec('command -v qrencode 2>/dev/null') ?? '');
        if ($qrencode === '') {
            return null;
        }
        $size = max(128, min(512, $size));
        $moduleSize = max(3, (int) round($size / 33));
        $cmd = sprintf(
            '%s -l H -t PNG -s %d -m 2 -o - %s 2>/dev/null',
            escapeshellcmd($qrencode),
            $moduleSize,
            escapeshellarg($text)
        );
        $out = shell_exec($cmd);
        if (!is_string($out) || strlen($out) < 8) {
            return null;
        }
        return $out;
    }

    private static function overlayLogo(string $pngBytes): ?string {
        if (!extension_loaded('gd')) {
            return null;
        }
        $logoPath = self::logoPath();
        if ($logoPath === null) {
            return null;
        }
        $qr = @imagecreatefromstring($pngBytes);
        if ($qr === false) {
            return null;
        }
        $logo = self::loadLogoImage($logoPath);
        if ($logo === false) {
            imagedestroy($qr);
            return null;
        }
        $qrW = imagesx($qr);
        $qrH = imagesy($qr);
        if ($qrW < 32 || $qrH < 32) {
            imagedestroy($qr);
            imagedestroy($logo);
            return null;
        }

        $logoBox = (int) round(min($qrW, $qrH) * self::LOGO_FRACTION);
        $border = max(2, (int) round(min($qrW, $qrH) * self::BORDER_FRACTION));
        $plate = $logoBox + 2 * $border;
        $plateX = (int) floor(($qrW - $plate) / 2);
        $plateY = (int) floor(($qrH - $plate) / 2);

        $white = imagecolorallocate($qr, 255, 255, 255);
        imagefilledrectangle($qr, $plateX, $plateY, $plateX + $plate - 1, $plateY + $plate - 1, $white);

        $srcW = imagesx($logo);
        $srcH = imagesy($logo);
        $dstX = $plateX + $border;
        $dstY = $plateY + $border;
        imagecopyresampled($qr, $logo, $dstX, $dstY, 0, 0, $logoBox, $logoBox, $srcW, $srcH);

        ob_start();
        imagepng($qr);
        $out = ob_get_clean();
        imagedestroy($qr);
        imagedestroy($logo);
        if (!is_string($out) || strlen($out) < 8) {
            return null;
        }
        return $out;
    }
}