<?php
/**
 * CS-Cart thumbnail pre-generator + cache warmer (GuardLabs test stand).
 *
 * The pain in real CS-Cart: thumbnails are generated LAZILY. The file
 * images/thumbnails/<W>/<H>/detailed/<pack>/<img>.jpg does not exist until
 * the first visitor requests it. The request falls through to PHP
 * (fn_generate_thumbnail -> fn_resize_image), which decodes the source,
 * resizes and writes the file. On a catalog of thousands of SKUs this means:
 *   - first page views after "Clear cache" or theme size change are slow
 *     (every product card waits for GD/ImageMagick),
 *   - CPU spikes right when a promo email lands traffic on a cold cache,
 *   - Google crawls cold thumbnails and records bad TTFB.
 *
 * This tool pre-generates every thumbnail size ahead of time (cron friendly),
 * so visitors always hit static files served by nginx.
 *
 * Demo mode scans images/detailed/ on disk. In a live CS-Cart install the
 * image list comes from the DB instead:
 *   db_get_array("SELECT pair_id, image_id, object_type FROM ?:images_links");
 * and sizes come from the active theme settings (fn_get_theme_settings).
 *
 * Usage:
 *   php thumb_warmup.php --warm     pre-generate all missing thumbnails
 *   php thumb_warmup.php --bench    cold vs warm benchmark (full report)
 *   php thumb_warmup.php --purge    drop thumbnail cache (simulate "Clear cache")
 */

error_reporting(E_ALL);

$ROOT = __DIR__;
$SRC_DIR = $ROOT . '/images/detailed';
$THUMB_ROOT = $ROOT . '/images/thumbnails';

/* Thumbnail sizes used by a typical responsive theme (category grid,
 * product page, cart mini). In CS-Cart these come from theme manifest. */
$SIZES = [
    [200, 200],   // category / grid listing
    [500, 500],   // product page main image
    [80, 80],     // mini cart / admin lists
];

$JPEG_QUALITY = 85;

function list_sources($src_dir) {
    $out = [];
    foreach (glob($src_dir . '/*/*.{jpg,jpeg,png}', GLOB_BRACE) as $f) {
        $out[] = $f;
    }
    sort($out);
    return $out;
}

function thumb_path($thumb_root, $src_dir, $src, $w, $h) {
    /* Mirrors CS-Cart layout: images/thumbnails/<W>/<H>/detailed/<pack>/<file> */
    $rel = substr($src, strlen(dirname($src_dir)) + 1); // detailed/<pack>/<file>
    return sprintf('%s/%d/%d/%s', $thumb_root, $w, $h, $rel);
}

function generate_thumbnail($src, $dest, $w, $h, $quality) {
    /* Same core steps as fn_resize_image: decode, fit inside WxH keeping
     * aspect ratio, resample, save. */
    $info = getimagesize($src);
    if ($info === false) return false;
    [$sw, $sh] = $info;
    $img = ($info[2] === IMAGETYPE_PNG) ? imagecreatefrompng($src) : imagecreatefromjpeg($src);
    if (!$img) return false;

    $scale = min($w / $sw, $h / $sh, 1);
    $nw = max(1, (int) round($sw * $scale));
    $nh = max(1, (int) round($sh * $scale));

    $thumb = imagecreatetruecolor($nw, $nh);
    imagecopyresampled($thumb, $img, 0, 0, 0, 0, $nw, $nh, $sw, $sh);

    $dir = dirname($dest);
    if (!is_dir($dir) && !mkdir($dir, 0755, true) && !is_dir($dir)) return false;
    $ok = imagejpeg($thumb, $dest, $quality);
    imagedestroy($img);
    imagedestroy($thumb);
    return $ok;
}

function warm($sources, $SIZES, $THUMB_ROOT, $SRC_DIR, $JPEG_QUALITY, &$stats) {
    $t0 = microtime(true);
    $made = 0; $skipped = 0;
    foreach ($sources as $src) {
        foreach ($SIZES as [$w, $h]) {
            $dest = thumb_path($THUMB_ROOT, $SRC_DIR, $src, $w, $h);
            if (file_exists($dest)) { $skipped++; continue; }
            if (generate_thumbnail($src, $dest, $w, $h, $JPEG_QUALITY)) $made++;
        }
    }
    $stats = ['generated' => $made, 'already_cached' => $skipped, 'seconds' => microtime(true) - $t0];
    return $stats;
}

function serve_warm($sources, $SIZES, $THUMB_ROOT, $SRC_DIR) {
    /* Warm path: what nginx does per request, approximated as stat+read. */
    $t0 = microtime(true);
    $bytes = 0; $n = 0;
    foreach ($sources as $src) {
        foreach ($SIZES as [$w, $h]) {
            $dest = thumb_path($THUMB_ROOT, $SRC_DIR, $src, $w, $h);
            if (file_exists($dest)) { $bytes += strlen(file_get_contents($dest)); $n++; }
        }
    }
    return ['served' => $n, 'mb' => round($bytes / 1048576, 1), 'seconds' => microtime(true) - $t0];
}

function purge($THUMB_ROOT) {
    $n = 0;
    if (is_dir($THUMB_ROOT)) {
        $it = new RecursiveIteratorIterator(
            new RecursiveDirectoryIterator($THUMB_ROOT, FilesystemIterator::SKIP_DOTS),
            RecursiveIteratorIterator::CHILD_FIRST
        );
        foreach ($it as $f) {
            if ($f->isFile()) { unlink($f->getPathname()); $n++; }
            elseif ($f->isDir()) { rmdir($f->getPathname()); }
        }
    }
    return $n;
}

$mode = $argv[1] ?? '--bench';
$sources = list_sources($SRC_DIR);
if (!$sources) { fwrite(STDERR, "no source images in $SRC_DIR\n"); exit(1); }

printf("CS-Cart thumbnail warmer (test stand) | %d source images x %d sizes = %d thumbnails\n",
    count($sources), count($SIZES), count($sources) * count($SIZES));

if ($mode === '--purge') {
    printf("purged %d cached thumbnails (simulated admin 'Clear cache')\n", purge($THUMB_ROOT));
    exit(0);
}

if ($mode === '--warm') {
    warm($sources, $SIZES, $THUMB_ROOT, $SRC_DIR, $JPEG_QUALITY, $stats);
    printf("generated: %d, already cached: %d, took %.2fs\n",
        $stats['generated'], $stats['already_cached'], $stats['seconds']);
    exit(0);
}

/* --bench: full cold vs warm story */
echo str_repeat('=', 64) . "\n";
echo "STEP 1. Purge thumbnail cache (what admin 'Clear cache' does)\n";
printf("        removed %d files\n", purge($THUMB_ROOT));

echo "STEP 2. COLD: generate every thumbnail (lazy path visitors hit)\n";
warm($sources, $SIZES, $THUMB_ROOT, $SRC_DIR, $JPEG_QUALITY, $cold);
$total = $cold['generated'];
printf("        %d thumbnails in %.2fs => %.1f ms per thumbnail\n",
    $total, $cold['seconds'], 1000 * $cold['seconds'] / max(1, $total));

$per_page = 24; // product cards on one category page
$page_cost = ($cold['seconds'] / max(1, $total)) * $per_page;
printf("        => first view of a %d-card category page pays ~%.2fs of image work alone\n",
    $per_page, $page_cost);

echo "STEP 3. WARM: same catalog again (files exist, nginx static path)\n";
$w = serve_warm($sources, $SIZES, $THUMB_ROOT, $SRC_DIR);
printf("        %d thumbnails (%.1f MB) read in %.3fs => %.2f ms per thumbnail\n",
    $w['served'], $w['mb'], $w['seconds'], 1000 * $w['seconds'] / max(1, $w['served']));

$speedup = ($cold['seconds'] / max(1, $total)) / ($w['seconds'] / max(1, $w['served']));
printf("RESULT: cold lazy generation is ~%.0fx slower than serving a warmed cache.\n", $speedup);
printf("        Pre-warm after every cache clear / size change, and visitors never pay it.\n");