<?php
ob_clean();

list ($height, $imgpath) = explode('/', ltrim($Args, '/'), 2);
$width= 1000;
$imgpath = preg_replace('{^(?=[0-9]+/)}', 'data/', $imgpath, 1);

if (!file_exists($imgpath)) {
	http_response_code(404);
	$imgpath = '404.png';
	if (!file_exists($imgpath)) {
		exit;
	}
}

$target = "thumb/$height/$imgpath";
try {
	mkthumb($imgpath, $target, $width, $height);
}
catch (Exception $e) {
	http_response_code($e->getCode() ?: 500);
	$target = '500.png';
	if (file_exists($target)) {
		header("X-Error: ".$e->getMessage());
		header('Content-type: '.mime_content_type($target));
		readfile($target);
		exit;
	}
	trigger_error("thumbnail creation failed: ".$e->getMessage(), E_USER_WARNING);
	exit;
}

header('Content-type: '.mime_content_type($target));
readfile($target);
exit;

function mkthumb($source, $target, $width, $height)
{
	if (isset($_GET['backend'])) {
		$backend = $_GET['backend'];
	}
	elseif (file_exists($target)) {
		return;
	}
	else {
		$backend = 'exec';
	}
	$backend = "mkthumb_$backend";

	@mkdir(dirname($target), 0777, TRUE);
	$backend($source, $target, $width, $height);
}

function mkthumb_exec($source, $target, $width, $height)
{
	if (!function_exists('popen')) {
		throw new Exception("exec disallowed on this server", 501);
	}
	$cmd = implode(' ', array_map('escapeshellarg', [
		'convert',
		'-trim',
		'-resize', "${width}x${height}",
		'-quality', '90%',
		$source, $target
	]));
	$return = shell_exec("$cmd 2>&1");
	if ($return) {
		throw new Exception($return);
	}
}