<?php
ob_clean();

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

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

try {
	$target = mkthumb($imgpath, $size);
}
catch (Throwable $e) {
	http_response_code($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, $size)
{
	if (strpos($size, 'x') !== FALSE) {
		list ($width, $height) = explode('x', $size);
		if (empty($height)) {
			$height = $width * 4;
		}
	}
	else {
		$height = $size;
	}
	if (empty($width)) {
		$width = $height * 4;
	}
	$target = "thumb/$size/$source";

	if (isset($_GET['backend'])) {
		$backend = $_GET['backend'];
	}
	elseif (file_exists($target)) {
		return $target;
	}
	elseif (extension_loaded('gd')) {
		$backend = 'gd';
	}
	else {
		$backend = 'exec';
	}
	$backend = "mkthumb_$backend";

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

function mkthumb_gd($source, $target, $width, $height)
{
	$data = imagecreatefromstring(file_get_contents($source));
	if (!$data) throw new Exception("error reading $source");
	$orgwidth = imagesx($data);
	$orgheight = imagesy($data);
	$width = min($width, $orgwidth * $height / $orgheight);
	$gd = imagecreatetruecolor($width, $height);
	//TODO: trim
	imagecopyresampled($gd, $data, 0, 0, 0, 0,
			$width, $height, $orgwidth, $orgheight);
	imagejpeg($gd, $target, 90);
}

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%',
		$source, "jpg:$target"
	]));
	$return = shell_exec("$cmd 2>&1");
	if ($return) {
		throw new Exception($return);
	}
}