<?php
/**
 * Load and save the game.
 *
 * @package inc\savegame.inc
 * @author     Alexandre Renoux
 * @author     Pierre-Emmanuel Novac
 */

require_once("inc/messages.inc");
require_once("inc/Inventory.inc");
require_once("inc/Item.inc");

/**
 * Directory to save to and load from.
 * The PHP/Apache user must have write permission on this directory.
 * Use the following commands to give write permissions to the http group:
 * <samp>
 * sudo chown :http data/save
 * sudo chmod g+w data/save
 * </samp>
 */
define("SAVEDIR", "data/save");

/**
 * Recursively generates an XML tree from an array.
 * If objects are found, call addToXML() methods which should serialize the object as a child of the XML tree passed as parameter.
 *
 * @param array $table  an array with mixed type elements to convert to XML
 * @param SimpleXMLElement $xml  root XML to add the elements to
 * @return void
 */
function genXML($table, $xml) {
	foreach($table as $k => $v) {
		if(is_object($v)) { // Object: either Item or Inventory
			if(is_callable(array($v, "addToXML"))) // Check if the object has a addToXML method
				$v->addToXML($xml->addChild($k));
		} elseif(is_array($v)) // Nested array
			genXML($v, $xml->addChild($k));
		else // Single value (numeric or string)
			$xml->addChild($k, $v);
	}
}

/**
 * Generates the XML save tree from the session.
 *
 * @return void
 */
function genSave() {
	$save = new SimpleXMLElement("<save/>");
	genXML($_SESSION, $save);
	return $save;
}

/**
 * Generates the save file name using current date/time.
 * The date function will use the server's timezone which could be inconsistent with the client timezone.
 * 
 * @return string  the generated file name
 */
function genFilename() {
	return "craftmine-".date("d-m-Y_H-i-s").".save.xml";
}

/**
 * Save the XML save tree as an XML file named after the results of genFilename in SAVEDIR.
 * Fails and send an error the the client if permissions are incorrectly set. Watch for errors in PHP log.
 *
 * @return void
 */
function saveGame() {
	$save = genSave();
	if($save->asXML(SAVEDIR."/".genFilename())) sendInfo("gamesave_ok");
	else sendError("gamesave_error");
}

/**
 * Sends the current game or a specific save file given by the filename GET parameter to the client.
 *
 * @return void
 */
function downSave() {
	$save = "";
	$filename = "";

	if(empty($_GET["filename"])) {
		$filename = genFilename();
		$save = genSave()->asXML(); // Send current game save file if no file specified
	} else {
		$filename = $_GET["filename"];
		$save = file_get_contents(SAVEDIR . "/" . $filename);
		if(empty($save)) return; // Probably file not found
	}

	header("Content-Type: application/xml"); // Force browser to intepret the file as XML
	header("Content-Disposition: attachment; filename=".$filename); // Force download with specific filename
	header("Cache-Control: no-cache"); // Avoid storing save file in proxy/browser cache
	echo $save;
}

/**
 * Sends the list of available saves to the client.
 * Warning: this function changes directory.
 *
 * @return void
 */
function listSaves() {
	chdir(SAVEDIR); // Go to SAVEDIR folder, avoiding leading folder name in file list
	echo json_encode(glob("*.save.xml"));
}

/**
 * Reads an XML tree and deserializes it to an array.
 *
 * @param SimpleXMLElement $xml  root XML to read the elements from
 * @param array $table  an empty array to stores the elements to, passed by reference
 * @return void
 */
function parseSave($xml, &$table) { // Passing $table by reference
	foreach($xml as $k => $v) {
		if($v->count() == 0) { // No child, treat as string
			$v = (string)$v;
			if(is_numeric($v)) $v = +$v; // If it is in fact a number, treat it that way using PHP unary '+' coercion
			$table[$k] = $v;
		} elseif($k == "inventory") { // Special case for inventory: objects need to be created
			foreach($v as $item) {
				for($i=0; $i<+$item->count; $i++) // Add the right count of items to Inventory
					Inventory::addItem(Item::fromXML($item));
			}
		} else { // If nested array
			$table[$k] = array();
			parseSave($v, $table[$k]);
		} // Other types unsupported (unused)
	}
}

/**
 * Deletes a save file given as the filename POST parameter.
 *
 * @return void
 */
function deleteSave() {
	if(empty($_POST["filename"])) return;
	$path = SAVEDIR . "/" . basename($_POST["filename"]); // remove any leading directory
	if(file_exists($path) && unlink($path))
		sendInfo("gamesave_delete_success");
	else sendError("gamesave_delete_fail");
}

/**
 * Loads a save file given as the filename POST parameter to the session.
 * Empties the session beforehand.
 *
 * @return void
 */
function loadSave() {
	if(empty($_POST["filename"])) return;
	$xml = simplexml_load_file(SAVEDIR . "/" . $_POST["filename"]);
	if(empty($xml)) {
		sendError("gamesave_not_found");
		return;
	}
	$_SESSION = array(); // drop current game
	parseSave($xml, $_SESSION);
}

/**
 * Reads a save file sent by the client.
 * Parse the received file then generate it again to clean it for any unwanted 
 * and make sure that it is a valid XML save file.
 * XML errors are simply ignored and an error is sent to the client if something wrong happens.
 *
 * @return void
 */
function uploadSave() {
	$fname = basename($_FILES['savefile']['name']);
	$src = $_FILES['savefile']['tmp_name'];

	libxml_use_internal_errors(true); // Ignore errors when loading the received file
	$xml = simplexml_load_file($src);
	libxml_use_internal_errors(false);
	if(!$xml) {
		sendError("upload_fail");
		return;
	}
	$table = array();
	parseSave($xml, $table); // Parse received file

	$save = new SimpleXMLElement("<save/>");
	genXML($table, $save); // Regenerate it
	if($save->asXML(SAVEDIR."/".$fname)) sendInfo("upload_success", array($fname));
	else sendError("upload_error");
}
?>