<?php
/**
 * @author Frank Karlitschek
 * @author Jakob Sack
 * @copyright 2012 Frank Karlitschek frank@owncloud.org
 *
 * This file is licensed under the Affero General Public License version 3 or
 * later.
 * See the COPYING-README file.
 */

namespace OC;

/**
 * This class is responsible for reading and writing config.php, the very basic
 * configuration file of ownCloud.
 */
class Config {
	/** @var array Associative array ($key => $value) */
	protected $cache = array();
	/** @var string */
	protected $configDir;
	/** @var string */
	protected $configFilePath;
	/** @var string */
	protected $configFileName;
	/** @var bool */
	protected $debugMode;

	/**
	 * @param string $configDir Path to the config dir, needs to end with '/'
	 * @param string $fileName (Optional) Name of the config file. Defaults to config.php
	 */
	public function __construct($configDir, $fileName = 'config.php') {
		$this->configDir = $configDir;
		$this->configFilePath = $this->configDir.$fileName;
		$this->configFileName = $fileName;
		$this->readData();
		$this->debugMode = (defined('DEBUG') && DEBUG);
	}

	/**
	 * Lists all available config keys
	 *
	 * Please note that it does not return the values.
	 *
	 * @return array an array of key names
	 */
	public function getKeys() {
		return array_keys($this->cache);
	}

	/**
	 * Gets a value from config.php
	 *
	 * If it does not exist, $default will be returned.
	 *
	 * @param string $key key
	 * @param mixed $default = null default value
	 * @return mixed the value or $default
	 */
	public function getValue($key, $default = null) {
		if (isset($this->cache[$key])) {
			return $this->cache[$key];
		}

		return $default;
	}

	/**
	 * Sets and deletes values and writes the config.php
	 *
	 * @param array $configs Associative array with `key => value` pairs
	 *                       If value is null, the config key will be deleted
	 */
	public function setValues(array $configs) {
		$needsUpdate = false;
		foreach ($configs as $key => $value) {
			if ($value !== null) {
				$needsUpdate |= $this->set($key, $value);
			} else {
				$needsUpdate |= $this->delete($key);
			}
		}

		if ($needsUpdate) {
			// Write changes
			$this->writeData();
		}
	}

	/**
	 * Sets the value and writes it to config.php if required
	 *
	 * @param string $key key
	 * @param mixed $value value
	 */
	public function setValue($key, $value) {
		if ($this->set($key, $value)) {
			// Write changes
			$this->writeData();
		}
	}

	/**
	 * This function sets the value
	 *
	 * @param string $key key
	 * @param mixed $value value
	 * @return bool True if the file needs to be updated, false otherwise
	 */
	protected function set($key, $value) {
		if (!isset($this->cache[$key]) || $this->cache[$key] !== $value) {
			// Add change
			$this->cache[$key] = $value;
			return true;
		}

		return false;
	}

	/**
	 * Removes a key from the config and removes it from config.php if required
	 * @param string $key
	 */
	public function deleteKey($key) {
		if ($this->delete($key)) {
			// Write changes
			$this->writeData();
		}
	}

	/**
	 * This function removes a key from the config
	 *
	 * @param string $key
	 * @return bool True if the file needs to be updated, false otherwise
	 */
	protected function delete($key) {
		if (isset($this->cache[$key])) {
			// Delete key from cache
			unset($this->cache[$key]);
			return true;
		}
		return false;
	}

	/**
	 * Loads the config file
	 *
	 * Reads the config file and saves it to the cache
	 *
	 * @throws \Exception If no lock could be acquired or the config file has not been found
	 */
	private function readData() {
		// Default config should always get loaded
		$configFiles = array($this->configFilePath);

		// Add all files in the config dir ending with the same file name
		$extra = glob($this->configDir.'*.'.$this->configFileName);
		if (is_array($extra)) {
			natsort($extra);
			$configFiles = array_merge($configFiles, $extra);
		}

		// Include file and merge config
		foreach ($configFiles as $file) {
			$filePointer = @fopen($file, 'r');
			if($file === $this->configFilePath &&
				$filePointer === false &&
				@!file_exists($this->configFilePath)) {
				// Opening the main config might not be possible, e.g. if the wrong
				// permissions are set (likely on a new installation)
				continue;
			}

			// Try to acquire a file lock
			if(!flock($filePointer, LOCK_SH)) {
				throw new \Exception(sprintf('Could not acquire a shared lock on the config file %s', $file));
			}

			unset($CONFIG);
			include $file;
			if(isset($CONFIG) && is_array($CONFIG)) {
				$this->cache = array_merge($this->cache, $CONFIG);
			}

			// Close the file pointer and release the lock
			flock($filePointer, LOCK_UN);
			fclose($filePointer);
		}
	}

	/**
	 * Writes the config file
	 *
	 * Saves the config to the config file.
	 *
	 * @throws HintException If the config file cannot be written to
	 * @throws \Exception If no file lock can be acquired
	 */
	private function writeData() {
		// Create a php file ...
		$content = "<?php\n";
		if ($this->debugMode) {
			$content .= "define('DEBUG',true);\n";
		}
		$content .= '$CONFIG = ';
		$content .= var_export($this->cache, true);
		$content .= ";\n";

		touch ($this->configFilePath);
		$filePointer = fopen($this->configFilePath, 'r+');

		// Prevent others not to read the config
		chmod($this->configFilePath, 0640);

		// File does not exist, this can happen when doing a fresh install
		if(!is_resource ($filePointer)) {
			$url = \OC_Helper::linkToDocs('admin-dir_permissions');
			throw new HintException(
				"Can't write into config directory!",
				'This can usually be fixed by '
				.'<a href="' . $url . '" target="_blank">giving the webserver write access to the config directory</a>.');
		}

		// Try to acquire a file lock
		if(!flock($filePointer, LOCK_EX)) {
			throw new \Exception(sprintf('Could not acquire an exclusive lock on the config file %s', $this->configFilePath));
		}

		// Write the config and release the lock
		ftruncate ($filePointer, 0);
		fwrite($filePointer, $content);
		fflush($filePointer);
		flock($filePointer, LOCK_UN);
		fclose($filePointer);

		// Try invalidating the opcache just for the file we wrote...
		if (!\OC_Util::deleteFromOpcodeCache($this->configFilePath)) {
			// But if that doesn't work, clear the whole cache.
			\OC_Util::clearOpcodeCache();
		}
	}
}