simple_storage.class.php

<?php

/**
*	SIMPLE FLAT FILE STORAGE CLASS
*
*	@version 1.1
*	@author Matthew Colf <mattcolf@mattcolf.com>
*
*	@section LICENSE
*
*	Copyright 2011 Matthew Colf <mattcolf@mattcolf.com>
*
*	Licensed under the Apache License, Version 2.0 (the "License");
*	you may not use this file except in compliance with the License.
*	You may obtain a copy of the License at
*
*	http://www.apache.org/licenses/LICENSE-2.0
*
*	Unless required by applicable law or agreed to in writing, software
*	distributed under the License is distributed on an "AS IS" BASIS,
*	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
*	See the License for the specific language governing permissions and
*	limitations under the License.
*/

class SimpleStorage {

	protected $file;
	protected $dirty = FALSE;
	protected $domain = "default";

	protected $data = array(
		"meta" => array(
			"updated" => "",
			"checksum" => ""
		),
		"domains" => array(
			"default" => array(
				"foo" => "bar"
			)
		)
	);

	public function __construct($domain = null, $file = null)
	{
		// determine which file to use
		if ($file == null)
			$this->file = __DIR__ . '/storage.json';
		else
			$this->file = $file;

		// check if file is writeable
		if (!is_writable($this->file))
			throw new Exception("File is not writeable.");

		// load data
		$json = file_get_contents($this->file);

		if ( strlen($json) == 0 )
			return;

		if ( ($this->data = json_decode($json,$assoc = TRUE)) === NULL )
			throw new Exception("Unable to decode $this->file.");

		// verify data integrity
		if ( $this->data["meta"]["checksum"] != md5($this->data["domains"]) )
			throw new Exception("Data from $this->file is not valid. Fails checksum.");

		// import data
		if ( ($this->data["domains"] = json_decode($this->data["domains"],$assoc = TRUE)) === NULL )
			throw new Exception("Unable to unserialize data from $file.");

		// setup domain
		if ( $domain )
		{
			if ( $this->domain_exists($domain) == FALSE ) $this->domain_add($domain);
			$this->domain = $domain;
		}
	}

	public function __destruct()
	{
		$this->flush();
	}

	public function flush()
	{
		// check if writeback is needed
		if ( $this->dirty == FALSE ) return TRUE;

		// prepare to writeback to file
		$data = $this->data;
		$data["domains"] = json_encode($this->data["domains"]);
		$data["meta"]["updated"] = date("c");
		$data["meta"]["checksum"] = md5($data["domains"]);

		// overwrite existing data
		if ( file_put_contents($this->file,json_encode($data)) )
			return TRUE;
		else
			throw new Exception("Unable to write back to $this->file. Data will be lost.");
	}

	// save data
	public function put($key,$data,$domain = NULL)
	{
		if ( $domain == NULL ) $domain = $this->domain;

		if ( is_string($key.$domain) AND $this->domain_exists($domain) )
		{
			$this->data["domains"][$domain][$key] = $data;
			$this->dirty = TRUE;
			return TRUE;
		}

		return FALSE;
	}

	// check if data exists
	public function exists($key,$domain = NULL)
	{
		if ( $domain == NULL ) $domain = $this->domain;

		if ( is_string($key.$domain) AND $this->domain_exists($domain) )
		{
			return array_key_exists($key,$this->data["domains"][$domain]);
		}

		return false;
	}

	// retrieve data
	public function get($key,$domain = NULL)
	{
		if ( $domain == NULL ) $domain = $this->domain;

		if ( is_string($key.$domain) AND $this->domain_exists($domain) )
		{
			if ( array_key_exists($key,$this->data["domains"][$domain]) )
			{
				return $this->data["domains"][$domain][$key];
			}
		}

		return NULL;
	}

	// delete data
	public function remove($key,$domain = NULL)
	{
		if ( $domain == NULL ) $domain = $this->domain;

		if ( is_string($key.$domain) AND $this->domain_exists($domain) )
		{
			if ( array_key_exists($key,$this->data["domains"][$domain]) )
			{
				unset($this->data["domains"][$domain][$key]);
				$this->dirty = TRUE;
				return TRUE;
			}
		}

		return NULL;
	}

	// check if a domain exists
	public function domain_exists($domain)
	{
		return array_key_exists($domain,$this->data["domains"]);
	}

	// add a new domain
	public function domain_add($domain)
	{
		if ( $this->domain_exists($domain) ) return FALSE;

		$this->data["domains"][$domain] = array();
		$this->dirty = TRUE;
	}

	// remove an existing domain and all associated data
	public function domain_remove($domain)
	{
		if ( $this->domain_exists($domain) )
		{
			unset($this->data["domains"][$domain]);
			$this->dirty = TRUE;
			return TRUE;
		}

		return FALSE;
	}

}