Added Migrations library, config and an example controller/migration file.
diff --git a/system/libraries/Migration.php b/system/libraries/Migration.php
new file mode 100644
index 0000000..73c55c3
--- /dev/null
+++ b/system/libraries/Migration.php
@@ -0,0 +1,336 @@
+<?php defined('BASEPATH') OR exit('No direct script access allowed');
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP 5.1.6 or newer
+ *
+ * @package CodeIgniter
+ * @author EllisLab Dev Team
+ * @copyright Copyright (c) 2006 - 2011, EllisLab, Inc.
+ * @license http://codeigniter.com/user_guide/license.html
+ * @link http://codeigniter.com
+ * @since Version 1.0
+ * @filesource
+ */
+
+// ------------------------------------------------------------------------
+
+/**
+ * Migration Class
+ *
+ * All migrations should implement this, forces up() and down() and gives
+ * access to the CI super-global.
+ *
+ * @package CodeIgniter
+ * @subpackage Libraries
+ * @category Libraries
+ * @author Reactor Engineers
+ * @link
+ */
+class CI_Migration {
+
+ private $_migration_enabled = FALSE;
+ private $_migration_path = NULL;
+ private $_migration_version = 0;
+
+ public $error = '';
+
+ function __construct($config = array())
+ {
+ # Only run this constructor on main library load
+ if (get_parent_class($this) !== FALSE)
+ {
+ return;
+ }
+
+ foreach ($config as $key => $val)
+ {
+ $this->{'_' . $key} = $val;
+ }
+
+ log_message('debug', 'Migrations class initialized');
+
+ // Are they trying to use migrations while it is disabled?
+ if ($this->_migration_enabled !== TRUE)
+ {
+ show_error('Migrations has been loaded but is disabled or set up incorrectly.');
+ }
+
+ // If not set, set it
+ $this->_migration_path == '' OR $this->_migration_path = APPPATH . 'migrations/';
+
+ // Add trailing slash if not set
+ $this->_migration_path = rtrim($this->_migration_path, '/').'/';
+
+ // They'll probably be using dbforge
+ $this->load->dbforge();
+
+ // If the migrations table is missing, make it
+ if ( ! $this->db->table_exists('migrations'))
+ {
+ $this->dbforge->add_field(array(
+ 'version' => array('type' => 'INT', 'constraint' => 3),
+ ));
+
+ $this->dbforge->create_table('migrations', TRUE);
+
+ $this->db->insert('migrations', array('version' => 0));
+ }
+ }
+
+ // --------------------------------------------------------------------
+
+ /**
+ * Migrate to a schema version
+ *
+ * Calls each migration step required to get to the schema version of
+ * choice
+ *
+ * @access public
+ * @param $version integer Target schema version
+ * @return mixed TRUE if already latest, FALSE if failed, int if upgraded
+ */
+ function version($target_version)
+ {
+ $start = $current_version = $this->_get_version();
+ $stop = $target_version;
+
+ if ($target_version > $current_version)
+ {
+ // Moving Up
+ ++$start;
+ ++$stop;
+ $step = 1;
+ }
+
+ else
+ {
+ // Moving Down
+ $step = -1;
+ }
+
+ $method = $step === 1 ? 'up' : 'down';
+ $migrations = array();
+
+ // We now prepare to actually DO the migrations
+ // But first let's make sure that everything is the way it should be
+ for ($i = $start; $i != $stop; $i += $step)
+ {
+ $f = glob(sprintf($this->_migration_path . '%03d_*.php', $i));
+
+ // Only one migration per step is permitted
+ if (count($f) > 1)
+ {
+ $this->error = sprintf($this->lang->line('multiple_migration_version'), $i);
+ return FALSE;
+ }
+
+ // Migration step not found
+ if (count($f) == 0)
+ {
+ // If trying to migrate up to a version greater than the last
+ // existing one, migrate to the last one.
+ if ($step == 1)
+ {
+ break;
+ }
+
+ // If trying to migrate down but we're missing a step,
+ // something must definitely be wrong.
+ $this->error = sprintf($this->lang->line('migration_not_found'), $i);
+ return FALSE;
+ }
+
+ $file = basename($f[0]);
+ $name = basename($f[0], '.php');
+
+ // Filename validations
+ if (preg_match('/^\d{3}_(\w+)$/', $name, $match))
+ {
+ $match[1] = strtolower($match[1]);
+
+ // Cannot repeat a migration at different steps
+ if (in_array($match[1], $migrations))
+ {
+ $this->error = sprintf($this->lang->line('multiple_migrations_name'), $match[1]);
+ return FALSE;
+ }
+
+ include $f[0];
+ $class = 'Migration_' . ucfirst($match[1]);
+
+ if ( ! class_exists($class))
+ {
+ $this->error = sprintf($this->lang->line('migration_class_doesnt_exist'), $class);
+ return FALSE;
+ }
+
+ if ( ! is_callable(array($class, 'up')) || ! is_callable(array($class, 'down')))
+ {
+ $this->error = sprintf($this->lang->line('wrong_migration_interface'), $class);
+ return FALSE;
+ }
+
+ $migrations[] = $match[1];
+ }
+ else
+ {
+ $this->error = sprintf($this->lang->line('invalid_migration_filename'), $file);
+ return FALSE;
+ }
+ }
+
+ $this->log('Current schema version: ' . $current_version);
+
+ $version = $i + ($step == 1 ? -1 : 0);
+
+ // If there is nothing to do so quit
+ if ($migrations === array())
+ {
+ return TRUE;
+ }
+
+ $this->log('Moving ' . $method . ' to version ' . $version);
+
+ // Loop through the migrations
+ foreach ($migrations AS $migration)
+ {
+ // Run the migration class
+ $class = 'Migration_' . ucfirst(strtolower($migration));
+ call_user_func(array(new $class, $method));
+
+ $current_version += $step;
+ $this->_update_version($current_version);
+ }
+
+ $this->log('All done. Schema is at version '.$current_version);
+
+ return $current_version;
+ }
+
+ // --------------------------------------------------------------------
+
+ /**
+ * Set's the schema to the latest migration
+ *
+ * @access public
+ * @return mixed true if already latest, false if failed, int if upgraded
+ */
+ public function latest()
+ {
+ if ( ! $migrations = $this->find_migrations())
+ {
+ throw new Exception('no_migrations_found');
+ return false;
+ }
+
+ $last_migration = basename(end($migrations));
+
+ // Calculate the last migration step from existing migration
+ // filenames and procceed to the standard version migration
+ $last_version = intval(substr($last_migration, 0, 3));
+ return $this->version($last_version);
+ }
+
+ // --------------------------------------------------------------------
+
+ /**
+ * Set's the schema to the migration version set in config
+ *
+ * @access public
+ * @return mixed true if already current, false if failed, int if upgraded
+ */
+ public function current()
+ {
+ $version = $this->_migration_version;
+ return $this->version($version);
+ }
+
+ // --------------------------------------------------------------------
+
+ /**
+ * Set's the schema to the latest migration
+ *
+ * @access public
+ * @return mixed true if already latest, false if failed, int if upgraded
+ */
+
+ protected static function find_migrations()
+ {
+ // Load all *_*.php files in the migrations path
+ $files = glob($this->_migration_path . '*_*.php');
+ $file_count = count($files);
+
+ for ($i = 0; $i < $file_count; $i++)
+ {
+ // Mark wrongly formatted files as false for later filtering
+ $name = basename($files[$i], '.php');
+ if ( ! preg_match('/^\d{3}_(\w+)$/', $name))
+ {
+ $files[$i] = FALSE;
+ }
+ }
+
+ sort($files);
+
+ return $files;
+ }
+
+ // --------------------------------------------------------------------
+
+ /**
+ * Retrieves current schema version
+ *
+ * @access private
+ * @return integer Current Schema version
+ */
+ private function _get_version()
+ {
+ $row = $this->db->get('migrations')->row();
+ return $row ? $row->version : 0;
+ }
+
+ // --------------------------------------------------------------------
+
+ /**
+ * Stores the current schema version
+ *
+ * @access private
+ * @param $migrations integer Schema version reached
+ * @return void Outputs a report of the migration
+ */
+ private function _update_version($migrations)
+ {
+ return $this->db->update('migrations', array(
+ 'version' => $migrations
+ ));
+ }
+
+ // --------------------------------------------------------------------
+
+ /**
+ * Stores the current schema version
+ *
+ * @access private
+ * @param $migrations integer Schema version reached
+ * @return void Outputs a report of the migration
+ */
+ private function log($text)
+ {
+ echo $text.'<br/>';
+ }
+
+ // --------------------------------------------------------------------
+
+ /**
+ * Enable the use of CI super-global
+ *
+ * @access public
+ * @param $var
+ * @return mixed
+ */
+ public function __get($var)
+ {
+ return get_instance()->$var;
+ }
+}
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