version.php

<?php 
/**
 * Version management for database migrations.
 * 
 * Database changes require special care:
 * - the model has to be adjusted for users installing the plugin
 * - the current setup has to be migrated for current users
 * 
 * These migrations are a way to handle current users. They do *not*
 * run on plugin activation.
 * 
 * Pattern:
 * 
 * - increment \PodloveSubscribeButton\DATABASE_VERSION constant by 1, e.g.
 * 		```php
 * 		define( __NAMESPACE__ . '\DATABASE_VERSION', 2 );
 * 		```
 * 		
 * - add a case in `\PodloveSubscribeButton\run_migrations_for_version`, e.g.
 * 		```php
 * 		function run_migrations_for_version( $version ) {
 *			global $wpdb;
 *			switch ( $version ) {
 *				case 2:
 *					$wbdb-> // run sql or whatever
 *					break;
 *			}
 *		}
 *		```
 *		
 *		Feel free to move the migration code into a separate function if it's
 *		rather complex.
 *		
 * - adjust the main model / setup process so new users installing the plugin
 *   will have these changes too
 *   
 * - Test the migrations! :)
 */

namespace PodloveSubscribeButton;
use \PodloveSubscribeButton\Model;

define( __NAMESPACE__ . '\DATABASE_VERSION', 2 );

add_action( 'admin_init', '\PodloveSubscribeButton\maybe_run_database_migrations' );
add_action( 'admin_init', '\PodloveSubscribeButton\run_database_migrations', 5 );

function maybe_run_database_migrations() {
	$database_version = get_option('podlove_subscribe_button_plugin_database_version');

	if ( $database_version === false ) {
		// plugin has just been installed or Plugin Version < 1.3
		update_option( 'podlove_subscribe_button_plugin_database_version', DATABASE_VERSION );
	}
}

function run_database_migrations() {
	if (get_option('podlove_subscribe_button_plugin_database_version') >= DATABASE_VERSION)
		return;

	if (is_multisite()) {
		set_time_limit(0); // may take a while, depending on network size
		\PodloveSubscribeButton\for_every_podcast_blog(function() { migrate_for_current_blog(); });
	} else {
		migrate_for_current_blog();
	}

	if (isset($_REQUEST['_wp_http_referer']) && $_REQUEST['_wp_http_referer']) {
		wp_redirect($_REQUEST['_wp_http_referer']);
		exit;
	}
}

function migrate_for_current_blog() {
	$database_version = get_option('podlove_subscribe_button_plugin_database_version');

	for ($i = $database_version+1; $i <= DATABASE_VERSION; $i++) { 
		\PodloveSubscribeButton\run_migrations_for_version($i);
		update_option('podlove_subscribe_button_plugin_database_version', $i);
	}
}

/**
 * Find and run migration for given version number.
 *
 * @todo  move migrations into separate files
 * 
 * @param  int $version
 */
function run_migrations_for_version( $version ) {
	global $wpdb;
	
	switch ( $version ) {}

}