How to Rewrite WordPress URL for a Plugin

I am trying to build a WordPress plugin here with a custom user admin area. What I would like to do is when the user adds /edit at the end of the page, it should open a page from my plugin. So for example

example.com/page-1/edit
should load
example.com/wp-content/plugins/custom-user-admin-area/index.php?u=page-1

I am trying to make use of WP_Rewrite but in vain.

class MyPlugin {
    function create_rewrite_rules($rules) {
        global $wp_rewrite;
        $newRule = array('([A-Za-z0-9-].+)/edit/' => 'wp-content/plugins/custom-user-admin-area/index.php?u=' . $wp_rewrite->preg_index(1));
        $newRules = $newRule + $rules;
        return $newRules;
    }

    function flush_rewrite_rules() {
        global $wp_rewrite;
        $wp_rewrite->flush_rules();
    }

}

$MyPluginCode = new MyPlugin();
add_filter('rewrite_rules_array', array($MyPluginCode, 'create_rewrite_rules'));
add_filter('init', array($MyPluginCode, 'flush_rewrite_rules'));

Answers:

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Method 1

Create an endpoint. In the callback function for the endpoint call your plugin functions internally, so the whole WordPress environment is available and you are still on the same domain, no matter where the plugin URL is.

Plus, make sure not to flush the rewrite rules on every page load, use the (de)activation hook for that.

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