plugin_concept.php

<?php

use atk4\core\AppScopeTrait;
use atk4\core\DIContainerTrait;
use atk4\core\FactoryTrait;
use atk4\core\InitializerTrait;
use atk4\core\TrackableTrait;
use atk4\ui\CRUD;

trait PluginTrait
{

    use CollectionTrait;
    use FactoryTrait;

    public $_pluginTrait = true;

    protected $plugins = [];

    public function addPlugin($seed, $defaults = []): Plugin
    {

        $plugin = $this->factory($seed, $defaults);

        $plugin_classname = get_class($plugin);

        /** To avoid proliferation of method in trait i leave this validations here */
        /** Validation is done in TargetComponent, before add to it */
        // validate added plugin
        if (!is_a($plugin, Plugin::class, true)) {
            throw new \atk4\core\Exception(['Error adding plugin, Plugin must a subclass of ComponentPlugin']);
        }

        if (!in_array(__CLASS__, $plugin->getPluggableTargets())) {
            throw new \atk4\core\Exception([__CLASS__ . ' is not in the list of target components to use ' . $plugin_classname]);
        }
        
        $missing_plugins = array_diff($this->plugins, $plugin->getRequiredPlugins());

        if (!empty($missing_plugins)) {
            throw new \atk4\core\Exception([$plugin_classname . ' require plugins : ' . implode(', ', $missing_plugins)]);
        }

        $this->_addIntoCollection($plugin->alias ?? $plugin_classname, $plugin, 'plugins');

        $plugin->activate();

        return $plugin;
    }

    public function getPlugin(string $alias): ?Plugin
    {
        return $this->_hasInCollection($alias, 'plugins');
    }
    
    /**
     * at the moment i think remove and deactivation can be revaluated
     * 
     * deactivate needs a check of the the other plugins that required the plugin being deactivated
     * remove is the same sh...
     */
}

abstract class Plugin
{

    use AppScopeTrait;
    use InitializerTrait {
        init as _init;
    }
    use TrackableTrait;
    use DIContainerTrait;

    public $alias;

    protected $required_plugins = [];
    protected $pluggable_targets = [];

    public function __construct($defaults = [])
    {
        $this->setDefaults($defaults);
    }

    public function getPluggableTargets(): array
    {
        return $this->pluggable_targets;
    }

    public function getRequiredPlugins(): array
    {
        return $this->required_plugins;
    }

    abstract function activate();
}

// possible implementation

class CRUDPluggable extends CRUD
{
    use PluginTrait;
}

$crud = new CRUDPluggable();

class PluginSearch extends Plugin
{

    protected $required_plugins = [
        'plugin_menu'
    ];

    protected $pluggable_targets = [
        \atk4\ui\CRUD::class
    ];

    protected $fields = [];

    public function activate()
    {
        $this->owner->menu->addItem(['search', 'icon' => 'search'])->on('click', function ($g) {
            /*
            you have $this->app and $this->owner here, $this->owner is already validated.
            */
        });
    }
}

$crud->addPlugin([PluginSearch::class, 'fields' => ['name', 'title', 'phone']]);