felixarntz/oop-admin-pages

<?php
/**
 * Abstract_Admin_Page class
 *
 * @package Leaves_And_Love\OOP_Admin_Pages\Admin_Page
 * @since 1.0.0
 */

namespace Leaves_And_Love\OOP_Admin_Pages\Admin_Page;

use Leaves_And_Love\OOP_Admin_Pages\Admin_Page;
use Leaves_And_Love\OOP_Admin_Pages\Exception\Config_Invalid_Exception;
use BrightNucleus\Config\ConfigInterface as Config;
use BrightNucleus\Config\ConfigTrait;

/**
 * Abstract class representing an admin page.
 *
 * @since 1.0.0
 */
abstract class Abstract_Admin_Page implements Admin_Page {

    use ConfigTrait;

    const SLUG                = 'slug';
    const TITLE               = 'title';
    const RENDER_CALLBACK     = 'render_callback';
    const INITIALIZE_CALLBACK = 'initialize_callback';

    /**
     * Constructor.
     *
     * Sets the configuration.
     *
     * @since 1.0.0
     *
     * @param Config $config Admin page configuration. Must contain keys 'slug' (admin page identifier), 'title'
     *                       and 'render_callback' (callable that receives the configuration as sole parameter).
     *                       May also contain an 'initialize_callback' key.
     *
     * @throws Config_Invalid_Exception Thrown when the configuration is invalid.
     */
    public function __construct( Config $config ) {
        $this->processConfig( $config );

        $required_keys = $this->get_required_config_keys();

        foreach ( $required_keys as $required_key ) {
            if ( ! $this->hasConfigKey( $required_key ) ) {
                throw new Config_Invalid_Exception( sprintf( 'The required configuration key %s is missing.', $required_key ) );
            }

            $value = $this->getConfigKey( $required_key );
            if ( empty( $value ) ) {
                throw new Config_Invalid_Exception( sprintf( 'The required configuration key %s is empty.', $required_key ) );
            }
        }
    }

    /**
     * Gets the slug of the admin page.
     *
     * @since 1.0.0
     *
     * @return string Admin page slug.
     */
    public function get_slug() : string {
        return $this->getConfigKey( self::SLUG );
    }

    /**
     * Gets the title of the admin page.
     *
     * @since 1.0.0
     *
     * @return string Admin page title.
     */
    public function get_title() : string {
        return $this->getConfigKey( self::TITLE );
    }

    /**
     * Initializes the admin page on pageload.
     *
     * This method must be called before any output is printed.
     *
     * @since 1.0.0
     */
    public function initialize() {
        if ( ! $this->hasConfigKey( self::INITIALIZE_CALLBACK ) ) {
            return;
        }

        call_user_func( $this->getConfigKey( self::INITIALIZE_CALLBACK ), $this->config );
    }

    /**
     * Renders the admin page content.
     *
     * @since 1.0.0
     */
    public function render() {
        call_user_func( $this->getConfigKey( self::RENDER_CALLBACK ), $this->config );
    }

    /**
     * Gets the configuration keys that are required for an admin page.
     *
     * @since 1.0.0
     *
     * @return array Array of configuration keys.
     */
    protected function get_required_config_keys() {
        return array( self::SLUG, self::TITLE, self::RENDER_CALLBACK );
    }
}