felixarntz/plugin-lib

<?php
/**
 * Service instantiator class
 *
 * @package Leaves_And_Love\Plugin_Lib
 * @since 1.0.0
 */

namespace Leaves_And_Love\Plugin_Lib;

use Leaves_And_Love\Plugin_Lib\Translations\Translations;
use ReflectionClass;

if ( ! class_exists( 'Leaves_And_Love\Plugin_Lib\Service_Instantiator' ) ) :

    /**
     * Class to instantiate services comfortably.
     *
     * @since 1.0.0
     */
    final class Service_Instantiator {
        /**
         * Contains the service instances for all plugins.
         *
         * @since 1.0.0
         * @static
         *
         * @var array
         */
        private static $instances = array();

        /**
         * Instantiates a specific class.
         *
         * @since 1.0.0
         * @static
         *
         * @param string $class_name Fully qualified service class name.
         * @param string $prefix     Prefix for the plugin the service should be instantiated for.
         * @param mixed  $args,...   Further arguments to pass to the constructor.
         * @return Service|null The service instance, or null if invalid.
         */
        public static function instantiate( $class_name, $prefix ) {
            if ( ! class_exists( $class_name ) || ! is_subclass_of( $class_name, 'Leaves_And_Love\Plugin_Lib\Service' ) ) {
                return null;
            }

            if ( ! isset( self::$instances[ $prefix ][ $class_name ] ) ) {
                if ( ! isset( self::$instances[ $prefix ] ) ) {
                    self::$instances[ $prefix ] = array();
                }

                $reflected_class = new ReflectionClass( $class_name );

                $args = func_num_args() === 2 ? array() : array_slice( func_get_args(), 2 );

                $instantiation_args = array();
                foreach ( self::get_constructor_params( $reflected_class ) as $param ) {
                    if ( $param->isOptional() ) {
                        continue;
                    }

                    $instantiation_args[] = self::fill_constructor_param( $param->name, $class_name, $prefix, $args );
                }

                self::$instances[ $prefix ][ $class_name ] = $reflected_class->newInstanceArgs( $instantiation_args );
            }

            return self::$instances[ $prefix ][ $class_name ];
        }

        /**
         * Fills a specific parameter for a class constructor.
         *
         * @since 1.0.0
         * @static
         *
         * @param string $param      Parameter name.
         * @param string $class_name Fully qualified service class name.
         * @param string $prefix     Prefix for the plugin the class should be instantiated for.
         * @param array  $args       Further arguments.
         * @return mixed Value for the parameter.
         */
        private static function fill_constructor_param( $param, $class_name, $prefix, $args ) {
            switch ( $param ) {
                case 'prefix':
                    return $prefix;
                case 'services':
                    return self::fill_constructor_services( $class_name, $prefix, $args );
                case 'args':
                    return self::fill_constructor_args( $class_name, $args );
                case 'translations':
                    return self::fill_constructor_translations( $class_name, $args );
            }

            return null;
        }

        /**
         * Fills the $services parameter of a constructor.
         *
         * @since 1.0.0
         * @static
         *
         * @param string $class_name Fully qualified service class name.
         * @param string $prefix     Prefix for the plugin the class should be instantiated for.
         * @param array  $args       Further arguments.
         * @return array Array of required service instances.
         */
        private static function fill_constructor_services( $class_name, $prefix, $args ) {
            $service_definitions = call_user_func( array( $class_name, 'get_service_definitions' ) );

            $services_arg = array();
            foreach ( $args as $arg ) {
                if ( ! is_array( $arg ) ) {
                    continue;
                }

                foreach ( $arg as $key => $value ) {
                    if ( isset( $service_definitions[ $key ] ) && is_a( $value, $service_definitions[ $key ] ) ) {
                        $services_arg = $arg;
                        break 2;
                    }
                }
            }

            $services = array();
            foreach ( $service_definitions as $name => $class_name ) {
                if ( isset( $services_arg[ $name ] ) ) {
                    $services[ $name ] = $services_arg[ $name ];
                } else {
                    $services[ $name ] = self::instantiate( $class_name, $prefix );
                }
            }

            return $services;
        }

        /**
         * Fills the $args parameter of a constructor.
         *
         * @since 1.0.0
         * @static
         *
         * @param string $class_name Fully qualified service class name.
         * @param array  $args       Further arguments.
         * @return array Array of arguments.
         */
        private static function fill_constructor_args( $class_name, $args ) {
            $args_parsers = call_user_func( array( $class_name, 'get_args_parsers' ) );

            foreach ( $args as $arg ) {
                if ( ! is_array( $arg ) ) {
                    continue;
                }

                foreach ( $arg as $key => $value ) {
                    if ( isset( $args_parsers[ $key ] ) && ! is_a( $value, 'Leaves_And_Love\Plugin_Lib\Service' ) ) {
                        return $arg;
                    }
                }
            }

            return array();
        }

        /**
         * Fills the $translations parameter of a constructor.
         *
         * @since 1.0.0
         * @static
         *
         * @param string $class_name Fully qualified service class name.
         * @param array  $args       Further arguments.
         * @return Translations|null Translations object, or null on failure.
         */
        private static function fill_constructor_translations( $class_name, $args ) {
            foreach ( $args as $arg ) {
                if ( is_object( $arg ) && is_a( $arg, 'Leaves_And_Love\Plugin_Lib\Translations\Translations' ) ) {
                    return $arg;
                }
            }

            $class_name_parts = explode( '\\', $class_name );
            if ( count( $class_name_parts ) < 3 ) {
                return null;
            }

            $translations_class_name = $class_name_parts[0] . '\\' . $class_name_parts[1] . '\\Translations\\Translations_' . array_pop( $class_name_parts );
            if ( ! class_exists( $translations_class_name ) ) {
                return null;
            }

            return new $translations_class_name();
        }

        /**
         * Returns the parameters for a specific class constructor.
         *
         * @since 1.0.0
         * @static
         *
         * @param ReflectionClass $reflected_class The reflected class.
         * @return array Array of ReflectionParam elements.
         */
        private static function get_constructor_params( $reflected_class ) {
            $reflected_constructor = $reflected_class->getConstructor();
            if ( ! $reflected_constructor ) {
                return array();
            }

            return $reflected_constructor->getParameters();
        }
    }

endif;