Added template loader class.

Added empty template.
Rearranged some code.

codeup-advent-calendar.php

@@ -12,9 +12,17 @@
  * @package         Codeup_Advent_Calendar
  */
 
-require_once __DIR__ . '/inc/class-codeup-advent-calendar.php';
-require_once __DIR__ . '/inc/class-advent-calendar-settings-page.php';
+define( 'CAC_ADVENT_DAY_TYPE', 'advent_day' );
+define( 'CAC_PLUGIN_DIR', plugin_dir_path( __FILE__ ) );
 
 add_action( 'plugins_loaded', function () {
+	require_once __DIR__ . '/inc/class-codeup-advent-calendar.php';
+	require_once __DIR__ . '/inc/class-advent-calendar-template-loader.php';
+
 	Codeup_Advent_Calendar::get_instance()->bootstrap();
+
+	if ( is_admin() ) {
+		require_once __DIR__ . '/inc/class-advent-calendar-settings-page.php';
+		Advent_Calendar_Settings_Page::get_instance();
+	}
 } );

inc/class-advent-calendar-settings-page.php

 <?php
+/**
+ * Part of the Codeup advent Calendar plugin.
+ */
 
 /**
  * Class Advent_Calendar_Settings_Page

inc/class-advent-calendar-template-loader.php

+<?php
+/**
+ * Part of the Codeup advent Calendar plugin.
+ */
+
+if ( ! class_exists( 'Gamajo_Template_Loader' ) ) {
+	require plugin_dir_path( __FILE__ ) . 'class-gamajo-template-loader.php';
+}
+
+/**
+ * Template loader for Meal Planner.
+ *
+ * Only need to specify class properties here.
+ *
+ * @package Advent_Calendar
+ * @author  Gary Jones
+ */
+class Advent_Calendar_Template_Loader extends Gamajo_Template_Loader {
+	/**
+	 * Prefix for filter names.
+	 *
+	 * @since 1.0.0
+	 *
+	 * @var string
+	 */
+	protected $filter_prefix = 'advent_calendar';
+
+	/**
+	 * Directory name where custom templates for this plugin should be found in the theme.
+	 *
+	 * @since 1.0.0
+	 *
+	 * @var string
+	 */
+	protected $theme_template_directory = '';
+
+	/**
+	 * Reference to the root directory path of this plugin.
+	 *
+	 * Can either be a defined constant, or a relative reference from where the subclass lives.
+	 *
+	 * In this case, `MEAL_PLANNER_PLUGIN_DIR` would be defined in the root plugin file as:
+	 *
+	 * ~~~
+	 * define( 'MEAL_PLANNER_PLUGIN_DIR', plugin_dir_path( __FILE__ ) );
+	 * ~~~
+	 *
+	 * @since 1.0.0
+	 *
+	 * @var string
+	 */
+	protected $plugin_directory = CAC_PLUGIN_DIR;
+
+	/**
+	 * Directory name where templates are found in this plugin.
+	 *
+	 * Can either be a defined constant, or a relative reference from where the subclass lives.
+	 *
+	 * e.g. 'templates' or 'includes/templates', etc.
+	 *
+	 * @since 1.1.0
+	 *
+	 * @var string
+	 */
+	protected $plugin_template_directory = 'templates';
+}

inc/class-codeup-advent-calendar.php

 <?php
 /**
  * Part of the Codeup advent Calendar plugin.
- * User: mikelittle
- * Date: 31/10/2018
- * Time: 17:55
  */
 
-define( 'CAC_ADVENT_DAY_TYPE', 'advent_day' );
-
 class Codeup_Advent_Calendar {
 
 	/**
@@ -17,6 +12,13 @@ class Codeup_Advent_Calendar {
 	 */
 	protected static $instance;
 
+	/**
+	 *  Store the Template Loader instance
+	 *
+	 * @var  Advent_Calendar_Template_Loader
+	 */
+	protected static $template_loader;
+
 	/**
 	 * Create singleton instance.
 	 *
@@ -34,13 +36,67 @@ class Codeup_Advent_Calendar {
 	 * Bootstrap the plugin. Set up hooks. Create types, etc.
 	 */
 	public function bootstrap() {
+		self::$template_loader = new Advent_Calendar_Template_Loader;
+		add_filter( 'template_include', function ( $original_template ) {
+			if ( CAC_ADVENT_DAY_TYPE === get_post_type() && is_archive() ) {
+				return self::$template_loader->get_template_part( 'archive', CAC_ADVENT_DAY_TYPE, false );
+			} else {
+				return $original_template;
+			}
+		} );
+
 		if ( is_admin() ) {
-			Advent_Calendar_Settings_Page::get_instance();
 			add_action( 'pre_get_posts', [ $this, 'sort_by_day' ] );
+			add_filter( 'manage_' . CAC_ADVENT_DAY_TYPE . '_posts_columns', [ $this, 'manage_posts_columns' ], 11 );
+			add_action( 'manage_' . CAC_ADVENT_DAY_TYPE . '_posts_custom_column', [ $this, 'manage_posts_custom_column' ], 10, 2 );
 		}
 
 	}
 
+	/**
+	 * Add our extra post columns.
+	 *
+	 * @param array $columns The current set of columns.
+	 *
+	 * @return array The modified list.
+	 */
+	public function manage_posts_columns( array $columns ) : array {
+
+		// Add these after title.
+		$new_columns = [
+			'image' => __( 'Image', 'ias-questions' ),
+		];
+
+		$pos     = array_search( 'title', array_keys( $columns ) );
+		$columns = array_merge(
+			array_slice( $columns, 0, $pos + 1, true ),
+			$new_columns,
+			array_slice( $columns, $pos + 1, count( $columns ) - 1, true )
+		);
+
+		return $columns;
+	}
+
+	/**
+	 * Output the information for each of our columns.
+	 *
+	 * @param string $column_name The column to output.
+	 * @param int    $post_id     The post in question.
+	 */
+	public function manage_posts_custom_column( $column_name, $post_id ) {
+
+		switch ( $column_name ) {
+			case 'image':
+				$image = get_field( 'acd_image' );
+				if ( $image ) {
+					?>
+					<img class="acd-thumbnail" src="<?php echo $image['sizes']['thumbnail']; ?>">
+					<?php
+				}
+				break;
+		}
+	}
+
 	/**
 	 * Create all 25 default pages. Setting the title and slug.
 	 */

inc/class-gamajo-template-loader.php

+<?php
+/**
+ * Template Loader for Plugins.
+ *
+ * @package   Gamajo_Template_Loader
+ * @author    Gary Jones
+ * @link      http://github.com/GaryJones/Gamajo-Template-Loader
+ * @copyright 2013 Gary Jones
+ * @license   GPL-2.0-or-later
+ * @version   1.3.1
+ */
+
+if ( ! class_exists( 'Gamajo_Template_Loader' ) ) {
+
+	/**
+	 * Template loader.
+	 *
+	 * Originally based on functions in Easy Digital Downloads (thanks Pippin!).
+	 *
+	 * When using in a plugin, create a new class that extends this one and just overrides the properties.
+	 *
+	 * @package Gamajo_Template_Loader
+	 * @author  Gary Jones
+	 */
+	class Gamajo_Template_Loader {
+		/**
+		 * Prefix for filter names.
+		 *
+		 * @since 1.0.0
+		 *
+		 * @var string
+		 */
+		protected $filter_prefix = 'your_plugin';
+
+		/**
+		 * Directory name where custom templates for this plugin should be found in the theme.
+		 *
+		 * For example: 'your-plugin-templates'.
+		 *
+		 * @since 1.0.0
+		 *
+		 * @var string
+		 */
+		protected $theme_template_directory = 'plugin-templates';
+
+		/**
+		 * Reference to the root directory path of this plugin.
+		 *
+		 * Can either be a defined constant, or a relative reference from where the subclass lives.
+		 *
+		 * e.g. YOUR_PLUGIN_TEMPLATE or plugin_dir_path( dirname( __FILE__ ) ); etc.
+		 *
+		 * @since 1.0.0
+		 *
+		 * @var string
+		 */
+		protected $plugin_directory = 'YOUR_PLUGIN_DIR';
+
+		/**
+		 * Directory name where templates are found in this plugin.
+		 *
+		 * Can either be a defined constant, or a relative reference from where the subclass lives.
+		 *
+		 * e.g. 'templates' or 'includes/templates', etc.
+		 *
+		 * @since 1.1.0
+		 *
+		 * @var string
+		 */
+		protected $plugin_template_directory = 'templates';
+
+		/**
+		 * Internal use only: Store located template paths.
+		 *
+		 * @var array
+		 */
+		private $template_path_cache = array();
+
+		/**
+		 * Internal use only: Store variable names used for template data.
+		 *
+		 * Means unset_template_data() can remove all custom references from $wp_query.
+		 *
+		 * Initialized to contain the default 'data'.
+		 *
+		 * @var array
+		 */
+		private $template_data_var_names = array( 'data' );
+
+		/**
+		 * Clean up template data.
+		 *
+		 * @since 1.2.0
+		 */
+		public function __destruct() {
+			$this->unset_template_data();
+		}
+
+		/**
+		 * Retrieve a template part.
+		 *
+		 * @since 1.0.0
+		 *
+		 * @param string $slug Template slug.
+		 * @param string $name Optional. Template variation name. Default null.
+		 * @param bool   $load Optional. Whether to load template. Default true.
+		 * @return string
+		 */
+		public function get_template_part( $slug, $name = null, $load = true ) {
+			// Execute code for this part.
+			do_action( 'get_template_part_' . $slug, $slug, $name );
+			do_action( $this->filter_prefix . '_get_template_part_' . $slug, $slug, $name );
+
+			// Get files names of templates, for given slug and name.
+			$templates = $this->get_template_file_names( $slug, $name );
+
+			// Return the part that is found.
+			return $this->locate_template( $templates, $load, false );
+		}
+
+		/**
+		 * Make custom data available to template.
+		 *
+		 * Data is available to the template as properties under the `$data` variable.
+		 * i.e. A value provided here under `$data['foo']` is available as `$data->foo`.
+		 *
+		 * When an input key has a hyphen, you can use `$data->{foo-bar}` in the template.
+		 *
+		 * @since 1.2.0
+		 *
+		 * @param mixed  $data     Custom data for the template.
+		 * @param string $var_name Optional. Variable under which the custom data is available in the template.
+		 *                         Default is 'data'.
+		 * @return Gamajo_Template_Loader
+		 */
+		public function set_template_data( $data, $var_name = 'data' ) {
+			global $wp_query;
+
+			$wp_query->query_vars[ $var_name ] = (object) $data;
+
+			// Add $var_name to custom variable store if not default value.
+			if ( 'data' !== $var_name ) {
+				$this->template_data_var_names[] = $var_name;
+			}
+
+			return $this;
+		}
+
+		/**
+		 * Remove access to custom data in template.
+		 *
+		 * Good to use once the final template part has been requested.
+		 *
+		 * @since 1.2.0
+		 *
+		 * @return Gamajo_Template_Loader
+		 */
+		public function unset_template_data() {
+			global $wp_query;
+
+			// Remove any duplicates from the custom variable store.
+			$custom_var_names = array_unique( $this->template_data_var_names );
+
+			// Remove each custom data reference from $wp_query.
+			foreach ( $custom_var_names as $var ) {
+				if ( isset( $wp_query->query_vars[ $var ] ) ) {
+					unset( $wp_query->query_vars[ $var ] );
+				}
+			}
+
+			return $this;
+		}
+
+		/**
+		 * Given a slug and optional name, create the file names of templates.
+		 *
+		 * @since 1.0.0
+		 *
+		 * @param string $slug Template slug.
+		 * @param string $name Template variation name.
+		 * @return array
+		 */
+		protected function get_template_file_names( $slug, $name ) {
+			$templates = array();
+			if ( isset( $name ) ) {
+				$templates[] = $slug . '-' . $name . '.php';
+			}
+			$templates[] = $slug . '.php';
+
+			/**
+			 * Allow template choices to be filtered.
+			 *
+			 * The resulting array should be in the order of most specific first, to least specific last.
+			 * e.g. 0 => recipe-instructions.php, 1 => recipe.php
+			 *
+			 * @since 1.0.0
+			 *
+			 * @param array  $templates Names of template files that should be looked for, for given slug and name.
+			 * @param string $slug      Template slug.
+			 * @param string $name      Template variation name.
+			 */
+			return apply_filters( $this->filter_prefix . '_get_template_part', $templates, $slug, $name );
+		}
+
+		/**
+		 * Retrieve the name of the highest priority template file that exists.
+		 *
+		 * Searches in the STYLESHEETPATH before TEMPLATEPATH so that themes which
+		 * inherit from a parent theme can just overload one file. If the template is
+		 * not found in either of those, it looks in the theme-compat folder last.
+		 *
+		 * @since 1.0.0
+		 *
+		 * @param string|array $template_names Template file(s) to search for, in order.
+		 * @param bool         $load           If true the template file will be loaded if it is found.
+		 * @param bool         $require_once   Whether to require_once or require. Default true.
+		 *                                     Has no effect if $load is false.
+		 * @return string The template filename if one is located.
+		 */
+		public function locate_template( $template_names, $load = false, $require_once = true ) {
+
+			// Use $template_names as a cache key - either first element of array or the variable itself if it's a string.
+			$cache_key = is_array( $template_names ) ? $template_names[0] : $template_names;
+
+			// If the key is in the cache array, we've already located this file.
+			if ( isset( $this->template_path_cache[ $cache_key ] ) ) {
+				$located = $this->template_path_cache[ $cache_key ];
+			} else {
+
+				// No file found yet.
+				$located = false;
+
+				// Remove empty entries.
+				$template_names = array_filter( (array) $template_names );
+				$template_paths = $this->get_template_paths();
+
+				// Try to find a template file.
+				foreach ( $template_names as $template_name ) {
+					// Trim off any slashes from the template name.
+					$template_name = ltrim( $template_name, '/' );
+
+					// Try locating this template file by looping through the template paths.
+					foreach ( $template_paths as $template_path ) {
+						if ( file_exists( $template_path . $template_name ) ) {
+							$located = $template_path . $template_name;
+							// Store the template path in the cache.
+							$this->template_path_cache[ $cache_key ] = $located;
+							break 2;
+						}
+					}
+				}
+			}
+
+			if ( $load && $located ) {
+				load_template( $located, $require_once );
+			}
+
+			return $located;
+		}
+
+		/**
+		 * Return a list of paths to check for template locations.
+		 *
+		 * Default is to check in a child theme (if relevant) before a parent theme, so that themes which inherit from a
+		 * parent theme can just overload one file. If the template is not found in either of those, it looks in the
+		 * theme-compat folder last.
+		 *
+		 * @since 1.0.0
+		 *
+		 * @return mixed|void
+		 */
+		protected function get_template_paths() {
+			$theme_directory = trailingslashit( $this->theme_template_directory );
+
+			$file_paths = array(
+				10  => trailingslashit( get_template_directory() ) . $theme_directory,
+				100 => $this->get_templates_dir(),
+			);
+
+			// Only add this conditionally, so non-child themes don't redundantly check active theme twice.
+			if ( get_stylesheet_directory() !== get_template_directory() ) {
+				$file_paths[1] = trailingslashit( get_stylesheet_directory() ) . $theme_directory;
+			}
+
+			/**
+			 * Allow ordered list of template paths to be amended.
+			 *
+			 * @since 1.0.0
+			 *
+			 * @param array $var Default is directory in child theme at index 1, parent theme at 10, and plugin at 100.
+			 */
+			$file_paths = apply_filters( $this->filter_prefix . '_template_paths', $file_paths );
+
+			// Sort the file paths based on priority.
+			ksort( $file_paths, SORT_NUMERIC );
+
+			return array_map( 'trailingslashit', $file_paths );
+		}
+
+		/**
+		 * Return the path to the templates directory in this plugin.
+		 *
+		 * May be overridden in subclass.
+		 *
+		 * @since 1.0.0
+		 *
+		 * @return string
+		 */
+		protected function get_templates_dir() {
+			return trailingslashit( $this->plugin_directory ) . $this->plugin_template_directory;
+		}
+	}
+}

templates/archive-advent_day.php

+<?php
+echo "<p>advent calendar archive template.</p>";