<?php
/**
 * Example code for tutorial post on custom meta boxes:
 * https://wptheming.com/2010/08/custom-metabox-for-post-type/
 */

/**
 * Registers the event post type.
 */
function wpt_event_post_type() {

	$labels = array(
		'name'               => __( 'Events' ),
		'singular_name'      => __( 'Event' ),
		'add_new'            => __( 'Add New Event' ),
		'add_new_item'       => __( 'Add New Event' ),
		'edit_item'          => __( 'Edit Event' ),
		'new_item'           => __( 'Add New Event' ),
		'view_item'          => __( 'View Event' ),
		'search_items'       => __( 'Search Event' ),
		'not_found'          => __( 'No events found' ),
		'not_found_in_trash' => __( 'No events found in trash' )
	);

	$supports = array(
		'title',
		'editor',
		'thumbnail',
		'comments',
		'revisions',
	);

	$args = array(
		'labels'               => $labels,
		'supports'             => $supports,
		'public'               => true,
		'capability_type'      => 'post',
		'rewrite'              => array( 'slug' => 'events' ),
		'has_archive'          => true,
		'menu_position'        => 30,
		'menu_icon'            => 'dashicons-calendar-alt',
		'register_meta_box_cb' => 'wpt_add_event_metaboxes',
	);

	register_post_type( 'events', $args );

}
add_action( 'init', 'wpt_event_post_type' );

/**
 * Adds a metabox to the right side of the screen under the “Publish” box
 */
function wpt_add_event_metaboxes() {
	add_meta_box(
		'wpt_events_location',
		'Event Location',
		'wpt_events_location',
		'events',
		'side',
		'default'
	);
}

/**
 * If you wanted to have two sets of metaboxes.
 */
function add_events_metaboxes_v2() {

	add_meta_box(
		'wpt_events_date',
		'Event Date',
		'wpt_events_date',
		'events',
		'side',
		'default'
	);

	add_meta_box(
		'wpt_events_location',
		'Event Location',
		'wpt_events_location',
		'events',
		'normal',
		'high'
	);

}

/**
 * Output the HTML for the metabox.
 */
function wpt_events_location() {
	global $post;

	// Nonce field to validate form request came from current site
	wp_nonce_field( basename( __FILE__ ), 'event_fields' );

	// Get the location data if it's already been entered
	$location = get_post_meta( $post->ID, 'location', true );

	// Output the field
	echo '<input type="text" name="location" value="' . esc_textarea( $location )  . '" class="widefat">';

}

/**
 * Save the metabox data
 */
function wpt_save_events_meta( $post_id, $post ) {

	// Return if the user doesn't have edit permissions.
	if ( ! current_user_can( 'edit_post', $post_id ) ) {
		return $post_id;
	}

	// Verify this came from the our screen and with proper authorization,
	// because save_post can be triggered at other times.
	if ( ! isset( $_POST['location'] ) || ! wp_verify_nonce( $_POST['event_fields'], basename(__FILE__) ) ) {
		return $post_id;
	}

	// Now that we're authenticated, time to save the data.
	// This sanitizes the data from the field and saves it into an array $events_meta.
	$events_meta['location'] = esc_textarea( $_POST['location'] );

	// Cycle through the $events_meta array.
	// Note, in this example we just have one item, but this is helpful if you have multiple.
	foreach ( $events_meta as $key => $value ) :

		// Don't store custom data twice
		if ( 'revision' === $post->post_type ) {
			return;
		}

		if ( get_post_meta( $post_id, $key, false ) ) {
			// If the custom field already has a value, update it.
			update_post_meta( $post_id, $key, $value );
		} else {
			// If the custom field doesn't have a value, add it.
			add_post_meta( $post_id, $key, $value);
		}

		if ( ! $value ) {
			// Delete the meta key if there's no value
			delete_post_meta( $post_id, $key );
		}

	endforeach;

}
add_action( 'save_post', 'wpt_save_events_meta', 1, 2 );