/**
 * Adds a meta box to the post editing screen
 */
function gwrrest_custom_meta() {
    $post_types = array ( 'supplier' );
    foreach( $post_types as $post_type ) {
        add_meta_box(
            'gwrrest_meta',
            __( 'Restaurant Options', 'gwrrest-textdomain' ),
            'gwrrest_meta_callback',
            $post_type,
            'normal',
            'high'
        );
    }
}
add_action( 'add_meta_boxes', 'gwrrest_custom_meta' );

/**
 * Outputs the content of the meta box
 */
function gwrrest_meta_callback( $post ) {
    wp_nonce_field( basename( __FILE__ ), 'gwrrest_nonce' );
    $gwrrest_stored_meta = get_post_meta( $post->ID );
    ?>

    <?php _e( 'Is this a restaurant? ', 'gwrrest-textdomain' )?>
    </span>
    <div class="gwrrest-row-content">
        <label for="restaurant-options">
        <input type="checkbox" name="restaurant-options" id="restaurant-options" value="yes" <?php if ( isset ( $gwrrest_stored_meta['restaurant-options'] ) ) checked( $gwrrest_stored_meta['restaurant-options'][0], 'yes' ); ?> />
        <?php _e( 'Check to add a specials section to the restaurant pages', 'gwrrest-textdomain' )?>
        </label>
    </div>
    </p>
    <p>
        <label for="specials-textarea" class="prfx-row-title"><?php _e( 'Enter Specials Content Here', 'prfx-textdomain' )?></label>
        <textarea name="specials-textarea" id="specials-textarea"><?php if ( isset ( $prfx_stored_meta['specials-textarea'] ) ) echo $prfx_stored_meta['specials-textarea'][0]; ?></textarea>
    </p>
    <?php
}

/**
 * Saves the custom meta input
 */
function gwrrest_meta_save( $post_id ) {
    // Checks save status
    $is_autosave = wp_is_post_autosave( $post_id );
    $is_revision = wp_is_post_revision( $post_id );
    $is_valid_nonce = ( isset( $_POST[ 'gwrrest_nonce' ] ) && wp_verify_nonce( $_POST[ 'gwrrest_nonce' ], basename( __FILE__ ) ) ) ? 'true' : 'false';

    // Exits script depending on save status
    if ( $is_autosave || $is_revision || !$is_valid_nonce ) {
        return;
    }

    // Checks for input and saves
    if ( isset( $_POST['restaurant-options'] ) && $_POST['restaurant-options'] ) {
        add_post_meta( $post_id, 'restaurant-options', 'yes', true );
    } else {
        delete_post_meta( $post_id, 'restaurant-options' );
    }

    // Checks for input and saves if needed
    if( isset( $_POST[ 'specials-textarea' ] ) ) {
        update_post_meta( $post_id, 'specials-textarea', $_POST[ 'specials-textarea' ] );
    } else {
        delete_post_meta( $post_id, 'specials-textarea' );
    }
}
add_action( 'save_post', 'gwrrest_meta_save' );