<?php
/**
 * Deals with fields used for ordering.
 *
 * First, it allows backend admin ordering.
 * Then, it makes sure numbers in order fields cannot be duplicated, or in wrong sequence.
 * It also deals with delete posts.
 */

/**
 * Dynamic Values
 */
$field_slug     = 'wpcf-order';
$post_type_slug = 'features';

add_filter( 'manage_' . $post_type_slug . '_posts_columns', 'pp_filter_posts_order_columns' );
add_action( 'manage_' . $post_type_slug . '_posts_custom_column', 'pp_filter_posts_order_column', 10, 2 );
add_filter( 'manage_edit-' . $post_type_slug . '_sortable_columns', 'pp_filter_posts_order_sortable_columns' );
add_action( 'pre_get_posts', 'pp_posts_orderby_order_field' );
add_action( 'wp_trash_post', 'pp_orchestrate_orderby_fields_on_delete' );
add_action( 'save_post', 'pp_orchestrate_orderby_fields', 10, 2 );

/**
 * Add order by in WP Admin for order number fields
 */
function pp_filter_posts_order_columns( $columns ) {
    $columns[ $field_slug ] = __( 'Order' );
    return $columns;
}
/**
 * Add order by in WP Admin for order number fields
 */
function pp_filter_posts_order_column( $column, $post_id ) {
    // Image column
    if ( $field_slug === $column ) {
        echo (int) get_post_meta( $post_id, $field_slug, true );
    }
}
/**
 * Add order by in WP Admin for order number fields
 */
function pp_filter_posts_order_sortable_columns( $columns ) {
    $columns[ $field_slug ] = $field_slug;
    return $columns;
}

/**
 * Add order by in WP Admin for order number fields
 */
function pp_posts_orderby_order_field( $query ) {
    if ( ! is_admin() || ! $query->is_main_query() ) {
        return;
    }

    if ( $field_slug === $query->get( 'orderby' ) ) {
        $query->set( 'orderby', 'meta_value' );
        $query->set( 'meta_key', $field_slug );
        $query->set( 'meta_type', 'numeric' );
    }
}

/**
 * Ensure logic to update fields when post is trashed
 *
 * Does not yet deal with "what if removed, but the number actually was wrong" (such as duplicated)
 * Technically this should never happen, because validated on save... but, you know.
 */
function pp_orchestrate_orderby_fields_on_delete( $post_id ) {

    // If this is just a revision, don't send the email.
    if ( wp_is_post_revision( $post_id ) ) {
        return;
    }

    if ( get_post_type( $post_id ) == $post_type_slug ) {

        $args = array(
            'numberposts' => -1,
            'post_type'   => $post_type_slug,
            'fields'      => 'ids',
        );

        $all_posts_of_this_type = get_posts( $args );

        $removed_value = get_post_meta( $post_id, $field_slug, true );

        $all_field_values = array();
        foreach ( $all_posts_of_this_type as  $post_id_available ) {
            $all_field_values[ $post_id_available ] = get_post_meta( $post_id_available, $field_slug, true );
        }
        asort( $all_field_values, SORT_NUMERIC );

        ksort( $all_field_values, SORT_NUMERIC );
        $post_id_to_start_from = array_search( $removed_value + 1, $all_field_values );
        $position_in_array     = array_search( $post_id_to_start_from, array_keys( $all_field_values ) );
        $posts_to_update       = array_slice( $all_field_values, $position_in_array, null, true );
        foreach ( $posts_to_update as $post_to_update ) {
            update_post_meta( $post_to_update, $field_slug, $all_field_values[ $post_to_update ] - 1 );
        }
    }

}

/**
 * Ensure logic to update felds when field a field is updated.
 */
function pp_orchestrate_orderby_fields( $post_id, $post ) {

    // If this is just a revision, don't send the email.
    if ( wp_is_post_revision( $post_id ) ) {
        return;
    }

    if ( $post->post_type == $post_type_slug ) {

        $field_value_added = $_POST[ $field_slug ];
        $args              = array(
            'numberposts' => -1,
            'post_type'   => $post_type_slug,
            'fields'      => 'ids',
        );

        $all_posts_of_this_type = get_posts( $args );
        $all_field_values       = array();
        foreach ( $all_posts_of_this_type as  $post_id_available ) {
            $all_field_values[ $post_id_available ] = get_post_meta( $post_id_available, $field_slug, true );
        }
        asort( $all_field_values, SORT_NUMERIC );

        /**
         * If number added matches a already used number, it keeps the number and increase all others
         */
        if ( in_array( $field_value_added, $all_field_values ) ) {
            ksort( $all_field_values, SORT_NUMERIC );
            $post_id_to_start_from = array_search( $field_value_added, $all_field_values );
            $position_in_array     = array_search( $post_id_to_start_from, array_keys( $all_field_values ) );
            $posts_to_update       = array_slice( $all_field_values, $position_in_array, null, true );
            foreach ( $posts_to_update as $post_to_update ) {
                update_post_meta( $post_to_update, $field_slug, $all_field_values[ $post_to_update ] + 1 );
            }
        }

        /**
         * If there are missing numbers in the array, it adds this new number in the empty slot
         */
        $missing_number = missing_number( $all_field_values );
        if ( ! empty( $missing_number ) ) {
            asort( $missing_number, SORT_NUMERIC );
            $field_value_added = $missing_number[0];
        }

        update_post_meta( $post_id, $field_slug, $field_value_added );

    }

}

function missing_number( $num_list ) {

    $new_arr = range( $num_list[0], max( $num_list ) );

    return array_diff( $new_arr, $num_list );

}