Add an extra filter nav to filter ideas by category or only get unrated ideas (Needs the WP Idea Stream WordPress plugin)

wp-idea-stream-custom.php

<?php
/**
 * For more infos about how to use the wp-idea-stream-custom.php file
 * @see https://github.com/imath/wp-idea-stream/wiki/wp-idea-stream-custom.php
 */

// Exit if accessed directly
defined( 'ABSPATH' ) || exit;

/**
 * Add some inline style and script.
 * 
 * In a regular plugin or theme, using wp_enque_style() & wp_enqueue_script()
 * would be a lot better!
 */ 
function xwara_extra_enqueue_scripts() {
	// Only enqueue inline script and inline style id viewing an Idea loop
	if ( ! wp_idea_stream_is_idea_archive() && ! wp_idea_stream_is_category() && ! wp_idea_stream_is_tag() ) {
		return;
	}

	// Inline style
	wp_add_inline_style( 'wp-idea-stream-style', '
		#xwara-extra-filters {
			margin: 1.5em 0;
			background-color: #f1f1f1;
			padding: 0.5em;
			overflow: hidden;
			display: table;
			width: 100%;
			border: solid 1px #ccc;
		}

		#xwara-extra-filters label,
		#xwara-extra-filters .submit {
			width: auto;
			display: table-cell;
		}
	' );

	// Get term links.
	$term_links = array();
	if ( wp_idea_stream_ideas_has_terms() ) {
		$idea_terms = wp_idea_stream_get_idea_var( 'edit_form_terms' );

		foreach ( $idea_terms as $idea_term ) {
			$term_links[ $idea_term->term_id ] = esc_url_raw( wp_idea_stream_get_category_url( $idea_term ) );
		}
	}

	if ( ! empty( $term_links ) ) {
		// As we will use jQuery, make sure it is enqueue
		wp_enqueue_script( 'jquery' );
		wp_add_inline_script( 'jquery-migrate', sprintf( '
			var WPideaTerms  = %1$s;
			var WPformAction = \'%2$s\';

			jQuery( document ).ready( function( $ ) {
				// Replace term IDs by term links.
				$.each( $( \'#select_idea_category option\' ), function( i, o ) {
					if ( WPideaTerms[ $( o ).val() ] ) {
						$( o ).prop( \'value\', WPideaTerms[ $( o ).val() ] );
					}
				} );

				$( \'#xwara-extra-filters\' ).on( \'submit\', function( f ) {
					if ( \'-1\' !== $( \'#select_idea_category\' ).val() ) {
						$( f.currentTarget ).prop( \'action\', $( \'#select_idea_category\' ).val() );
					} else {
						$( f.currentTarget ).prop( \'action\', WPformAction );
					}
					
					$( \'#select_idea_category\' ).prop( \'disabled\', true );
					
					return f;
				} );
			} );
		', wp_json_encode( $term_links ), esc_url_raw( wp_idea_stream_get_root_url() ) ) );
	}
}
add_action( 'wp_idea_stream_enqueue_scripts', 'xwara_extra_enqueue_scripts', 20 );

/**
 * Add an extra filter nav after the main one.
 * 
 * Another option for a theme could be to override the
 * /templates/archive.php within its folder 
 * eg: nameoftheme/wp-idea-stream/archive.php
 * 
 * @return string HTML Output.
 */ 
function xwara_extra_filtering_bar() {
	$dropdown_args = array(
		'show_option_none' => __( 'Select Category' ),
		'taxonomy'         => wp_idea_stream_get_category(),
		'id'               => 'select_idea_category',
		'name'             => 'select_idea_category',
	);

	// If viewing a category archive, set the selected dropdown value.
	if ( wp_idea_stream_is_category() ) {
		$dropdown_args['selected'] = wp_idea_stream_get_current_term()->term_id;
	}

	// Output the extra filter nav.
	?>
	<form id="xwara-extra-filters" class="nav-form" action="" method="get">
		<label for="select_idea_category">
			<?php esc_html_e( 'Filter by:', 'custom-text-domain' ); ?>
			<?php wp_dropdown_categories( $dropdown_args ); ?>
		</label>
		<label for="unrated_ideas">
			<input type="checkbox" name="unrated_ideas" id="unrated_ideas" value="1" <?php checked( ! empty( $_GET['unrated_ideas'] ) ); ?>>
			<?php esc_html_e( 'Only show unrated ideas', 'custom-text-domain' ); ?>
		</label>
		
		<div class="submit">
			<input type="submit" value="<?php esc_attr_e( 'Filter', 'custom-text-domain' ); ?>">
		</div>
	</form>
	<?php
}
add_action( 'wp_idea_stream_after_archive_main_nav', 'xwara_extra_filtering_bar' );

/**
 * Edit the main query arguments to only fetch
 * unrated ideas if needed.
 * 
 * @param WP_Query $q The WordPress main Query object.
 */ 
function xwara_parse_query( WP_Query $q ) {
	if ( ! wp_idea_stream_is_idea_archive() && ! wp_idea_stream_is_category() && ! wp_idea_stream_is_tag() ) {
		return;
	}

	if ( empty( $_GET['unrated_ideas'] ) ) {
		return;
	}

	$orderby = $q->get( 'orderby' );

	if ( 'rates_count' === $orderby ) {
		$q->set( 'orderby', 'date' );
	}

	$q->set( 'meta_query', array(
		array(
			'key'     => '_ideastream_average_rate',
			'compare' => 'NOT EXISTS'
		)
	) );
}
add_action( 'parse_query', 'xwara_parse_query', 10 );