I have really tried my best but nothing is working out,

I want to replace my wp search permalink [spaces] and + to -

Example:

 love you

to

and also

+love+you

to

I found a plugin that can do that but I dont need plugin, I just need this on my theme function

Here is the link of code from the plugin that I think did it.

/**
 * Replace the search permallink.
 *
 * @param array $search_rewrite
 * @return string
 */
function ssp_change_search_permalink( $search_rewrite ) {
    global $ssp_settings;

    if( ! is_array( $search_rewrite ) ) {
        return $search_rewrite;
    }

    $new_rewrite = array();

    foreach ( $search_rewrite as $pattern => $s ) {
        $regex = str_replace( 'search/', "$ssp_settings[ssp_permalink]/", $pattern );
        $new_rewrite[$regex] = $s;
    }

    $search_rewrite = $new_rewrite;

    unset( $new_rewrite );

    return $search_rewrite;
}

/**
 * Redirect the search query to the new search permallink URL.
 */
function ssp_search_redirect() {
    global $wp_rewrite, $ssp_settings;

    if (   ! isset( $wp_rewrite ) 
        || ! is_object( $wp_rewrite ) 
        || ! $wp_rewrite->using_permalinks() 
        || ! isset( $_SERVER['REQUEST_URI'] ) 
        || '' === $ssp_settings['ssp_permalink'] 
    ) {
        return;
    }

    $search_base = $wp_rewrite->search_base;

    if ( is_search() && ! is_admin() && false === strpos( $_SERVER['REQUEST_URI'], "/$ssp_settings[ssp_permalink]/" ) ) {
        $search_query_vars = ssp_filter_spec_chars( get_query_var('s') );
        $search_query_vars = ssp_filter_bad_words( $search_query_vars );

        switch ( $ssp_settings['ssp_separate_symbol_option'] ) {
            case 1: $search_query_vars = str_replace( ' ', '+', $search_query_vars ); break;
            case 2: $search_query_vars = str_replace( ' ', '-', $search_query_vars ); break;
            case 3: $search_query_vars = str_replace( ' ', '/', $search_query_vars ); break;
            case 4: $search_query_vars = str_replace( ' ', '_', $search_query_vars ); break;
        }
        if ( 2 === $ssp_settings['ssp_letter_type_option'] ) {
            $search_query_vars = strtolower( $search_query_vars );
        }
        wp_redirect( home_url( "/$ssp_settings[ssp_permalink]/" . $search_query_vars ) );
        exit();
    }
}

/**
 * Keep search structure.
 * 
 * @param $object $query
 */
function ssp_keep_structure( $query ) {
    global $wp_query;

    if ( $query->get('s') && empty( $_GET['s'] ) && $wp_query->is_main_query() ) {

        $s_vars_tmp          = urldecode( $query->get('s') );
        $ssp_separate_symbol = array( '/', '_', '+', '-' );
        $s_vars_tmp          = str_replace( $ssp_separate_symbol, ' ', $s_vars_tmp );

        $query->set( 's', $s_vars_tmp );
    }
}

/**
 * Remove unwanted characters.
 *
 * @param string $query_strings
 * @return string
 */
function ssp_filter_spec_chars($query_strings) {
    global $ssp_settings;

    if ( $ssp_settings['ssp_filter_character_option'] == 2 ) {
        $ssp_unwanted_characters = array( '"', "'", '[', ']', '~', '=', ',', '*', '&', '^', '$', '#', '@', '!', '<', '>', ';', '.', '|', '/', '+', '-', '_' );
    }
    if ( is_array( $ssp_unwanted_characters ) ) {
        $query_strings = trim( str_replace( $ssp_unwanted_characters, ' ', $query_strings ) );
    }

    return $query_strings;
}

/**
 * Remove bad words.
 *
 * @param string $query_strings
 * @return string
 */
function ssp_filter_bad_words( $query_strings ) {
    if ( '' !== $ssp_settings['ssp_filter_words'] ) {
        $ssp_bad_words = explode( ',', $ssp_settings['ssp_filter_words'] );
        $query_strings = str_replace( $ssp_bad_words, ' ', $query_strings );
    }
    $query_strings = preg_replace( '/\s{2,}/', ' ', $query_strings );

    return $query_strings;
}

//============================================

if ( ! defined( 'WPINC' ) ) {
    die;
}

/**
 * Assign default setting values while activating SSP.
 */
function ssp_admin_activation() {
    add_option( 'ssp_permalink', '' );
    add_option( 'ssp_letter_type_option', '1' );
    add_option( 'ssp_filter_words', '' );
    add_option( 'ssp_filter_character_option', '1' );
    add_option( 'ssp_separate_symbol_option', '1' );
}

// Activating plugin.
register_activation_hook( plugin_dir_path( __FILE__ ), 'ssp_admin_activation' );

/**
 * Register the plugin setting page.
 */
function ssp_admin_option_hook() {

    if ( function_exists( 'add_options_page' ) ) {
        add_options_page(
            __( 'SEO Search Permalink', 'ssp-plugin' ),
            __( 'SEO Search Permalink', 'ssp-plugin' ),
            'manage_options',
            'seo-search-permalink.php',
            'ssp_administrator_page'
        );
    }
}

// Load SSP settings.
$ssp_settings = array(
    'ssp_permalink'               => get_option( 'ssp_permalink' ),
    'ssp_filter_words'            => get_option( 'ssp_filter_words' ),
    'ssp_filter_character_option' => get_option( 'ssp_filter_character_option' ),
    'ssp_separate_symbol_option'  => get_option( 'ssp_separate_symbol_option' ),
    'ssp_letter_type_option'      => get_option( 'ssp_letter_type_option' )
);

function ssp_init() {

    load_plugin_textdomain( 'seo-search-permalink', false, basename( dirname( __FILE__ ) ) . '/languages' ); 

    // Only load SSP setting page in admin panel.
    if ( is_admin() ) {
        require_once plugin_dir_path( __FILE__ ) . 'inc/setting.php';

        // Detect form submitting in setting page.
        ssp_update_form_options();
    }

    // Load SSP functions.
    require_once plugin_dir_path( __FILE__ ) . 'inc/functions.php';

    // The magical things are happened here.
    add_filter( 'search_rewrite_rules', 'ssp_change_search_permalink' );
    add_action( 'admin_menu', 'ssp_admin_option_hook' );
    add_action( 'template_redirect', 'ssp_search_redirect' );
    add_action( 'pre_get_posts', 'ssp_keep_structure' );
}

add_action( 'init', 'ssp_init' );

But I dont need want to use plugin, Please gurus in the house help me out,

Is there anyway I can modify this line of code to work on theme function from the above task I mention?