How to condition TYPO3 Solr sortBy

We have a TYPO3 project and use SOLR as search engine. I'm wondering how does an if-statement/conditional look like in the config files written in TypoScript?

TYPO3: 8.7 Apache Solr for TYPO3 - ES: 7.5.3

for example: we use

plugin.tx_solr.search.query.sortBy = data_datax_title_stringS asc

as sort setting for the following facet block:

plugin.tx_solr.search.faceting.facets {

but we only want that sorting if a certain part of the url query string is empty (q= or q=Searchtext)

so the sortBy should be applied if the query string looks like

http://localhost/?tx_solr%5Bq%5D=&L=0&id=2883

and should not be applied on

http://localhost/?tx_solr%5Bq%5D=Searchtext&L=0&id=2883

here is the actual block:

[globalVar = TSFE:id={$site.config.search_page_blasts}]

    plugin.tx_solr.search.targetPage = {$site.config.search_page_blasts}

config.defaultGetVars {
    tx_solr.filter.0 = result_type_filter:blast
}

plugin.tx_solr.search.query.sortBy = dynamic_field_A_stringS asc
plugin.tx_solr.search.faceting.facets {

    facetX < lib.solr.facets.directBlast
    facetX.field = dynamic_field_X_boolS

}

Any help is highly appreciated.

edit: I found

plugin.tx_solr.search.query.getParameter = q

but this only defines the name for the query get-parameter in case another service needs a specific name. But I would need the value of this parameter and condition the sortBy by its value.

edit:

after some research I'm now at this state: the sort works if a query string is set - but not if its empty

[globalVar = GP:q = ""]
    plugin.tx_solr.search.query.sortBy = wine_winery_title_stringS asc
[else]
    plugin.tx_solr.search.query.sortBy =
[end]

[globalVar = TSFE:id={$site.config.search_page_wineries}]
    plugin.tx_solr.search.targetPage = {$site.config.search_page_wineries}

    config.defaultGetVars {
        tx_solr.filter.0 = result_type_filter:winery
    }


    plugin.tx_solr.search.faceting.facets {

        direct_sale < lib.solr.facets.directSale
        direct_sale.field = winery_direct_sale_boolS

I don't really know how to format this the right way - nested conditions are not supported right?

Solution

I ended up extending the outer condition and just having two blocks for that page - it feels redundant but works perfectly fine. The condition outside of the existing one was not working - and nested conditions were not possible.

So here is the solution:

With globalString to use regex for comparison

[globalVar = TSFE:id={$site.config.search_page_x}] && [globalString = GP:tx_solr|q = /.+/]

And globalVar for an empty parameter

[globalVar = TSFE:id={$site.config.search_page_x}] && [globalVar = GP:tx_solr|q =]

Hope I can save someone a little time researching - thanks to everyone for their input.