Pre-processing Redux state (location for business logic) - redux

Question

I have created an application in react, which has the purpose to find flights and display them in a results window. With filter settings in the sidebar, you are able to filter these results. Currently I am converting the react app to Redux.
I have the following state in my store:
const defaultState = {
flightOffers,
filteredFlightOffers,
filters
}
Where flightOffers is an array of objects with flightresults:
flightOffers = [{
"inboundFlight": {
"departureDate": "2016-06-02",
"departureTime": "09:00",
"departureTimeSpan": "morning",
"arrivalDate": "2016-06-02",
"arrivalTime": "12:32",
"arrivalTimeSpan": "afternoon",
"marketingAirline": {
"companyShortName": "KL",
"name": KLM,
"imageurl": "images/logos/kl.png"
},
"flightNumber": 5131,
"departureAirport": {
"locationCode": "BCN",
"name": "Barcelona"
},
"arrivalAirport": {
"locationCode": "AMS",
"name": "Amsterdam"
}},
];
The state of filteredFlightOffers is the same, but a subset of the flightOffers state object.
And the filters state object has the following format:
filters = [{
"type": "airlines",
"checked": true,
"label": "Air France",
"count": 579
},
{
"type": "airlines",
"checked": true,
"label": "Brittish Airways",
"count": 554
},
{
"type": "airlines",
"checked": true,
"label": "CityJet",
"count": 576
}
];
The flightOffers state object is retrieved by an API call.
The filteredFlightOffers state object should be created based on all the checked / non-checked items in the filters state object, and should be recreated every time a filter is changed.
The filter stateobject will have a changed checked value every time an item is clicked, but also updated count items for all elements every time the new filteredFlightOffers state object is recreated.
Now I have the following questions:
My filters state object is derived from the flightOffers state object and should be created on the fly when the data from the flightOffers is retreived by the API call. Where in the redux pattern is the good place to implement this logic?
I have a dispatcher for my flightOffers state and for my settings state. When a filter setting is clicked, an action will go to the filter dispatcher and return the new filter state. But how can I calculate all the new filter counts based on the flightOffer state? e.g. Do I need to fire a FlightOfferCounter action and give the filter state as input parameter? If so, can I fire this call from my filter reducer? Or do I have to create a FlightOfferCounter reducer which listenes to the same action as the filter reducer? Problem then would be that these reducers cannot be executed in parallel since the flightOfferCounter is based on the checked values in the filter state.
I am reading things about redux thunk (for implementing business logic). Is that something I need here?
Hope my questions are a bit clear.