Daily allowance calculation by country, city and start and end dates

gistfile1.clj

(def country-list
  {:fi {:default {:full 3900 :big 2600 :small 1300}}
   :de {:default {:full 2400 :big 1200 :small 600}}
   :uk {:default {:full 4200 :big 2800 :small 1400}
        :london  {:full 5700 :big 3800 :small 1900}}})

(defn country-allowance
  ([country]
    (country-allowance country "default"))
  ([country city]
    (if-let [c ((keyword country) country-list)]
      (get c (keyword city) (:default c))
      (throw (Exception. "You fool!")))))

(defn end-of-day
  "return end of the day (midnight)"
  [day]
  (ct/plus (ct/date-time (ct/year day) (ct/month day) (ct/day day)) (ct/days 1)))

(defn start-of-day
  "return start of the day (midnight)"
  [day]
  (ct/date-time (ct/year day) (ct/month day) (ct/day day)))

(defn big-small
  [interval]
  (let [h (ct/in-hours interval)]
    (cond
     (>= 14 h 8) {:full 0 :small 1 :big 0}
     (> h 14) {:full 0 :small 0 :big 1}
     :else {:full 0 :small 0 :big 0})))


(defn allowance-days
  "takes start and end and returns allowance days"
  [start end]
  (let [end-of-first (end-of-day start)
        end-of-last (end-of-day end)]
    (if (not= end-of-first end-of-last)
      (let [start-of-last (start-of-day end)
            fd (ct/in-days (ct/interval end-of-first start-of-last))
            edges (map big-small [(ct/interval start end-of-first) (ct/interval start-of-last end)])]
        (merge-with + {:full fd :big 0 :small 0} (nth edges 0) (nth edges 1)))
    (big-small (ct/interval start end)))))

(defn calc-allowance
  [claim]
  (let [ca (country-allowance (:destinationCountry claim) (:destinationCity claim))
        adays (allowance-days (:startDate claim) (:endDate claim))]
    (->> 
      (merge-with * ca adays)
      vals
      (reduce +))))

Credits to @ovan !