;; This program asks the user to select Fahrenheit or Celsius conversion
;; and input a given temperature. Then the program converts the given 
;; temperature and displays the result.
;;
;; References:
;;     https://www.mathsisfun.com/temperature-conversion.html

(defn get-choice []
  (println "Enter C to convert to Celsius or F to convert to Fahrenheit:")
  (let [choice (read-line)]
    choice))

(defn get-temperature [choice]
  (println "Enter" choice "temperature:")
  (let [temperature (Float/parseFloat (read-line))]
    temperature))

(defn display-error []
   (println "You must enter C to convert to Celsius or F to convert to Fahrenheit."))

(defn calculate-celsius [temperature]
  (let [result
    (-> temperature
      (* 9)
      (/ 5)
      (+ 32))]
    result))

(defn calculate-fahrenheit [temperature]
  (def result (+(/(* temperature 9)5)32))
  result)

(defn display-result [temperature from-label result to-label]
  (println (str temperature "° " from-label "is " result "° " to-label ".")))

(defn main []
  (def choice (get-choice))  
  (cond 
    (or (= choice "C") (= choice "c"))
    (do
      (def temperature (get-temperature "Fahrenheit"))
      (def result (calculate-celsius temperature))
      (display-result temperature "Fahrenheit" result "Celsius"))
    (or (= choice "F") (= choice "f"))
    (do
      (def temperature (get-temperature "Celsius"))
      (def result (calculate-fahrenheit temperature))
      (display-result temperature "Celsius" result "Fahrenheit"))
    :else
      (display-error)))

(main)