Clean up code and show number diffs

src/need_for_speed/results.cljs

@@ -4,19 +4,72 @@
    [need-for-speed.data :as data]
    [need-for-speed.form :as form]))
 
+(defn fuel-consumption-multiplier [speed]
+  (Math/pow 1.009 (dec speed)))
+
+(defn fuel-per-100km [base-consumption speed]
+  (* base-consumption (fuel-consumption-multiplier speed)))
+
+(defn total-fuel [consumption distance]
+  (* consumption (/ distance 100)))
+
+(defn total-time [distance speed]
+  (/ distance speed))
+
+(def format-number
+  (let [formatter (js/Intl.NumberFormat. "en" #js {:minimumFractionDigits 2
+                                                   :maximumFractionDigits 2})]
+    (fn [number]
+      (.format formatter number))))
+
+(def diff-numbers
+  (let [formatter (js/Intl.NumberFormat. "en" #js {:signDisplay "always"
+                                                   :minimumFractionDigits 2
+                                                   :maximumFractionDigits 2})]
+    (fn [x y]
+      (let [number (- x y)]
+        (if (= 0 number)
+          "±0"
+          (.format formatter number))))))
+
 (defn view []
-  (let [base-fuel (-> (@form/state :car) data/cars :consumption)
-        distance (@form/state :distance)
-        speed-x (@form/state :speed-x)
-        speed-x-multiplier (Math/pow 1.009 (dec speed-x))
-        speed-y (@form/state :speed-y)
-        speed-y-multiplier (Math/pow 1.009 (dec speed-y))
-        fuel-x-per-100 (* (/ distance 100) base-fuel speed-x-multiplier)
-        fuel-y-per-100 (* (/ distance 100) base-fuel speed-y-multiplier)
-        time-x (/ distance speed-x)
-        time-y (/ distance speed-y)]
-    [:div
-     [:div (gstring/format "Fuel at speed X: %.2f litres" fuel-x-per-100)]
-     [:div (gstring/format "Fuel at speed Y: %.2f litres" fuel-y-per-100)]
-     [:div (gstring/format "Time at speed X: %.2f hours" time-x)]
-     [:div (gstring/format "Time at speed Y: %.2f hours" time-y)]]))
+  (let [{:keys [car distance speed-x speed-y]} @form/state
+        base-fuel (-> car data/cars :consumption)
+        fuel-x-per-100km (fuel-per-100km base-fuel speed-x)
+        fuel-y-per-100km (fuel-per-100km base-fuel speed-y)
+        fuel-x (total-fuel fuel-x-per-100km distance)
+        fuel-y (total-fuel fuel-y-per-100km distance)
+        time-x (total-time distance speed-x)
+        time-y (total-time distance speed-y)]
+    [:pre.mt-4
+     [:div
+      (gstring/format "Fuel per 100km at %d km/h: %s litres (%s)"
+                      speed-x
+                      (format-number fuel-x-per-100km)
+                      (diff-numbers fuel-x-per-100km fuel-y-per-100km))]
+     [:div
+      (gstring/format "Total fuel     at %d km/h: %s litres (%s)"
+                      speed-x
+                      (format-number fuel-x)
+                      (diff-numbers fuel-x fuel-y))]
+     [:div
+      (gstring/format "Total time     at %d km/h: %s hours (%s)"
+                      speed-x
+                      (format-number time-x)
+                      (diff-numbers time-x time-y))]
+     [:hr.my-4]
+     [:div
+      (gstring/format "Fuel per 100km at %d km/h: %s litres (%s)"
+                      speed-y
+                      (format-number fuel-y-per-100km)
+                      (diff-numbers fuel-y-per-100km fuel-x-per-100km))]
+     [:div
+      (gstring/format "Total fuel     at %d km/h: %s litres (%s)"
+                      speed-y
+                      (format-number fuel-y)
+                      (diff-numbers fuel-y fuel-x))]
+     [:div
+      (gstring/format "Total time     at %d km/h: %s hours (%s)"
+                      speed-y
+                      (format-number time-y)
+                      (diff-numbers time-y time-x))]]))