add a range compression for the average creepiness

package.json

@@ -21,7 +21,7 @@
     "optimize:png": "find source/images -type f -name '*.png' -print0 | xargs -0 -n 1 -P 6 optipng",
     "optimize": "run-p optimize:**",
     "server": "pipenv run python network-api/manage.py runserver",
-    "start": "npm i && npm run build-uncompressed && run-p server watch:**",
+    "start": "npm i && run-p build-uncompressed server watch:**",
     "snyk": "snyk test --file=package.json",
     "test:procfile": "node test/test-procfile.js",
     "test:eslint": "eslint --config ./.eslintrc.yaml \"source/js/**/*.js\" \"source/js/**/*.jsx\" webpack.config.js",

source/js/buyers-guide/homepage-c-slider.js

@@ -1,13 +1,28 @@
 import CREEPINESS_LABELS from "./components/creepiness-labels.js";
 
-// Height of a single frame, see the
-// ".current-creepiness" rule in homagepage.sccs
-const creepStep = 70;
+// Height of a single frame in the emoji sprite sheet,
+// see the ".current-creepiness" rule in homagepage.sccs
+const EMOJI_FRAME_HEIGHT = 70;
 
-// Total number of frames in our sprite sheet,
-// see the "./source/images/buyers-guide/faces/sprite.png" file
-const totalSteps = 40;
+// Total number of frames in our sprite sheet, see the
+// "./source/images/buyers-guide/faces/sprite.png" file.
+const SPRITE_FRAME_COUNT = 40;
 
+// Our threshold value for which average creepiness ratings
+// still count as "happy face" for the purpose of showing
+// the emoji while scrolling.
+//
+// Note: this is a cosmetic value for scroll only.
+const MINIMUM_HAPPINESS_RATING = 25;
+
+// Our threshold value beyond which everything is super
+// creepy by default.
+//
+// Note: this is a cosmetic value for scroll only.
+const MAXIMUM_CREEPINESS_RATING = 80;
+
+// Helper function to determine whether products are
+// in view, and so need to be considered for averaging.
 function isElementInViewport(element) {
   let rect = element.getBoundingClientRect();
 
@@ -19,6 +34,18 @@ function isElementInViewport(element) {
   );
 }
 
+// map a value from one range to another
+function map(v, s1,e1, s2,e2) {
+  return s2 + (v-s1) * (e2-s2) / (e1-s1);
+}
+
+// cap a value to a range
+function cap(v, m, M) {
+  m = m || 0;
+  M = M || 100;
+  return v < m ? m : v > M ? M : v;
+}
+
 export default {
   init: () => {
     let face = document.querySelector(`.current-creepiness`);
@@ -40,15 +67,18 @@ export default {
 
       let averageCreepiness = visible.reduce( (tally, v) => tally + parseFloat(v.dataset.creepiness)/n, 0);
 
+      // compress the value so that we show a smiley face even for products with a lowish creepiness score.
+      let mappedAverageCreepiness = cap(map(averageCreepiness, MINIMUM_HAPPINESS_RATING, MAXIMUM_CREEPINESS_RATING, 0, 100), 1, 100);
+
       // The averageCreepiness will be in range [1,100] so we can dec1 the
       // valueto make sure we're in frame range [0,frames.length-1]:
-      let frame = Math.round((totalSteps-1) * (averageCreepiness-1)/100);
+      let frame = Math.round((SPRITE_FRAME_COUNT-1) * (mappedAverageCreepiness-1)/100);
 
-      face.style.backgroundPositionY = `${-frame * creepStep}px`;
+      face.style.backgroundPositionY = `${-frame * EMOJI_FRAME_HEIGHT}px`;
 
       // Figure out what the corresponding creepiness label should be:
       let len = CREEPINESS_LABELS.length;
-      let bin = Math.floor(len * (averageCreepiness-1)/100);
+      let bin = Math.floor(len * (mappedAverageCreepiness-1)/100);
 
       if (bin === -1) {
         bubbleText.textContent = ``;