Merge pull request #3973 from overleaf/as-clean-up-hue-generator

Clean up hue generator

GitOrigin-RevId: 1b7fad05d7c2f6519efbbe0379f2449c273e4f4b

services/web/frontend/js/shared/utils/colors.js

@@ -0,0 +1,38 @@
+import md5 from 'crypto-js/md5'
+
+const ANONYMOUS_HUE = 100
+const OWN_HUE = 200 // We will always appear as this color to ourselves
+const OWN_HUE_BLOCKED_SIZE = 20 // no other user should have a HUE in this range
+const TOTAL_HUES = 360 // actually 361, but 360 for legacy reasons
+
+export function getHueForUserId(userId, currentUserId) {
+  if (userId == null || userId === 'anonymous-user') {
+    return ANONYMOUS_HUE
+  }
+
+  if (currentUserId === userId) {
+    return OWN_HUE
+  }
+
+  let hue = getHueForId(userId)
+
+  // if `hue` is within `OWN_HUE_BLOCKED_SIZE` degrees of the personal hue
+  // (`OWN_HUE`), shift `hue` to the end of available hues by adding
+  if (
+    hue > OWN_HUE - OWN_HUE_BLOCKED_SIZE &&
+    hue < OWN_HUE + OWN_HUE_BLOCKED_SIZE
+  ) {
+    hue = hue - OWN_HUE // `hue` now at 0 +/- `OWN_HUE_BLOCKED_SIZE`
+    hue = hue + TOTAL_HUES - OWN_HUE_BLOCKED_SIZE
+  }
+
+  return hue
+}
+
+function getHueForId(id) {
+  const hash = md5(id)
+  const hue =
+    parseInt(hash.toString().slice(0, 8), 16) %
+    (TOTAL_HUES - OWN_HUE_BLOCKED_SIZE * 2)
+  return hue
+}