refactor: replace hash-based license badge coloring with a deterministic, collision-resistant palette based on sort order

apps/backoffice/src/app/features/certificate-requirements/components/PersonalDocumentsCard.tsx

@@ -49,32 +49,62 @@ const SEARCH_DEBOUNCE_MS = 300;
 /**
  * Badge colours for licence types.
  *
- * Red and yellow are left out on purpose: they read as a problem, and a
- * licence type is not one. Green is out too — it means verified elsewhere in
- * the backoffice.
+ * Red is left out: it reads as a problem, and a licence type is not one.
+ * Everything else the theme offers is in, because the point of the colour is
+ * telling two licence types apart at a glance.
  */
 const SCOPE_COLORS = [
-  'grape',
-  'violet',
-  'indigo',
-  'cyan',
-  'teal',
-  'pink',
-  'orange',
   'blue',
+  'grape',
+  'teal',
+  'orange',
+  'violet',
+  'cyan',
+  'pink',
+  'lime',
+  'indigo',
+  'green',
+  'yellow',
+  'gray',
 ];
 
+/** Doubles the palette: the same hue, a visibly different badge. */
+const SCOPE_VARIANTS = ['light', 'outline'] as const;
+
 /**
- * The same licence type keeps the same colour on every row and every visit —
- * derived from its id rather than its position, so a colour is something the
- * eye can learn instead of a lottery per render.
+ * A colour per licence type, assigned by position in the catalogue.
+ *
+ * Hashing the id looked tidier and was wrong: eight buckets over sixteen
+ * licence types collide by the pigeonhole principle, so Vessel Registration
+ * and Freight Forwarder came out the same colour and the badge stopped
+ * carrying information. Walking the sorted catalogue instead gives every type
+ * a distinct colour until the palette runs out, and only then repeats a hue in
+ * the other variant — 24 distinct badges before any two can look alike.
+ *
+ * Sorted by `sortOrder` so the assignment is the same for every officer and
+ * survives a refresh; a type added later takes the next free style rather than
+ * reshuffling the ones already learned.
  */
-function scopeColor(licenseTypeId: string): string {
-  let hash = 0;
-  for (let i = 0; i < licenseTypeId.length; i += 1) {
-    hash = (hash * 31 + licenseTypeId.charCodeAt(i)) % 997;
-  }
-  return SCOPE_COLORS[hash % SCOPE_COLORS.length];
+function buildScopeStyles(
+  types: { id: string; sortOrder: number }[],
+): Map<string, { color: string; variant: (typeof SCOPE_VARIANTS)[number] }> {
+  const styles = new Map<
+    string,
+    { color: string; variant: (typeof SCOPE_VARIANTS)[number] }
+  >();
+  types
+    .slice()
+    .sort((a, b) => a.sortOrder - b.sortOrder)
+    .forEach((type, index) => {
+      styles.set(type.id, {
+        color: SCOPE_COLORS[index % SCOPE_COLORS.length],
+        variant:
+          SCOPE_VARIANTS[
+            Math.floor(index / SCOPE_COLORS.length) % SCOPE_VARIANTS.length
+          ],
+      });
+    });
+  return styles;
 }
 
 /** `application/vnd.openxmlformats-…-document` is nobody's idea of a column. */
@@ -173,6 +203,11 @@ export function PersonalDocumentsCard() {
     setPageIndex(0);
   }
 
+  const scopeStyles = useMemo(
+    () => buildScopeStyles(licenseTypes?.items ?? []),
+    [licenseTypes],
+  );
+
   const typeName = (id: string) => {
     const found = (licenseTypes?.items ?? []).find((lt) => lt.id === id);
     return found ? localized(found.name) || found.key : id;
@@ -206,11 +241,15 @@ export function PersonalDocumentsCard() {
             </Badge>
           ) : (
             <Group gap={4}>
-              {row.original.scope.map((id) => (
-                <Badge key={id} size="sm" variant="light" color={scopeColor(id)}>
-                  {typeName(id)}
-                </Badge>
-              ))}
+              {row.original.scope.map((id) => {
+                // A type the catalogue no longer lists still needs a badge.
+                const style = scopeStyles.get(id) ?? { color: 'gray', variant: 'light' };
+                return (
+                  <Badge key={id} size="sm" variant={style.variant} color={style.color}>
+                    {typeName(id)}
+                  </Badge>
+                );
+              })}
             </Group>
           ),
       },
@@ -274,9 +313,9 @@ export function PersonalDocumentsCard() {
         ),
       },
     ],
-    // `typeName` closes over the licence-type list, which `localized` also reads.
+    // `typeName` and `scopeStyles` both close over the licence-type list.
     // eslint-disable-next-line react-hooks/exhaustive-deps
-    [t, localized, licenseTypes],
+    [t, localized, licenseTypes, scopeStyles],
   );
 
   /**