From 1d33b1f7dce0a88e462766f462251101c468b373 Mon Sep 17 00:00:00 2001
From: Janpeter Visser <janpetervisser2@gmail.com>
Date: Fri, 24 Apr 2026 22:11:54 +0200
Subject: [PATCH] Add documentation for float sort_order pattern

Document the float sort_order pattern with TypeScript examples for calculating sort order and reindexing when precision is low.
---
 patterns/sort-order.md | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 patterns/sort-order.md

diff --git a/patterns/sort-order.md b/patterns/sort-order.md
new file mode 100644
index 0000000..5fd6d94
--- /dev/null
+++ b/patterns/sort-order.md
@@ -0,0 +1,29 @@
+# Patroon: Float sort_order (drag-and-drop volgorde)
+
+## Berekening bij tussenvoeging
+
+```ts
+function getSortOrder(before: number | null, after: number | null): number {
+  if (before === null && after === null) return 1.0
+  if (before === null) return after! / 2
+  if (after === null) return before + 1.0
+  return (before + after) / 2
+}
+```
+
+## Herindexeer als precisie opraakt
+
+Trigger wanneer het kleinste verschil tussen twee opeenvolgende items < 0.001 is.
+
+```ts
+async function reindexIfNeeded(items: { id: string; sort_order: number }[]) {
+  const minGap = Math.min(...items.slice(1).map((item, i) =>
+    item.sort_order - items[i].sort_order
+  ))
+  if (minGap < 0.001) {
+    await Promise.all(items.map((item, i) =>
+      prisma.pbi.update({ where: { id: item.id }, data: { sort_order: i + 1.0 } })
+    ))
+  }
+}
+```