From 743d7fa7828cc8d03a1c98bf1e42ab3843ef32b5 Mon Sep 17 00:00:00 2001
From: Alex Christoffer Rasmussen <ac@omnivox.dk>
Date: Mon, 6 Jan 2025 13:12:03 +0100
Subject: [PATCH] fix: validateLinkStart (#1430)

* fix validateLinkStart

* update comment

* use fallback

* cast to MaybeString

* update comment

Co-authored-by: Carlos Valente <34649812+cpvalente@users.noreply.github.com>

---------

Co-authored-by: Carlos Valente <34649812+cpvalente@users.noreply.github.com>
---
 apps/server/src/utils/parser.ts                     |  2 +-
 packages/utils/src/validate-events/validateEvent.ts | 10 +++++++---
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/apps/server/src/utils/parser.ts b/apps/server/src/utils/parser.ts
index 3caf5e311..f76c1f73f 100644
--- a/apps/server/src/utils/parser.ts
+++ b/apps/server/src/utils/parser.ts
@@ -376,7 +376,7 @@ export function createPatch(originalEvent: OntimeEvent, patchEvent: Partial<Onti
     timeEnd,
     duration,
     timeStrategy,
-    linkStart: validateLinkStart(patchEvent.linkStart),
+    linkStart: validateLinkStart(patchEvent.linkStart, originalEvent.linkStart),
     endAction: validateEndAction(patchEvent.endAction, originalEvent.endAction),
     timerType: validateTimerType(patchEvent.timerType, originalEvent.timerType),
     countToEnd: typeof patchEvent.countToEnd === 'boolean' ? patchEvent.countToEnd : originalEvent.countToEnd,
diff --git a/packages/utils/src/validate-events/validateEvent.ts b/packages/utils/src/validate-events/validateEvent.ts
index 89e661eab..f6601af5d 100644
--- a/packages/utils/src/validate-events/validateEvent.ts
+++ b/packages/utils/src/validate-events/validateEvent.ts
@@ -2,12 +2,16 @@ import type { MaybeString } from 'ontime-types';
 import { EndAction, TimerType, TimeStrategy } from 'ontime-types';
 
 /**
- * Check if a given value is a valid type of string, returns null otherwise
+ * Check if a given value is a valid type linkStart, returns the fallback otherwise
+ * linkStart can be a string (id of an event to link) or null (unlinked)
  * @param {MaybeString} maybeLinkStart
  * @returns {MaybeString}
  */
-export function validateLinkStart(maybeLinkStart: unknown): MaybeString {
-  return typeof maybeLinkStart === 'string' ? maybeLinkStart : null;
+export function validateLinkStart(maybeLinkStart: unknown, fallback: MaybeString = null): MaybeString {
+  if (typeof maybeLinkStart === 'string' || maybeLinkStart === null) {
+    return maybeLinkStart as MaybeString;
+  }
+  return fallback;
 }
 
 /**