From db76865ccee3cc09706c225752d45fa1d475a14b Mon Sep 17 00:00:00 2001
From: maelstrom <maelstrom@maelstrom.dev>
Date: Fri, 1 May 2026 22:41:31 +0200
Subject: [PATCH] validation code

---
 src/lib/post.ts | 52 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/src/lib/post.ts b/src/lib/post.ts
index 1754a38..d2869c9 100644
--- a/src/lib/post.ts
+++ b/src/lib/post.ts
@@ -22,4 +22,54 @@ export type ThreadPost = Post & {
   // The CID as it was, referenced by the current thread
   // Can be compared with the current cid to check if a post has been edited
   contextCid: CidString;
-};
\ No newline at end of file
+};
+
+function refsEqual(ref1?: strongRef.Main, ref2?: strongRef.Main) {
+  return ref1?.uri === ref2?.uri && ref1?.cid === ref2?.cid
+}
+
+export function validatePost(post: Post) {
+  // Require threadless posts to be not have a thread chain
+  if (post.thread.length === 0 && post.reblog !== undefined)
+    return false
+
+  // First item in thread must match root, last item must match parent
+  if (post.thread.length > 0 && (post.reblog === undefined || !refsEqual(post.reblog.root, post.thread.at(0)) || !refsEqual(post.reblog.parent, post.thread.at(-1))))
+    return false
+
+  return true
+}
+
+// TODO: Actually use this somewhere
+export function validatePostThread(threadRefs: Post['thread'], threadItems: ThreadPost[]) {
+  // Each thread item must either be undefined (not found by us), or:
+  // 1. Must be valid
+  // 2. Thread field must match threadRefs[0:i]
+
+  function validateThreadRefs(bottomThreadRefs: Post['thread'], itemThreadRefs: Post['thread'], itemIndex: number) {
+    // The number of thread refs each post has must reflect its position in the chain
+    if (itemThreadRefs.length !== itemIndex) return false
+
+    for (const [i] of itemThreadRefs.entries()) {
+      if (bottomThreadRefs[i] !== itemThreadRefs[i]) {
+        return false
+      }
+    }
+    return true
+  }
+
+  for (const [i] of threadRefs.entries()) {
+    const threadItem = threadItems[i]
+
+    // If the item is not found by us, don't check it
+    if (threadItem === undefined) continue;
+
+    // Otherwise, validate it
+    if (!validatePost(threadItem)) return false;
+
+    // Validate the thread refs
+    if (!validateThreadRefs(threadRefs, threadItem.thread, i)) return false
+  }
+
+  return true
+}
\ No newline at end of file
-- 
2.51.2