From 31ec544522f1d706503cd0b5587ae67a182cbe50 Mon Sep 17 00:00:00 2001
From: Andre Staltz <andre@staltz.com>
Date: Tue, 26 Sep 2023 15:31:19 +0300
Subject: [PATCH] fix tangle getShortestPath against cycles

---
 lib/msg-v3/tangle.js | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/lib/msg-v3/tangle.js b/lib/msg-v3/tangle.js
index a540ecb..96cdc3e 100644
--- a/lib/msg-v3/tangle.js
+++ b/lib/msg-v3/tangle.js
@@ -228,14 +228,21 @@ class Tangle {
     }
     const path = []
     let current = msgID
+    let lastPrev = undefined
     while (true) {
       const prev = this.#prev.get(current)
       if (!prev) break
+      if (prev === lastPrev) {
+        // prettier-ignore
+        throw new Error(`Tangle "${this.#rootID}" has a cycle or lacking a trail to root`)
+      } else {
+        lastPrev = prev
+      }
       let minDepth = /** @type {number} */ (this.#depth.get(current))
       let min = current
       for (const p of prev) {
         const d = /** @type {number} */ (this.#depth.get(p))
-        if (d < minDepth) {
+        if (typeof d === 'number' && d < minDepth) {
           minDepth = d
           min = p
         } else if (d === minDepth && compareMsgIDs(p, min) < 0) {