From bede558347a4da4b0795ecb35b2b1897f46a4791 Mon Sep 17 00:00:00 2001
From: xenofem <xenofem@xeno.science>
Date: Tue, 9 Sep 2025 20:52:09 -0400
Subject: [PATCH] Switch to a hash-based shuffle so adding new items won't
 change the shuffled order of existing items

---
 dlibrary/static/index.js | 51 ++++++++++++++++++++++------------------
 1 file changed, 28 insertions(+), 23 deletions(-)

diff --git a/dlibrary/static/index.js b/dlibrary/static/index.js
index de74bb0..f8ebcdb 100644
--- a/dlibrary/static/index.js
+++ b/dlibrary/static/index.js
@@ -1,31 +1,36 @@
-const LCG_M = Math.pow(2, 32);
-const LCG_A = 0xd9f5;
-const LCG_C = 69;
-
-function lcg(seed) {
-    let value = seed % LCG_M;
-
-    return (n) => {
-        value = (LCG_A * value + LCG_C) % LCG_M;
-        return Math.floor(n * value / LCG_M);
-    };
+// cyrb53a beta (c) 2023 bryc (github.com/bryc)
+function cyrb53a_beta(str, seed = 0) {
+    let h1 = 0xdeadbeef ^ seed, h2 = 0x41c6ce57 ^ seed;
+    for (const codePoint of str) {
+        ch = codePoint.codePointAt(0);
+        h1 = Math.imul(h1 ^ ch, 0x85ebca77);
+        h2 = Math.imul(h2 ^ ch, 0xc2b2ae3d);
+    }
+    h1 ^= Math.imul(h1 ^ (h2 >>> 15), 0x735a2d97);
+    h2 ^= Math.imul(h2 ^ (h1 >>> 15), 0xcaf649a9);
+    h1 ^= h2 >>> 16;
+    h2 ^= h1 >>> 16;
+    return 2097152 * (h2 >>> 0) + (h1 >>> 11);
 }
 
-function seedableShuffledCopy(list, seed) {
-    const gen = lcg(seed);
-    const l = [...list];
+const SEED_BOUND = Math.pow(2, 32);
 
-    for (let i = 0; i < l.length - 1; ++i) {
-        j = i + gen(l.length - i);
-        const tmp = l[i];
-        l[i] = l[j];
-        l[j] = tmp;
-    }
-    return l;
+function seedableShuffledCopy(list, key, seed) {
+    const hashedIndices = list.map((elem, idx) => ({ idx, hash: cyrb53a_beta(key(elem), seed) }));
+    hashedIndices.sort((a, b) => {
+        if (a.hash > b.hash) {
+            return 1;
+        }
+        if (a.hash < b.hash) {
+            return -1;
+        }
+        return 0;
+    });
+    return hashedIndices.map((entry) => list[entry.idx]);
 }
 
 function newSeed() {
-    return Math.floor(Math.random() * LCG_M);
+    return Math.floor(Math.random() * SEED_BOUND);
 }
 
 let receivedStore = JSON.parse(localStorage.getItem('receivedStore')) || {};
@@ -96,7 +101,7 @@ function setupIndex() {
 
         switch (ordering) {
         case 'shuffle':
-            orderedWorks = seedableShuffledCopy(WORKS, shuffleSeed);
+            orderedWorks = seedableShuffledCopy(WORKS, (work) => work.id, shuffleSeed);
             break;
         case 'dateAsc':
             orderedWorks = WORKS.toReversed();