From 77e0845a714914058383258d6ccadcc9b4a7e212 Mon Sep 17 00:00:00 2001
From: jessikitty <jess.rogerson.29@outlook.com>
Date: Fri, 14 Aug 2026 21:53:36 +1000
Subject: [PATCH] =?UTF-8?q?v3:=20hardened=20opencv.js=20loader=20=E2=80=94?=
 =?UTF-8?q?=20fetch=20with=20download=20progress,=20robust=20runtime=20det?=
 =?UTF-8?q?ection,=2045s=20failover,=20retryable?=
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---
 public/js/ar/solve-cv.js | 80 ++++++++++++++++++++++++++++------------
 1 file changed, 57 insertions(+), 23 deletions(-)

diff --git a/public/js/ar/solve-cv.js b/public/js/ar/solve-cv.js
index 7b79ee3..4e2a295 100644
--- a/public/js/ar/solve-cv.js
+++ b/public/js/ar/solve-cv.js
@@ -26,32 +26,66 @@ export function isCvReady() { return !!(_cv && _cv.Mat); }
 export function getCv() { return _cv; }
 export function _injectCv(m) { _cv = m; }   // test hook (node)
 
-export function loadOpenCV(url = '/vendor/opencv.js') {
+export function loadOpenCV(url = '/vendor/opencv.js', onProgress = null) {
   if (isCvReady()) return Promise.resolve(_cv);
   if (_loading) return _loading;
-  _loading = new Promise((resolve, reject) => {
-    const s = document.createElement('script');
-    s.src = url;
-    s.async = true;
-    s.onerror = () => reject(new Error('opencv.js failed to load'));
-    s.onload = () => {
+  _loading = (async () => {
+    // 1) download with progress (13MB — visitors on exhibit wifi deserve a %)
+    const resp = await fetch(url);
+    if (!resp.ok) throw new Error(`opencv.js HTTP ${resp.status}`);
+    const total = +resp.headers.get('content-length') || 0;
+    let blob;
+    if (resp.body && resp.body.getReader) {
+      const reader = resp.body.getReader();
+      const chunks = [];
+      let got = 0;
+      for (;;) {
+        const { done, value } = await reader.read();
+        if (done) break;
+        chunks.push(value); got += value.length;
+        if (onProgress) onProgress(total ? Math.round(got / total * 100) : Math.round(got / 1e6) + 'MB');
+      }
+      blob = new Blob(chunks, { type: 'text/javascript' });
+    } else {
+      blob = await resp.blob();
+    }
+    // 2) evaluate
+    if (onProgress) onProgress('init');
+    const src = URL.createObjectURL(blob);
+    try {
+      await new Promise((res, rej) => {
+        const s = document.createElement('script');
+        s.src = src;
+        s.onload = res;
+        s.onerror = () => rej(new Error('opencv.js eval failed'));
+        document.head.appendChild(s);
+      });
+    } finally {
+      setTimeout(() => URL.revokeObjectURL(src), 5000);
+    }
+    // 3) resolve the runtime — window.cv may be the module, a thenable that
+    //    resolves to it, or get swapped mid-init depending on the emscripten
+    //    build. Poll fresh every tick; hard 45s ceiling so a hang becomes a
+    //    visible failover instead of an eternal "loading".
+    const t0 = performance.now();
+    let thenAttached = false;
+    for (;;) {
       const mod = window.cv;
-      const finish = (m) => { _cv = m; resolve(m); };
-      if (!mod) return reject(new Error('opencv.js loaded but window.cv missing'));
-      if (mod.Mat) return finish(mod);                    // already initialized
-      if (typeof mod.then === 'function') return mod.then(finish, reject); // promise build
-      mod.onRuntimeInitialized = () => finish(mod);       // classic emscripten
-      // safety: poll in case onRuntimeInitialized was already consumed
-      const t0 = performance.now();
-      (function poll() {
-        if (_cv) return;
-        if (mod.Mat) return finish(mod);
-        if (performance.now() - t0 > 30000) return reject(new Error('opencv.js init timeout'));
-        setTimeout(poll, 100);
-      })();
-    };
-    document.head.appendChild(s);
-  });
+      if (mod && mod.Mat) { _cv = mod; return mod; }
+      if (mod && typeof mod.then === 'function' && !thenAttached) {
+        thenAttached = true;
+        mod.then((m) => { if (m && m.Mat) { window.cv = m; } }, () => {});
+      }
+      if (mod && !mod.Mat && typeof mod.then !== 'function' && !mod.__nbxHook) {
+        mod.__nbxHook = true;
+        const prev = mod.onRuntimeInitialized;
+        mod.onRuntimeInitialized = () => { if (typeof prev === 'function') prev(); };
+      }
+      if (performance.now() - t0 > 45000) throw new Error('opencv.js init timeout');
+      await new Promise(r => setTimeout(r, 100));
+    }
+  })();
+  _loading.catch(() => { _loading = null; });   // allow retry after failure
   return _loading;
 }