From ef585cc779ec0d70b675a3377fd7ba91acf413f4 Mon Sep 17 00:00:00 2001
From: Felix Roos <flix91@gmail.com>
Date: Sun, 5 Feb 2023 19:15:42 +0100
Subject: [PATCH] basic offline cache

---
 packages/webaudio/package.json |  3 +-
 packages/webaudio/sampler.mjs  | 61 ++++++++++++++++++++++++++--------
 pnpm-lock.yaml                 | 12 +++++++
 3 files changed, 61 insertions(+), 15 deletions(-)

diff --git a/packages/webaudio/package.json b/packages/webaudio/package.json
index 3bc7de38b..a0d8cbdbe 100644
--- a/packages/webaudio/package.json
+++ b/packages/webaudio/package.json
@@ -34,7 +34,8 @@
   },
   "homepage": "https://github.com/tidalcycles/strudel#readme",
   "dependencies": {
-    "@strudel.cycles/core": "workspace:*"
+    "@strudel.cycles/core": "workspace:*",
+    "idb-keyval": "^6.2.0"
   },
   "devDependencies": {
     "vite": "^3.2.2"
diff --git a/packages/webaudio/sampler.mjs b/packages/webaudio/sampler.mjs
index f94b6b5a8..260c658e0 100644
--- a/packages/webaudio/sampler.mjs
+++ b/packages/webaudio/sampler.mjs
@@ -1,5 +1,6 @@
 import { logger, toMidi, valueToMidi } from '@strudel.cycles/core';
 import { getAudioContext } from './index.mjs';
+import { get, set } from 'idb-keyval';
 
 const bufferCache = {}; // string: Promise<ArrayBuffer>
 const loadCache = {}; // string: Promise<ArrayBuffer>
@@ -74,22 +75,37 @@ export const getSampleBufferSource = async (s, n, note, speed, freq) => {
   return bufferSource;
 };
 
-export const loadBuffer = (url, ac, s, n = 0) => {
+const useOfflineCache = true;
+
+export const loadBuffer = async (url, ac, s, n = 0) => {
   const label = s ? `sound "${s}:${n}"` : 'sample';
+  // only load if not already requested (loadCache = cache promises loading buffers by url)
   if (!loadCache[url]) {
-    logger(`[sampler] load ${label}..`, 'load-sample', { url });
-    const timestamp = Date.now();
-    loadCache[url] = fetch(url)
-      .then((res) => res.arrayBuffer())
-      .then(async (res) => {
-        const took = Date.now() - timestamp;
-        const size = humanFileSize(res.byteLength);
-        // const downSpeed = humanFileSize(res.byteLength / took);
-        logger(`[sampler] load ${label}... done! loaded ${size} in ${took}ms`, 'loaded-sample', { url });
-        const decoded = await ac.decodeAudioData(res);
-        bufferCache[url] = decoded;
-        return decoded;
-      });
+    loadCache[url] = (async () => {
+      logger(`[sampler] load ${label}..`, 'load-sample', { url });
+      const timestamp = Date.now();
+      if (useOfflineCache) {
+        const cachedDataUrl = await get(url);
+        if (cachedDataUrl) {
+          // buffer has been loaded into offline cache in a previous session
+          logger(`[sampler] load ${label}... done! found in offline cache!`, 'loaded-sample', { url });
+          return dataUrlToAudioBuffer(ac, cachedDataUrl);
+        }
+      }
+      // buffer not cached offline => fetch from url =>
+      const res = await fetch(url);
+      const buf = await res.arrayBuffer();
+      if (useOfflineCache) {
+        // we don't need to wait for the offline cache to finish here
+        bufferToDataUrl(buf).then((dataUrl) => set(url, dataUrl));
+      }
+      const audioBuffer = await ac.decodeAudioData(buf);
+      const took = Date.now() - timestamp;
+      const size = humanFileSize(buf.byteLength);
+      logger(`[sampler] load ${label}... done! loaded ${size} in ${took}ms`, 'loaded-sample', { url });
+      bufferCache[url] = audioBuffer;
+      return audioBuffer;
+    })();
   }
   return loadCache[url];
 };
@@ -179,3 +195,20 @@ export const resetLoadedSamples = () => {
 };
 
 export const getLoadedSamples = () => sampleCache.current;
+
+async function bufferToDataUrl(buf) {
+  return new Promise((resolve) => {
+    var blob = new Blob([buf], { type: 'application/octet-binary' });
+    var reader = new FileReader();
+    reader.onload = function (event) {
+      resolve(event.target.result);
+    };
+    reader.readAsDataURL(blob);
+  });
+}
+
+function dataUrlToAudioBuffer(ctx, dataUrl) {
+  return fetch(dataUrl)
+    .then((res) => res.arrayBuffer())
+    .then((res) => ctx.decodeAudioData(res));
+}
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index ce03f49cf..d1f9d0464 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -313,9 +313,11 @@ importers:
   packages/webaudio:
     specifiers:
       '@strudel.cycles/core': workspace:*
+      idb-keyval: ^6.2.0
       vite: ^3.2.2
     dependencies:
       '@strudel.cycles/core': link:../core
+      idb-keyval: 6.2.0
     devDependencies:
       vite: 3.2.5
 
@@ -6296,6 +6298,12 @@ packages:
     dev: true
     optional: true
 
+  /idb-keyval/6.2.0:
+    resolution: {integrity: sha512-uw+MIyQn2jl3+hroD7hF8J7PUviBU7BPKWw4f/ISf32D4LoGu98yHjrzWWJDASu9QNrX10tCJqk9YY0ClWm8Ng==}
+    dependencies:
+      safari-14-idb-fix: 3.0.0
+    dev: false
+
   /ieee754/1.2.1:
     resolution: {integrity: sha512-dcyqhDvX1C46lXZcVqCpK+FtMRQVdIMN6/Df5js2zouUsqG7I6sFxitIC+7KYK29KdXOLHdu9zL4sFnoVQnqaA==}
 
@@ -9968,6 +9976,10 @@ packages:
       mri: 1.2.0
     dev: false
 
+  /safari-14-idb-fix/3.0.0:
+    resolution: {integrity: sha512-eBNFLob4PMq8JA1dGyFn6G97q3/WzNtFK4RnzT1fnLq+9RyrGknzYiM/9B12MnKAxuj1IXr7UKYtTNtjyKMBog==}
+    dev: false
+
   /safe-buffer/5.1.2:
     resolution: {integrity: sha512-Gd2UZBJDkXlY7GbJxfsE8/nvKkUEU1G38c1siN6QP6a9PT9MmHB8GnpscSmMJSoF8LOIrt8ud/wPtojys4G6+g==}