Use indexedDB directly via idb-keyval

DESCRIPTION

@@ -10,7 +10,7 @@ Authors@R: c(
   person(family = "Ajax.org B.V.", role=c("ctb", "cph"), comment= "Ace library"),
   person("Zeno", "Rocha", role = c("ctb", "cph"), comment = "clipboard.js library"),
   person("Nick", "Payne", role = c("ctb", "cph"), comment = "Bootbox library"),
-  person(family = "Mozilla", role = c("ctb", "cph"), comment = "localforage library")
+  person("Jake", "Archibald", role = c("ctb", "cph"), comment = "idb-keyval library")
   )
 Description: Create interactive tutorials using R Markdown. Use a combination
   of narrative, figures, videos, exercises, and quizzes to create self-paced

NEWS.md

@@ -25,6 +25,7 @@ learnr 0.10.0 (unreleased)
 
 * A version number has been added to `question_submission` events.  This will help when using custom storage methods. ([#291](https://github.com/rstudio/learnr/pull/291))
 
+* Tutorial storage on the browser is now executed directly on `indexedDB` using `idb-keyval` (dropping `localforage`). ([#305](https://github.com/rstudio/learnr/pull/305))
 
 ## Bug fixes
 

R/html-dependencies.R

@@ -46,13 +46,13 @@ html_dependency_src <- function(...) {
   }
 }
 
-
-localforage_html_dependency <- function() {
+idb_html_dependency <- function() {
   htmltools::htmlDependency(
-    name = "localforage",
-    version = "1.5",
-    src = system.file("lib/localforage", package = "learnr"),
-    script = "localforage.min.js"
+    name = "idb-keyvalue",
+    version = "3.2.0",
+    src = system.file("lib/idb-keyval", package = "learnr"),
+    script = "idb-keyval-iife-compat.min.js",
+    all_files = FALSE
   )
 }
 

R/initialize.R

@@ -19,7 +19,7 @@ initialize_tutorial <- function() {
       rmarkdown::html_dependency_jquery(),
       rmarkdown::html_dependency_font_awesome(),
       bootbox_html_dependency(),
-      localforage_html_dependency(),
+      idb_html_dependency(),
       tutorial_html_dependency(),
       tutorial_autocompletion_html_dependency(),
       tutorial_diagnostics_html_dependency()
@@ -45,4 +45,3 @@ dput_to_string <- function(x) {
   dput(x, file = conn)
   paste0(textConnectionValue(conn), collapse = "")
 }
-

inst/lib/idb-keyval/idb-keyval-iife.js

@@ -0,0 +1,88 @@
+var idbKeyval = (function (exports) {
+  'use strict';
+
+  const promiseStore = (openreq, storeName) => new Promise((resolve, reject) => {
+    openreq.onerror = () => reject(openreq.error);
+    openreq.onsuccess = () => resolve(openreq.result);
+    // First time setup: create an empty object store
+    openreq.onupgradeneeded = () => {
+      openreq.result.createObjectStore(storeName);
+    };
+  });
+  class Store {
+    constructor(dbName = 'keyval-store', storeName = 'keyval') {
+      this.storeName = storeName;
+      this._dbp = promiseStore(indexedDB.open(dbName), storeName)
+        .then(db => {
+          if (db.objectStoreNames.contains(storeName))
+            return db;
+          db.close();
+          return promiseStore(indexedDB.open(dbName, db.version + 1), storeName);
+        });
+    }
+    _withIDBStore(type, callback) {
+      return this._dbp.then(db => new Promise((resolve, reject) => {
+        const transaction = db.transaction(this.storeName, type);
+        transaction.oncomplete = () => resolve();
+        transaction.onabort = transaction.onerror = () => reject(transaction.error);
+        callback(transaction.objectStore(this.storeName));
+      }));
+    }
+  }
+  let store;
+
+  function getDefaultStore() {
+    if (!store)
+      store = new Store();
+    return store;
+  }
+
+  function get(key, store = getDefaultStore()) {
+    let req;
+    return store._withIDBStore('readonly', store => {
+      req = store.get(key);
+    }).then(() => req.result);
+  }
+
+  function set(key, value, store = getDefaultStore()) {
+    return store._withIDBStore('readwrite', store => {
+      store.put(value, key);
+    });
+  }
+
+  function del(key, store = getDefaultStore()) {
+    return store._withIDBStore('readwrite', store => {
+      store.delete(key);
+    });
+  }
+
+  function clear(store = getDefaultStore()) {
+    return store._withIDBStore('readwrite', store => {
+      store.clear();
+    });
+  }
+
+  function keys(store = getDefaultStore()) {
+    const keys = [];
+    return store._withIDBStore('readonly', store => {
+      // This would be store.getAllKeys(), but it isn't supported by Edge or Safari.
+      // And openKeyCursor isn't supported by Safari.
+      (store.openKeyCursor || store.openCursor).call(store).onsuccess = function () {
+        if (!this.result)
+          return;
+        keys.push(this.result.key);
+        this.result.continue();
+      };
+    }).then(() => keys);
+  }
+
+  exports.Store = Store;
+  exports.get = get;
+  exports.set = set;
+  exports.del = del;
+  exports.clear = clear;
+  exports.keys = keys;
+
+  return exports;
+
+}({}));

inst/lib/idb-keyval/note.md

@@ -0,0 +1,3 @@
+[Original File Location](https://github.com/jakearchibald/idb-keyval/blob/master/dist/idb-keyval-iife-compat.min.js)
+[New File Location](https://github.com/schloerke/idb-keyval/blob/idb-keyval/dist/idb-keyval-iife-compat.min.js)
+[PR](https://github.com/jakearchibald/idb-keyval/pull/73)