Audio download timeout (#2187)

* Add support for an idle timeout when downloading audio

* Update eslint rules

* Pass idleTimeout to the downloader from DisplayAnki

* Add anki.downloadTimeout setting

* Update tests

* Assign _audioDownloadIdleTimeout using settings

* Show info about cancelled downloads

* Handle Firefox bug

* Improve audio errors

* Refactor

* Move functions to RequestBuilder

11 files changed, 230 insertions, 23 deletions

diff --git a/.eslintrc.json b/.eslintrc.json
index 02660d0a..dad145be 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -291,6 +291,14 @@
             "rules": {
                 "no-implicit-globals": "error"
             }
+        },
+        {
+            "files": [
+                "ext/js/**/*.js"
+            ],
+            "globals": {
+                "AbortController": "readonly"
+            }
         }
     ]
 }
diff --git a/ext/data/schemas/options-schema.json b/ext/data/schemas/options-schema.json
index d7e3b5f4..37b32bbf 100644
--- a/ext/data/schemas/options-schema.json
+++ b/ext/data/schemas/options-schema.json
@@ -878,7 +878,8 @@
                                     "suspendNewCards",
                                     "displayTags",
                                     "noteGuiMode",
-                                    "apiKey"
+                                    "apiKey",
+                                    "downloadTimeout"
                                 ],
                                 "properties": {
                                     "enable": {
@@ -1002,6 +1003,11 @@
                                     "apiKey": {
                                         "type": "string",
                                         "default": ""
+                                    },
+                                    "downloadTimeout": {
+                                        "type": "number",
+                                        "default": 0,
+                                        "minimum": 0
                                     }
                                 }
                             },
diff --git a/ext/issues.html b/ext/issues.html
index 4d74ae76..df6e6135 100644
--- a/ext/issues.html
+++ b/ext/issues.html
@@ -42,6 +42,18 @@
         </div></div></div></div>
     </div>
 
+    <h2 id="audio-download-idle-timeout">Audio download was cancelled due to an idle timeout</h2>
+    <div class="settings-group">
+        <div class="settings-item"><div class="settings-item-inner"><div class="settings-item-left"><div class="settings-item-label">
+            <p>
+                Audio files can be downloaded from remote servers when creating Anki cards,
+                and sometimes these downloads can stall due to server or internet connectivity issues.
+                The <em>Idle download timeout</em> setting on the <a href="/settings.html#!anki">settings page</a>
+                specifies a time limit for stalled downloads.
+            </p>
+        </div></div></div></div>
+    </div>
+
     <div class="footer-padding"></div>
 
 </div>
diff --git a/ext/js/background/backend.js b/ext/js/background/backend.js
index 75ff7bee..f3c76311 100644
--- a/ext/js/background/backend.js
+++ b/ext/js/background/backend.js
@@ -1809,7 +1809,7 @@ class Backend {
             return null;
         }
 
-        const {sources, preferredAudioIndex} = details;
+        const {sources, preferredAudioIndex, idleTimeout} = details;
         let data;
         let contentType;
         try {
@@ -1817,7 +1817,8 @@ class Backend {
                 sources,
                 preferredAudioIndex,
                 term,
-                reading
+                reading,
+                idleTimeout
             ));
         } catch (e) {
             const error = this._getAudioDownloadError(e);
@@ -1918,6 +1919,9 @@ class Backend {
             const {errors} = error.data;
             if (Array.isArray(errors)) {
                 for (const error2 of errors) {
+                    if (error2.name === 'AbortError') {
+                        return this._createAudioDownloadError('Audio download was cancelled due to an idle timeout', 'audio-download-idle-timeout', errors);
+                    }
                     if (!isObject(error2.data)) { continue; }
                     const {details} = error2.data;
                     if (!isObject(details)) { continue; }
@@ -1925,12 +1929,7 @@ class Backend {
                         // This is potentially an error due to the extension not having enough URL privileges.
                         // The message logged to the console looks like this:
                         //  Access to fetch at '<URL>' from origin 'chrome-extension://<ID>' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
-                        const result = new Error('Audio download failed due to possible extension permissions error');
-                        result.data = {
-                            errors,
-                            referenceUrl: '/issues.html#audio-download-failed'
-                        };
-                        return result;
+                        return this._createAudioDownloadError('Audio download failed due to possible extension permissions error', 'audio-download-failed', errors);
                     }
                 }
             }
@@ -1938,6 +1937,23 @@ class Backend {
         return null;
     }
 
+    _createAudioDownloadError(message, issueId, errors) {
+        const error = new Error(message);
+        const hasErrors = Array.isArray(errors);
+        const hasIssueId = (typeof issueId === 'string');
+        if (hasErrors || hasIssueId) {
+            error.data = {};
+            if (hasErrors) {
+                // Errors need to be serialized since they are passed to other frames
+                error.data.errors = errors.map((e) => serializeError(e));
+            }
+            if (hasIssueId) {
+                error.data.referenceUrl = `/issues.html#${issueId}`;
+            }
+        }
+        return error;
+    }
+
     _generateAnkiNoteMediaFileName(prefix, extension, timestamp, definitionDetails) {
         let fileName = prefix;
 
diff --git a/ext/js/background/request-builder.js b/ext/js/background/request-builder.js
index ad1536f1..2cdd6f0e 100644
--- a/ext/js/background/request-builder.js
+++ b/ext/js/background/request-builder.js
@@ -42,6 +42,58 @@ class RequestBuilder {
         return await this._fetchInternal(url, init, headerModifications);
     }
 
+    static async readFetchResponseArrayBuffer(response, onProgress) {
+        let reader;
+        try {
+            if (typeof onProgress === 'function') {
+                reader = response.body.getReader();
+            }
+        } catch (e) {
+            // Not supported
+        }
+
+        if (typeof reader === 'undefined') {
+            const result = await response.arrayBuffer();
+            if (typeof onProgress === 'function') {
+                onProgress(true);
+            }
+            return result;
+        }
+
+        const contentLengthString = response.headers.get('Content-Length');
+        const contentLength = contentLengthString !== null ? Number.parseInt(contentLengthString, 10) : null;
+        let target = Number.isFinite(contentLength) ? new Uint8Array(contentLength) : null;
+        let targetPosition = 0;
+        let totalLength = 0;
+        const targets = [];
+
+        while (true) {
+            const {done, value} = await reader.read();
+            if (done) { break; }
+            onProgress(false);
+            if (target === null) {
+                targets.push({array: value, length: value.length});
+            } else if (targetPosition + value.length > target.length) {
+                targets.push({array: target, length: targetPosition});
+                target = null;
+            } else {
+                target.set(value, targetPosition);
+                targetPosition += value.length;
+            }
+            totalLength += value.length;
+        }
+
+        if (target === null) {
+            target = this._joinUint8Arrays(targets, totalLength);
+        } else if (totalLength < target.length) {
+            target = target.slice(0, totalLength);
+        }
+
+        onProgress(true);
+
+        return target;
+    }
+
     // Private
 
     async _fetchInternal(url, init, headerModifications) {
@@ -92,7 +144,10 @@ class RequestBuilder {
                 }, 100);
             }
             const details = await errorDetailsPromise;
-            e.data = {details};
+            if (details !== null) {
+                const data = {details};
+                this._assignErrorData(e, data);
+            }
             throw e;
         } finally {
             this._removeWebRequestEventListeners(eventListeners);
@@ -295,4 +350,37 @@ class RequestBuilder {
         }
         return result;
     }
+
+    _assignErrorData(error, data) {
+        try {
+            error.data = data;
+        } catch (e) {
+            // On Firefox, assigning DOMException.data can fail in certain contexts.
+            // https://bugzilla.mozilla.org/show_bug.cgi?id=1776555
+            try {
+                Object.defineProperty(error, 'data', {
+                    configurable: true,
+                    enumerable: true,
+                    writable: true,
+                    value: data
+                });
+            } catch (e2) {
+                // NOP
+            }
+        }
+    }
+
+    static _joinUint8Arrays(items, totalLength) {
+        if (items.length === 1) {
+            const {array, length} = items[0];
+            if (array.length === length) { return array; }
+        }
+        const result = new Uint8Array(totalLength);
+        let position = 0;
+        for (const {array, length} of items) {
+            result.set(array, position);
+            position += length;
+        }
+        return result;
+    }
 }
diff --git a/ext/js/data/anki-note-builder.js b/ext/js/data/anki-note-builder.js
index 53cc29f6..9691aadb 100644
--- a/ext/js/data/anki-note-builder.js
+++ b/ext/js/data/anki-note-builder.js
@@ -320,8 +320,8 @@ class AnkiNoteBuilder {
         if (injectAudio && dictionaryEntryDetails.type !== 'kanji') {
             const audioOptions = mediaOptions.audio;
             if (typeof audioOptions === 'object' && audioOptions !== null) {
-                const {sources, preferredAudioIndex} = audioOptions;
-                audioDetails = {sources, preferredAudioIndex};
+                const {sources, preferredAudioIndex, idleTimeout} = audioOptions;
+                audioDetails = {sources, preferredAudioIndex, idleTimeout};
             }
         }
         if (injectScreenshot) {
diff --git a/ext/js/data/options-util.js b/ext/js/data/options-util.js
index a163580f..8c50493a 100644
--- a/ext/js/data/options-util.js
+++ b/ext/js/data/options-util.js
@@ -468,7 +468,8 @@ class OptionsUtil {
             {async: false, update: this._updateVersion16.bind(this)},
             {async: false, update: this._updateVersion17.bind(this)},
             {async: false, update: this._updateVersion18.bind(this)},
-            {async: false, update: this._updateVersion19.bind(this)}
+            {async: false, update: this._updateVersion19.bind(this)},
+            {async: false, update: this._updateVersion20.bind(this)}
         ];
         if (typeof targetVersion === 'number' && targetVersion < result.length) {
             result.splice(targetVersion);
@@ -975,4 +976,13 @@ class OptionsUtil {
         }
         return options;
     }
+
+    _updateVersion20(options) {
+        // Version 20 changes:
+        //  Added anki.downloadTimeout.
+        for (const profile of options.profiles) {
+            profile.options.anki.downloadTimeout = 0;
+        }
+        return options;
+    }
 }
diff --git a/ext/js/display/display-anki.js b/ext/js/display/display-anki.js
index 12133ad0..e2101481 100644
--- a/ext/js/display/display-anki.js
+++ b/ext/js/display/display-anki.js
@@ -48,6 +48,7 @@ class DisplayAnki {
         this._screenshotQuality = 100;
         this._scanLength = 10;
         this._noteGuiMode = 'browse';
+        this._audioDownloadIdleTimeout = null;
         this._noteTags = [];
         this._modeOptions = new Map();
         this._dictionaryEntryTypeModeMap = new Map([
@@ -133,7 +134,19 @@ class DisplayAnki {
     _onOptionsUpdated({options}) {
         const {
             general: {resultOutputMode, glossaryLayoutMode, compactTags},
-            anki: {tags, duplicateScope, duplicateScopeCheckAllModels, suspendNewCards, checkForDuplicates, displayTags, kanji, terms, noteGuiMode, screenshot: {format, quality}},
+            anki: {
+                tags,
+                duplicateScope,
+                duplicateScopeCheckAllModels,
+                suspendNewCards,
+                checkForDuplicates,
+                displayTags,
+                kanji,
+                terms,
+                noteGuiMode,
+                screenshot: {format, quality},
+                downloadTimeout
+            },
             scanning: {length: scanLength}
         } = options;
 
@@ -150,6 +163,7 @@ class DisplayAnki {
         this._scanLength = scanLength;
         this._noteGuiMode = noteGuiMode;
         this._noteTags = [...tags];
+        this._audioDownloadIdleTimeout = (Number.isFinite(downloadTimeout) && downloadTimeout > 0 ? downloadTimeout : null);
         this._modeOptions.clear();
         this._modeOptions.set('kanji', kanji);
         this._modeOptions.set('term-kanji', terms);
@@ -536,7 +550,7 @@ class DisplayAnki {
         const fields = Object.entries(modeOptions.fields);
         const contentOrigin = this._display.getContentOrigin();
         const details = this._ankiNoteBuilder.getDictionaryEntryDetailsForNote(dictionaryEntry);
-        const audioDetails = (details.type === 'term' ? this._displayAudio.getAnkiNoteMediaAudioDetails(details.term, details.reading) : null);
+        const audioDetails = this._getAnkiNoteMediaAudioDetails(details);
         const optionsContext = this._display.getOptionsContext();
 
         const {note, errors, requirements: outputRequirements} = await this._ankiNoteBuilder.createNote({
@@ -586,6 +600,12 @@ class DisplayAnki {
         return {text, offset};
     }
 
+    _getAnkiNoteMediaAudioDetails(details) {
+        if (details.type !== 'term') { return null; }
+        const {sources, preferredAudioIndex} = this._displayAudio.getAnkiNoteMediaAudioDetails(details.term, details.reading);
+        return {sources, preferredAudioIndex, idleTimeout: this._audioDownloadIdleTimeout};
+    }
+
     // View note functions
 
     _onViewNoteButtonClick(e) {
diff --git a/ext/js/media/audio-downloader.js b/ext/js/media/audio-downloader.js
index 0991d14d..4142e3f4 100644
--- a/ext/js/media/audio-downloader.js
+++ b/ext/js/media/audio-downloader.js
@@ -18,6 +18,7 @@
 /* global
  * JsonSchema
  * NativeSimpleDOMParser
+ * RequestBuilder
  * SimpleDOMParser
  * StringUtil
  */
@@ -50,7 +51,7 @@ class AudioDownloader {
         return [];
     }
 
-    async downloadTermAudio(sources, preferredAudioIndex, term, reading) {
+    async downloadTermAudio(sources, preferredAudioIndex, term, reading, idleTimeout) {
         const errors = [];
         for (const source of sources) {
             let infoList = await this.getTermAudioInfoList(source, term, reading);
@@ -61,7 +62,7 @@ class AudioDownloader {
                 switch (info.type) {
                     case 'url':
                         try {
-                            return await this._downloadAudioFromUrl(info.url, source.type);
+                            return await this._downloadAudioFromUrl(info.url, source.type, idleTimeout);
                         } catch (e) {
                             errors.push(e);
                         }
@@ -241,21 +242,42 @@ class AudioDownloader {
         return url.replace(/\{([^}]*)\}/g, (m0, m1) => (Object.prototype.hasOwnProperty.call(data, m1) ? `${data[m1]}` : m0));
     }
 
-    async _downloadAudioFromUrl(url, sourceType) {
+    async _downloadAudioFromUrl(url, sourceType, idleTimeout) {
+        let signal;
+        let onProgress = null;
+        let idleTimer = null;
+        if (typeof idleTimeout === 'number') {
+            const abortController = new AbortController();
+            ({signal} = abortController);
+            const onIdleTimeout = () => {
+                abortController.abort('Idle timeout');
+            };
+            onProgress = (done) => {
+                clearTimeout(idleTimer);
+                idleTimer = done ? null : setTimeout(onIdleTimeout, idleTimeout);
+            };
+            idleTimer = setTimeout(onIdleTimeout, idleTimeout);
+        }
+
         const response = await this._requestBuilder.fetchAnonymous(url, {
             method: 'GET',
             mode: 'cors',
             cache: 'default',
             credentials: 'omit',
             redirect: 'follow',
-            referrerPolicy: 'no-referrer'
+            referrerPolicy: 'no-referrer',
+            signal
         });
 
         if (!response.ok) {
             throw new Error(`Invalid response: ${response.status}`);
         }
 
-        const arrayBuffer = await response.arrayBuffer();
+        const arrayBuffer = await RequestBuilder.readFetchResponseArrayBuffer(response, onProgress);
+
+        if (idleTimer !== null) {
+            clearTimeout(idleTimer);
+        }
 
         if (!await this._isAudioBinaryValid(arrayBuffer, sourceType)) {
             throw new Error('Could not retrieve audio');
diff --git a/ext/settings.html b/ext/settings.html
index a3cc40f5..4dfa3100 100644
--- a/ext/settings.html
+++ b/ext/settings.html
@@ -1763,7 +1763,31 @@
                 </div>
             </div>
         </div></div>
-
+        <div class="settings-item advanced-only">
+            <div class="settings-item-inner settings-item-inner-wrappable">
+                <div class="settings-item-left">
+                    <div class="settings-item-label">Idle download timeout <span class="light">(in milliseconds)</span></div>
+                    <div class="settings-item-description">
+                        The maximum time before an idle download will be cancelled; 0 = no limit.
+                        <a tabindex="0" class="more-toggle more-only" data-parent-distance="4">More&hellip;</a>
+                    </div>
+                </div>
+                <div class="settings-item-right">
+                    <input type="number" data-setting="anki.downloadTimeout" min="0">
+                </div>
+            </div>
+            <div class="settings-item-children more" hidden>
+                <p>
+                    Audio files can be downloaded from remote servers when creating Anki cards,
+                    and sometimes these downloads can stall due to server or internet connectivity issues.
+                    When this setting has a non-zero value, if a download has stalled for longer than the time specified,
+                    the download will be cancelled.
+                </p>
+                <p class="margin-above">
+                    <a tabindex="0" class="more-toggle" data-parent-distance="3">Less&hellip;</a>
+                </p>
+            </div>
+        </div>
         <div class="settings-item advanced-only"><div class="settings-item-inner">
             <div class="settings-item-left">
                 <div class="settings-item-label">Suspend new cards</div>
diff --git a/test/test-options-util.js b/test/test-options-util.js
index 16660fd0..af64e7dd 100644
--- a/test/test-options-util.js
+++ b/test/test-options-util.js
@@ -470,7 +470,8 @@ function createProfileOptionsUpdatedTestData1() {
             fieldTemplates: null,
             suspendNewCards: false,
             noteGuiMode: 'browse',
-            apiKey: ''
+            apiKey: '',
+            downloadTimeout: 0
         },
         sentenceParsing: {
             scanExtent: 200,
@@ -619,7 +620,7 @@ function createOptionsUpdatedTestData1() {
             }
         ],
         profileCurrent: 0,
-        version: 19,
+        version: 20,
         global: {
             database: {
                 prefixWildcardsSupported: false