Add API for getting media data

ext/bg/js/backend.js

@@ -111,7 +111,8 @@ class Backend {
             ['getAnkiModelFieldNames', {handler: this._onApiGetAnkiModelFieldNames.bind(this), async: true}],
             ['getDictionaryInfo', {handler: this._onApiGetDictionaryInfo.bind(this), async: true}],
             ['getDictionaryCounts', {handler: this._onApiGetDictionaryCounts.bind(this), async: true}],
-            ['purgeDatabase', {handler: this._onApiPurgeDatabase.bind(this), async: true}]
+            ['purgeDatabase', {handler: this._onApiPurgeDatabase.bind(this), async: true}],
+            ['getMedia', {handler: this._onApiGetMedia.bind(this), async: true}]
         ]);
 
         this._commandHandlers = new Map([
@@ -762,6 +763,10 @@ class Backend {
         return await this.translator.purgeDatabase();
     }
 
+    async _onApiGetMedia({targets}) {
+        return await this.database.getMedia(targets);
+    }
+
     // Command handlers
 
     async _onCommandSearch(params) {

ext/bg/js/database.js

@@ -277,6 +277,34 @@ class Database {
         return result;
     }
 
+    async getMedia(targets) {
+        this._validate();
+
+        const count = targets.length;
+        const promises = [];
+        const results = new Array(count).fill(null);
+        const createResult = Database._createMedia;
+        const processRow = (row, [index, dictionaryName]) => {
+            if (row.dictionary === dictionaryName) {
+                results[index] = createResult(row, index);
+            }
+        };
+
+        const transaction = this.db.transaction(['media'], 'readonly');
+        const objectStore = transaction.objectStore('media');
+        const index = objectStore.index('path');
+
+        for (let i = 0; i < count; ++i) {
+            const {path, dictionaryName} = targets[i];
+            const only = IDBKeyRange.only(path);
+            promises.push(Database._getAll(index, only, [i, dictionaryName], processRow));
+        }
+
+        await Promise.all(promises);
+
+        return results;
+    }
+
     async getDictionaryInfo() {
         this._validate();
 
@@ -441,6 +469,10 @@ class Database {
         return {character, mode, data, dictionary, index};
     }
 
+    static _createMedia(row, index) {
+        return Object.assign({}, row, {index});
+    }
+
     static _getAll(dbIndex, query, context, processRow) {
         const fn = typeof dbIndex.getAll === 'function' ? Database._getAllFast : Database._getAllUsingCursor;
         return fn(dbIndex, query, context, processRow);

ext/mixed/js/api.js

@@ -140,6 +140,10 @@ function apiPurgeDatabase() {
     return _apiInvoke('purgeDatabase');
 }
 
+function apiGetMedia(targets) {
+    return _apiInvoke('getMedia', {targets});
+}
+
 function _apiInvoke(action, params={}) {
     const data = {action, params};
     return new Promise((resolve, reject) => {