Migrate to SQLCipher for messages/cache

Quite a few other fixes, including:
  - Sending to contact with no avatar yet (not synced from mobile)
  - Left pane doesn't update quickly or at all on new message
  - Left pane doesn't show sent or error status

Also:
 - Contributing.md: Ensure set of linux dev dependencies is complete

js/modules/migrate_to_sql.js

@@ -0,0 +1,167 @@
+/* global window, IDBKeyRange */
+
+const { includes, isFunction, isString, last } = require('lodash');
+const { saveMessages, saveUnprocesseds } = require('./data');
+const {
+  getMessageExportLastIndex,
+  setMessageExportLastIndex,
+  getUnprocessedExportLastIndex,
+  setUnprocessedExportLastIndex,
+} = require('./settings');
+
+module.exports = {
+  migrateToSQL,
+};
+
+async function migrateToSQL({ db, clearStores, handleDOMException }) {
+  if (!db) {
+    throw new Error('Need db for IndexedDB connection!');
+  }
+  if (!isFunction(clearStores)) {
+    throw new Error('Need clearStores function!');
+  }
+  if (!isFunction(handleDOMException)) {
+    throw new Error('Need handleDOMException function!');
+  }
+
+  window.log.info('migrateToSQL: start');
+
+  let lastIndex = await getMessageExportLastIndex(db);
+  let complete = false;
+
+  while (!complete) {
+    // eslint-disable-next-line no-await-in-loop
+    const status = await migrateStoreToSQLite({
+      db,
+      save: saveMessages,
+      storeName: 'messages',
+      handleDOMException,
+      lastIndex,
+    });
+
+    ({ complete, lastIndex } = status);
+
+    // eslint-disable-next-line no-await-in-loop
+    await setMessageExportLastIndex(db, lastIndex);
+  }
+  window.log.info('migrateToSQL: migrate of messages complete');
+
+  lastIndex = await getUnprocessedExportLastIndex(db);
+  complete = false;
+
+  while (!complete) {
+    // eslint-disable-next-line no-await-in-loop
+    const status = await migrateStoreToSQLite({
+      db,
+      save: saveUnprocesseds,
+      storeName: 'unprocessed',
+      handleDOMException,
+      lastIndex,
+    });
+
+    ({ complete, lastIndex } = status);
+
+    // eslint-disable-next-line no-await-in-loop
+    await setUnprocessedExportLastIndex(db, lastIndex);
+  }
+  window.log.info('migrateToSQL: migrate of unprocessed complete');
+
+  await clearStores(['messages', 'unprocessed']);
+
+  window.log.info('migrateToSQL: complete');
+}
+
+async function migrateStoreToSQLite({
+  db,
+  save,
+  storeName,
+  handleDOMException,
+  lastIndex = null,
+  batchSize = 20,
+}) {
+  if (!db) {
+    throw new Error('Need db for IndexedDB connection!');
+  }
+  if (!isFunction(save)) {
+    throw new Error('Need save function!');
+  }
+  if (!isString(storeName)) {
+    throw new Error('Need storeName!');
+  }
+  if (!isFunction(handleDOMException)) {
+    throw new Error('Need handleDOMException for error handling!');
+  }
+
+  if (!includes(db.objectStoreNames, storeName)) {
+    return {
+      complete: true,
+      count: 0,
+    };
+  }
+
+  const queryPromise = new Promise((resolve, reject) => {
+    const items = [];
+    const transaction = db.transaction(storeName, 'readonly');
+    transaction.onerror = () => {
+      handleDOMException(
+        'migrateToSQLite transaction error',
+        transaction.error,
+        reject
+      );
+    };
+    transaction.oncomplete = () => {};
+
+    const store = transaction.objectStore(storeName);
+    const excludeLowerBound = true;
+    const range = lastIndex
+      ? IDBKeyRange.lowerBound(lastIndex, excludeLowerBound)
+      : undefined;
+    const request = store.openCursor(range);
+    request.onerror = () => {
+      handleDOMException(
+        'migrateToSQLite: request error',
+        request.error,
+        reject
+      );
+    };
+    request.onsuccess = event => {
+      const cursor = event.target.result;
+
+      if (!cursor || !cursor.value) {
+        return resolve({
+          complete: true,
+          items,
+        });
+      }
+
+      const item = cursor.value;
+      items.push(item);
+
+      if (items.length >= batchSize) {
+        return resolve({
+          complete: false,
+          items,
+        });
+      }
+
+      return cursor.continue();
+    };
+  });
+
+  const { items, complete } = await queryPromise;
+
+  if (items.length) {
+    // We need to pass forceSave parameter, because these items already have an
+    //   id key. Normally, this call would be interpreted as an update request.
+    await save(items, { forceSave: true });
+  }
+
+  const lastItem = last(items);
+  const id = lastItem ? lastItem.id : null;
+
+  return {
+    complete,
+    count: items.length,
+    lastIndex: id,
+  };
+}