1 files changed, 154 insertions, 0 deletions
diff --git a/app/assets/javascripts/ide/lib/mirror.js b/app/assets/javascripts/ide/lib/mirror.js
new file mode 100644
index 00000000000..a516c28ad7a
--- /dev/null
+++ b/app/assets/javascripts/ide/lib/mirror.js
@@ -0,0 +1,154 @@
+import createDiff from './create_diff';
+import { getWebSocketUrl, mergeUrlParams } from '~/lib/utils/url_utility';
+import { __ } from '~/locale';
+
+export const SERVICE_NAME = 'webide-file-sync';
+export const PROTOCOL = 'webfilesync.gitlab.com';
+export const MSG_CONNECTION_ERROR = __('Could not connect to Web IDE file mirror service.');
+
+// Before actually connecting to the service, we must delay a bit
+// so that the service has sufficiently started.
+
+const noop = () => {};
+export const SERVICE_DELAY = 8000;
+
+const cancellableWait = time => {
+  let timeoutId = 0;
+
+  const cancel = () => clearTimeout(timeoutId);
+
+  const promise = new Promise(resolve => {
+    timeoutId = setTimeout(resolve, time);
+  });
+
+  return [promise, cancel];
+};
+
+const isErrorResponse = error => error && error.code !== 0;
+
+const isErrorPayload = payload => payload && payload.status_code !== 200;
+
+const getErrorFromResponse = data => {
+  if (isErrorResponse(data.error)) {
+    return { message: data.error.Message };
+  } else if (isErrorPayload(data.payload)) {
+    return { message: data.payload.error_message };
+  }
+
+  return null;
+};
+
+const getFullPath = path => mergeUrlParams({ service: SERVICE_NAME }, getWebSocketUrl(path));
+
+const createWebSocket = fullPath =>
+  new Promise((resolve, reject) => {
+    const socket = new WebSocket(fullPath, [PROTOCOL]);
+    const resetCallbacks = () => {
+      socket.onopen = null;
+      socket.onerror = null;
+    };
+
+    socket.onopen = () => {
+      resetCallbacks();
+      resolve(socket);
+    };
+
+    socket.onerror = () => {
+      resetCallbacks();
+      reject(new Error(MSG_CONNECTION_ERROR));
+    };
+  });
+
+export const canConnect = ({ services = [] }) => services.some(name => name === SERVICE_NAME);
+
+export const createMirror = () => {
+  let socket = null;
+  let cancelHandler = noop;
+  let nextMessageHandler = noop;
+
+  const cancelConnect = () => {
+    cancelHandler();
+    cancelHandler = noop;
+  };
+
+  const onCancelConnect = fn => {
+    cancelHandler = fn;
+  };
+
+  const receiveMessage = ev => {
+    const handle = nextMessageHandler;
+    nextMessageHandler = noop;
+    handle(JSON.parse(ev.data));
+  };
+
+  const onNextMessage = fn => {
+    nextMessageHandler = fn;
+  };
+
+  const waitForNextMessage = () =>
+    new Promise((resolve, reject) => {
+      onNextMessage(data => {
+        const err = getErrorFromResponse(data);
+
+        if (err) {
+          reject(err);
+        } else {
+          resolve();
+        }
+      });
+    });
+
+  const uploadDiff = ({ toDelete, patch }) => {
+    if (!socket) {
+      return Promise.resolve();
+    }
+
+    const response = waitForNextMessage();
+
+    const msg = {
+      code: 'EVENT',
+      namespace: '/files',
+      event: 'PATCH',
+      payload: { diff: patch, delete_files: toDelete },
+    };
+
+    socket.send(JSON.stringify(msg));
+
+    return response;
+  };
+
+  return {
+    upload(state) {
+      return uploadDiff(createDiff(state));
+    },
+    connect(path) {
+      if (socket) {
+        this.disconnect();
+      }
+
+      const fullPath = getFullPath(path);
+      const [wait, cancelWait] = cancellableWait(SERVICE_DELAY);
+
+      onCancelConnect(cancelWait);
+
+      return wait
+        .then(() => createWebSocket(fullPath))
+        .then(newSocket => {
+          socket = newSocket;
+          socket.onmessage = receiveMessage;
+        });
+    },
+    disconnect() {
+      cancelConnect();
+
+      if (!socket) {
+        return;
+      }
+
+      socket.close();
+      socket = null;
+    },
+  };
+};
+
+export default createMirror();