Feat/session readonly (#25)

* updated backend to incorporate read only sessions

* updated backend to incorporate readonly session

* fixed bug in getSessionDetails function

* updated backend with shorter ids for generated sessions

* Removed console.log and added extra layer of readonly check on backend

* changed document implementation to Map to support sublinear lookup. Added checking of shortIds generated to prevent repeat

* Add empty line at end-of-file

* Fix format

* Restore empty line

---------

Co-authored-by: Richard Dominick <[email protected]>

index.js

@@ -12,47 +12,59 @@ const app = new Koa();
 const db = new ShareDB();
 
 db.use('connect', (ctx, done) => {
-  // use custom to store the allowed document ID
+  // use custom to store the allowed document ID and readOnly setting
   ctx.agent.custom = ctx.req;
   done();
 });
 db.use('submit', (ctx, done) => {
-  const allowed = ctx.collection === COLLECTION_NAME && ctx.id === ctx.agent.custom;
+  const allowed =
+    ctx.collection === COLLECTION_NAME &&
+    ctx.id === ctx.agent.custom.docId &&
+    !ctx.agent.custom.readOnly;
   done(allowed ? undefined : 'Cannot write to this document');
 });
 db.use('readSnapshots', (ctx, done) => {
   const allowed =
     ctx.collection === COLLECTION_NAME &&
-    !ctx.snapshots.find((snapshot) => snapshot.id !== ctx.agent.custom);
+    !ctx.snapshots.find((snapshot) => snapshot.id !== ctx.agent.custom.docId);
   done(allowed ? undefined : 'Cannot read these document(s)');
 });
 
-const documents = new Set();
+const documents = new Map();
 
 app.use(cors());
 app.use(websocket());
 app.use(bodyParser({ enableTypes: ['json', 'text'], strict: false }));
 app.use(async (ctx) => {
   if (ctx.method === 'POST' && ctx.path === '/') {
-    const contents = isEmptyObject(ctx.request.body) ? '' : ctx.request.body;
+    const { contents } = ctx.request.body;
+
+    // Creates various IDs
     const docId = uuid();
-    const doc = db.connect(undefined, docId).get(COLLECTION_NAME, docId);
+    const sessionEditingId = generateShortId();
+    documents.set(sessionEditingId, [docId, false]);
+    const sessionViewingId = generateShortId();
+    documents.set(sessionViewingId, [docId, true]);
+
+    const connection = db.connect(undefined, { docId, readOnly: false });
+    const doc = connection.get(COLLECTION_NAME, docId);
     await new Promise((resolve, reject) => {
-      doc.create(contents, (err) => {
+      doc.create({ contents }, (err) => {
         if (err) {
           reject(err);
         } else {
           resolve();
         }
       });
     });
-    documents.add(docId);
-    ctx.body = docId;
+    ctx.body = { docId, sessionEditingId, sessionViewingId };
     return;
   }
 
-  const docId = ctx.path.substr(1);
-  if (!documents.has(docId)) {
+  const sessionId = ctx.path.substr(1);
+  const [docId, readOnly] = getSessionDetails(sessionId);
+
+  if (docId === null) {
     ctx.status = 404;
     return;
   }
@@ -64,14 +76,24 @@ app.use(async (ctx) => {
 
   if (ctx.ws) {
     const ws = new WebSocketJSONStream(await ctx.ws());
-    db.listen(ws, docId);
+    db.listen(ws, { docId, readOnly }); // docId and readOnly is passed to 'connect' middleware as ctx.req
   } else {
-    ctx.body = 'Document exists.';
+    ctx.body = { docId, readOnly };
   }
 });
 
 app.listen(process.env.PORT || 8080);
 
-function isEmptyObject(obj) {
-  return Object.keys(obj).length === 0 && obj.constructor === Object;
+function getSessionDetails(sessionId) {
+  const sessionDetails = documents.get(sessionId);
+  return sessionDetails === undefined ? [null, null] : sessionDetails;
+}
+
+function generateShortId() {
+  const id = uuid().slice(0, 6);
+  if (documents.has(id)) {
+    return generateShortId();
+  } else {
+    return id;
+  }
 }