Implement live chat bidi stream endpoint

.gitignore

@@ -1,2 +1,4 @@
 node_modules
 dist
+db.json
+chat-*.txt

package.json

@@ -23,6 +23,7 @@
     "scripts": {
         "lint": "yarn run eslint --fix --ext .ts src",
         "prebuild": "yarn run lint",
+        "clean": "rm -rf ./src/proto && mkdir -p ./src/proto && rm -f chat-*.txt && rm -f db.json",
         "build": "sh ./scripts/build-protos.sh ./songs.proto ./src/proto && yarn run tsc",
         "start": "PORT=6789 node ./dist/index.js"
     }

scripts/build-protos.sh

@@ -5,7 +5,6 @@ cd ${BASEDIR}/../
 
 PROTO_DEST=./src/proto
 
-rm -rf ${PROTO_DEST}
 mkdir -p ${PROTO_DEST}
 
 # JavaScript code generation

src/client/live-chat.ts

@@ -0,0 +1,54 @@
+import fs from 'fs';
+import inquirer from 'inquirer';
+import client from './client';
+import { Comment } from '../proto/songs_pb';
+
+async function liveChat(): Promise<void> {
+    const { name, songId } = await inquirer.prompt([
+        {
+            name: 'name',
+            message: 'What is your name?',
+        },
+        {
+            name: 'songId',
+            message: 'Which song do you want to discuss?',
+        },
+    ]);
+    const stream = client.liveChat();
+    return new Promise(async (resolve, reject) => {
+        stream.on('data', (comment: Comment) => {
+            fs.writeFileSync(
+                `chat-${name}-${comment.getSongId()}.txt`,
+                `(${comment.getUsername()}) ${comment.getBody()}\n`,
+                {
+                    flag: 'a',
+                },
+            );
+        });
+        stream.on('end', resolve);
+        stream.on('error', reject);
+
+        while (true) {
+            const answer = await inquirer.prompt([
+                {
+                    name: 'message',
+                    message: 'Type message:',
+                },
+            ]);
+            const comment = new Comment();
+            comment.setUsername(name);
+            comment.setBody(answer.message);
+            comment.setSongId(songId);
+            stream.write(comment);
+        }
+    });
+}
+
+export default {
+    command: 'chat',
+    describe: 'Chat about a song',
+    builder: {},
+    handler: async (): Promise<void> => {
+        await liveChat();
+    },
+};

src/index.ts

@@ -3,10 +3,12 @@ import serve from './server/index';
 import getSong from './client/get-song';
 import addSongs from './client/add-songs';
 import getChat from './client/get-chat';
+import liveChat from './client/live-chat';
 
 yargs
     .command(serve)
     .command(getSong)
     .command(addSongs)
     .command(getChat)
+    .command(liveChat)
     .help().argv;

src/server/index.ts

@@ -5,6 +5,7 @@ import { ISongsServer, SongsService } from '../proto/songs_grpc_pb';
 import getSong from './get-song';
 import addSong from './add-song';
 import getChat from './get-chat';
+import { addComment, registerListener } from './live-chat';
 
 class SongsServer implements ISongsServer {
     getSong(call: grpc.ServerUnaryCall<Empty>, callback: grpc.sendUnaryData<Song>): void {
@@ -25,7 +26,11 @@ class SongsServer implements ISongsServer {
         call.end();
     }
     liveChat(call: grpc.ServerDuplexStream<Comment, Comment>): void {
-        console.log('liveChat', call);
+        registerListener(comment => call.write(comment));
+        call.on('data', (comment: Comment) => {
+            addComment(comment);
+        });
+        call.on('end', () => call.end());
     }
 }
 

src/server/live-chat.ts

@@ -0,0 +1,19 @@
+import { Comment } from '../proto/songs_pb';
+import db from './db';
+
+type ListenerFn = (c: Comment) => void;
+
+const listeners: ListenerFn[] = [];
+
+export function registerListener(fn: ListenerFn): void {
+    listeners.push(fn);
+}
+
+export function addComment(comment: Comment): void {
+    // Use of `any` required due to bug in @types/lowdb
+    // SEE: https://github.com/typicode/lowdb/issues/349
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const dbComments = db.get('comments') as any;
+    dbComments.push(comment.toObject()).write();
+    listeners.map(listener => listener(comment));
+}