1 files changed, 58 insertions, 0 deletions
diff --git a/backend/index.ts b/backend/index.ts
new file mode 100644
index 0000000..5a974d6
--- /dev/null
+++ b/backend/index.ts
@@ -0,0 +1,58 @@
+// Next.js API route support: https://nextjs.org/docs/api-routes/introduction
+import express from "express";
+import http from "http";
+import {
+    createPool,
+    DatabasePoolType,
+    DatabaseTransactionConnectionType,
+    sql,
+} from "slonik";
+import * as config from "./config";
+import { ValueRecord } from "../shared-types";
+import { Server as SocketIOServer, Socket } from "socket.io";
+
+const app = express();
+
+const httpServer = http.createServer(app);
+const io = new SocketIOServer(httpServer, {
+    cors: {
+        origin: "*",
+    },
+});
+
+type Connection = DatabasePoolType | DatabaseTransactionConnectionType;
+const _connection = createPool(config.postgresConnectionString);
+
+const getCurrentValue = async (conn: Connection): Promise<ValueRecord["value"]> => {
+    return await conn.oneFirst<ValueRecord["value"]>(sql`
+        SELECT value
+        FROM state
+    `);
+};
+
+const incrementCurrentValue = async (conn: Connection): Promise<number> =>
+    await conn.transaction(async (trans) => {
+        const current = await getCurrentValue(trans);
+
+        const newValue = current + 1;
+        await trans.query(sql`
+                UPDATE state
+                SET value = ${newValue}
+            `);
+        return newValue;
+    });
+
+io.on("connection", async (socket) => {
+    console.log(`a user connected: ${socket.id}`);
+    const currentValue = await getCurrentValue(_connection);
+    socket.emit("update", currentValue);
+
+    socket.on("increment", async () => {
+        const newValue = await incrementCurrentValue(_connection);
+        io.emit("update", newValue); // broadcast
+    });
+});
+
+httpServer.listen(config.port, () => {
+    console.log(`Listening on http://localhost:${config.port}`);
+});