feat: chat stream messages

frontend/src/stream.js

@@ -0,0 +1,62 @@
+export default class Stream {
+    constructor (id) {
+        this.id = id;
+        this.partialContent = "";
+        this.eof = false;
+
+        this.listeners = {
+            data: [],
+            end: [],
+        };
+
+        let onResponse = (msg) => {
+            if (this.eof) return;
+
+            if (msg.eof) {
+                this.eof = true;
+                this.handle('end');
+            } else {
+                this.partialContent += msg.data;
+                this.handle('data', msg.data);
+            }
+        };
+
+        this.contentPromise = new Promise((resolve, reject) => {
+            this.handle("end", () => {
+                resolve(this.partialContent);
+            });
+        });
+    }
+
+    feed (chunk) {
+        if (this.eof) return;
+        this.partialContent += chunk;
+        this.handle('data', chunk);
+    }
+
+    close () {
+        this.eof = true;
+        this.handle('end', this.partialContent);
+    }
+
+    getContent () {
+        return this.contentPromise;
+    }
+
+    handle (event, ...args) {
+        for (let fn of this.listeners[event]) {
+            fn(...args)
+        }
+    }
+
+    on (event, callback) {
+        this.listeners[event].push(callback);
+
+        if (event == "data" && this.partialContent) {
+            callback(this.partialContent);
+        }
+        if (event == "end" && this.eof) {
+            callback();
+        }
+    }
+}