Hello world

First open source release of Campfire 🎉

app/javascript/models/typing_tracker.js

@@ -0,0 +1,42 @@
+const REFRESH_INTERVAL = 1000
+const TYPING_TIMEOUT = 5000
+
+export default class TypingTracker {
+  constructor(callback) {
+    this.callback = callback
+    this.currentlyTyping = {}
+    this.timer = setInterval(this.#refresh.bind(this), REFRESH_INTERVAL)
+  }
+
+  close() {
+    clearInterval(this.timer)
+  }
+
+  add(name) {
+    this.currentlyTyping[name] = Date.now()
+    this.#refresh()
+  }
+
+  remove(name) {
+    delete this.currentlyTyping[name]
+    this.#refresh()
+  }
+
+  #refresh() {
+    this.#purgeInactive()
+    const names = Object.keys(this.currentlyTyping).sort()
+
+    if (names.length > 0) {
+      this.callback(`${names.join(", ")}`)
+    } else {
+      this.callback(null)
+    }
+  }
+
+  #purgeInactive() {
+    const cutoff = Date.now() - TYPING_TIMEOUT
+    this.currentlyTyping = Object.fromEntries(
+      Object.entries(this.currentlyTyping).filter(([_name, timestamp]) => timestamp > cutoff)
+   )
+  }
+}