Move heart and AuthType out of http

This file is going to get blasted in favor of Express.

src/node/heart.ts

@@ -0,0 +1,46 @@
+import { logger } from "@coder/logger"
+import { promises as fs } from "fs"
+
+/**
+ * Provides a heartbeat using a local file to indicate activity.
+ */
+export class Heart {
+  private heartbeatTimer?: NodeJS.Timeout
+  private heartbeatInterval = 60000
+  public lastHeartbeat = 0
+
+  public constructor(private readonly heartbeatPath: string, private readonly isActive: () => Promise<boolean>) {}
+
+  public alive(): boolean {
+    const now = Date.now()
+    return now - this.lastHeartbeat < this.heartbeatInterval
+  }
+  /**
+   * Write to the heartbeat file if we haven't already done so within the
+   * timeout and start or reset a timer that keeps running as long as there is
+   * activity. Failures are logged as warnings.
+   */
+  public beat(): void {
+    if (!this.alive()) {
+      logger.trace("heartbeat")
+      fs.writeFile(this.heartbeatPath, "").catch((error) => {
+        logger.warn(error.message)
+      })
+      this.lastHeartbeat = Date.now()
+      if (typeof this.heartbeatTimer !== "undefined") {
+        clearTimeout(this.heartbeatTimer)
+      }
+      this.heartbeatTimer = setTimeout(() => {
+        this.isActive()
+          .then((active) => {
+            if (active) {
+              this.beat()
+            }
+          })
+          .catch((error) => {
+            logger.warn(error.message)
+          })
+      }, this.heartbeatInterval)
+    }
+  }
+}