First attempt at an implementation; requires script be running

src/NetscriptFunctions.ts

@@ -55,7 +55,7 @@ import { makeRuntimeRejectMsg, netscriptDelay, resolveNetscriptRequestedThreads
 import { numeralWrapper } from "./ui/numeralFormat";
 import { convertTimeMsToTimeElapsedString } from "./utils/StringHelperFunctions";
 
-import { LogBoxEvents } from "./ui/React/LogBoxManager";
+import { LogBoxEvents, LogBoxCloserEvents } from "./ui/React/LogBoxManager";
 import { arrayToString } from "./utils/helpers/arrayToString";
 import { isString } from "./utils/helpers/isString";
 
@@ -826,8 +826,7 @@ export function NetscriptFunctions(workerScript: WorkerScript): NS {
         workerScript.log(
           "weaken",
           () =>
-            `'${server.hostname}' security level weakened to ${
+            `'${server.hostname}' security level weakened to ${server.hackDifficulty
-              server.hackDifficulty
             }. Gained ${numeralWrapper.formatExp(expGain)} hacking exp (t=${numeralWrapper.formatThreads(threads)})`,
         );
         workerScript.scriptRef.onlineExpGained += expGain;
@@ -990,7 +989,21 @@ export function NetscriptFunctions(workerScript: WorkerScript): NS {
     },
     closeTail: function (fn: any, hostname: any = workerScript.hostname, ...scriptArgs: any[]): void {
       updateDynamicRam("closeTail", getRamCost(Player, "closeTail"));
-      // TODO
+      //Get the script object
+      let runningScriptObj;
+      if (arguments.length === 0) {
+        runningScriptObj = workerScript.scriptRef;
+      } else if (typeof fn === "number") {
+        runningScriptObj = getRunningScriptByPid(fn, "tail");
+      } else {
+        runningScriptObj = getRunningScript(fn, hostname, "tail", scriptArgs);
+      }
+      if (runningScriptObj == null) {
+        workerScript.log("closeTail", () => getCannotFindRunningScriptErrorMessage(fn, hostname, scriptArgs));
+        return;
+      }
+      //Emit an event to tell the game to close the tail window
+      LogBoxCloserEvents.emit(runningScriptObj);
     },
     nuke: function (_hostname: unknown): boolean {
       updateDynamicRam("nuke", getRamCost(Player, "nuke"));

src/ui/React/LogBoxManager.tsx

@@ -23,6 +23,7 @@ import { Settings } from "../../Settings/Settings";
 let layerCounter = 0;
 
 export const LogBoxEvents = new EventEmitter<[RunningScript]>();
+export const LogBoxCloserEvents = new EventEmitter<[RunningScript]>();
 export const LogBoxClearEvents = new EventEmitter<[]>();
 
 interface Log {
@@ -51,6 +52,16 @@ export function LogBoxManager(): React.ReactElement {
     [],
   );
 
+  //Event used by ns.closeTail to close tail windows
+  useEffect(
+    () =>
+      LogBoxCloserEvents.subscribe((script: RunningScript) => {
+        const id = script.server + "-" + script.filename + script.args.map((x: any): string => `${x}`).join("-");
+        close(id);
+      }),
+    [],
+  );
+
   useEffect(() =>
     LogBoxClearEvents.subscribe(() => {
       logs = [];