feat: add error handling and toast notifications (#8)

- Add errorMessage() utility for user-friendly toast messages
- Show toast on tailscale up/down/set/status failures
- Detect missing tailscale binary (exit code 127)
- Guard toggleTailscale and setExitNode when binary unavailable
- Show 'Tailscale not available' in popout when binary missing

tailscalectl/TailscaleWidget.qml

@@ -11,6 +11,7 @@ PluginComponent {
     id: root
 
     property bool isConnected: false
+    property bool binaryAvailable: true
     property string tailscaleIP: ""
     property string currentExitNode: ""
     property var peers: []
@@ -35,6 +36,10 @@ PluginComponent {
         id: toggleProcess
 
         onExited: (code, status) => {
+            if (code !== 0) {
+                var action = root.isConnected ? "disconnect" : "connect"
+                ToastService.showError("tailscalectl", TailscaleLib.errorMessage(action))
+            }
             statusCheck.running = true
         }
     }
@@ -48,7 +53,7 @@ PluginComponent {
 
         onExited: (code, status) => {
             if (code !== 0) {
-                ToastService.showError("tailscalectl", "Failed to set exit node")
+                ToastService.showError("tailscalectl", TailscaleLib.errorMessage("set"))
             }
             statusCheck.running = true
         }
@@ -99,11 +104,21 @@ PluginComponent {
                 root.tailscaleIP = ""
                 root.currentExitNode = ""
                 root.peers = []
+                if (code === 127) {
+                    root.binaryAvailable = false
+                    ToastService.showError("tailscalectl", "Tailscale binary not found")
+                } else {
+                    ToastService.showError("tailscalectl", TailscaleLib.errorMessage("status"))
+                }
             }
         }
     }
 
     function toggleTailscale() {
+        if (!root.binaryAvailable) {
+            ToastService.showError("tailscalectl", "Tailscale not available")
+            return
+        }
         if (root.isConnected) {
             toggleProcess.command = ["tailscale", "down"]
         } else {
@@ -113,6 +128,10 @@ PluginComponent {
     }
 
     function setExitNode(hostname) {
+        if (!root.binaryAvailable) {
+            ToastService.showError("tailscalectl", "Tailscale not available")
+            return
+        }
         exitNodeProcess.command = TailscaleLib.makeExitNodeCommand(hostname)
         exitNodeProcess.running = true
     }
@@ -138,6 +157,14 @@ PluginComponent {
                 width: parent.width
                 height: Theme.spacingM + statusRow.implicitHeight + Theme.spacingM + peerList.height + Theme.spacingM
 
+                StyledText {
+                    visible: !root.binaryAvailable
+                    text: "Tailscale not available"
+                    anchors.centerIn: parent
+                    font.pixelSize: Theme.fontSizeSmall
+                    color: Theme.surfaceVariantText
+                }
+
                 Row {
                     id: statusRow
                     y: Theme.spacingM

tailscalectl/lib.js

@@ -15,7 +15,19 @@ function makeExitNodeCommand(hostname) {
     return ["tailscale", "set", "--exit-node=" + hostname]
 }
 
+function errorMessage(cmd) {
+    var messages = {
+        "up": "Failed to connect to Tailscale",
+        "connect": "Failed to connect to Tailscale",
+        "down": "Failed to disconnect from Tailscale",
+        "disconnect": "Failed to disconnect from Tailscale",
+        "set": "Failed to set exit node",
+        "status": "Failed to read Tailscale status"
+    }
+    return messages[cmd] || "Tailscale command failed"
+}
+
 // CommonJS export for Node.js tests (ignored by QML)
 if (typeof module !== "undefined" && module.exports) {
-    module.exports = { parsePeers, makeExitNodeCommand }
+    module.exports = { parsePeers, makeExitNodeCommand, errorMessage }
 }

test/lib.test.js

@@ -1,7 +1,7 @@
 import { test } from "node:test"
 import assert from "node:assert"
 import lib from "../tailscalectl/lib.js"
-const { parsePeers, makeExitNodeCommand } = lib
+const { parsePeers, makeExitNodeCommand, errorMessage } = lib
 
 test("parsePeers extracts exitNode from ExitNodeOption", () => {
     const peerMap = {
@@ -34,3 +34,28 @@ test("makeExitNodeCommand with empty string clears exit node", () => {
     const cmd = makeExitNodeCommand("")
     assert.deepStrictEqual(cmd, ["tailscale", "set", "--exit-node="])
 })
+
+test("errorMessage returns user-friendly message for tailscale up failure", () => {
+    const msg = errorMessage("up", 1)
+    assert.strictEqual(msg, "Failed to connect to Tailscale")
+})
+
+test("errorMessage returns user-friendly message for tailscale down failure", () => {
+    const msg = errorMessage("down", 1)
+    assert.strictEqual(msg, "Failed to disconnect from Tailscale")
+})
+
+test("errorMessage returns user-friendly message for tailscale set failure", () => {
+    const msg = errorMessage("set", 1)
+    assert.strictEqual(msg, "Failed to set exit node")
+})
+
+test("errorMessage returns user-friendly message for tailscale status failure", () => {
+    const msg = errorMessage("status", 1)
+    assert.strictEqual(msg, "Failed to read Tailscale status")
+})
+
+test("errorMessage returns generic message for unknown command", () => {
+    const msg = errorMessage("unknown", 1)
+    assert.strictEqual(msg, "Tailscale command failed")
+})