Enhance single instance management and deep link processing

- Refactored single instance handling to improve lock management and signal processing.
- Introduced functions for acquiring and releasing primary locks, along with handling instance signals.
- Updated deep link processing to utilize a signal file for better communication between instances.
- Enhanced Windows-specific launch argument retrieval to improve deep link handling on that platform.

src/desktop/single-instance.js

@@ -1,21 +1,27 @@
-import { mkdirSync, readFileSync, unlinkSync, writeFileSync, existsSync } from 'node:fs'
+import {
+  closeSync,
+  existsSync,
+  mkdirSync,
+  openSync,
+  readFileSync,
+  unlinkSync,
+  watch,
+  writeFileSync
+} from 'node:fs'
 import { join } from 'node:path'
 import { getWindowsLaunchSources } from './windows-launch-args.js'
 
-const SINGLE_INSTANCE_HOSTS = ['127.0.0.1', 'localhost']
-const SINGLE_INSTANCE_PATH = '/farmcontrol-instance'
+const LOCK_FILE = 'primary.lock'
+const SIGNAL_FILE = 'instance-signal.json'
 
-// Keep below Electrobun's RPC server range (50000+).
-function getSingleInstancePort() {
-  const identifier = 'com.tombutcher.farmcontrol'
-  let hash = 0
-
-  for (const char of identifier) {
-    hash = (hash * 31 + char.charCodeAt(0)) | 0
-  }
-
-  return 30000 + (Math.abs(hash) % 10000)
+let lockFd = null
+let pollInterval = null
+let fsWatcher = null
+let handlers = {
+  onDeepLink: null,
+  onFocus: null
 }
+const pendingMessages = []
 
 function getInstanceDir() {
   if (process.platform === 'win32') {
@@ -28,8 +34,77 @@ function getInstanceDir() {
   return join(process.env.TMPDIR || '/tmp', 'com.tombutcher.farmcontrol', 'instance')
 }
 
-function getPendingDeeplinkPath() {
-  return join(getInstanceDir(), 'pending-deeplink.json')
+function getLockPath() {
+  return join(getInstanceDir(), LOCK_FILE)
+}
+
+function getSignalPath() {
+  return join(getInstanceDir(), SIGNAL_FILE)
+}
+
+function isProcessAlive(pid) {
+  if (!Number.isInteger(pid) || pid <= 0) {
+    return false
+  }
+
+  try {
+    process.kill(pid, 0)
+    return true
+  } catch {
+    return false
+  }
+}
+
+function tryAcquirePrimaryLock() {
+  mkdirSync(getInstanceDir(), { recursive: true })
+  const lockPath = getLockPath()
+
+  if (existsSync(lockPath)) {
+    try {
+      const existingPid = Number.parseInt(readFileSync(lockPath, 'utf8').trim(), 10)
+
+      if (existingPid === process.pid) {
+        return true
+      }
+
+      if (isProcessAlive(existingPid)) {
+        return false
+      }
+
+      unlinkSync(lockPath)
+    } catch {
+      try {
+        unlinkSync(lockPath)
+      } catch {
+        // Ignore cleanup failures.
+      }
+    }
+  }
+
+  try {
+    lockFd = openSync(lockPath, 'wx')
+    writeFileSync(lockFd, String(process.pid))
+    return true
+  } catch {
+    return false
+  }
+}
+
+function releasePrimaryLock() {
+  if (lockFd !== null) {
+    try {
+      closeSync(lockFd)
+    } catch {
+      // Ignore close failures.
+    }
+    lockFd = null
+  }
+
+  try {
+    unlinkSync(getLockPath())
+  } catch {
+    // Ignore cleanup failures.
+  }
 }
 
 export function findProtocolUrl(args) {
@@ -70,11 +145,7 @@ function collectLaunchSources() {
   return sources
 }
 
-function getLaunchProtocolUrl() {
-  return findProtocolUrl(collectLaunchSources())
-}
-
-function buildSecondInstanceMessage() {
+function buildLaunchPayload() {
   const sources = collectLaunchSources()
   const url = findProtocolUrl(sources)
 
@@ -83,51 +154,33 @@ function buildSecondInstanceMessage() {
     : { type: 'focus', argv: sources }
 }
 
-function stagePendingDeeplink(message) {
-  const url = message?.url || findProtocolUrl(message?.argv || [])
-  if (!url) return
+function writeInstanceSignal(payload) {
+  const signalPath = getSignalPath()
+  mkdirSync(getInstanceDir(), { recursive: true })
 
-  try {
-    mkdirSync(getInstanceDir(), { recursive: true })
-    writeFileSync(
-      getPendingDeeplinkPath(),
-      JSON.stringify({ url, timestamp: Date.now() }),
-      'utf8'
-    )
-  } catch (error) {
-    console.warn('Failed to stage pending deeplink:', error)
-  }
+  const tempPath = `${signalPath}.${process.pid}.${Date.now()}.tmp`
+  writeFileSync(tempPath, JSON.stringify({ ...payload, timestamp: Date.now() }), 'utf8')
+  writeFileSync(signalPath, readFileSync(tempPath))
+  unlinkSync(tempPath)
 }
 
-function clearPendingDeeplinkFile() {
-  const filePath = getPendingDeeplinkPath()
-  if (!existsSync(filePath)) return
-
-  try {
-    unlinkSync(filePath)
-  } catch {
-    // Ignore cleanup failures.
-  }
-}
-
-function consumePendingDeeplinkFile() {
-  const filePath = getPendingDeeplinkPath()
-  if (!existsSync(filePath)) return null
-
-  try {
-    const data = JSON.parse(readFileSync(filePath, 'utf8'))
-    clearPendingDeeplinkFile()
-    return data?.url || null
-  } catch {
-    clearPendingDeeplinkFile()
+function readAndClearInstanceSignal() {
+  const signalPath = getSignalPath()
+  if (!existsSync(signalPath)) {
     return null
   }
-}
 
-function processPendingDeeplinkFile() {
-  const url = consumePendingDeeplinkFile()
-  if (url) {
-    dispatchMessage({ type: 'deeplink', url })
+  try {
+    const payload = JSON.parse(readFileSync(signalPath, 'utf8'))
+    unlinkSync(signalPath)
+    return payload
+  } catch {
+    try {
+      unlinkSync(signalPath)
+    } catch {
+      // Ignore cleanup failures.
+    }
+    return null
   }
 }
 
@@ -148,13 +201,6 @@ function resolveIncomingMessage(message) {
   return null
 }
 
-let server = null
-let handlers = {
-  onDeepLink: null,
-  onFocus: null
-}
-const pendingMessages = []
-
 function dispatchMessage(message) {
   const resolved = resolveIncomingMessage(message)
   if (!resolved) return
@@ -166,68 +212,38 @@ function dispatchMessage(message) {
 
   if (resolved.type === 'deeplink' && resolved.url) {
     handlers.onDeepLink?.(resolved.url)
-  } else if (resolved.type === 'focus') {
+    handlers.onFocus?.()
+    return
+  }
+
+  if (resolved.type === 'focus') {
     handlers.onFocus?.()
   }
 }
 
-function getSingleInstanceUrl(host) {
-  return `http://${host}:${getSingleInstancePort()}${SINGLE_INSTANCE_PATH}`
+function processInstanceSignal() {
+  dispatchMessage(readAndClearInstanceSignal())
 }
 
-async function tryForwardToPrimaryInstance(message) {
-  const body = JSON.stringify(message)
-
-  for (const host of SINGLE_INSTANCE_HOSTS) {
-    try {
-      const response = await fetch(getSingleInstanceUrl(host), {
-        method: 'POST',
-        headers: { 'Content-Type': 'application/json' },
-        body,
-        signal: AbortSignal.timeout(1000)
-      })
-
-      if (response.ok) {
-        return true
-      }
-    } catch {
-      // Try the next host.
-    }
+function startInstanceSignalWatcher() {
+  if (process.platform === 'darwin' || pollInterval) {
+    return
   }
 
-  return false
-}
+  mkdirSync(getInstanceDir(), { recursive: true })
+  processInstanceSignal()
 
-function startPrimaryInstanceServer() {
-  server = Bun.serve({
-    hostname: '127.0.0.1',
-    port: getSingleInstancePort(),
-    fetch: async (req) => {
-      const { pathname } = new URL(req.url)
-
-      if (req.method !== 'POST' || pathname !== SINGLE_INSTANCE_PATH) {
-        return new Response('Not found', { status: 404 })
+  try {
+    fsWatcher = watch(getInstanceDir(), (_event, filename) => {
+      if (!filename || filename === SIGNAL_FILE) {
+        setTimeout(processInstanceSignal, 25)
       }
+    })
+  } catch {
+    // Polling below covers filesystems without reliable watch support.
+  }
 
-      let message
-      try {
-        message = await req.json()
-      } catch {
-        return new Response('Bad request', { status: 400 })
-      }
-
-      dispatchMessage(message)
-
-      const resolved = resolveIncomingMessage(message)
-      if (resolved?.type === 'deeplink' && resolved.url) {
-        clearPendingDeeplinkFile()
-      } else {
-        processPendingDeeplinkFile()
-      }
-
-      return new Response('ok')
-    }
-  })
+  pollInterval = setInterval(processInstanceSignal, 250)
 }
 
 export async function ensureSingleInstanceLock() {
@@ -235,39 +251,39 @@ export async function ensureSingleInstanceLock() {
     return true
   }
 
-  const message = buildSecondInstanceMessage()
-  stagePendingDeeplink(message)
-
-  if (await tryForwardToPrimaryInstance(message)) {
-    return false
-  }
-
-  try {
-    startPrimaryInstanceServer()
-    return true
-  } catch (error) {
-    if (error?.code === 'EADDRINUSE') {
-      if (await tryForwardToPrimaryInstance(message)) {
-        return false
-      }
-    }
-
-    console.warn('Single instance lock failed:', error)
+  if (tryAcquirePrimaryLock()) {
     return true
   }
+
+  writeInstanceSignal(buildLaunchPayload())
+  return false
 }
 
 export function setSingleInstanceHandlers({ onDeepLink, onFocus }) {
   handlers = { onDeepLink, onFocus }
+  startInstanceSignalWatcher()
 
   while (pendingMessages.length > 0) {
     dispatchMessage(pendingMessages.shift())
   }
 
-  processPendingDeeplinkFile()
+  processInstanceSignal()
 }
 
 export function closeSingleInstanceServer() {
-  server?.stop?.()
-  server = null
+  if (pollInterval) {
+    clearInterval(pollInterval)
+    pollInterval = null
+  }
+
+  if (fsWatcher) {
+    try {
+      fsWatcher.close()
+    } catch {
+      // Ignore close failures.
+    }
+    fsWatcher = null
+  }
+
+  releasePrimaryLock()
 }

src/desktop/window.js

@@ -22,8 +22,14 @@ export function getMainWindow() {
 }
 
 export function showMainWindow() {
-  mainWindow?.show?.()
-  mainWindow?.activate?.()
+  if (!mainWindow) return
+
+  if (mainWindow.isMinimized?.()) {
+    mainWindow.restore?.()
+  }
+
+  mainWindow.show?.()
+  mainWindow.activate?.()
 }
 
 export async function getMainViewUrl() {
@@ -45,8 +51,15 @@ export async function getMainViewUrl() {
 
 function deliverNavigation(redirectPath) {
   sendToRenderer('navigate', redirectPath)
-  mainWindow?.show?.()
-  mainWindow?.activate?.()
+
+  if (!mainWindow) return
+
+  if (mainWindow.isMinimized?.()) {
+    mainWindow.restore?.()
+  }
+
+  mainWindow.show?.()
+  mainWindow.activate?.()
 }
 
 function flushPendingNavigations() {

src/desktop/windows-launch-args.js

@@ -1,8 +1,42 @@
-export function getWindowsLaunchSources() {
-  if (process.platform !== 'win32') {
-    return []
-  }
+function runCommand(command) {
+  try {
+    const proc = Bun.spawnSync({
+      cmd: ['cmd.exe', '/c', command],
+      stdout: 'pipe',
+      stderr: 'pipe'
+    })
 
+    if (proc.exitCode !== 0) {
+      return ''
+    }
+
+    return proc.stdout.toString()
+  } catch {
+    return ''
+  }
+}
+
+function getWmicValue(output, key) {
+  const match = output.match(new RegExp(`${key}=(.+?)(?:\\r?\\n|$)`, 'i'))
+  return match?.[1]?.trim() ?? ''
+}
+
+function getProcessCommandLine(pid) {
+  const output = runCommand(
+    `wmic process where "ProcessId=${pid}" get CommandLine /value`
+  )
+  return getWmicValue(output, 'CommandLine')
+}
+
+function getParentProcessId(pid) {
+  const output = runCommand(
+    `wmic process where "ProcessId=${pid}" get ParentProcessId /value`
+  )
+  const parentPid = getWmicValue(output, 'ParentProcessId')
+  return parentPid ? Number.parseInt(parentPid, 10) : null
+}
+
+function getPowerShellCommandLines() {
   try {
     const proc = Bun.spawnSync({
       cmd: [
@@ -37,3 +71,35 @@ for ($i = 0; $i -lt 6; $i++) {
     return []
   }
 }
+
+export function getWindowsLaunchSources() {
+  if (process.platform !== 'win32') {
+    return []
+  }
+
+  const sources = []
+  let pid = process.pid
+
+  for (let depth = 0; depth < 6; depth += 1) {
+    const commandLine = getProcessCommandLine(pid)
+    if (commandLine) {
+      sources.push(commandLine)
+      if (/farmcontrol:\/\//i.test(commandLine)) {
+        return sources
+      }
+    }
+
+    const parentPid = getParentProcessId(pid)
+    if (!parentPid || parentPid === pid) {
+      break
+    }
+
+    pid = parentPid
+  }
+
+  if (sources.length === 0) {
+    return getPowerShellCommandLines()
+  }
+
+  return sources
+}