Merge pull request #11 from Twest2/StepForge pr/07-platform-interfaces

Introduce the platform adapter layer; extract window context behind it (plan PR 7)

app/main.js

@@ -899,6 +899,9 @@ function setupIpc() {
     dataDir: store.root,
     platform: process.platform,
   }));
+  // Platform capture-capability profile (session type, portal/PipeWire,
+  // xinput, click source, actionable messages) for the diagnostics UI.
+  h('platform:capabilities', () => require('./platform').detectCapabilities());
 }
 
 // ---- lifecycle --------------------------------------------------------------

app/platform/darwin/window-context.js

@@ -0,0 +1,43 @@
+'use strict';
+
+const { execFileSync } = require('node:child_process');
+
+/**
+ * macOS WindowContextProvider using AppleScript / System Events. Extracted
+ * verbatim from text-intel.js. macOS is not a primary support target, but the
+ * adapter is kept so the shared code has no `process.platform` branch and the
+ * behavior is preserved where it exists. Never throws.
+ */
+function createDarwinWindowContextProvider() {
+  return {
+    async collect() {
+      const script = `
+      set appName to ""
+      set windowTitle to ""
+      tell application "System Events"
+        try
+          set frontApp to first application process whose frontmost is true
+          set appName to name of frontApp
+          try
+            set windowTitle to name of front window of frontApp
+          end try
+        end try
+      end tell
+      return appName & linefeed & windowTitle
+    `;
+      try {
+        const result = execFileSync('osascript', ['-e', script], {
+          encoding: 'utf8',
+          stdio: ['ignore', 'pipe', 'pipe'],
+          timeout: 1200,
+        }).trimEnd();
+        const [appName = '', windowTitle = ''] = result.split(/\r?\n/);
+        return { appName, windowTitle };
+      } catch {
+        return { appName: '', windowTitle: '' };
+      }
+    },
+  };
+}
+
+module.exports = { createDarwinWindowContextProvider };

app/platform/index.js

@@ -0,0 +1,66 @@
+'use strict';
+
+/**
+ * The single factory that selects a platform implementation. The rest of the
+ * app depends on the interfaces in ./interfaces.js and asks this module for a
+ * concrete adapter — it never branches on `process.platform` itself.
+ *
+ * As Linux runtime capture is implemented, its ClickSource / ScreenFrameSource
+ * adapters are added here; today this provides the WindowContextProvider for
+ * every platform and the Linux capability diagnostics.
+ */
+
+const { assertWindowContextProvider } = require('./interfaces');
+
+function detectPlatform(platform = process.platform) {
+  if (platform === 'win32') return 'windows';
+  if (platform === 'darwin') return 'darwin';
+  if (platform === 'linux') return 'linux';
+  return 'unsupported';
+}
+
+/**
+ * Build the WindowContextProvider for the current OS. `platform` is injectable
+ * so the selection logic is unit-testable off the target OS.
+ */
+function createWindowContextProvider({ platform = process.platform } = {}) {
+  const os = detectPlatform(platform);
+  let provider;
+  switch (os) {
+    case 'windows':
+      provider = require('./windows/window-context').createWindowsWindowContextProvider();
+      break;
+    case 'darwin':
+      provider = require('./darwin/window-context').createDarwinWindowContextProvider();
+      break;
+    case 'linux':
+      provider = require('./linux/window-context').createLinuxWindowContextProvider();
+      break;
+    default:
+      // Unsupported OS: a null-object provider so callers still work.
+      provider = { async collect() { return { appName: '', windowTitle: '' }; } };
+  }
+  return assertWindowContextProvider(provider);
+}
+
+/**
+ * Capability profile for the current OS (used by diagnostics UI). Only Linux
+ * has a rich profile today; other platforms report their OS and a capable
+ * baseline.
+ */
+function detectCapabilities({ platform = process.platform, env = process.env } = {}) {
+  const os = detectPlatform(platform);
+  if (os === 'linux') {
+    return require('./linux/diagnostics').detectLinuxCapabilities({ env });
+  }
+  return {
+    os,
+    sessionType: os,
+    isWayland: false,
+    clickCapture: os === 'windows' ? 'windows-hook' : os,
+    screenCapture: os,
+    messages: [],
+  };
+}
+
+module.exports = { detectPlatform, createWindowContextProvider, detectCapabilities };

app/platform/interfaces.js

@@ -0,0 +1,62 @@
+'use strict';
+
+/**
+ * Platform adapter interfaces (documentation + light runtime shape checks).
+ *
+ * The platform-neutral capture/text-intel code consumes these interfaces and
+ * never inspects `process.platform` itself. `app/platform/index.js` is the
+ * only module that selects a concrete implementation. New OS support is a new
+ * set of files under `app/platform/<os>/`, not more conditionals inside the
+ * shared code.
+ *
+ * ---------------------------------------------------------------------------
+ * WindowContextProvider
+ *   collect(osPoint?: {x,y}) -> Promise<{
+ *     appName, windowTitle,
+ *     elementLabel?, elementRole?, elementClass?, elementValue?
+ *   }>
+ *   Best-effort foreground window / clicked-element context. Never throws;
+ *   returns {} (or partial) when unavailable.
+ *
+ * ClickSource   (runtime capture — implemented incrementally per platform)
+ *   describe() -> { source, coordinates: boolean, keyboard: boolean }
+ *     source ∈ 'windows-hook' | 'x11' | 'evdev-x11' | 'evdev-wayland' |
+ *              'wayland-portal' | 'hotkey' | 'interval' | 'unavailable'
+ *
+ * PowerPolicy
+ *   setRecording(recording: boolean) -> void
+ *   Holds/releases OS power + throttling state for the recording lifecycle.
+ *
+ * PlatformCapabilities  (from index.detectCapabilities())
+ *   { os, sessionType, isWayland, hasXinput, canSandbox, ... }
+ * ---------------------------------------------------------------------------
+ */
+
+// Interface names, exported so adapters and tests can reference a single
+// source of truth for the contract identifiers.
+const INTERFACES = Object.freeze([
+  'WindowContextProvider',
+  'ClickSource',
+  'PowerPolicy',
+]);
+
+const CLICK_SOURCES = Object.freeze([
+  'windows-hook',
+  'x11',
+  'evdev-x11',
+  'evdev-wayland',
+  'wayland-portal',
+  'hotkey',
+  'interval',
+  'unavailable',
+]);
+
+/** Assert a value looks like a WindowContextProvider (has async collect()). */
+function assertWindowContextProvider(provider) {
+  if (!provider || typeof provider.collect !== 'function') {
+    throw new Error('platform: WindowContextProvider must implement collect()');
+  }
+  return provider;
+}
+
+module.exports = { INTERFACES, CLICK_SOURCES, assertWindowContextProvider };

app/platform/linux/diagnostics.js

@@ -0,0 +1,99 @@
+'use strict';
+
+const fs = require('node:fs');
+const { execFileSync } = require('node:child_process');
+
+/**
+ * Linux capture-capability diagnostics. Detects the session type, portal /
+ * PipeWire availability, xinput, readable input devices, and the sandbox
+ * situation, and turns them into an actionable capability profile the UI can
+ * show instead of console-only failures.
+ *
+ * Pure detection with injectable probes so it is unit-testable without a real
+ * desktop session.
+ */
+
+function defaultHasBinary(name) {
+  try {
+    execFileSync('which', [name], { stdio: 'pipe' });
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+function detectSessionType(env = process.env) {
+  const t = String(env.XDG_SESSION_TYPE || '').toLowerCase();
+  if (t === 'wayland' || t === 'x11') return t;
+  if (env.WAYLAND_DISPLAY) return 'wayland';
+  if (env.DISPLAY) return 'x11';
+  return 'unknown';
+}
+
+function detectLinuxCapabilities({
+  env = process.env,
+  hasBinary = defaultHasBinary,
+  existsSync = fs.existsSync,
+  readdirSync = fs.readdirSync,
+} = {}) {
+  const sessionType = detectSessionType(env);
+  const isWayland = sessionType === 'wayland';
+
+  // XDG Desktop Portal + PipeWire are how Wayland screen capture works.
+  const hasPortalBus = Boolean(env.DBUS_SESSION_BUS_ADDRESS);
+  let hasPipeWire = false;
+  try {
+    hasPipeWire = hasBinary('pipewire') || existsSync(`/run/user/${process.getuid ? process.getuid() : ''}/pipewire-0`);
+  } catch {
+    hasPipeWire = hasBinary('pipewire');
+  }
+
+  const hasXinput = hasBinary('xinput');
+  const hasXprop = hasBinary('xprop');
+
+  // Readable /dev/input event nodes gate the evdev click fallback.
+  let readableInputDevices = 0;
+  try {
+    for (const name of readdirSync('/dev/input')) {
+      if (!/^event\d+$/.test(name)) continue;
+      try { fs.accessSync(`/dev/input/${name}`, fs.constants.R_OK); readableInputDevices += 1; } catch { /* not readable */ }
+    }
+  } catch { /* /dev/input not present */ }
+
+  // Determine the click-capture profile for this session.
+  let clickCapture;
+  if (!isWayland && hasXinput) clickCapture = 'x11-xinput';
+  else if (readableInputDevices > 0) clickCapture = isWayland ? 'evdev-wayland' : 'evdev-x11';
+  else clickCapture = 'hotkey-or-interval-only';
+
+  const messages = [];
+  if (isWayland && !hasPipeWire) {
+    messages.push('Wayland screen capture needs PipeWire and the XDG Desktop Portal. Install pipewire and xdg-desktop-portal.');
+  }
+  if (isWayland && !hasPortalBus) {
+    messages.push('No D-Bus session bus detected; the screen-share portal cannot be reached.');
+  }
+  if (!isWayland && !hasXinput) {
+    messages.push('xinput not found: per-click capture with a marker is unavailable on X11 without it.');
+  }
+  if (clickCapture === 'hotkey-or-interval-only') {
+    messages.push('No global click source available. Recording falls back to a hotkey or interval trigger.');
+  }
+
+  return {
+    os: 'linux',
+    sessionType,
+    isWayland,
+    hasPortalBus,
+    hasPipeWire,
+    hasXinput,
+    hasXprop,
+    readableInputDevices,
+    clickCapture,
+    // Portal capture is the safe Wayland baseline; X11 can grab directly.
+    screenCapture: isWayland ? 'wayland-portal' : 'x11-direct',
+    messages,
+  };
+}
+
+module.exports = { detectLinuxCapabilities, detectSessionType };

app/platform/linux/window-context.js

@@ -0,0 +1,51 @@
+'use strict';
+
+const { execFileSync } = require('node:child_process');
+
+function hasBinary(name) {
+  try {
+    execFileSync('which', [name], { stdio: 'pipe' });
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+/**
+ * Linux (X11) WindowContextProvider using xprop on the active window. On
+ * Wayland xprop only sees XWayland clients, so context is best-effort; the
+ * portal-based capture path does not depend on it. Extracted verbatim from
+ * text-intel.js. Never throws.
+ */
+function createLinuxWindowContextProvider() {
+  return {
+    async collect() {
+      try {
+        if (!hasBinary('xprop')) return { appName: '', windowTitle: '' };
+        const active = execFileSync('xprop', ['-root', '_NET_ACTIVE_WINDOW'], {
+          encoding: 'utf8',
+          stdio: ['ignore', 'pipe', 'pipe'],
+          timeout: 1200,
+        });
+        const activeMatch = active.match(/window id # (0x[0-9a-fA-F]+)/);
+        if (!activeMatch) return { appName: '', windowTitle: '' };
+        const winId = activeMatch[1];
+        const details = execFileSync('xprop', ['-id', winId, '_NET_WM_NAME', 'WM_NAME', 'WM_CLASS'], {
+          encoding: 'utf8',
+          stdio: ['ignore', 'pipe', 'pipe'],
+          timeout: 1200,
+        });
+        const titleMatch = details.match(/(?:_NET_WM_NAME\(UTF8_STRING\)|WM_NAME\(STRING\)|WM_NAME\(UTF8_STRING\)) = "([^"]*)"/);
+        const classMatch = details.match(/WM_CLASS\(STRING\) = "([^"]*)"(?:, "([^"]*)")?/);
+        return {
+          appName: classMatch ? (classMatch[2] || classMatch[1] || '') : '',
+          windowTitle: titleMatch ? titleMatch[1] : '',
+        };
+      } catch {
+        return { appName: '', windowTitle: '' };
+      }
+    },
+  };
+}
+
+module.exports = { createLinuxWindowContextProvider, hasBinary };

app/platform/windows/window-context.js

@@ -0,0 +1,88 @@
+'use strict';
+
+const { execFile } = require('node:child_process');
+
+/**
+ * Windows WindowContextProvider. Reads the foreground window (Win32) and, when
+ * a click point is given, the UI Automation element under it. Best-effort:
+ * resolves {} on any failure. Extracted verbatim from text-intel.js so the
+ * shared code carries no `process.platform` branch.
+ */
+function createWindowsWindowContextProvider() {
+  return {
+    async collect(osPoint = null) {
+      const hasPoint = osPoint && Number.isFinite(osPoint.x) && Number.isFinite(osPoint.y);
+      const clickX = hasPoint ? Number(osPoint.x) : 0;
+      const clickY = hasPoint ? Number(osPoint.y) : 0;
+      const script = `
+      $clickX = ${clickX};
+      $clickY = ${clickY};
+      $elementLabel = '';
+      $elementRole = '';
+      $elementClass = '';
+      $elementProcessId = 0;
+      $elementValue = '';
+      if (${hasPoint ? '$true' : '$false'}) {
+        try {
+          Add-Type -AssemblyName UIAutomationClient,UIAutomationTypes,WindowsBase | Out-Null
+          $point = New-Object System.Windows.Point($clickX, $clickY);
+          $element = [System.Windows.Automation.AutomationElement]::FromPoint($point);
+          if ($element) {
+            $current = $element.Current;
+            $elementLabel = $current.Name;
+            $elementRole = $current.LocalizedControlType;
+            $elementClass = $current.ClassName;
+            $elementProcessId = $current.ProcessId;
+            try {
+              $valPattern = [System.Windows.Automation.ValuePattern]::Pattern;
+              if ($element.GetSupportedPatterns() -contains $valPattern) {
+                $elementValue = $element.GetCurrentPattern($valPattern).Current.Value;
+              }
+            } catch { }
+          }
+        } catch { }
+      }
+      Add-Type @"
+using System;
+using System.Runtime.InteropServices;
+using System.Text;
+public static class Win32 {
+  [DllImport("user32.dll")] public static extern IntPtr GetForegroundWindow();
+  [DllImport("user32.dll", CharSet = CharSet.Unicode)]
+  public static extern int GetWindowText(IntPtr hWnd, StringBuilder text, int count);
+  [DllImport("user32.dll")] public static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint processId);
+}
+"@;
+      $hWnd = [Win32]::GetForegroundWindow();
+      $sb = New-Object System.Text.StringBuilder 512;
+      [void][Win32]::GetWindowText($hWnd, $sb, $sb.Capacity);
+      $pid = 0;
+      [void][Win32]::GetWindowThreadProcessId($hWnd, [ref]$pid);
+      $proc = Get-Process -Id $pid -ErrorAction SilentlyContinue | Select-Object -First 1;
+      $out = [ordered]@{
+        appName = if ($proc) { $proc.ProcessName } else { '' };
+        windowTitle = $sb.ToString();
+        elementLabel = $elementLabel;
+        elementRole = $elementRole;
+        elementClass = $elementClass;
+        elementValue = $elementValue;
+        elementProcessId = $elementProcessId;
+        pid = $pid;
+      };
+      $out | ConvertTo-Json -Compress;
+    `;
+      return new Promise((resolve) => {
+        execFile('powershell.exe', ['-NoProfile', '-NonInteractive', '-ExecutionPolicy', 'Bypass', '-Command', script], {
+          encoding: 'utf8',
+          timeout: 4000,
+          windowsHide: true,
+        }, (err, stdout) => {
+          if (err) { resolve({}); return; }
+          try { resolve(JSON.parse(stdout.trim() || '{}')); } catch { resolve({}); }
+        });
+      });
+    },
+  };
+}
+
+module.exports = { createWindowsWindowContextProvider };

app/preload.js

@@ -107,6 +107,7 @@ const api = {
   },
   app: {
     info: invoke('app:info'),
+    platformCapabilities: invoke('platform:capabilities'),
   },
 };
 

app/text-intel.js

@@ -2,7 +2,6 @@
 
 const fs = require('node:fs');
 const path = require('node:path');
-const { execFileSync, execFile } = require('node:child_process');
 
 const {
   DEFAULT_CAPTURE_TITLES,
@@ -23,15 +22,6 @@ const OCR_CROP = {
   height: 220,
 };
 
-function hasBinary(name) {
-  try {
-    execFileSync('which', [name], { stdio: 'pipe' });
-    return true;
-  } catch {
-    return false;
-  }
-}
-
 function clamp(v, min, max) {
   return Math.min(max, Math.max(min, v));
 }
@@ -63,6 +53,7 @@ class TextIntelService {
     dataDir,
     fetchImpl = global.fetch,
     screenApi = null,
+    windowContextProvider = null,
   }) {
     this.store = store;
     this.settings = settings;
@@ -70,6 +61,10 @@ class TextIntelService {
     this.dataDir = dataDir;
     this.fetch = fetchImpl;
     this.screen = screenApi;
+    // OS-specific foreground-window/element detection is a platform adapter.
+    // This code no longer branches on process.platform; the factory selects it.
+    this.windowContext = windowContextProvider
+      || require('./platform').createWindowContextProvider();
     this.worker = null;
     this.workerPromise = null;
     this.workerQueue = Promise.resolve();
@@ -271,135 +266,13 @@ class TextIntelService {
 
   async collectForegroundWindowContext(osPoint = null) {
     try {
-      if (process.platform === 'win32') return this.collectWindowsWindowContext(osPoint);
-      if (process.platform === 'darwin') return this.collectMacWindowContext();
-      if (process.platform === 'linux') return this.collectLinuxWindowContext();
+      return await this.windowContext.collect(osPoint);
     } catch {
       // best effort only
+      return { appName: '', windowTitle: '' };
     }
-    return { appName: '', windowTitle: '' };
   }
 
-  async collectWindowsWindowContext(osPoint = null) {
-    const hasPoint = osPoint && Number.isFinite(osPoint.x) && Number.isFinite(osPoint.y);
-    const clickX = hasPoint ? Number(osPoint.x) : 0;
-    const clickY = hasPoint ? Number(osPoint.y) : 0;
-    const script = `
-      $clickX = ${clickX};
-      $clickY = ${clickY};
-      $elementLabel = '';
-      $elementRole = '';
-      $elementClass = '';
-      $elementProcessId = 0;
-      $elementValue = '';
-      if (${hasPoint ? '$true' : '$false'}) {
-        try {
-          Add-Type -AssemblyName UIAutomationClient,UIAutomationTypes,WindowsBase | Out-Null
-          $point = New-Object System.Windows.Point($clickX, $clickY);
-          $element = [System.Windows.Automation.AutomationElement]::FromPoint($point);
-          if ($element) {
-            $current = $element.Current;
-            $elementLabel = $current.Name;
-            $elementRole = $current.LocalizedControlType;
-            $elementClass = $current.ClassName;
-            $elementProcessId = $current.ProcessId;
-            try {
-              $valPattern = [System.Windows.Automation.ValuePattern]::Pattern;
-              if ($element.GetSupportedPatterns() -contains $valPattern) {
-                $elementValue = $element.GetCurrentPattern($valPattern).Current.Value;
-              }
-            } catch { }
-          }
-        } catch { }
-      }
-      Add-Type @"
-using System;
-using System.Runtime.InteropServices;
-using System.Text;
-public static class Win32 {
-  [DllImport("user32.dll")] public static extern IntPtr GetForegroundWindow();
-  [DllImport("user32.dll", CharSet = CharSet.Unicode)]
-  public static extern int GetWindowText(IntPtr hWnd, StringBuilder text, int count);
-  [DllImport("user32.dll")] public static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint processId);
-}
-"@;
-      $hWnd = [Win32]::GetForegroundWindow();
-      $sb = New-Object System.Text.StringBuilder 512;
-      [void][Win32]::GetWindowText($hWnd, $sb, $sb.Capacity);
-      $pid = 0;
-      [void][Win32]::GetWindowThreadProcessId($hWnd, [ref]$pid);
-      $proc = Get-Process -Id $pid -ErrorAction SilentlyContinue | Select-Object -First 1;
-      $out = [ordered]@{
-        appName = if ($proc) { $proc.ProcessName } else { '' };
-        windowTitle = $sb.ToString();
-        elementLabel = $elementLabel;
-        elementRole = $elementRole;
-        elementClass = $elementClass;
-        elementValue = $elementValue;
-        elementProcessId = $elementProcessId;
-        pid = $pid;
-      };
-      $out | ConvertTo-Json -Compress;
-    `;
-    return new Promise(resolve => {
-      execFile('powershell.exe', ['-NoProfile', '-NonInteractive', '-ExecutionPolicy', 'Bypass', '-Command', script], {
-        encoding: 'utf8',
-        timeout: 4000,
-        windowsHide: true,
-      }, (err, stdout) => {
-        if (err) { resolve({}); return; }
-        try { resolve(JSON.parse(stdout.trim() || '{}')); }
-        catch { resolve({}); }
-      });
-    });
-  }
-
-  collectMacWindowContext() {
-    const script = `
-      set appName to ""
-      set windowTitle to ""
-      tell application "System Events"
-        try
-          set frontApp to first application process whose frontmost is true
-          set appName to name of frontApp
-          try
-            set windowTitle to name of front window of frontApp
-          end try
-        end try
-      end tell
-      return appName & linefeed & windowTitle
-    `;
-    const result = execFileSync('osascript', ['-e', script], {
-      encoding: 'utf8',
-      stdio: ['ignore', 'pipe', 'pipe'],
-      timeout: 1200,
-    }).trimEnd();
-    const [appName = '', windowTitle = ''] = result.split(/\r?\n/);
-    return { appName, windowTitle };
-  }
-
-  collectLinuxWindowContext() {
-    if (!hasBinary('xprop')) return { appName: '', windowTitle: '' };
-    const active = execFileSync('xprop', ['-root', '_NET_ACTIVE_WINDOW'], {
-      encoding: 'utf8',
-      stdio: ['ignore', 'pipe', 'pipe'],
-      timeout: 1200,
-    });
-    const activeMatch = active.match(/window id # (0x[0-9a-fA-F]+)/);
-    if (!activeMatch) return { appName: '', windowTitle: '' };
-    const winId = activeMatch[1];
-    const details = execFileSync('xprop', ['-id', winId, '_NET_WM_NAME', 'WM_NAME', 'WM_CLASS'], {
-      encoding: 'utf8',
-      stdio: ['ignore', 'pipe', 'pipe'],
-      timeout: 1200,
-    });
-    const titleMatch = details.match(/(?:_NET_WM_NAME\(UTF8_STRING\)|WM_NAME\(STRING\)|WM_NAME\(UTF8_STRING\)) = "([^"]*)"/);
-    const classMatch = details.match(/WM_CLASS\(STRING\) = "([^"]*)"(?:, "([^"]*)")?/);
-    return {
-      appName: classMatch ? (classMatch[2] || classMatch[1] || '') : '',
-      windowTitle: titleMatch ? titleMatch[1] : '',
-    };
-  }
 
   async buildCaptureTitle({ mode, frame, clickPos, clickMeta = null }) {
     const ctx = await this.buildCaptureContext({ mode, frame, clickPos, clickMeta });

tests/unit/platform.test.js

@@ -0,0 +1,139 @@
+'use strict';
+
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+const { detectPlatform, createWindowContextProvider, detectCapabilities } = require('../../app/platform');
+const { assertWindowContextProvider, CLICK_SOURCES } = require('../../app/platform/interfaces');
+const { detectLinuxCapabilities, detectSessionType } = require('../../app/platform/linux/diagnostics');
+
+// ---- platform selection -----------------------------------------------------
+
+test('detectPlatform maps process.platform to an adapter family', () => {
+  assert.equal(detectPlatform('win32'), 'windows');
+  assert.equal(detectPlatform('darwin'), 'darwin');
+  assert.equal(detectPlatform('linux'), 'linux');
+  assert.equal(detectPlatform('sunos'), 'unsupported');
+});
+
+test('the factory returns a valid WindowContextProvider for every OS', () => {
+  for (const platform of ['win32', 'darwin', 'linux', 'sunos']) {
+    const provider = createWindowContextProvider({ platform });
+    assert.doesNotThrow(() => assertWindowContextProvider(provider));
+    assert.equal(typeof provider.collect, 'function');
+  }
+});
+
+test('an unsupported platform provider returns an empty context, never throws', async () => {
+  const provider = createWindowContextProvider({ platform: 'sunos' });
+  assert.deepEqual(await provider.collect(), { appName: '', windowTitle: '' });
+});
+
+test('the shared code delegates window context to the injected provider', async () => {
+  // The text-intel service must consume the provider, not branch on platform.
+  const { TextIntelService } = require('../../app/text-intel');
+  const { makeTmpDir, rmrf } = require('./helpers');
+  const root = makeTmpDir('platform-ctx');
+  let sawPoint = null;
+  const service = new TextIntelService({
+    store: { settingsDir: root },
+    settings: { get: () => null },
+    dataDir: root,
+    windowContextProvider: {
+      async collect(osPoint) { sawPoint = osPoint; return { appName: 'TestApp', windowTitle: 'Test Window' }; },
+    },
+  });
+  const ctx = await service.collectForegroundWindowContext({ x: 5, y: 6 });
+  assert.deepEqual(ctx, { appName: 'TestApp', windowTitle: 'Test Window' });
+  assert.deepEqual(sawPoint, { x: 5, y: 6 });
+  rmrf(root);
+});
+
+// ---- Linux diagnostics ------------------------------------------------------
+
+test('session type prefers XDG_SESSION_TYPE then display env', () => {
+  assert.equal(detectSessionType({ XDG_SESSION_TYPE: 'wayland' }), 'wayland');
+  assert.equal(detectSessionType({ XDG_SESSION_TYPE: 'x11' }), 'x11');
+  assert.equal(detectSessionType({ WAYLAND_DISPLAY: 'wayland-0' }), 'wayland');
+  assert.equal(detectSessionType({ DISPLAY: ':0' }), 'x11');
+  assert.equal(detectSessionType({}), 'unknown');
+});
+
+test('X11 with xinput reports marker-capable per-click capture', () => {
+  const caps = detectLinuxCapabilities({
+    env: { XDG_SESSION_TYPE: 'x11', DISPLAY: ':0', DBUS_SESSION_BUS_ADDRESS: 'unix:x' },
+    hasBinary: (n) => n === 'xinput' || n === 'xprop',
+    existsSync: () => false,
+    readdirSync: () => [],
+  });
+  assert.equal(caps.isWayland, false);
+  assert.equal(caps.clickCapture, 'x11-xinput');
+  assert.equal(caps.screenCapture, 'x11-direct');
+});
+
+test('Wayland without PipeWire reports an actionable message', () => {
+  const caps = detectLinuxCapabilities({
+    env: { XDG_SESSION_TYPE: 'wayland', WAYLAND_DISPLAY: 'wayland-0' },
+    hasBinary: () => false,
+    existsSync: () => false,
+    readdirSync: () => [],
+  });
+  assert.equal(caps.isWayland, true);
+  assert.equal(caps.screenCapture, 'wayland-portal');
+  assert.ok(caps.messages.some((m) => /PipeWire|portal/i.test(m)));
+});
+
+test('no click source falls back to hotkey/interval with a message', () => {
+  const caps = detectLinuxCapabilities({
+    env: { XDG_SESSION_TYPE: 'x11', DISPLAY: ':0' },
+    hasBinary: () => false, // no xinput
+    existsSync: () => false,
+    readdirSync: () => [], // no readable input devices
+  });
+  assert.equal(caps.clickCapture, 'hotkey-or-interval-only');
+  assert.ok(caps.messages.some((m) => /hotkey|interval/i.test(m)));
+});
+
+test('readable evdev devices enable an evdev click source', () => {
+  const caps = detectLinuxCapabilities({
+    env: { XDG_SESSION_TYPE: 'wayland', WAYLAND_DISPLAY: 'wayland-0' },
+    hasBinary: (n) => n === 'pipewire',
+    existsSync: () => true,
+    readdirSync: () => ['event0', 'event1', 'mouse0'],
+  });
+  // event0/event1 are readable (accessSync is real, but /dev/input/eventN
+  // likely won't exist in CI; the profile still resolves without throwing).
+  assert.ok(['evdev-wayland', 'hotkey-or-interval-only'].includes(caps.clickCapture));
+  assert.equal(caps.os, 'linux');
+});
+
+// ---- capability facade ------------------------------------------------------
+
+test('detectCapabilities returns a Linux profile with valid click source', () => {
+  const caps = detectCapabilities({ platform: 'linux', env: { XDG_SESSION_TYPE: 'x11', DISPLAY: ':0' } });
+  assert.equal(caps.os, 'linux');
+});
+
+test('detectCapabilities reports windows-hook for Windows', () => {
+  const caps = detectCapabilities({ platform: 'win32', env: {} });
+  assert.equal(caps.os, 'windows');
+  assert.equal(caps.clickCapture, 'windows-hook');
+});
+
+test('every documented click source is a known token', () => {
+  for (const s of ['windows-hook', 'x11', 'evdev-x11', 'evdev-wayland', 'wayland-portal', 'hotkey', 'interval', 'unavailable']) {
+    assert.ok(CLICK_SOURCES.includes(s));
+  }
+});
+
+// ---- refactor guard ---------------------------------------------------------
+
+const fs = require('node:fs');
+const path = require('node:path');
+
+test('text-intel no longer branches on process.platform for window context', () => {
+  const src = fs.readFileSync(path.join(__dirname, '..', '..', 'app', 'text-intel.js'), 'utf8');
+  assert.doesNotMatch(src, /collectWindowsWindowContext|collectMacWindowContext|collectLinuxWindowContext/);
+  assert.doesNotMatch(src, /process\.platform === 'win32'/);
+  assert.match(src, /this\.windowContext\.collect/);
+});