macos audio capture for sample creation

app/src/lib/hooks/useSystemAudioCapture.ts

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+import { useState, useRef, useCallback, useEffect } from 'react';
+import { invoke } from '@tauri-apps/api/core';
+import { isTauri } from '@/lib/tauri';
+
+interface UseSystemAudioCaptureOptions {
+  maxDurationSeconds?: number;
+  onRecordingComplete?: (blob: Blob) => void;
+}
+
+/**
+ * Hook for native system audio capture using Tauri commands.
+ * Uses ScreenCaptureKit on macOS and WASAPI loopback on Windows.
+ */
+export function useSystemAudioCapture({
+  maxDurationSeconds = 30,
+  onRecordingComplete,
+}: UseSystemAudioCaptureOptions = {}) {
+  const [isRecording, setIsRecording] = useState(false);
+  const [duration, setDuration] = useState(0);
+  const [error, setError] = useState<string | null>(null);
+  const [isSupported, setIsSupported] = useState(false);
+  const timerRef = useRef<number | null>(null);
+  const startTimeRef = useRef<number | null>(null);
+  const stopRecordingRef = useRef<(() => Promise<void>) | null>(null);
+
+  // Check if system audio capture is supported
+  useEffect(() => {
+    if (!isTauri()) {
+      setIsSupported(false);
+      return;
+    }
+
+    invoke<boolean>('is_system_audio_supported')
+      .then((supported) => {
+        setIsSupported(supported);
+      })
+      .catch(() => {
+        setIsSupported(false);
+      });
+  }, []);
+
+  const startRecording = useCallback(async () => {
+    if (!isTauri()) {
+      const errorMsg = 'System audio capture is only available in the desktop app.';
+      setError(errorMsg);
+      return;
+    }
+
+    if (!isSupported) {
+      const errorMsg = 'System audio capture is not supported on this platform.';
+      setError(errorMsg);
+      return;
+    }
+
+    try {
+      setError(null);
+      setDuration(0);
+
+      // Start native capture
+      await invoke('start_system_audio_capture', {
+        maxDurationSecs: maxDurationSeconds,
+      });
+
+      setIsRecording(true);
+      startTimeRef.current = Date.now();
+
+      // Start timer
+      timerRef.current = window.setInterval(() => {
+        if (startTimeRef.current) {
+          const elapsed = (Date.now() - startTimeRef.current) / 1000;
+          setDuration(elapsed);
+
+          // Auto-stop at max duration
+          if (elapsed >= maxDurationSeconds && stopRecordingRef.current) {
+            void stopRecordingRef.current();
+          }
+        }
+      }, 100);
+    } catch (err) {
+      const errorMessage =
+        err instanceof Error
+          ? err.message
+          : 'Failed to start system audio capture. Please check permissions.';
+      setError(errorMessage);
+      setIsRecording(false);
+    }
+  }, [maxDurationSeconds, isSupported]);
+
+  const stopRecording = useCallback(async () => {
+    if (!isRecording || !isTauri()) {
+      return;
+    }
+
+    try {
+      setIsRecording(false);
+
+      if (timerRef.current !== null) {
+        clearInterval(timerRef.current);
+        timerRef.current = null;
+      }
+
+      // Stop capture and get base64 WAV data
+      const base64Data = await invoke<string>('stop_system_audio_capture');
+
+      // Convert base64 to Blob
+      const binaryString = atob(base64Data);
+      const bytes = new Uint8Array(binaryString.length);
+      for (let i = 0; i < binaryString.length; i++) {
+        bytes[i] = binaryString.charCodeAt(i);
+      }
+
+      const blob = new Blob([bytes], { type: 'audio/wav' });
+      onRecordingComplete?.(blob);
+    } catch (err) {
+      const errorMessage =
+        err instanceof Error
+          ? err.message
+          : 'Failed to stop system audio capture.';
+      setError(errorMessage);
+    }
+  }, [isRecording, onRecordingComplete]);
+
+  // Store stopRecording in ref for use in timer
+  useEffect(() => {
+    stopRecordingRef.current = stopRecording;
+  }, [stopRecording]);
+
+  const cancelRecording = useCallback(async () => {
+    if (isRecording) {
+      await stopRecording();
+    }
+
+    setIsRecording(false);
+    setDuration(0);
+
+    if (timerRef.current !== null) {
+      clearInterval(timerRef.current);
+      timerRef.current = null;
+    }
+  }, [isRecording, stopRecording]);
+
+  // Cleanup on unmount
+  useEffect(() => {
+    return () => {
+      if (timerRef.current !== null) {
+        clearInterval(timerRef.current);
+      }
+      // Cancel recording on unmount if still recording
+      if (isRecording) {
+        void cancelRecording();
+      }
+    };
+    // biome-ignore lint/correctness/useExhaustiveDependencies: cancelRecording is stable
+  }, [isRecording]);
+
+  return {
+    isRecording,
+    duration,
+    error,
+    isSupported,
+    startRecording,
+    stopRecording,
+    cancelRecording,
+  };
+}