feat(41-02): create AudioInputNode component with waveform visualization

- File upload via drag-and-drop or click
- Waveform visualization using useAudioVisualization hook
- Play/pause controls with scrub bar
- Canvas-based rendering with ResizeObserver for responsive sizing
- Audio handle (purple/violet) on right side
- Min dimensions: 250px width, 150px height
- Remove button to clear audio file

src/components/nodes/AudioInputNode.tsx

@@ -0,0 +1,373 @@
+"use client";
+
+import { useCallback, useRef, useState, useEffect } from "react";
+import { Handle, Position, NodeProps, Node } from "@xyflow/react";
+import { BaseNode } from "./BaseNode";
+import { useCommentNavigation } from "@/hooks/useCommentNavigation";
+import { useWorkflowStore } from "@/store/workflowStore";
+import { AudioInputNodeData } from "@/types";
+import { useAudioVisualization } from "@/hooks/useAudioVisualization";
+
+type AudioInputNodeType = Node<AudioInputNodeData, "audioInput">;
+
+export function AudioInputNode({ id, data, selected }: NodeProps<AudioInputNodeType>) {
+  const nodeData = data;
+  const commentNavigation = useCommentNavigation(id);
+  const updateNodeData = useWorkflowStore((state) => state.updateNodeData);
+  const fileInputRef = useRef<HTMLInputElement>(null);
+  const audioRef = useRef<HTMLAudioElement | null>(null);
+  const canvasRef = useRef<HTMLCanvasElement>(null);
+  const waveformContainerRef = useRef<HTMLDivElement>(null);
+  const animationFrameRef = useRef<number>();
+
+  const [isPlaying, setIsPlaying] = useState(false);
+  const [currentTime, setCurrentTime] = useState(0);
+  const [audioBlob, setAudioBlob] = useState<Blob | null>(null);
+
+  // Use the audio visualization hook
+  const { waveformData, isLoading } = useAudioVisualization(audioBlob);
+
+  // Convert base64 data URL to Blob for the hook
+  useEffect(() => {
+    if (nodeData.audioFile) {
+      fetch(nodeData.audioFile)
+        .then((r) => r.blob())
+        .then(setAudioBlob)
+        .catch(() => setAudioBlob(null));
+    } else {
+      setAudioBlob(null);
+    }
+  }, [nodeData.audioFile]);
+
+  // Setup audio element
+  useEffect(() => {
+    if (nodeData.audioFile && !audioRef.current) {
+      const audio = new Audio(nodeData.audioFile);
+      audioRef.current = audio;
+
+      audio.addEventListener("ended", () => {
+        setIsPlaying(false);
+        setCurrentTime(0);
+      });
+
+      audio.addEventListener("timeupdate", () => {
+        setCurrentTime(audio.currentTime);
+      });
+    }
+
+    return () => {
+      if (audioRef.current) {
+        audioRef.current.pause();
+        audioRef.current = null;
+      }
+    };
+  }, [nodeData.audioFile]);
+
+  // Draw waveform on canvas
+  useEffect(() => {
+    if (!waveformData || !canvasRef.current || !waveformContainerRef.current) return;
+
+    const canvas = canvasRef.current;
+    const container = waveformContainerRef.current;
+    const ctx = canvas.getContext("2d");
+    if (!ctx) return;
+
+    // Use ResizeObserver for responsive sizing
+    const resizeObserver = new ResizeObserver((entries) => {
+      for (const entry of entries) {
+        const width = entry.contentRect.width;
+        const height = entry.contentRect.height;
+
+        // Set canvas size
+        canvas.width = width;
+        canvas.height = height;
+
+        // Draw waveform
+        ctx.clearRect(0, 0, width, height);
+
+        const peaks = waveformData.peaks;
+        const barCount = Math.min(peaks.length, width);
+        const barWidth = width / barCount;
+        const barGap = 1;
+
+        ctx.fillStyle = "rgb(167, 139, 250)"; // violet-400
+
+        for (let i = 0; i < barCount; i++) {
+          const peakIndex = Math.floor((i / barCount) * peaks.length);
+          const peak = peaks[peakIndex] || 0;
+          const barHeight = peak * height;
+          const x = i * barWidth;
+          const y = (height - barHeight) / 2;
+
+          ctx.fillRect(x, y, barWidth - barGap, barHeight);
+        }
+
+        // Draw playback position
+        if (isPlaying && nodeData.duration) {
+          const progress = currentTime / nodeData.duration;
+          const x = progress * width;
+
+          ctx.strokeStyle = "rgba(255, 255, 255, 0.8)";
+          ctx.lineWidth = 2;
+          ctx.beginPath();
+          ctx.moveTo(x, 0);
+          ctx.lineTo(x, height);
+          ctx.stroke();
+        }
+      }
+    });
+
+    resizeObserver.observe(container);
+
+    return () => {
+      resizeObserver.disconnect();
+    };
+  }, [waveformData, isPlaying, currentTime, nodeData.duration]);
+
+  // Animation loop for smooth playback position updates
+  useEffect(() => {
+    if (isPlaying && audioRef.current) {
+      const updatePosition = () => {
+        if (audioRef.current) {
+          setCurrentTime(audioRef.current.currentTime);
+        }
+        animationFrameRef.current = requestAnimationFrame(updatePosition);
+      };
+      animationFrameRef.current = requestAnimationFrame(updatePosition);
+    }
+
+    return () => {
+      if (animationFrameRef.current) {
+        cancelAnimationFrame(animationFrameRef.current);
+      }
+    };
+  }, [isPlaying]);
+
+  const handleFileChange = useCallback(
+    (e: React.ChangeEvent<HTMLInputElement>) => {
+      const file = e.target.files?.[0];
+      if (!file) return;
+
+      if (!file.type.match(/^audio\//)) {
+        alert("Unsupported format. Use MP3, WAV, OGG, AAC, or other audio formats.");
+        return;
+      }
+
+      if (file.size > 50 * 1024 * 1024) {
+        alert("Audio file too large. Maximum size is 50MB.");
+        return;
+      }
+
+      const reader = new FileReader();
+      reader.onload = (event) => {
+        const base64 = event.target?.result as string;
+
+        // Extract duration using HTML Audio element
+        const audio = new Audio(base64);
+        audio.onloadedmetadata = () => {
+          updateNodeData(id, {
+            audioFile: base64,
+            filename: file.name,
+            format: file.type,
+            duration: audio.duration,
+          });
+        };
+      };
+      reader.readAsDataURL(file);
+    },
+    [id, updateNodeData]
+  );
+
+  const handleDrop = useCallback(
+    (e: React.DragEvent) => {
+      e.preventDefault();
+      e.stopPropagation();
+
+      const file = e.dataTransfer.files?.[0];
+      if (!file) return;
+
+      const dt = new DataTransfer();
+      dt.items.add(file);
+      if (fileInputRef.current) {
+        fileInputRef.current.files = dt.files;
+        fileInputRef.current.dispatchEvent(new Event("change", { bubbles: true }));
+      }
+    },
+    []
+  );
+
+  const handleDragOver = useCallback((e: React.DragEvent) => {
+    e.preventDefault();
+    e.stopPropagation();
+  }, []);
+
+  const handleRemove = useCallback(() => {
+    if (audioRef.current) {
+      audioRef.current.pause();
+      audioRef.current = null;
+    }
+    setIsPlaying(false);
+    setCurrentTime(0);
+    setAudioBlob(null);
+    updateNodeData(id, {
+      audioFile: null,
+      filename: null,
+      duration: null,
+      format: null,
+    });
+  }, [id, updateNodeData]);
+
+  const handlePlayPause = useCallback(() => {
+    if (!audioRef.current) return;
+
+    if (isPlaying) {
+      audioRef.current.pause();
+      setIsPlaying(false);
+    } else {
+      audioRef.current.play();
+      setIsPlaying(true);
+    }
+  }, [isPlaying]);
+
+  const handleSeek = useCallback((e: React.MouseEvent<HTMLDivElement>) => {
+    if (!audioRef.current || !nodeData.duration || !waveformContainerRef.current) return;
+
+    const rect = waveformContainerRef.current.getBoundingClientRect();
+    const x = e.clientX - rect.left;
+    const progress = x / rect.width;
+    const newTime = progress * nodeData.duration;
+
+    audioRef.current.currentTime = newTime;
+    setCurrentTime(newTime);
+  }, [nodeData.duration]);
+
+  const formatTime = (seconds: number) => {
+    const mins = Math.floor(seconds / 60);
+    const secs = Math.floor(seconds % 60);
+    return `${mins}:${secs.toString().padStart(2, "0")}`;
+  };
+
+  return (
+    <BaseNode
+      id={id}
+      title="Audio Input"
+      customTitle={nodeData.customTitle}
+      comment={nodeData.comment}
+      onCustomTitleChange={(title) => updateNodeData(id, { customTitle: title || undefined })}
+      onCommentChange={(comment) => updateNodeData(id, { comment: comment || undefined })}
+      selected={selected}
+      commentNavigation={commentNavigation ?? undefined}
+      minWidth={250}
+      minHeight={150}
+    >
+      <input
+        ref={fileInputRef}
+        type="file"
+        accept="audio/mp3,audio/mpeg,audio/wav,audio/ogg,audio/aac,audio/mp4,audio/*"
+        onChange={handleFileChange}
+        className="hidden"
+      />
+
+      {nodeData.audioFile ? (
+        <div className="relative group flex-1 flex flex-col min-h-0 gap-2">
+          {/* Filename and duration */}
+          <div className="flex items-center justify-between shrink-0">
+            <span className="text-[10px] text-neutral-400 truncate max-w-[150px]" title={nodeData.filename || ""}>
+              {nodeData.filename}
+            </span>
+            {nodeData.duration && (
+              <span className="text-[10px] text-neutral-500 bg-neutral-700/50 px-1.5 py-0.5 rounded">
+                {formatTime(nodeData.duration)}
+              </span>
+            )}
+          </div>
+
+          {/* Waveform visualization */}
+          {isLoading ? (
+            <div className="flex-1 flex items-center justify-center bg-neutral-900/50 rounded min-h-[60px]">
+              <span className="text-xs text-neutral-500">Loading waveform...</span>
+            </div>
+          ) : waveformData ? (
+            <div
+              ref={waveformContainerRef}
+              className="flex-1 min-h-[60px] bg-neutral-900/50 rounded cursor-pointer relative"
+              onClick={handleSeek}
+            >
+              <canvas ref={canvasRef} className="w-full h-full" />
+            </div>
+          ) : (
+            <div className="flex-1 flex items-center justify-center bg-neutral-900/50 rounded min-h-[60px]">
+              <span className="text-xs text-neutral-500">Processing...</span>
+            </div>
+          )}
+
+          {/* Play/pause controls */}
+          <div className="flex items-center gap-2 shrink-0">
+            <button
+              onClick={handlePlayPause}
+              className="w-7 h-7 flex items-center justify-center bg-violet-600 hover:bg-violet-500 rounded transition-colors"
+              title={isPlaying ? "Pause" : "Play"}
+            >
+              {isPlaying ? (
+                <svg className="w-3 h-3 text-white" fill="currentColor" viewBox="0 0 24 24">
+                  <path d="M6 4h4v16H6V4zm8 0h4v16h-4V4z" />
+                </svg>
+              ) : (
+                <svg className="w-3 h-3 text-white" fill="currentColor" viewBox="0 0 24 24">
+                  <path d="M8 5v14l11-7z" />
+                </svg>
+              )}
+            </button>
+
+            {/* Progress bar / scrubber */}
+            <div className="flex-1 h-1 bg-neutral-700 rounded-full overflow-hidden relative">
+              {nodeData.duration && (
+                <div
+                  className="h-full bg-violet-500 transition-all"
+                  style={{ width: `${(currentTime / nodeData.duration) * 100}%` }}
+                />
+              )}
+            </div>
+
+            {/* Current time */}
+            <span className="text-[10px] text-neutral-500 min-w-[32px] text-right">
+              {formatTime(currentTime)}
+            </span>
+          </div>
+
+          {/* Remove button */}
+          <button
+            onClick={handleRemove}
+            className="absolute top-1 right-1 w-5 h-5 bg-black/60 text-white rounded text-xs opacity-0 group-hover:opacity-100 transition-opacity flex items-center justify-center"
+          >
+            <svg className="w-3 h-3" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
+              <path strokeLinecap="round" strokeLinejoin="round" d="M6 18L18 6M6 6l12 12" />
+            </svg>
+          </button>
+        </div>
+      ) : (
+        <div
+          onClick={() => fileInputRef.current?.click()}
+          onDrop={handleDrop}
+          onDragOver={handleDragOver}
+          className="w-full flex-1 min-h-[112px] border border-dashed border-neutral-600 rounded flex flex-col items-center justify-center cursor-pointer hover:border-neutral-500 hover:bg-neutral-700/50 transition-colors"
+        >
+          <svg className="w-6 h-6 text-neutral-500" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={1.5}>
+            <path strokeLinecap="round" strokeLinejoin="round" d="M9 9l10.5-3m0 6.553v3.75a2.25 2.25 0 01-1.632 2.163l-1.32.377a1.803 1.803 0 11-.99-3.467l2.31-.66a2.25 2.25 0 001.632-2.163zm0 0V2.25L9 5.25v10.303m0 0v3.75a2.25 2.25 0 01-1.632 2.163l-1.32.377a1.803 1.803 0 01-.99-3.467l2.31-.66A2.25 2.25 0 009 15.553z" />
+          </svg>
+          <span className="text-[10px] text-neutral-400 mt-1">
+            Drop audio or click
+          </span>
+        </div>
+      )}
+
+      <Handle
+        type="source"
+        position={Position.Right}
+        id="audio"
+        data-handletype="audio"
+        style={{ background: "rgb(167, 139, 250)" }}
+      />
+    </BaseNode>
+  );
+}