feat(interview): 음성 답변 녹음 중 실시간 레벨 미터 + 타이머

frontend/src/features/interview/lib/media/useVoiceRecorder.ts

@@ -22,12 +22,15 @@ export function useVoiceRecorder() {
   const recorderRef = useRef<MediaRecorder | null>(null)
   const streamRef = useRef<MediaStream | null>(null)
   const chunksRef = useRef<Blob[]>([])
+  // 녹음 중 실시간 레벨 미터(MicLevelMeter)가 구독할 수 있도록 스트림을 상태로도 노출.
+  const [stream, setStream] = useState<MediaStream | null>(null)
 
   const cleanup = useCallback(() => {
     streamRef.current?.getTracks().forEach((t) => t.stop())
     streamRef.current = null
     recorderRef.current = null
     chunksRef.current = []
+    setStream(null)
   }, [])
 
   useEffect(() => cleanup, [cleanup])
@@ -51,6 +54,7 @@ export function useVoiceRecorder() {
     recorder.start()
     streamRef.current = stream
     recorderRef.current = recorder
+    setStream(stream)
     setStatus('recording')
     return true
   }, [status])
@@ -86,5 +90,5 @@ export function useVoiceRecorder() {
     setStatus('idle')
   }, [cleanup])
 
-  return { status, start, stop, cancel }
+  return { status, stream, start, stop, cancel }
 }

frontend/src/features/interview/ui/live/AnswerComposer.tsx

@@ -1,8 +1,15 @@
-import { useState } from 'react'
+import { useEffect, useState } from 'react'
 import type { KeyboardEvent } from 'react'
 import { TextArea } from '@/shared/ui/TextArea'
 import { Button } from '@/shared/ui/Button'
 import { useVoiceRecorder } from '../../lib/media/useVoiceRecorder'
+import { MicLevelMeter } from './MicLevelMeter'
+
+function formatElapsed(sec: number): string {
+  const m = Math.floor(sec / 60)
+  const s = sec % 60
+  return `${String(m).padStart(2, '0')}:${String(s).padStart(2, '0')}`
+}
 
 function MicIcon() {
   return (
@@ -37,10 +44,24 @@ export function AnswerComposer({
   voiceUploading?: boolean
 }) {
   const [value, setValue] = useState('')
-  const { status: recStatus, start, stop, cancel } = useVoiceRecorder()
+  const { status: recStatus, stream, start, stop, cancel } = useVoiceRecorder()
   const recording = recStatus === 'recording' || recStatus === 'requesting'
   const voiceSupported = recStatus !== 'unsupported' && Boolean(onSubmitVoice)
 
+  // 녹음 경과 시간(초). recording 상태에서만 흐른다. 리셋은 시작 시점(이벤트)에서.
+  const [elapsed, setElapsed] = useState(0)
+  useEffect(() => {
+    if (recStatus !== 'recording') return
+    const startedAt = Date.now()
+    const id = setInterval(() => setElapsed(Math.floor((Date.now() - startedAt) / 1000)), 250)
+    return () => clearInterval(id)
+  }, [recStatus])
+
+  const beginRecording = () => {
+    setElapsed(0)
+    void start()
+  }
+
   const submit = () => {
     const trimmed = value.trim()
     if (!trimmed || disabled || submitLocked) return
@@ -62,20 +83,29 @@ export function AnswerComposer({
 
   // 녹음/업로드 중에는 전용 바를 보여준다.
   if (recording || voiceUploading) {
+    const requesting = recStatus === 'requesting'
     return (
       <div className="flex items-center justify-between gap-3 border-t border-border bg-surface-raised px-4 py-3">
-        <span className="flex items-center gap-2 text-body text-fg">
-          {voiceUploading ? (
-            '음성 답변 업로드 중…'
-          ) : (
-            <>
+        {voiceUploading ? (
+          <span className="text-body text-fg">음성 답변 업로드 중…</span>
+        ) : requesting ? (
+          <span className="text-body text-fg-muted">마이크 준비 중…</span>
+        ) : (
+          <span className="flex min-w-0 items-center gap-3 text-body text-fg">
+            <span className="flex items-center gap-2">
               <span className="inline-block h-2.5 w-2.5 animate-pulse rounded-full bg-danger" />
-              녹음 중… 답변이 끝나면 전송을 누르세요
-            </>
-          )}
-        </span>
-        {!voiceUploading && (
-          <div className="flex items-center gap-2">
+              <span className="font-medium tabular-nums" aria-label={`녹음 중 ${formatElapsed(elapsed)}`}>
+                {formatElapsed(elapsed)}
+              </span>
+            </span>
+            <MicLevelMeter stream={stream} />
+            <span className="hidden truncate text-caption text-fg-muted sm:inline">
+              답변이 끝나면 전송을 누르세요
+            </span>
+          </span>
+        )}
+        {!voiceUploading && !requesting && (
+          <div className="flex shrink-0 items-center gap-2">
             <Button variant="ghost" onClick={cancel}>
               취소
             </Button>
@@ -107,7 +137,7 @@ export function AnswerComposer({
         {voiceSupported && (
           <Button
             variant="secondary"
-            onClick={start}
+            onClick={beginRecording}
             disabled={disabled || submitLocked}
             aria-label="음성으로 답변"
             title="음성으로 답변"

frontend/src/features/interview/ui/live/MicLevelMeter.tsx

@@ -0,0 +1,58 @@
+import { useEffect, useRef } from 'react'
+
+const BARS = 5
+
+// 녹음 중 마이크 입력을 실시간 막대로 보여주는 레벨 미터.
+// AnalyserNode 의 주파수 데이터를 BARS 개 밴드로 묶어 각 막대 높이에 반영한다.
+// 프레임마다 리렌더하지 않도록 ref 로 DOM transform 을 직접 갱신한다.
+export function MicLevelMeter({ stream }: { stream: MediaStream | null }) {
+  const barRefs = useRef<(HTMLSpanElement | null)[]>([])
+
+  useEffect(() => {
+    if (!stream || typeof AudioContext === 'undefined') return
+    const ctx = new AudioContext()
+    void ctx.resume()
+    const source = ctx.createMediaStreamSource(stream)
+    const analyser = ctx.createAnalyser()
+    analyser.fftSize = 64
+    analyser.smoothingTimeConstant = 0.7
+    source.connect(analyser)
+    const data = new Uint8Array(analyser.frequencyBinCount)
+    const band = Math.max(1, Math.floor(data.length / BARS))
+
+    let raf = 0
+    const tick = () => {
+      analyser.getByteFrequencyData(data)
+      for (let i = 0; i < BARS; i++) {
+        let sum = 0
+        for (let j = 0; j < band; j++) sum += data[i * band + j]
+        const level = sum / band / 255 // 0..1
+        const el = barRefs.current[i]
+        if (el) el.style.transform = `scaleY(${Math.max(0.18, Math.min(1, level * 1.8))})`
+      }
+      raf = requestAnimationFrame(tick)
+    }
+    tick()
+
+    return () => {
+      cancelAnimationFrame(raf)
+      source.disconnect()
+      void ctx.close()
+    }
+  }, [stream])
+
+  return (
+    <span className="flex h-6 items-center gap-[3px]" aria-hidden>
+      {Array.from({ length: BARS }).map((_, i) => (
+        <span
+          key={i}
+          ref={(el) => {
+            barRefs.current[i] = el
+          }}
+          className="h-full w-1 origin-center rounded-full bg-danger/70 transition-transform duration-75"
+          style={{ transform: 'scaleY(0.18)' }}
+        />
+      ))}
+    </span>
+  )
+}