keyboard/keyBoard/Class/AiTalk/VM/AudioCaptureManager.m

//
//  AudioCaptureManager.m
//  keyBoard
//
//  Created by Mac on 2026/1/15.
//

#import "AudioCaptureManager.h"
#import <AVFoundation/AVFoundation.h>

// 音频采集参数常量
const double kAudioSampleRate = 16000.0;
const int kAudioChannels = 1;
const NSUInteger kAudioFrameDuration = 20; // ms
const NSUInteger kAudioFrameSamples = 320; // 16000 * 0.02
const NSUInteger kAudioFrameBytes = 640;   // 320 * 2 (Int16)

@interface AudioCaptureManager ()

@property(nonatomic, strong) AVAudioEngine *audioEngine;
@property(nonatomic, strong) dispatch_queue_t audioQueue;
@property(nonatomic, assign) BOOL capturing;

// Ring buffer for accumulating samples to form 20ms frames
@property(nonatomic, strong) NSMutableData *ringBuffer;
@property(nonatomic, assign) NSUInteger ringBufferWriteIndex;

@end

@implementation AudioCaptureManager

- (instancetype)init {
  self = [super init];
  if (self) {
    _audioEngine = [[AVAudioEngine alloc] init];
    _audioQueue = dispatch_queue_create("com.keyboard.aitalk.audiocapture",
                                        DISPATCH_QUEUE_SERIAL);
    _ringBuffer = [[NSMutableData alloc]
        initWithLength:kAudioFrameBytes * 4]; // Buffer for multiple frames
    _ringBufferWriteIndex = 0;
    _capturing = NO;
  }
  return self;
}

- (void)dealloc {
  [self stopCapture];
}

#pragma mark - Public Methods

- (BOOL)startCapture:(NSError **)error {
  if (self.capturing) {
    return YES;
  }

  AVAudioInputNode *inputNode = self.audioEngine.inputNode;

  // 获取输入格式
  AVAudioFormat *inputFormat = [inputNode outputFormatForBus:0];

  // 目标格式：16kHz, Mono, Int16
  AVAudioFormat *targetFormat =
      [[AVAudioFormat alloc] initWithCommonFormat:AVAudioPCMFormatInt16
                                       sampleRate:kAudioSampleRate
                                         channels:kAudioChannels
                                      interleaved:YES];

  // 创建格式转换器
  AVAudioConverter *converter =
      [[AVAudioConverter alloc] initFromFormat:inputFormat
                                      toFormat:targetFormat];
  if (!converter) {
    if (error) {
      *error = [NSError errorWithDomain:@"AudioCaptureManager"
                                   code:-1
                               userInfo:@{
                                 NSLocalizedDescriptionKey :
                                     @"Failed to create audio converter"
                               }];
    }
    return NO;
  }

  // 计算合适的 buffer size（约 20ms 的输入采样数）
  AVAudioFrameCount bufferSize =
      (AVAudioFrameCount)(inputFormat.sampleRate * 0.02);

  // 安装 tap
  __weak typeof(self) weakSelf = self;
  [inputNode installTapOnBus:0
                  bufferSize:bufferSize
                      format:inputFormat
                       block:^(AVAudioPCMBuffer *_Nonnull buffer,
                               AVAudioTime *_Nonnull when) {
                         [weakSelf processAudioBuffer:buffer
                                        withConverter:converter
                                         targetFormat:targetFormat];
                       }];

  // 启动引擎
  NSError *startError = nil;
  [self.audioEngine prepare];

  if (![self.audioEngine startAndReturnError:&startError]) {
    [inputNode removeTapOnBus:0];
    if (error) {
      *error = startError;
    }
    NSLog(@"[AudioCaptureManager] Failed to start engine: %@",
          startError.localizedDescription);
    return NO;
  }

  self.capturing = YES;
  self.ringBufferWriteIndex = 0;

  NSLog(@"[AudioCaptureManager] Started capturing at %.0f Hz",
        inputFormat.sampleRate);
  return YES;
}

- (void)stopCapture {
  if (!self.capturing) {
    return;
  }

  [self.audioEngine.inputNode removeTapOnBus:0];
  [self.audioEngine stop];

  self.capturing = NO;
  self.ringBufferWriteIndex = 0;

  NSLog(@"[AudioCaptureManager] Stopped capturing");
}

#pragma mark - Audio Processing

- (void)processAudioBuffer:(AVAudioPCMBuffer *)buffer
             withConverter:(AVAudioConverter *)converter
              targetFormat:(AVAudioFormat *)targetFormat {

  if (!self.capturing) {
    return;
  }

  // 计算输出帧数
  AVAudioFrameCount outputFrameCapacity =
      (AVAudioFrameCount)(buffer.frameLength *
                          (kAudioSampleRate / buffer.format.sampleRate)) +
      1;

  // 创建输出 buffer
  AVAudioPCMBuffer *outputBuffer =
      [[AVAudioPCMBuffer alloc] initWithPCMFormat:targetFormat
                                    frameCapacity:outputFrameCapacity];

  // 格式转换
  NSError *conversionError = nil;
  AVAudioConverterInputBlock inputBlock = ^AVAudioBuffer *_Nullable(
      AVAudioPacketCount inNumberOfPackets,
      AVAudioConverterInputStatus *_Nonnull outStatus) {
    *outStatus = AVAudioConverterInputStatus_HaveData;
    return buffer;
  };

  AVAudioConverterOutputStatus status =
      [converter convertToBuffer:outputBuffer
                           error:&conversionError
              withInputFromBlock:inputBlock];

  if (status == AVAudioConverterOutputStatus_Error) {
    NSLog(@"[AudioCaptureManager] Conversion error: %@",
          conversionError.localizedDescription);
    return;
  }

  // 获取 Int16 数据
  int16_t *samples = (int16_t *)outputBuffer.int16ChannelData[0];
  NSUInteger sampleCount = outputBuffer.frameLength;
  NSUInteger byteCount = sampleCount * sizeof(int16_t);

  // 计算 RMS
  [self calculateAndReportRMS:samples sampleCount:sampleCount];

  // 将数据添加到 ring buffer 并输出完整帧
  dispatch_async(self.audioQueue, ^{
    [self appendToRingBuffer:samples byteCount:byteCount];
  });
}

- (void)appendToRingBuffer:(int16_t *)samples byteCount:(NSUInteger)byteCount {
  // 将新数据追加到 ring buffer
  uint8_t *ringBufferBytes = (uint8_t *)self.ringBuffer.mutableBytes;
  NSUInteger ringBufferLength = self.ringBuffer.length;

  NSUInteger bytesToCopy = byteCount;
  NSUInteger sourceOffset = 0;

  while (bytesToCopy > 0) {
    NSUInteger spaceAvailable = ringBufferLength - self.ringBufferWriteIndex;
    NSUInteger copySize = MIN(bytesToCopy, spaceAvailable);

    memcpy(ringBufferBytes + self.ringBufferWriteIndex,
           (uint8_t *)samples + sourceOffset, copySize);
    self.ringBufferWriteIndex += copySize;
    sourceOffset += copySize;
    bytesToCopy -= copySize;

    // 检查是否有完整的 20ms 帧
    while (self.ringBufferWriteIndex >= kAudioFrameBytes) {
      // 提取一个完整帧
      NSData *frame = [NSData dataWithBytes:ringBufferBytes
                                     length:kAudioFrameBytes];

      // 移动剩余数据到开头
      NSUInteger remaining = self.ringBufferWriteIndex - kAudioFrameBytes;
      if (remaining > 0) {
        memmove(ringBufferBytes, ringBufferBytes + kAudioFrameBytes, remaining);
      }
      self.ringBufferWriteIndex = remaining;

      // 回调输出帧
      [self outputPCMFrame:frame];
    }

    // 如果 ring buffer 已满，从头开始
    if (self.ringBufferWriteIndex >= ringBufferLength) {
      self.ringBufferWriteIndex = 0;
    }
  }
}

- (void)outputPCMFrame:(NSData *)frame {
  if (!self.capturing) {
    return;
  }

  dispatch_async(dispatch_get_main_queue(), ^{
    if ([self.delegate respondsToSelector:@selector
                       (audioCaptureManagerDidOutputPCMFrame:)]) {
      [self.delegate audioCaptureManagerDidOutputPCMFrame:frame];
    }
  });
}

- (void)calculateAndReportRMS:(int16_t *)samples
                  sampleCount:(NSUInteger)sampleCount {
  if (sampleCount == 0)
    return;

  // 计算 RMS
  double sum = 0.0;
  for (NSUInteger i = 0; i < sampleCount; i++) {
    double sample = (double)samples[i] / 32768.0; // Normalize to -1.0 ~ 1.0
    sum += sample * sample;
  }
  double rms = sqrt(sum / sampleCount);
  float rmsFloat = (float)MIN(rms * 2.0, 1.0); // Scale and clamp to 0.0 ~ 1.0

  dispatch_async(dispatch_get_main_queue(), ^{
    if ([self.delegate
            respondsToSelector:@selector(audioCaptureManagerDidUpdateRMS:)]) {
      [self.delegate audioCaptureManagerDidUpdateRMS:rmsFloat];
    }
  });
}

@end