meetingnotes/notetaker/Managers/AudioManager.swift

// AudioManager.swift
// Unified audio manager for microphone and system audio capture

import AVFoundation
import Foundation
import SwiftUI
import ScreenCaptureKit

// Distinguish which source (mic vs system) an audio buffer belongs to
private enum AudioSource {
    case mic
    case system
}

/// Manages audio capture from microphone and/or system audio and handles real-time transcription via Deepgram
class AudioManager: NSObject, ObservableObject {
    @Published var transcript = ""
    @Published var isRecording = false
    @Published var captureSystemAudio = true
    
    private var audioEngine = AVAudioEngine()
    private var micSocketTask: URLSessionWebSocketTask?
    private var systemSocketTask: URLSessionWebSocketTask?
    private let deepgramURL = URL(string: "wss://api.deepgram.com/v1/listen?encoding=linear16&sample_rate=16000&channels=1&interim_results=true")!
    
    // ScreenCaptureKit properties
    private var stream: SCStream?
    
    func startRecording() {
        print("Starting recording...")
        
        // First ensure everything is stopped and cleaned up
        stopRecordingInternal()
        
        if captureSystemAudio {
            // Start microphone capture in parallel with system audio
            startMicrophoneTap()
            // Start system audio capture asynchronously
            Task {
                await startSystemAudioCapture()
            }
        } else {
            startMicrophoneOnly()
        }
    }
    
    private func stopRecordingInternal() {
        print("Internal cleanup...")
        
        // Stop system audio capture
        if let stream = stream {
            stream.stopCapture()
            self.stream = nil
            print("System audio capture stopped")
        }
        
        // Stop microphone capture
        cleanupAudioEngine()
        
        // Close WebSocket
        micSocketTask?.cancel(with: .normalClosure, reason: nil)
        micSocketTask = nil
        systemSocketTask?.cancel(with: .normalClosure, reason: nil)
        systemSocketTask = nil
        
        // Reset state
        DispatchQueue.main.async {
            self.isRecording = false
        }
        
        print("Internal cleanup completed")
    }
    
    private func startMicrophoneOnly() {
        print("Starting microphone-only recording...")
        
        // Ensure audio engine is stopped and cleaned up
        cleanupAudioEngine()
        
        // Set up audio engine for microphone capture
        let inputNode = audioEngine.inputNode
        let recordingFormat = inputNode.outputFormat(forBus: 0)
        
        // Convert to the format Deepgram expects: 16kHz, 16-bit, mono
        let targetFormat = AVAudioFormat(commonFormat: .pcmFormatInt16, 
                                       sampleRate: 16000, 
                                       channels: 1, 
                                       interleaved: false)!
        
        let converter = AVAudioConverter(from: recordingFormat, to: targetFormat)!
        
        inputNode.installTap(onBus: 0, bufferSize: 1024, format: recordingFormat) { [weak self] (buffer, time) in
            self?.processAudioBuffer(buffer, converter: converter, targetFormat: targetFormat, source: .mic)
        }
        
        audioEngine.prepare()
        
        do {
            try audioEngine.start()
            DispatchQueue.main.async {
                self.isRecording = true
            }
            connectToDeepgram(source: .mic)
            print("Microphone recording started")
        } catch {
            print("Failed to start audio engine: \(error)")
        }
    }
    
    /// Starts a microphone tap without creating a new Deepgram connection (used when also capturing system audio)
    private func startMicrophoneTap() {
        // Ensure audio engine is stopped and cleaned up
        cleanupAudioEngine()

        let inputNode = audioEngine.inputNode
        let recordingFormat = inputNode.outputFormat(forBus: 0)

        let targetFormat = AVAudioFormat(commonFormat: .pcmFormatInt16,
                                         sampleRate: 16000,
                                         channels: 1,
                                         interleaved: false)!

        let converter = AVAudioConverter(from: recordingFormat, to: targetFormat)!

        inputNode.installTap(onBus: 0, bufferSize: 1024, format: recordingFormat) { [weak self] buffer, _ in
            // Debug mic RMS
            if let ch = buffer.floatChannelData?[0] {
                let frameCount = Int(buffer.frameLength)
                let samples = UnsafeBufferPointer(start: ch, count: frameCount)
                let rms = sqrt(samples.map { $0 * $0 }.reduce(0, +) / Float(frameCount))
                print("🎤 Mic RMS: \(rms)")
            }
            self?.processAudioBuffer(buffer, converter: converter, targetFormat: targetFormat, source: .mic)
        }

        audioEngine.prepare()

        do {
            try audioEngine.start()
            connectToDeepgram(source: .mic)
        } catch {
            print("Failed to start microphone tap: \(error)")
        }
    }
    
    private func cleanupAudioEngine() {
        if audioEngine.isRunning {
            audioEngine.stop()
        }
        
        // Reset the audio engine - this safely removes all taps
        audioEngine.reset()
    }
    
    private func startSystemAudioCapture() async {
        print("🎧 Starting system audio capture...")
        
        do {
            // Request screen capture permission
            let content = try await SCShareableContent.excludingDesktopWindows(true, onScreenWindowsOnly: true)
            
            // Exclude self to avoid feedback
            let excludedApps = content.applications.filter { app in
                Bundle.main.bundleIdentifier == app.bundleIdentifier
            }
            
            guard let display = content.displays.first else {
                print("❌ No display found")
                startMicrophoneOnly()
                return
            }
            
            // Create filter
            let filter = SCContentFilter(display: display, excludingApplications: excludedApps, exceptingWindows: [])
            
            // Configure stream
            let configuration = SCStreamConfiguration()
            configuration.width = 2  // Minimal video settings
            configuration.height = 2
            configuration.minimumFrameInterval = CMTime(value: 1, timescale: CMTimeScale.max)
            configuration.capturesAudio = true
            configuration.sampleRate = 48000
            configuration.channelCount = 2
            
            // Create stream
            let stream = SCStream(filter: filter, configuration: configuration, delegate: self)
            
            // Add stream output for audio processing
            try stream.addStreamOutput(self, type: .audio, sampleHandlerQueue: .global(qos: .userInitiated))
            // Add a minimal screen output so SCStream doesn't complain about missing video output
            try stream.addStreamOutput(self, type: .screen, sampleHandlerQueue: .global(qos: .userInitiated))
            
            // Start capture
            try await stream.startCapture()
            
            // Store reference
            self.stream = stream
            
            DispatchQueue.main.async {
                self.isRecording = true
            }
            
            connectToDeepgram(source: .system)
            print("✅ System audio capture started successfully")
            
        } catch {
            print("❌ Failed to start system audio capture: \(error)")
            
            if case SCStreamError.userDeclined = error {
                print("📍 Permission denied. User needs to enable screen recording in System Settings.")
            }
            
            // Fallback to microphone only
            startMicrophoneOnly()
        }
    }
    
    func stopRecording() {
        print("Stopping recording...")
        
        // Stop system audio capture
        if let stream = stream {
            stream.stopCapture()
            self.stream = nil
        }
        
        // Stop microphone capture
        cleanupAudioEngine()
        
        // Close WebSocket
        micSocketTask?.cancel(with: .normalClosure, reason: nil)
        micSocketTask = nil
        systemSocketTask?.cancel(with: .normalClosure, reason: nil)
        systemSocketTask = nil
        
        DispatchQueue.main.async {
            self.isRecording = false
        }
        
        print("Recording stopped")
    }
    
    private func processAudioBuffer(_ buffer: AVAudioPCMBuffer, converter: AVAudioConverter, targetFormat: AVAudioFormat, source: AudioSource) {
        var processBuffer = buffer
        
        // Convert to target format (16kHz int16 mono) in a single step – AVAudioConverter will handle resampling and downmixing
        let outputFrameCapacity = AVAudioFrameCount(Double(processBuffer.frameLength) * targetFormat.sampleRate / processBuffer.format.sampleRate)
        guard let outputBuffer = AVAudioPCMBuffer(pcmFormat: targetFormat, frameCapacity: outputFrameCapacity) else {
            return
        }
        
        var error: NSError?
        let status = converter.convert(to: outputBuffer, error: &error) { _, outStatus in
            outStatus.pointee = .haveData
            return processBuffer
        }
        
        guard status == .haveData, error == nil else {
            return
        }
        
        // Convert to Data for Deepgram
        guard let channelData = outputBuffer.int16ChannelData?[0] else {
            return
        }
        
        let frameCount = Int(outputBuffer.frameLength)
        let data = Data(bytes: channelData, count: frameCount * 2)
        
        sendAudioData(data, source: source)
    }
    
    private func connectToDeepgram(source: AudioSource) {
        guard let key = KeychainHelper.shared.get(forKey: "deepgramKey"), !key.isEmpty else {
            print("❌ No Deepgram key found")
            return
        }

        let session = URLSession(configuration: .default)
        var request = URLRequest(url: deepgramURL)
        request.addValue("Token \(key)", forHTTPHeaderField: "Authorization")

        let task = session.webSocketTask(with: request)
        task.resume()

        switch source {
        case .mic:
            micSocketTask = task
        case .system:
            systemSocketTask = task
        }

        receiveMessage(for: source)
        print("🌐 Connected to Deepgram (\(source))")
    }

    private func receiveMessage(for source: AudioSource) {
        let task: URLSessionWebSocketTask? = (source == .mic) ? micSocketTask : systemSocketTask
        task?.receive { [weak self] result in
            switch result {
            case .success(let message):
                switch message {
                case .string(let text):
                    self?.parseTranscription(text, source: source)
                case .data:
                    break
                @unknown default:
                    break
                }
                self?.receiveMessage(for: source) // continue loop
            case .failure(let error):
                print("❌ Receive error (\(source)): \(error)")
                // Attempt reconnect if still recording
                DispatchQueue.main.asyncAfter(deadline: .now() + 2) {
                    if self?.isRecording == true {
                        self?.connectToDeepgram(source: source)
                    }
                }
            }
        }
    }

    private func parseTranscription(_ text: String, source: AudioSource) {
        guard let data = text.data(using: .utf8),
              let json = try? JSONSerialization.jsonObject(with: data) as? [String: Any],
              let type = json["type"] as? String, type == "Results",
              let channel = json["channel"] as? [String: Any],
              let alternatives = channel["alternatives"] as? [[String: Any]],
              let alt = alternatives.first,
              let transcriptText = alt["transcript"] as? String,
              !transcriptText.isEmpty else { return }

        let prefix = (source == .mic) ? "[MIC]" : "[SYS]"
        DispatchQueue.main.async {
            if let isFinal = json["is_final"] as? Bool, isFinal {
                self.transcript += "\(prefix) \(transcriptText) "
            }
        }
    }

    private func sendAudioData(_ data: Data, source: AudioSource) {
        let task: URLSessionWebSocketTask? = (source == .mic) ? micSocketTask : systemSocketTask

        guard let socket = task, socket.state == .running else { return }

        socket.send(.data(data)) { error in
            if let error = error {
                print("❌ Send error (\(source)): \(error)")
            }
        }
    }
}

// MARK: - SCStreamDelegate & SCStreamOutput
extension AudioManager: SCStreamDelegate, SCStreamOutput {
    func stream(_ stream: SCStream, didOutputSampleBuffer sampleBuffer: CMSampleBuffer, of type: SCStreamOutputType) {
        guard type == .audio else { return }
        guard sampleBuffer.isValid else { return }
        
        // Convert CMSampleBuffer to AVAudioPCMBuffer
        guard let pcmBuffer = sampleBuffer.asPCMBuffer else { return }
        
        // Create converter for Deepgram format
        let targetFormat = AVAudioFormat(commonFormat: .pcmFormatInt16,
                                       sampleRate: 16000,
                                       channels: 1,
                                       interleaved: false)!
        
        guard let converter = AVAudioConverter(from: pcmBuffer.format, to: targetFormat) else { return }
        
        processAudioBuffer(pcmBuffer, converter: converter, targetFormat: targetFormat, source: .system)
    }
    
    func stream(_ stream: SCStream, didStopWithError error: Error) {
        print("❌ Stream stopped with error: \(error)")
        DispatchQueue.main.async {
            self.stream = nil
            self.isRecording = false
        }
    }
}

// MARK: - CMSampleBuffer Extension
extension CMSampleBuffer {
    var asPCMBuffer: AVAudioPCMBuffer? {
        try? self.withAudioBufferList { audioBufferList, _ -> AVAudioPCMBuffer? in
            guard let absd = self.formatDescription?.audioStreamBasicDescription else { return nil }
            guard let format = AVAudioFormat(standardFormatWithSampleRate: absd.mSampleRate, channels: absd.mChannelsPerFrame) else { return nil }
            return AVAudioPCMBuffer(pcmFormat: format, bufferListNoCopy: audioBufferList.unsafePointer)
        }
    }
}