import Foundation
import AVFoundation
import Combine

/// Detects system environment issues before starting a recording.
/// Checks background audio, media volume, and microphone permissions.
@Observable
final class RecordingEnvironmentDetector {
    
    // MARK: - Published Warnings
    
    var isOtherAudioPlaying: Bool = false
    var isVolumeTooHigh: Bool = false
    var micPermissionStatus: AVAudioSession.RecordPermission = .undetermined
    
    /// List of human-readable warnings based on current environment state.
    var activeWarnings: [String] = []
    
    init() {
        checkEnvironment()
        
        // Listen to volume changes or other audio notifications if necessary
        NotificationCenter.default.addObserver(
            self,
            selector: #selector(handleAudioRouteChanged),
            name: AVAudioSession.routeChangeNotification,
            object: nil
        )
    }
    
    /// Runs environment checks and updates warnings.
    func checkEnvironment() {
        let session = AVAudioSession.sharedInstance()
        
        // 1. Check if other audio is playing in the background
        self.isOtherAudioPlaying = session.isOtherAudioPlaying
        
        // 2. Check if output volume is too high (above 70%)
        self.isVolumeTooHigh = session.outputVolume > 0.7
        
        // 3. Check microphone permission status
        self.micPermissionStatus = session.recordPermission
        
        // Compile warning strings
        var warnings: [String] = []
        
        if isOtherAudioPlaying {
            warnings.append("⚠️ 检测到后台有其他音频播放中，建议关闭以防混入录音。")
        }
        
        if isVolumeTooHigh {
            warnings.append("⚠️ 系统媒体音量过高 (%.0f%%)，录音时建议降低音量。" .replacingOccurrences(of: "%.0f%%", with: String(format: "%.0f%%", session.outputVolume * 100)))
        }
        
        if micPermissionStatus == .denied {
            warnings.append("⚠️ 麦克风访问权限被禁用，请前往系统设置开启麦克风。")
        }
        
        self.activeWarnings = warnings
    }
    
    @objc private func handleAudioRouteChanged() {
        // Run checks on background thread to avoid blocking main loop, then dispatch updates
        DispatchQueue.main.async { [weak self] in
            self?.checkEnvironment()
        }
    }
}