import Foundation
import AVFoundation
import SwiftSignalKit
import TelegramCore

private let defaultFPS: Double = 30.0

final class CameraDevice {
    var position: Camera.Position = .back
    
    public private(set) var videoDevice: AVCaptureDevice? = nil {
        didSet {
            self.videoDevicePromise.set(.single(self.videoDevice))
        }
    }
    private var videoDevicePromise = Promise<AVCaptureDevice?>()
    
    public private(set) var audioDevice: AVCaptureDevice? = nil
        
    func configure(for session: AVCaptureSession, position: Camera.Position) {
        self.position = position
        if let videoDevice = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInDualCamera, .builtInWideAngleCamera, .builtInTelephotoCamera], mediaType: .video, position: position).devices.first {
            self.videoDevice = videoDevice
            self.videoDevicePromise.set(.single(videoDevice))
        }
        self.audioDevice = AVCaptureDevice.default(for: .audio)
    }
    
    func configureDeviceFormat(maxDimensions: CMVideoDimensions, maxFramerate: Double) {
        guard let device = self.videoDevice else {
            return
        }
        self.transaction(device) { device in
            var maxWidth: Int32 = 0
            var maxHeight: Int32 = 0
            var hasSecondaryZoomLevels = false
            var candidates: [AVCaptureDevice.Format] = []
     outer: for format in device.formats {
                if format.mediaType != .video || format.value(forKey: "isPhotoFormat") as? Bool == true {
                    continue
                }
                
                let dimensions = CMVideoFormatDescriptionGetDimensions(format.formatDescription)
                if dimensions.width >= maxWidth && dimensions.width <= maxDimensions.width && dimensions.height >= maxHeight && dimensions.height <= maxDimensions.height {
                    if dimensions.width > maxWidth {
                        hasSecondaryZoomLevels = false
                        candidates.removeAll()
                    }
                    let subtype = CMFormatDescriptionGetMediaSubType(format.formatDescription)
                    if subtype == kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange {
                        for range in format.videoSupportedFrameRateRanges {
                            if range.maxFrameRate > maxFramerate {
                                continue outer
                            }
                        }
                        
                        maxWidth = dimensions.width
                        maxHeight = dimensions.height
                        
                        if #available(iOS 16.0, *), !format.secondaryNativeResolutionZoomFactors.isEmpty {
                            hasSecondaryZoomLevels = true
                            candidates.append(format)
                        } else if !hasSecondaryZoomLevels {
                            candidates.append(format)
                        }
                    }
                }
            }
            
            if let bestFormat = candidates.last {
                device.activeFormat = bestFormat
                
                Logger.shared.log("Camera", "Available formats:")
                for format in device.formats {
                    Logger.shared.log("Camera", format.description)
                }
                
                Logger.shared.log("Camera", "Selected format:")
                Logger.shared.log("Camera", bestFormat.description)
            }
            
            if let targetFPS = device.actualFPS(maxFramerate) {
                device.activeVideoMinFrameDuration = targetFPS.duration
                device.activeVideoMaxFrameDuration = targetFPS.duration
            }
        }
    }
    
    func transaction(_ device: AVCaptureDevice, update: (AVCaptureDevice) -> Void) {
        if let _ = try? device.lockForConfiguration() {
            update(device)
            device.unlockForConfiguration()
        }
    }
    
    private func subscribeForChanges() {
        NotificationCenter.default.addObserver(self, selector: #selector(self.subjectAreaChanged), name: Notification.Name.AVCaptureDeviceSubjectAreaDidChange, object: self.videoDevice)
    }
    
    private func unsubscribeFromChanges() {
        NotificationCenter.default.removeObserver(self, name: Notification.Name.AVCaptureDeviceSubjectAreaDidChange, object: self.videoDevice)
    }
    
    @objc private func subjectAreaChanged() {
        self.setFocusPoint(CGPoint(x: 0.5, y: 0.5), focusMode: .continuousAutoFocus, exposureMode: .continuousAutoExposure, monitorSubjectAreaChange: false)
    }
    
    var fps: Double = defaultFPS {
        didSet {
            guard let device = self.videoDevice, let targetFPS = device.actualFPS(Double(self.fps)) else {
                return
            }
            
            self.fps = targetFPS.fps
            
            self.transaction(device) { device in
                device.activeVideoMinFrameDuration = targetFPS.duration
                device.activeVideoMaxFrameDuration = targetFPS.duration
            }
        }
    }
    
    var isTorchAvailable: Signal<Bool, NoError> {
        return self.videoDevicePromise.get()
        |> mapToSignal { device -> Signal<Bool, NoError> in
            return Signal { subscriber in
                guard let device else {
                    return EmptyDisposable
                }
                subscriber.putNext(device.isFlashAvailable)
                let observer = device.observe(\.isFlashAvailable, options: [.new], changeHandler: { device, _ in
                    subscriber.putNext(device.isFlashAvailable)
                })
                return ActionDisposable {
                    observer.invalidate()
                }
            }
            |> distinctUntilChanged
        }
    }
    
    var isAdjustingFocus: Signal<Bool, NoError> {
        return self.videoDevicePromise.get()
        |> mapToSignal { device -> Signal<Bool, NoError> in
            return Signal { subscriber in
                guard let device else {
                    return EmptyDisposable
                }
                subscriber.putNext(device.isAdjustingFocus)
                let observer = device.observe(\.isAdjustingFocus, options: [.new], changeHandler: { device, _ in
                    subscriber.putNext(device.isAdjustingFocus)
                })
                return ActionDisposable {
                    observer.invalidate()
                }
            }
            |> distinctUntilChanged
        }
    }
    
    func setFocusPoint(_ point: CGPoint, focusMode: Camera.FocusMode, exposureMode: Camera.ExposureMode, monitorSubjectAreaChange: Bool) {
        guard let device = self.videoDevice else {
            return
        }
        self.transaction(device) { device in
            if device.isExposurePointOfInterestSupported && device.isExposureModeSupported(exposureMode) {
                device.exposurePointOfInterest = point
                device.exposureMode = exposureMode
            }
            if device.isFocusPointOfInterestSupported && device.isFocusModeSupported(focusMode) {
                device.focusPointOfInterest = point
                device.focusMode = focusMode
            }
        }
    }
    
    func setExposureTargetBias(_ bias: Float) {
        guard let device = self.videoDevice else {
            return
        }
        self.transaction(device) { device in
            let extremum = (bias >= 0) ? device.maxExposureTargetBias : device.minExposureTargetBias;
            let value = abs(bias) * extremum * 0.85
            device.setExposureTargetBias(value, completionHandler: nil)
        }
    }
    
    func setTorchActive(_ active: Bool) {
        guard let device = self.videoDevice else {
            return
        }
        self.transaction(device) { device in
            device.torchMode = active ? .on : .off
        }
    }
    
    func setZoomLevel(_ zoomLevel: CGFloat) {
        guard let device = self.videoDevice else {
            return
        }
        self.transaction(device) { device in
            device.videoZoomFactor = max(1.0, min(10.0, zoomLevel))
        }
    }
}