import AVFoundation
import Combine
import Foundation
import Photos
import UIKit

final class SharingMiddleware {
    static let shared = SharingMiddleware()

    func middleware(state _: AppState, action: AppAction) -> AnyPublisher<AppAction, Never> {
        switch action {
        case .sharingAction(.checkCameraAccess):
            return Future<AppAction, Never> { promise in
                let status = AVCaptureDevice.authorizationStatus(for: .video)
                switch status {
                case .authorized:
                    promise(.success(.sharingAction(.setCameraAccess(true))))

                case .notDetermined:
                    AVCaptureDevice.requestAccess(for: .video) { granted in
                        promise(.success(.sharingAction(.setCameraAccess(granted))))
                    }

                case .denied, .restricted:
                    promise(.success(.sharingAction(.setCameraAccess(false))))

                @unknown default:
                    promise(.success(.sharingAction(.setCameraAccess(false))))
                }
            }
            .eraseToAnyPublisher()

        case .sharingAction(.checkGalleryAccess):
            return Future<AppAction, Never> { promise in
                let status = PHPhotoLibrary.authorizationStatus()
                switch status {
                case .authorized, .limited:
                    promise(.success(.sharingAction(.setGalleryAccess(true))))

                case .notDetermined:
                    PHPhotoLibrary.requestAuthorization { status in
                        promise(.success(.sharingAction(.setGalleryAccess(status == .authorized))))
                    }

                case .denied, .restricted:
                    promise(.success(.sharingAction(.setGalleryAccess(false))))

                @unknown default:
                    promise(.success(.sharingAction(.setGalleryAccess(false))))
                }
            }
            .eraseToAnyPublisher()

        case .sharingAction(.fetchGallery):
            return Future<AppAction, Never> { promise in
                let fetchOptions = PHFetchOptions()
                fetchOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
                let assets = PHAsset.fetchAssets(with: fetchOptions)
                var items: [SharingGalleryItem] = []
                assets.enumerateObjects { asset, _, _ in
                    if asset.mediaType == .image {
                        items.append(.init(id: asset.localIdentifier, type: .photo))
                    } else if asset.mediaType == .video {
                        items.append(.init(id: asset.localIdentifier, type: .video))
                    }
                }
                promise(.success(.sharingAction(.galleryFetched(items))))
            }
            .eraseToAnyPublisher()

        case .sharingAction(.galleryFetched(let items)):
            DispatchQueue.global().async {
                let ids = items
                    .filter { $0.thumbnail == nil }
                    .map { $0.id }
                let assets = PHAsset.fetchAssets(withLocalIdentifiers: ids, options: nil)
                assets.enumerateObjects { asset, _, _ in
                    if asset.mediaType == .image {
                        PHImageManager.default().requestImage(
                            for: asset,
                            targetSize: PHImageManagerMaximumSize,
                            contentMode: .aspectFill,
                            options: nil
                        ) { image, _ in
                            image?.scaleAndCropImage(toExampleSize: CGSize(width: Const.galleryGridSize, height: Const.galleryGridSize)) { image in
                                if let image {
                                    let data = image.jpegData(compressionQuality: 1.0) ?? Data()
                                    store.dispatch(.sharingAction(.thumbnailUpdated(data: data, id: asset.localIdentifier)))
                                }
                            }
                        }
                    } else if asset.mediaType == .video {
                        PHImageManager.default().requestAVAsset(forVideo: asset, options: nil) { avAsset, _, _ in
                            if let avAsset {
                                let imageGenerator = AVAssetImageGenerator(asset: avAsset)
                                imageGenerator.appliesPreferredTrackTransform = true
                                let time = CMTimeMake(value: 1, timescale: 2)
                                do {
                                    let imageRef = try imageGenerator.copyCGImage(at: time, actualTime: nil)
                                    let thumbnail = UIImage(cgImage: imageRef)
                                    thumbnail.scaleAndCropImage(toExampleSize: CGSize(width: Const.galleryGridSize, height: Const.galleryGridSize)) { image in
                                        if let image {
                                            let data = image.jpegData(compressionQuality: 1.0) ?? Data()
                                            store.dispatch(.sharingAction(.thumbnailUpdated(data: data, id: asset.localIdentifier)))
                                        }
                                    }
                                } catch {
                                    print("Failed to create thumbnail image")
                                }
                            }
                        }
                    }
                }
            }
            return Empty().eraseToAnyPublisher()

        default:
            return Empty().eraseToAnyPublisher()
        }
    }
}