import AVFoundation
import Combine
import Foundation
import Photos
import UIKit

final class SharingMiddleware {
    static let shared = SharingMiddleware()

    // swiftlint:disable:next function_body_length
    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
                DispatchQueue.global(qos: .background).async {
                    let fetchOptions = PHFetchOptions()
                    fetchOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
                    let assets = PHAsset.fetchAssets(with: fetchOptions)

                    let manager = PHImageManager.default()
                    let option = PHImageRequestOptions()
                    option.isSynchronous = true

                    var items: [SharingGalleryItem] = []
                    let group = DispatchGroup()
                    assets.enumerateObjects { asset, _, _ in
                        if asset.mediaType == .image {
                            group.enter()
                            manager.requestImage(
                                for: asset,
                                targetSize: PHImageManagerMaximumSize,
                                contentMode: .aspectFill,
                                options: option
                            ) { image, _ in
                                if image != nil {
                                    items.append(.init(id: asset.localIdentifier, type: .photo))
                                    group.leave()
                                }
                            }
                        } else if asset.mediaType == .video {
                            group.enter()
                            manager.requestAVAsset(forVideo: asset, options: nil) { avAsset, _, _ in
                                if avAsset != nil {
                                    items.append(.init(id: asset.localIdentifier, type: .video, duration: asset.duration.minAndSec))
                                    group.leave()
                                }
                            }
                        }
                    }
                    group.notify(queue: .main) {
                        promise(.success(.sharingAction(.galleryFetched(items))))
                    }
                }
            }
            .eraseToAnyPublisher()

        case .sharingAction(.galleryFetched(let items)):
            return Future<AppAction, Never> { promise in
                DispatchQueue.global(qos: .background).async {
                    let ids = items
                        .filter { $0.thumbnail == nil }
                        .map { $0.id }
                    let assets = PHAsset.fetchAssets(withLocalIdentifiers: ids, options: nil)
                    assets.enumerateObjects { asset, _, _ in
                        let manager = PHImageManager.default()
                        if asset.mediaType == .image {
                            manager.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()
                                        DispatchQueue.main.async {
                                            store.dispatch(.sharingAction(.thumbnailUpdated(data, asset.localIdentifier)))
                                        }
                                    }
                                }
                            }
                        } else if asset.mediaType == .video {
                            manager.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), completion: { image in
                                            if let image {
                                                let data = image.jpegData(compressionQuality: 1.0) ?? Data()
                                                DispatchQueue.main.async {
                                                    store.dispatch(.sharingAction(.thumbnailUpdated(data, asset.localIdentifier)))
                                                }
                                            }
                                        })
                                    } catch {
                                        print("Failed to create thumbnail image")
                                    }
                                }
                            }
                        }
                    }
                }
                promise(.success(.empty))
            }
            .eraseToAnyPublisher()

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