import Foundation
import Photos
import UIKit

final class FileProcessing {
    static let shared = FileProcessing()

    static var fileFolder: URL {
        // swiftlint:disable:next force_unwrapping
        let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
        let subdirectoryURL = documentsURL.appendingPathComponent(Const.fileFolder)
        if !FileManager.default.fileExists(atPath: subdirectoryURL.path) {
            try? FileManager.default.createDirectory(at: subdirectoryURL, withIntermediateDirectories: true, attributes: nil)
        }
        return subdirectoryURL
    }

    func createThumbnail(localName: String) -> String? {
        let thumbnailFileName = "thumb_\(localName)"
        let thumbnailUrl = FileProcessing.fileFolder.appendingPathComponent(thumbnailFileName)
        let localUrl = FileProcessing.fileFolder.appendingPathComponent(localName)

        // check if thumbnail already exists
        if FileManager.default.fileExists(atPath: thumbnailUrl.path) {
            return thumbnailFileName
        }

        // create thumbnail if not exists
        switch localName.attachmentType {
        case .image:
            guard let image = UIImage(contentsOfFile: localUrl.path) else { return nil }
            let targetSize = CGSize(width: Const.attachmentPreviewSize, height: Const.attachmentPreviewSize)
            guard let thumbnail = scaleAndCropImage(image, targetSize) else { return nil }
            guard let data = thumbnail.pngData() else { return nil }
            do {
                try data.write(to: thumbnailUrl)
                return thumbnailFileName
            } catch {
                return nil
            }

        default:
            return nil
        }
    }

    func fetchGallery() -> [SharingGalleryItem] {
        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))
            }
        }
        return items
    }

    func fillGalleryItemsThumbnails(items: [SharingGalleryItem]) -> [SharingGalleryItem] {
        var result: [SharingGalleryItem] = []
        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()
                            result.append(.init(id: asset.localIdentifier, type: .photo, thumbnail: data))
                        }
                    }
                }
            } 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()
                                    result.append(.init(id: asset.localIdentifier, type: .video, thumbnail: data))
                                }
                            }
                        } catch {
                            print("Failed to create thumbnail image")
                        }
                    }
                }
            }
        }
        return result
    }
}

private extension FileProcessing {
    func scaleAndCropImage(_ img: UIImage, _ size: CGSize) -> UIImage? {
        let aspect = img.size.width / img.size.height
        let targetAspect = size.width / size.height
        var newWidth: CGFloat
        var newHeight: CGFloat
        if aspect < targetAspect {
            newWidth = size.width
            newHeight = size.width / aspect
        } else {
            newHeight = size.height
            newWidth = size.height * aspect
        }

        UIGraphicsBeginImageContextWithOptions(size, false, 0.0)
        img.draw(in: CGRect(x: (size.width - newWidth) / 2, y: (size.height - newHeight) / 2, width: newWidth, height: newHeight))
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return newImage
    }

    func syncEnumrate(_ ids: [String]? = nil) -> [PHAsset] {
        var result: [PHAsset] = []

        let fetchOptions = PHFetchOptions()
        fetchOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
        if let ids {
            fetchOptions.predicate = NSPredicate(format: "localIdentifier IN %@", ids)
        }
        let assets = PHAsset.fetchAssets(with: fetchOptions)
        assets.enumerateObjects { asset, _, _ in
            result.append(asset)
        }
        return result
    }
}