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 items = syncGalleryEnumerate()
            .map {
                SharingGalleryItem(
                    id: $0.localIdentifier,
                    type: $0.mediaType == .image ? .photo : .video,
                    duration: $0.mediaType == .video ? $0.duration.minAndSec : nil
                )
            }
        return items
    }

    func fillGalleryItemsThumbnails(items: [SharingGalleryItem]) -> [SharingGalleryItem] {
        let ids = items
            .filter { $0.thumbnail == nil }
            .map { $0.id }

        let assets = syncGalleryEnumerate(ids)
        return assets.compactMap { asset in
            if asset.mediaType == .image {
                return syncGalleryProcessImage(asset) { [weak self] image in
                    if let thumbnail = self?.scaleAndCropImage(image, CGSize(width: Const.galleryGridSize, height: Const.galleryGridSize)) {
                        let data = thumbnail.jpegData(compressionQuality: 1.0) ?? Data()
                        return SharingGalleryItem(id: asset.localIdentifier, type: .photo, thumbnail: data)
                    } else {
                        return nil
                    }
                }
            } else if asset.mediaType == .video {
                return syncGalleryProcessVideo(asset) { [weak self] avAsset in
                    // swiftlint:disable:next force_cast
                    let assetURL = avAsset as! AVURLAsset
                    let url = assetURL.url
                    if let thumbnail = self?.generateVideoThumbnail(url, CGSize(width: Const.galleryGridSize, height: Const.galleryGridSize)) {
                        let data = thumbnail.jpegData(compressionQuality: 1.0) ?? Data()
                        return SharingGalleryItem(
                            id: asset.localIdentifier,
                            type: .video,
                            thumbnail: data,
                            duration: asset.duration.minAndSec
                        )
                    } else {
                        return nil
                    }
                }
            } else {
                return nil
            }
        }
    }

    // This function also creates new ids for messages for each new attachment
    func copyGalleryItemsForUploading(items: [SharingGalleryItem]) -> [(String, String)] {
        let assets = syncGalleryEnumerate(items.map { $0.id })
        return assets
            .compactMap { asset in
                let newMessageId = UUID().uuidString
                let fileId = UUID().uuidString
                if asset.mediaType == .image {
                    return syncGalleryProcessImage(asset) { image in
                        let localName = "\(newMessageId)_\(fileId).jpg"
                        let localUrl = FileProcessing.fileFolder.appendingPathComponent(localName)
                        if let data = image.jpegData(compressionQuality: 1.0) {
                            do {
                                try data.write(to: localUrl)
                                return (newMessageId, localName)
                            } catch {
                                return nil
                            }
                        } else {
                            return nil
                        }
                    }
                } else if asset.mediaType == .video {
                    return syncGalleryProcessVideo(asset) { avAsset in
                        // swiftlint:disable:next force_cast
                        let assetURL = avAsset as! AVURLAsset
                        let url = assetURL.url
                        let localName = "\(newMessageId)_\(fileId).mov"
                        let localUrl = FileProcessing.fileFolder.appendingPathComponent(localName)
                        do {
                            try FileManager.default.copyItem(at: url, to: localUrl)
                            return (newMessageId, localName)
                        } catch {
                            return nil
                        }
                    }
                } else {
                    return nil
                }
            }
    }

    // This function also creates new id for file from camera capturing
    func copyCameraCapturedForUploading(media: Data, type: SharingCameraMediaType) -> (String, String)? {
        let newMessageId = UUID().uuidString
        let fileId = UUID().uuidString
        let localName: String
        switch type {
        case .photo:
            localName = "\(newMessageId)_\(fileId).jpg"
        case .video:
            localName = "\(newMessageId)_\(fileId).mov"
        }
        let localUrl = FileProcessing.fileFolder.appendingPathComponent(localName)
        do {
            try media.write(to: localUrl)
            return (newMessageId, localName)
        } catch {
            return nil
        }
    }
}

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

        let group = DispatchGroup()
        DispatchQueue.global(qos: .userInitiated).sync {
            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
                group.enter()
                result.append(asset)
                group.leave()
            }
        }
        group.wait()
        return result
    }

    func syncGalleryProcess<T>(_ assets: [PHAsset], _ block: @escaping (PHAsset) -> T) -> [T] {
        var result: [T] = []
        let group = DispatchGroup()
        DispatchQueue.global(qos: .userInitiated).sync {
            for asset in assets {
                group.enter()
                let res = block(asset)
                result.append(res)
                group.leave()
            }
        }
        group.wait()
        return result
    }

    func syncGalleryProcessImage<T>(_ asset: PHAsset, _ block: @escaping (UIImage) -> T?) -> T? {
        var result: T?
        let semaphore = DispatchSemaphore(value: 0)
        DispatchQueue.global(qos: .userInitiated).sync {
            let options = PHImageRequestOptions()
            options.version = .original
            options.isSynchronous = true
            PHImageManager.default().requestImage(
                for: asset,
                targetSize: PHImageManagerMaximumSize,
                contentMode: .aspectFill,
                options: options
            ) { image, _ in
                if let image {
                    result = block(image)
                } else {
                    result = nil
                }
                semaphore.signal()
            }
        }
        semaphore.wait()
        return result
    }

    func syncGalleryProcessVideo<T>(_ asset: PHAsset, _ block: @escaping (AVAsset) -> T?) -> T? {
        var result: T?
        let semaphore = DispatchSemaphore(value: 0)
        _ = DispatchQueue.global(qos: .userInitiated).sync {
            PHImageManager.default().requestAVAsset(forVideo: asset, options: nil) { avAsset, _, _ in
                if let avAsset {
                    result = block(avAsset)
                } else {
                    result = nil
                }
                semaphore.signal()
            }
        }
        semaphore.wait()
        return result
    }

    func generateVideoThumbnail(_ url: URL, _ size: CGSize) -> UIImage? {
        let asset = AVAsset(url: url)
        let assetImgGenerate = AVAssetImageGenerator(asset: asset)
        assetImgGenerate.appliesPreferredTrackTransform = true
        let time = CMTimeMakeWithSeconds(Float64(1), preferredTimescale: 600)
        do {
            let cgImage = try assetImgGenerate.copyCGImage(at: time, actualTime: nil)
            let image = UIImage(cgImage: cgImage)
            return scaleAndCropImage(image, size)
        } catch {
            return nil
        }
    }
}