import Foundation
import AppKit
import SDWebImageAVIFCoder
import SDWebImageWebPCoder

private struct ImageJob {

    let image: String

    let version: String

    let maximumWidth: CGFloat

    let maximumHeight: CGFloat

    let quality: CGFloat

    let type: ImageFileType
}

final class ImageGenerator {

    private let storage: Storage

    //private let inputImageFolder: URL

    private let relativeImageOutputPath: String

    private var generatedImages: [String : [String]] = [:]

    private var jobs: [ImageJob] = []

    init(storage: Storage, relativeImageOutputPath: String) {
        self.storage = storage
        self.relativeImageOutputPath = relativeImageOutputPath
        do {
            self.generatedImages = try storage.loadListOfGeneratedImages()
        } catch {
            print("Failed to load list of previously generated images: \(error)")
            self.generatedImages = [:]
        }
    }

    func prepareForGeneration() -> Bool {
        inOutputImagesFolder { imagesFolder in
            do {
                try imagesFolder.ensureFolderExistence()
                return true
            } catch {
                print("Failed to create output images folder: \(error)")
                return false
            }
        }
    }

    func runJobs(callback: (String) -> Void) -> Bool {
        guard !jobs.isEmpty else {
            return true
        }
        print("Generating \(jobs.count) images...")
        for job in jobs {
            callback("Generating image \(job.version)")
            guard generate(job: job) else {
                return false
            }
        }
        return true
    }

    func save() -> Bool {
        do {
            try storage.save(listOfGeneratedImages: generatedImages)
            return true
        } catch {
            print("Failed to save list of generated images: \(error)")
            return false
        }
    }

    private func versionFileName(image: String, type: ImageFileType, width: CGFloat, height: CGFloat) -> String {
        let fileName = image.fileNameAndExtension.fileName
        let prefix = "\(fileName)@\(Int(width))x\(Int(height))"
        return "\(prefix).\(type.fileExtension)"
    }

    func generateImageSet(for image: String, maxWidth: CGFloat, maxHeight: CGFloat) {
        let type = ImageFileType(fileExtension: image.fileExtension!)!

        let width2x = maxWidth * 2
        let height2x = maxHeight * 2

        _ = generateVersion(for: image, type: .avif, maximumWidth: maxWidth, maximumHeight: maxHeight)
        _ = generateVersion(for: image, type: .avif, maximumWidth: width2x, maximumHeight: height2x)

        _ = generateVersion(for: image, type: .webp, maximumWidth: maxWidth, maximumHeight: maxHeight)
        _ = generateVersion(for: image, type: .webp, maximumWidth: width2x, maximumHeight: height2x)

        _ = generateVersion(for: image, type: type, maximumWidth: maxWidth, maximumHeight: maxHeight)
        _ = generateVersion(for: image, type: type, maximumWidth: width2x, maximumHeight: height2x)
    }

    func generateVersion(for image: String, type: ImageFileType, maximumWidth: CGFloat, maximumHeight: CGFloat) -> String {
        let version = versionFileName(image: image, type: type, width: maximumWidth, height: maximumHeight)
        let fullPath = "/" + relativeImageOutputPath + "/" + version
        if exists(version) {
            hasNowGenerated(version: version, for: image)
            return fullPath
        }
        if hasPreviouslyGenerated(version: version, for: image), exists(version) {
            // Don't add job again
            return fullPath
        }

        let job = ImageJob(
            image: image,
            version: version,
            maximumWidth: maximumWidth,
            maximumHeight: maximumHeight,
            quality: 0.7,
            type: type)

        jobs.append(job)
        return fullPath
    }

    private func hasPreviouslyGenerated(version: String, for image: String) -> Bool {
        guard let versions = generatedImages[image] else {
            return false
        }
        return versions.contains(version)
    }

    private func exists(imageVersion version: String) -> Bool {
        inOutputImagesFolder { $0.appendingPathComponent(version).exists }
    }

    private func hasNowGenerated(version: String, for image: String) {
        guard var versions = generatedImages[image] else {
            generatedImages[image] = [version]
            return
        }
        versions.append(version)
        generatedImages[image] = versions
    }

    private func removeVersions(for image: String) {
        generatedImages[image] = nil
    }

    // MARK: Image operations

    private func generate(job: ImageJob) -> Bool {
        if hasPreviouslyGenerated(version: job.version, for: job.image), exists(job.version),
           exists(imageVersion: job.version) {
            return true
        }

        let data: Data
        do {
            data = try storage.fileData(for: job.image)
        } catch {
            print("Failed to load image \(job.image): \(error)")
            return false
        }

        guard let originalImage = NSImage(data: data) else {
            print("Failed to load image")
            return false
        }

        let sourceRep = originalImage.representations[0]
        let sourceSize = NSSize(width: sourceRep.pixelsWide, height: sourceRep.pixelsHigh)
        let maximumSize = NSSize(width: job.maximumWidth, height: job.maximumHeight)
        let destinationSize = sourceSize.scaledToFit(in: maximumSize)

        // create NSBitmapRep manually, if using cgImage, the resulting size is wrong
        let rep = NSBitmapImageRep(bitmapDataPlanes: nil,
                                   pixelsWide: Int(destinationSize.width),
                                   pixelsHigh: Int(destinationSize.height),
                                   bitsPerSample: 8,
                                   samplesPerPixel: 4,
                                   hasAlpha: true,
                                   isPlanar: false,
                                   colorSpaceName: NSColorSpaceName.deviceRGB,
                                   bytesPerRow: Int(destinationSize.width) * 4,
                                   bitsPerPixel: 32)!

        let ctx = NSGraphicsContext(bitmapImageRep: rep)
        NSGraphicsContext.saveGraphicsState()
        NSGraphicsContext.current = ctx
        originalImage.draw(in: NSMakeRect(0, 0, destinationSize.width, destinationSize.height))
        ctx?.flushGraphics()
        NSGraphicsContext.restoreGraphicsState()

        guard let data = create(image: rep, type: job.type, quality: job.quality) else {
            print("Failed to get data for type \(job.type)")
            return false
        }



        let result = inOutputImagesFolder { folder in
            let url = folder.appendingPathComponent(job.version)
            if job.type == .avif {
                let out = url.path()
                let input = url.deletingPathExtension().appendingPathExtension(job.image.fileExtension!).path()
                print("avifenc -q 70 \(input) \(out)")
                return true
            }
            do {
                try data.write(to: url)
                return true
            } catch {
                print("Failed to write image \(job.version): \(error)")
                return false
            }
        }
        guard result else {
            return false
        }
        hasNowGenerated(version: job.version, for: job.image)
        return true
    }

    private func exists(_ relativePath: String) -> Bool {
        inOutputImagesFolder { folder in
            folder.appendingPathComponent(relativePath).exists
        }
    }

    private func inOutputImagesFolder(perform operation: (URL) -> Bool) -> Bool {
        storage.write(in: .outputPath) { outputFolder in
            let imagesFolder = outputFolder.appendingPathComponent(relativeImageOutputPath)
            return operation(imagesFolder)
        }
    }

    // MARK: Avif images

    private func create(image: NSBitmapImageRep, type: ImageFileType, quality: CGFloat) -> Data? {
        switch type {
        case .jpg:
            return image.representation(using: .jpeg, properties: [.compressionFactor: NSNumber(value: 0.6)])
        case .png:
            return image.representation(using: .png, properties: [.compressionFactor: NSNumber(value: 0.6)])
        case .avif:
            return createAvif(image: image, quality: 0.7)
        case .webp:
            return createWebp(image: image, quality: 0.8)
        case .gif:
            return image.representation(using: .gif, properties: [.compressionFactor: NSNumber(value: quality)])
        case .svg:
            return nil
        case .tiff:
            return nil
        }
    }

    private func createAvif(image: NSBitmapImageRep, quality: CGFloat) -> Data? {
        return Data()
        let newImage = NSImage(size: image.size)
        newImage.addRepresentation(image)
        return SDImageAVIFCoder.shared.encodedData(with: newImage, format: .AVIF, options: [.encodeCompressionQuality: quality])
    }

    private func createWebp(image: NSBitmapImageRep, quality: CGFloat) -> Data? {
        let newImage = NSImage(size: image.size)
        newImage.addRepresentation(image)
        return SDImageWebPCoder.shared.encodedData(with: newImage, format: .webP, options: [.encodeCompressionQuality: quality])
    }
}