import Foundation
import CreateML

final class ClassifierCreator {
    
    let server: URL
    
    let configuration: Configuration
    
    let imageDirectory: URL
    
    let thumbnailDirectory: URL
    
    let classifierUrl: URL
    
    let df = DateFormatter()
    
    
    // MARK: Step 1: Load configuration
    
    init(configuration: Configuration) throws {
        self.configuration = configuration
        self.server = try configuration.serverUrl()
        let contentDirectory = URL(fileURLWithPath: configuration.contentFolder)
        self.imageDirectory = contentDirectory.appendingPathComponent("images")
        self.classifierUrl = contentDirectory.appendingPathComponent("classifier.mlmodel")
        self.thumbnailDirectory = contentDirectory.appendingPathComponent("thumbnails")
        df.dateFormat = "yy-MM-dd-HH-mm-ss"
    }
    
    // MARK: Main function
    
    func run() async throws {
        let imagesSnapshotDate = Date()
        let (classes, changedImageCount, changedMainImages) = try await loadImages()

        guard !classes.isEmpty else {
            print("[INFO] No image classes found, exiting...")
            return
        }
        
        guard changedImageCount > 0 else {
            print("[INFO] No changed images, so no new classifier trained")
            await createThumbnails(changed: changedMainImages)
            print("[INFO] Done")
            return
        }

        let classifierVersion = try await getClassifierVersion()
        let newVersion = classifierVersion + 1

        print("[INFO] Image directory: \(imageDirectory.absoluteURL.path)")
        print("[INFO] Model path: \(classifierUrl.path)")
        print("[INFO] Version: \(newVersion)")
        print("[INFO] Classes: \(classes.count)")
        print("[INFO] Iterations: \(configuration.trainingIterations)")

        try trainModel()
        try await upload(version: newVersion)
        try await upload(classes: classes, lastUpdate: imagesSnapshotDate)
        await createThumbnails(changed: changedMainImages)
        print("[INFO] Done")
    }
    
    // MARK: Step 2: Load changed images
    
    func loadImages() async throws -> (classes: [Int], changedImageCount: Int, changedMainImages: [Int]) {
        guard createFolderIfMissing(imageDirectory) else {
            throw TrainingError.mainImageFolderNotCreated
        }
        let imageCounts = await getImageCounts()
        let missingImageList: [CapImage] = imageCounts
            .sorted { $0.key < $1.key }
            .reduce(into: []) { list, pair in
                let missingImagesForCap: [CapImage] = (0..<pair.value).compactMap { image in
                    let image = CapImage(cap: pair.key, image: image)
                    let url = imageUrl(base: imageDirectory, image: image)
                    guard !FileManager.default.fileExists(atPath: url.path) else {
                        return nil
                    }
                    return image
                }
                list.append(contentsOf: missingImagesForCap)
            }
        if missingImageList.isEmpty {
            print("[INFO] No missing images to load")
        } else {
            print("[INFO] Loading \(missingImageList.count) missing images...")
            try await loadImages(missingImageList)
        }
        
        
        let changedImageList = try await getChangedImageList()
        let filteredChangeList = changedImageList
            .filter { $0.image < imageCounts[$0.cap] ?? 0 } // Filter non-existent images
            .filter { !missingImageList.contains($0) }
        
        let imagesAlreadyLoad = changedImageList.count - filteredChangeList.count
        let suffix = imagesAlreadyLoad > 0 ? " (\(imagesAlreadyLoad) already loaded)" : ""
        if filteredChangeList.isEmpty {
            print("[INFO] No changed images to load" + suffix)
        } else {
            print("[INFO] Loading \(filteredChangeList.count) changed images" + suffix)
            try await loadImages(filteredChangeList)
        }
        
        let changedMainImages = changedImageList.filter { $0.image == 0 }.map { $0.cap }
        let classes = imageCounts.keys.sorted()
        
        // Delete any image folders not present as caps
        try deleteUnnecessaryImageFolders(caps: classes)
        
        return (classes, missingImageList.count + changedImageList.count, changedMainImages)
    }
    
    private func getImageCounts() async -> [Int : Int] {
        guard let data: Data = await get(server.appendingPathComponent("caps.json")) else {
            return [:]
        }
        do {
            return try JSONDecoder().decode([Cap].self, from: data)
                .reduce(into: [:]) { $0[$1.id] = $1.count }
        } catch {
            print("[ERROR] Failed to decode cap database: \(error)")
            return [:]
        }
    }
    
    private func deleteUnnecessaryImageFolders(caps: [Int]) throws {
        let validNames = caps.map { String(format: "%04d", $0) }
        let folders: [String]
        do {
            folders = try FileManager.default.contentsOfDirectory(atPath: imageDirectory.path)
        } catch {
            print("[ERROR] Failed to get list of image folders: \(error)")
            throw TrainingError.failedToGetListOfImageFolders
        }
        for folder in folders {
            if validNames.contains(folder) {
                continue
            }
            
            // Not a valid cap folder
            let url = imageDirectory.appendingPathComponent(folder)
            do {
                try FileManager.default.removeItem(at: url)
                print("[INFO] Removed unused image folder '\(folder)'")
            } catch {
                print("[ERROR] Failed to delete unused image folder \(folder): \(error)")
                throw TrainingError.failedToRemoveImageFolder
            }
        }
    }
    
    private func imageUrl(base: URL, image: CapImage) -> URL {
        base.appendingPathComponent(String(format: "%04d/%04d-%02d.jpg", image.cap, image.cap, image.image))
    }
    
    private func load(image: CapImage) async -> Bool {
        guard createFolderIfMissing(imageDirectory.appendingPathComponent(String(format: "%04d", image.cap))) else {
            return false
        }
        let url = imageUrl(base: server.appendingPathComponent("images"), image: image)
        let tempFile: URL, response: URLResponse
        do {
            (tempFile, response) = try await URLSession.shared.download(from: url)
        } catch {
            print("[ERROR] Failed to load \(image): \(error)")
            return false
        }
        let responseCode = (response as! HTTPURLResponse).statusCode
        guard responseCode == 200 else {
            print("[ERROR] Failed to load \(image): Response \(responseCode)")
            return false
        }
        do {
            let localUrl = imageUrl(base: imageDirectory, image: image)
            if FileManager.default.fileExists(atPath: localUrl.path) {
                try FileManager.default.removeItem(at: localUrl)
            }
            try FileManager.default.moveItem(at: tempFile, to: localUrl)
            return true
        } catch {
            print("[ERROR] Failed to save \(image): \(error)")
            return false
        }
    }
    
    private func loadImages(_ list: [CapImage]) async throws {
        var loadedImages = 0
        await withTaskGroup(of: Bool.self) { group in
            for image in list {
                group.addTask {
                    await self.load(image: image)
                }
            }
            for await loaded in group {
                if loaded {
                    loadedImages += 1
                }
            }
        }
        if loadedImages != list.count {
            print("[ERROR] Only \(loadedImages) of \(list.count) images loaded")
            throw TrainingError.failedToLoadImages
        }
    }
    
    func getChangedImageList() async throws -> [CapImage] {
        guard let string: String = await get(server.appendingPathComponent("changes.txt")) else {
            print("[ERROR] Failed to get list of changed images")
            throw TrainingError.failedToGetChangedImagesList
        }
        
        return string
            .components(separatedBy: "\n")
            .filter { $0 != "" }
            .compactMap {
                let parts = $0.components(separatedBy: ":")
                guard parts.count == 3 else {
                    return nil
                }
                /*
                guard let date = df.date(from: parts[0]) else {
                    print("[WARN] Invalid date \(parts[0]) in change list")
                    return nil
                }
                 */
                guard let cap = Int(parts[1]) else {
                    print("[WARN] Invalid cap id \(parts[1]) in change list")
                    return nil
                }
                guard let image = Int(parts[2]) else {
                    print("[WARN] Invalid image id \(parts[2]) in change list")
                    return nil
                }
                return CapImage(cap: cap, image: image)
            }
    }
    
    // MARK: Step 3: Compute version
    
    func getClassifierVersion() async throws -> Int {
        guard let string: String = await get(server.appendingPathComponent("version")) else {
            print("[ERROR] Failed to get classifier version")
            throw TrainingError.failedToGetClassifierVersion
        }
        guard let version = Int(string) else {
            print("[ERROR] Invalid classifier version \(string)")
            throw TrainingError.invalidClassifierVersion(string)
        }
        return version
    }
    
    // MARK: Step 4: Train classifier
    
    func trainModel() throws {
        var params = MLImageClassifier.ModelParameters(augmentation: [])
        params.maxIterations = configuration.trainingIterations
        let model: MLImageClassifier
        do {
            model = try MLImageClassifier(
                trainingData: .labeledDirectories(at: imageDirectory),
                parameters: params)
        } catch {
            print("[ERROR] Failed to create classifier: \(error)")
            throw TrainingError.failedToCreateClassifier(error)
        }

        print("[INFO] Saving classifier...")
        do {
            try model.write(to: classifierUrl)
        } catch {
            print("[ERROR] Failed to save model to file: \(error)")
            throw TrainingError.failedToWriteClassifier(error)
        }
    }
    
    // MARK: Step 5: Upload classifier
    
    func upload(version: Int) async throws {
        print("[INFO] Uploading classifier...")
        let modelData: Data
        do {
            modelData = try Data(contentsOf: classifierUrl)
        } catch {
            print("[ERROR] Failed to read classifier data: \(error)")
            throw TrainingError.failedToReadClassifierData(error)
        }
        
        let success = await post(
            url: server.appendingPathComponent("classifier/\(version)"),
            body: modelData)
        guard success else {
            throw TrainingError.failedToUploadClassifier
        }
    }
    
    // MARK: Step 6: Update classes
    
    func upload(classes: [Int], lastUpdate: Date) async throws {
        print("[INFO] Uploading trained classes...")
        let dateString = df.string(from: lastUpdate)
        let url = server.appendingPathComponent("classes/\(dateString)")
        let body = classes.map(String.init).joined(separator: ",").data(using: .utf8)!
        guard await post(url: url, body: body) else {
            throw TrainingError.failedToUploadClassifierClasses
        }
    }
    
    // MARK: Step 7: Create thumbnails
    
    func createThumbnails(changed: [Int]) async {
        guard checkMagickAvailability() else {
            return
        }
        guard createFolderIfMissing(thumbnailDirectory) else {
            print("[ERROR] Failed to create folder for thumbnails")
            return
        }
        let capIdsOfMissingThumbnails = await getMissingThumbnailIds()
        let all = Set(capIdsOfMissingThumbnails).union(changed)
        print("[INFO] Creating \(all.count) thumbnails...")
        for cap in all {
            await createThumbnail(for: cap)
        }
    }
    
    func checkMagickAvailability() -> Bool {
        do {
            let (code, output) = try safeShell("magick --version")
            guard code == 0, let version = output.components(separatedBy: "ImageMagick ").dropFirst().first?
                .components(separatedBy: " ").first else {
                print("[ERROR] Magick not found, install using 'brew install imagemagick'")
                return false
            }
            print("[INFO] Using magick \(version)")
        } catch {
            print("[ERROR] Failed to get version of magick: (\(error))")
            return false
        }
        return true
    }
    
    private func getMissingThumbnailIds() async -> [Int] {
        guard let string: String = await get(server.appendingPathComponent("thumbnails/missing")) else {
            print("[ERROR] Failed to get missing thumbnails")
            return []
        }
        return string.components(separatedBy: ",").compactMap(Int.init)
    }
    
    private func createThumbnail(for cap: Int) async {
        let mainImage = CapImage(cap: cap, image: 0)
        let inputUrl = imageUrl(base: imageDirectory, image: mainImage)
        guard FileManager.default.fileExists(atPath: inputUrl.path) else {
            print("[ERROR] Local main image not found for cap \(cap): \(inputUrl.path)")
            return
        }
        
        let output = thumbnailDirectory.appendingPathComponent(String(format: "%04d.jpg", cap))
        do {
            let command = "magick convert \(inputUrl.path) -quality 70% -resize 100x100 \(output.path)"
            let (code, output) = try safeShell(command)
            if code != 0 {
                print("Failed to create thumbnail for cap \(cap): \(output)")
                return
            }
        } catch {
            print("Failed to read created thumbnail for cap \(cap): \(error)")
            return
        }
        
        let data: Data
        do {
            data = try Data(contentsOf: output)
        } catch {
            print("Failed to read created thumbnail for cap \(cap): \(error)")
            return
        }
        guard await post(url: server.appendingPathComponent("thumbnails/\(cap)"), body: data) else {
            print("Failed to upload thumbnail for cap \(cap)")
            return
        }
    }
    
    // MARK: Helper
    
    @discardableResult
    private func safeShell(_ command: String) throws -> (code: Int32, output: String) {
        let task = Process()
        let pipe = Pipe()

        task.standardOutput = pipe
        task.standardError = pipe
        task.arguments = ["-cl", command]
        task.executableURL = URL(fileURLWithPath: "/bin/zsh")
        task.standardInput = nil

        try task.run()
        task.waitUntilExit()
        
        let data = pipe.fileHandleForReading.readDataToEndOfFile()
        let output = String(data: data, encoding: .utf8)!
        return (task.terminationStatus, output)
    }
    
    
    private func createFolderIfMissing(_ folder: URL) -> Bool {
        guard !FileManager.default.fileExists(atPath: folder.path) else {
            return true
        }
        do {
            try FileManager.default.createDirectory(at: folder, withIntermediateDirectories: true)
            return true
        } catch {
            print("[ERROR] Failed to create directory \(folder.path): \(error)")
            return false
        }
    }
    
    // MARK: Requests
    
    private func post(url: URL, body: Data) async -> Bool {
        var request = URLRequest(url: url)
        request.httpMethod = "POST"
        request.httpBody = body
        request.addValue(configuration.authenticationToken, forHTTPHeaderField: "key")
        return await perform(request) != nil
    }
    
    private func perform(_ request: URLRequest) async -> Data? {
        let data: Data
        let response: URLResponse
        do {
            (data, response) = try await URLSession.shared.data(for: request)
        } catch {
            print("[ERROR] Request to \(request.url!.absoluteString) failed: \(error)")
            return nil
        }
        let code = (response as! HTTPURLResponse).statusCode
        guard code == 200 else {
            print("[ERROR] Request to \(request.url!.absoluteString): Invalid response \(code)")
            return nil
        }
        return data
    }
    
    private func get(_ url: URL) async -> Data? {
        await perform(URLRequest(url: url))
    }
    
    private func get(_ url: URL) async -> String? {
        guard let data: Data = await get(url) else {
            return nil
        }
        guard let string = String(data: data, encoding: .utf8) else {
            print("[ERROR] Invalid string response \(data)")
            return nil
        }
        return string
    }
}