import CoreML
import Vision
import FirebaseStorage

struct SharedEngineResources {
    static let context = CIContext()
}

// MARK: - MODEL MANAGER (OTA Updates)
class ModelManager {
    static let shared = ModelManager()
    private let defaults = UserDefaults.standard

    func getModel(name: String) -> VNCoreMLModel? {
        // 1. Check Documents (Downloaded Update)
        if let docDir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first {
            let modelURL = docDir.appendingPathComponent("models/\(name).mlmodelc")
            if FileManager.default.fileExists(atPath: modelURL.path),
               let model = try? MLModel(contentsOf: modelURL),
               let vnModel = try? VNCoreMLModel(for: model) {
                return vnModel
            }
        }

        // 2. Check Bundle (Built-in Fallback)
        if let bundleURL = Bundle.main.url(forResource: name, withExtension: "mlmodelc"),
           let model = try? MLModel(contentsOf: bundleURL),
           let vnModel = try? VNCoreMLModel(for: model) {
            return vnModel
        }
        return nil
    }

    func checkForUpdates() {
        guard FirebaseApp.app() != nil else { return }
        let models = ["IYmtgFoilClassifier", "IYmtgConditionClassifier", "IYmtgStampClassifier", "IYmtgSetClassifier"]

        for name in models {
            let ref = Storage.storage().reference().child("models/\(name).mlmodel")
            ref.getMetadata { meta, error in
                guard let meta = meta, let remoteDate = meta.updated else { return }
                let localDate = self.defaults.object(forKey: "ModelDate_\(name)") as? Date ?? Date.distantPast

                if remoteDate > localDate {
                    let tempURL = FileManager.default.temporaryDirectory.appendingPathComponent("\(name).mlmodel")
                    ref.write(toFile: tempURL) { url, error in
                        guard let url = url else { return }
                        DispatchQueue.global(qos: .utility).async {
                            do {
                                let compiledURL = try MLModel.compileModel(at: url)
                                let docDir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0].appendingPathComponent("models")
                                try FileManager.default.createDirectory(at: docDir, withIntermediateDirectories: true)
                                let destURL = docDir.appendingPathComponent("\(name).mlmodelc")
                                let tempDestURL = docDir.appendingPathComponent("temp_\(name).mlmodelc")

                                try? FileManager.default.removeItem(at: tempDestURL)
                                try FileManager.default.copyItem(at: compiledURL, to: tempDestURL)

                                if FileManager.default.fileExists(atPath: destURL.path) {
                                    _ = try FileManager.default.replaceItem(at: destURL, withItemAt: tempDestURL, backupItemName: nil, options: [])
                                } else {
                                    try FileManager.default.moveItem(at: tempDestURL, to: destURL)
                                }
                                self.defaults.set(remoteDate, forKey: "ModelDate_\(name)")
                                print("✅ OTA Model Updated: \(name)")
                            } catch {
                                print("❌ Model Update Failed for \(name): \(error)")
                            }
                        }
                    }
                }
            }
        }
    }
}