import CoreData
import Foundation

// MARK: - Protocol Definition

/// A protocol that ensures a Data Transfer Object (DTO) can be stored in Core Data.
/// It requires a method to map the DTO to its corresponding Core Data managed object.
protocol ImportableDTO: Decodable {
    associatedtype ManagedObject: NSManagedObject
    /// Converts the DTO into a Core Data managed object.
    func store(in context: NSManagedObjectContext) -> ManagedObject
}

// MARK: - JSONImporter Class with Generic Import Function

/// Class responsible for importing JSON data into Core Data.
class JSONImporter {
    private let context: NSManagedObjectContext
    private let fileManager = FileManager.default

    /// Initializes the importer with a Core Data context.
    init(context: NSManagedObjectContext) {
        self.context = context
    }

    /// Generic function to import data from a JSON file into Core Data.
    /// - Parameters:
    ///   - userDefaultsKey: Key to check if data has already been imported.
    ///   - filePathComponent: Path component of the JSON file.
    ///   - dtoType: The DTO type conforming to `ImportableDTO`.
    ///   - dateDecodingStrategy: The date decoding strategy for JSON decoding.
//    func importDataIfNeeded<T: ImportableDTO>(
//        userDefaultsKey: String,
//        filePathComponent: String,
//        dtoType _: T.Type,
//        dateDecodingStrategy: JSONDecoder.DateDecodingStrategy = .iso8601
//    ) async {
//        let hasImported = UserDefaults.standard.bool(forKey: userDefaultsKey)
//
//        //        guard !hasImported else {
//        //            debugPrint("\(filePathComponent) already imported. Skipping import.")
//        //            return
//        //        }
//
//        do {
//            // Get the file path for the JSON file
//            guard let filePath = fileManager.urls(for: .documentDirectory, in: .userDomainMask)
//                .first?
//                .appendingPathComponent(filePathComponent),
//                fileManager.fileExists(atPath: filePath.path)
//            else {
//                debugPrint("\(filePathComponent) file not found at path \(filePathComponent)")
//                return
//            }
//
//            // Read data from the JSON file
//            let data = try Data(contentsOf: filePath)
//            let decoder = JSONDecoder()
//            decoder.dateDecodingStrategy = dateDecodingStrategy
//
//            // Decode the data into an array of DTOs
//            let entries = try decoder.decode([T].self, from: data)
//
//            // Save the DTOs into Core Data
//            await context.perform {
//                for entry in entries {
//                    _ = entry.store(in: self.context)
//                }
//
//                do {
//                    guard self.context.hasChanges else { return }
//                    try self.context.save()
//                    debugPrint("\(DebuggingIdentifiers.succeeded) \(filePathComponent) successfully imported into Core Data.")
//                } catch {
//                    debugPrint("\(DebuggingIdentifiers.failed) Failed to save \(filePathComponent) to Core Data: \(error)")
//                }
//            }
//
//            // Delete the JSON file after successful import
//            try fileManager.removeItem(at: filePath)
//            debugPrint("\(filePathComponent) deleted after successful import.")
//
//            // Update UserDefaults to indicate that the data has been imported
//            UserDefaults.standard.set(true, forKey: userDefaultsKey)
//        } catch {
//            debugPrint("Error importing \(filePathComponent): \(error)")
//        }
//    }

    func importDataIfNeeded<T: ImportableDTO>(
        userDefaultsKey: String,
        filePathComponent: String,
        dtoType _: T.Type,
        dateDecodingStrategy: JSONDecoder.DateDecodingStrategy = .iso8601
    ) async {
        let hasImported = UserDefaults.standard.bool(forKey: userDefaultsKey)

        //    if hasImported {
        //        debugPrint("\(filePathComponent) already imported. Skipping import.")
        //        return
        //    }

        do {
            guard let filePath = fileManager.urls(for: .documentDirectory, in: .userDomainMask)
                .first?
                .appendingPathComponent(filePathComponent),
                fileManager.fileExists(atPath: filePath.path)
            else {
                debugPrint("File not found: \(filePathComponent).")
                return
            }

            let data = try Data(contentsOf: filePath)
            let decoder = JSONDecoder()
            decoder.dateDecodingStrategy = dateDecodingStrategy

            var entries: [T] = []

            do {
                if let array = try? decoder.decode([T].self, from: data) {
                    debugPrint("Decoded \(array.count) entries as an array.")
                    entries = array
                } else if let singleObject = try? decoder.decode(T.self, from: data) {
                    debugPrint("Decoded a single object.")
                    entries = [singleObject]
                } else {
                    debugPrint("Failed to decode \(filePathComponent) as either an array or a single object.")
                    return
                }
            }

            await context.perform {
                for entry in entries {
                    _ = entry.store(in: self.context)
                }

                do {
                    guard self.context.hasChanges else {
                        return
                    }
                    try self.context.save()
                    debugPrint("\(DebuggingIdentifiers.succeeded) \(filePathComponent) successfully imported into Core Data.")
                } catch {
                    debugPrint("\(DebuggingIdentifiers.failed) Failed to save \(filePathComponent) to Core Data: \(error)")
                }
            }

            try fileManager.removeItem(at: filePath)
            debugPrint("\(filePathComponent) deleted after successful import.")
            UserDefaults.standard.set(true, forKey: userDefaultsKey)
        } catch {
            debugPrint("Error importing \(filePathComponent): \(error)")
        }
    }
}

// MARK: - Extension for Specific Import Functions

extension JSONImporter {
    func importPumpHistoryIfNeeded() async {
        await importDataIfNeeded(
            userDefaultsKey: "pumpHistoryImported",
            filePathComponent: OpenAPS.Monitor.pumpHistory,
            dtoType: PumpEventDTO.self,
            dateDecodingStrategy: .iso8601
        )
    }

    func importCarbHistoryIfNeeded() async {
        await importDataIfNeeded(
            userDefaultsKey: "carbHistoryImported",
            filePathComponent: OpenAPS.Monitor.carbHistory,
            dtoType: CarbEntryDTO.self,
            dateDecodingStrategy: .iso8601
        )
    }

    func importGlucoseHistoryIfNeeded() async {
        await importDataIfNeeded(
            userDefaultsKey: "glucoseHistoryImported",
            filePathComponent: OpenAPS.Monitor.glucose,
            dtoType: GlucoseEntryDTO.self,
            dateDecodingStrategy: .iso8601
        )
    }

    func importDeterminationHistoryIfNeeded() async {
        await importDataIfNeeded(
            userDefaultsKey: "enactedHistoryImported",
            filePathComponent: OpenAPS.Enact.enacted,
            dtoType: Determination2.self,
            dateDecodingStrategy: .iso8601
        )
    }
}