import Foundation
import Combine

enum BackupStatus: Equatable {
    case idle
    case preparing
    case running
    case paused
    case completed
    case failed(String)
    case cancelled

    var isActive: Bool {
        switch self {
        case .running, .paused, .preparing: return true
        default: return false
        }
    }
}

@MainActor
final class BackupJob: ObservableObject {
    @Published private(set) var status: BackupStatus = .idle
    @Published private(set) var totalFiles: Int = 0
    @Published private(set) var uploadedFiles: Int = 0
    @Published private(set) var skippedFiles: Int = 0
    @Published private(set) var failedFiles: Int = 0
    @Published private(set) var currentFileName: String = ""
    @Published private(set) var currentFileSizeBytes: Int64 = 0
    @Published private(set) var bytesTransferred: Int64 = 0
    @Published private(set) var totalBytes: Int64 = 0
    @Published private(set) var speedBytesPerSecond: Double = 0
    @Published private(set) var startDate: Date?
    @Published private(set) var endDate: Date?

    var progress: Double {
        guard totalFiles > 0 else { return 0 }
        return min(1.0, Double(uploadedFiles + skippedFiles + failedFiles) / Double(totalFiles))
    }

    var eta: TimeInterval? {
        guard speedBytesPerSecond > 0, totalBytes > bytesTransferred else { return nil }
        return Double(totalBytes - bytesTransferred) / speedBytesPerSecond
    }

    func prepare() { status = .preparing }

    func start(totalFiles: Int, totalBytes: Int64) {
        self.totalFiles = totalFiles
        self.totalBytes = totalBytes
        self.uploadedFiles = 0
        self.skippedFiles = 0
        self.failedFiles = 0
        self.bytesTransferred = 0
        self.startDate = Date()
        self.endDate = nil
        self.status = .running
    }

    func updateProgress(fileName: String, fileSize: Int64, bytesTransferred: Int64, speed: Double) {
        self.currentFileName = fileName
        self.currentFileSizeBytes = fileSize
        self.bytesTransferred = bytesTransferred
        self.speedBytesPerSecond = speed
    }

    func fileCompleted(skipped: Bool = false) {
        if skipped { skippedFiles += 1 } else { uploadedFiles += 1 }
    }

    func fileFailed() { failedFiles += 1 }

    func finish(result: BackupResult) {
        endDate = Date()
        status = result.failedCount == 0
            ? .completed
            : .failed("Completed with \(result.failedCount) error\(result.failedCount == 1 ? "" : "s")")
    }

    func fail(error: BackupError) {
        endDate = Date()
        status = .failed(error.errorDescription ?? error.localizedDescription)
    }

    func cancel() {
        endDate = Date()
        status = .cancelled
    }

    func pause() { if case .running = status { status = .paused } }
    func resume() { if case .paused = status { status = .running } }
}