import SwiftUI

struct DownloadsView: View {
    @StateObject private var viewModel = DownloadsViewModel()
    @State private var selectedTab: DownloadsViewModel.DownloadTab = .active
    @State private var showingClearAlert = false

    var body: some View {
        VStack(spacing: 0) {
            // Tab selector
            Picker("Tipo de descarga", selection: $selectedTab) {
                ForEach(DownloadsViewModel.DownloadTab.allCases, id: \.self) { tab in
                    Label(tab.rawValue, systemImage: tab.icon)
                        .tag(tab)
                }
            }
            .pickerStyle(.segmented)
            .padding()

            // Content
            ScrollView {
                VStack(spacing: 16) {
                    switch selectedTab {
                    case .active:
                        activeDownloadsView
                    case .completed:
                        completedDownloadsView
                    case .failed:
                        failedDownloadsView
                    }
                }
                .padding()
            }

            // Storage info footer
            storageInfoFooter
        }
        .navigationTitle("Descargas")
        .alert("Limpiar almacenamiento", isPresented: $showingClearAlert) {
            Button("Cancelar", role: .cancel) { }
            Button("Limpiar", role: .destructive) {
                viewModel.clearAllStorage()
            }
        } message: {
            Text("Esta acción eliminará todos los capítulos descargados. ¿Estás seguro?")
        }
    }

    private var activeDownloadsView: some View {
        VStack(spacing: 12) {
            if viewModel.downloadManager.activeDownloads.isEmpty {
                emptyStateView(
                    icon: "arrow.down.circle",
                    title: "No hay descargas activas",
                    message: "Las descargas aparecerán aquí cuando comiences a descargar capítulos"
                )
            } else {
                ForEach(viewModel.downloadManager.activeDownloads) { task in
                    ActiveDownloadCard(task: task)
                }

                // Cancel all button
                if !viewModel.downloadManager.activeDownloads.isEmpty {
                    Button(action: {
                        viewModel.downloadManager.cancelAllDownloads()
                    }) {
                        Label("Cancelar todas", systemImage: "xmark.circle")
                            .foregroundColor(.red)
                            .frame(maxWidth: .infinity)
                            .padding()
                            .background(
                                RoundedRectangle(cornerRadius: 10)
                                    .fill(Color.red.opacity(0.1))
                            )
                    }
                }
            }
        }
    }

    private var completedDownloadsView: some View {
        VStack(spacing: 12) {
            if viewModel.downloadManager.completedDownloads.isEmpty {
                emptyStateView(
                    icon: "checkmark.circle",
                    title: "No hay descargas completadas",
                    message: "Los capítulos descargados aparecerán aquí"
                )
            } else {
                ForEach(viewModel.downloadManager.completedDownloads.reversed()) { task in
                    CompletedDownloadCard(task: task)
                }

                // Clear history button
                Button(action: {
                    viewModel.downloadManager.clearCompletedHistory()
                }) {
                    Text("Limpiar historial")
                        .foregroundColor(.blue)
                        .padding()
                }
            }
        }
    }

    private var failedDownloadsView: some View {
        VStack(spacing: 12) {
            if viewModel.downloadManager.failedDownloads.isEmpty {
                emptyStateView(
                    icon: "exclamationmark.triangle",
                    title: "No hay descargas fallidas",
                    message: "Las descargas con errores aparecerán aquí"
                )
            } else {
                ForEach(viewModel.downloadManager.failedDownloads.reversed()) { task in
                    FailedDownloadCard(task: task)
                }

                // Clear history button
                Button(action: {
                    viewModel.downloadManager.clearFailedHistory()
                }) {
                    Text("Limpiar historial")
                        .foregroundColor(.blue)
                        .padding()
                }
            }
        }
    }

    private var storageInfoFooter: some View {
        VStack(spacing: 8) {
            Divider()

            HStack {
                VStack(alignment: .leading, spacing: 4) {
                    Text("Almacenamiento usado")
                        .font(.caption)
                        .foregroundColor(.secondary)

                    Text(viewModel.storageSizeString)
                        .font(.headline)
                }

                Spacer()

                Button(action: {
                    showingClearAlert = true
                }) {
                    Text("Limpiar todo")
                        .font(.caption)
                        .foregroundColor(.red)
                        .padding(.horizontal, 12)
                        .padding(.vertical, 6)
                        .background(
                            RoundedRectangle(cornerRadius: 6)
                                .fill(Color.red.opacity(0.1))
                        )
                }
            }
            .padding()
        }
        .background(Color(.systemGray6))
    }

    private func emptyStateView(icon: String, title: String, message: String) -> some View {
        VStack(spacing: 16) {
            Image(systemName: icon)
                .font(.system(size: 60))
                .foregroundColor(.gray)

            VStack(spacing: 8) {
                Text(title)
                    .font(.headline)
                    .foregroundColor(.primary)

                Text(message)
                    .font(.subheadline)
                    .foregroundColor(.secondary)
                    .multilineTextAlignment(.center)
                    .padding(.horizontal, 32)
            }
        }
        .frame(maxWidth: .infinity, minHeight: 300)
    }
}

// MARK: - ViewModel

@MainActor
class DownloadsViewModel: ObservableObject {
    @Published var downloadManager = DownloadManager.shared
    @Published var storage = StorageService.shared
    @Published var storageSize: Int64 = 0

    enum DownloadTab: String, CaseIterable {
        case active = "Activas"
        case completed = "Completadas"
        case failed = "Fallidas"

        var icon: String {
            switch self {
            case .active: return "arrow.down.circle"
            case .completed: return "checkmark.circle"
            case .failed: return "exclamationmark.triangle"
            }
        }
    }

    var storageSizeString: String {
        storage.formatFileSize(storage.getStorageSize())
    }

    init() {
        updateStorageSize()
    }

    func clearAllStorage() {
        storage.clearAllDownloads()
        downloadManager.clearCompletedHistory()
        downloadManager.clearFailedHistory()
        updateStorageSize()
    }

    private func updateStorageSize() {
        storageSize = storage.getStorageSize()
    }
}

// MARK: - Download Cards

struct ActiveDownloadCard: View {
    @ObservedObject var task: DownloadTask
    @StateObject private var downloadManager = DownloadManager.shared

    var body: some View {
        VStack(alignment: .leading, spacing: 12) {
            // Header
            HStack {
                VStack(alignment: .leading, spacing: 4) {
                    Text(task.mangaTitle)
                        .font(.headline)
                        .lineLimit(1)

                    Text("Capítulo \(task.chapterNumber)")
                        .font(.subheadline)
                        .foregroundColor(.secondary)
                }

                Spacer()

                // Cancel button
                Button(action: {
                    downloadManager.cancelDownload(taskId: task.id)
                }) {
                    Image(systemName: "xmark.circle.fill")
                        .foregroundColor(.red)
                        .font(.title3)
                }
                .buttonStyle(.plain)
            }

            // Progress bar
            VStack(alignment: .leading, spacing: 4) {
                ProgressView(value: task.progress)
                    .progressViewStyle(.linear)
                    .tint(.blue)

                HStack {
                    Text("\(task.downloadedPages) de \(task.imageURLs.count) páginas")
                        .font(.caption)
                        .foregroundColor(.secondary)

                    Spacer()

                    Text("\(Int(task.progress * 100))%")
                        .font(.caption)
                        .fontWeight(.semibold)
                        .foregroundColor(.blue)
                }
            }
        }
        .padding()
        .background(
            RoundedRectangle(cornerRadius: 12)
                .fill(Color(.systemBackground))
                .shadow(color: .black.opacity(0.05), radius: 3, x: 0, y: 1)
        )
    }
}

struct CompletedDownloadCard: View {
    let task: DownloadTask
    @StateObject private var storage = StorageService.shared

    var body: some View {
        HStack {
            VStack(alignment: .leading, spacing: 4) {
                Text(task.mangaTitle)
                    .font(.headline)
                    .lineLimit(1)

                Text("Capítulo \(task.chapterNumber)")
                    .font(.subheadline)
                    .foregroundColor(.secondary)

                Text("Completado")
                    .font(.caption)
                    .foregroundColor(.green)
            }

            Spacer()

            Image(systemName: "checkmark.circle.fill")
                .foregroundColor(.green)
                .font(.title3)
        }
        .padding()
        .background(
            RoundedRectangle(cornerRadius: 12)
                .fill(Color(.systemBackground))
                .shadow(color: .black.opacity(0.05), radius: 3, x: 0, y: 1)
        )
    }
}

struct FailedDownloadCard: View {
    let task: DownloadTask
    @StateObject private var downloadManager = DownloadManager.shared

    var body: some View {
        VStack(alignment: .leading, spacing: 12) {
            // Header
            HStack {
                VStack(alignment: .leading, spacing: 4) {
                    Text(task.mangaTitle)
                        .font(.headline)
                        .lineLimit(1)

                    Text("Capítulo \(task.chapterNumber)")
                        .font(.subheadline)
                        .foregroundColor(.secondary)
                }

                Spacer()

                Image(systemName: "exclamationmark.triangle.fill")
                    .foregroundColor(.red)
                    .font(.title3)
            }

            // Error message
            if let error = task.error {
                Text(error)
                    .font(.caption)
                    .foregroundColor(.red)
                    .lineLimit(2)
            }

            // Retry button
            Button(action: {
                // TODO: Implement retry functionality
                print("Retry download for chapter \(task.chapterNumber)")
            }) {
                Label("Reintentar", systemImage: "arrow.clockwise")
                    .font(.subheadline)
                    .foregroundColor(.blue)
                    .frame(maxWidth: .infinity)
                    .padding()
                    .background(
                        RoundedRectangle(cornerRadius: 8)
                            .fill(Color.blue.opacity(0.1))
                    )
            }
        }
        .padding()
        .background(
            RoundedRectangle(cornerRadius: 12)
                .fill(Color(.systemBackground))
                .shadow(color: .black.opacity(0.05), radius: 3, x: 0, y: 1)
        )
    }
}

#Preview {
    NavigationView {
        DownloadsView()
    }
}