import AppKit
import SwiftUI

struct ContentView: View {
    @Environment(SystemMonitor.self) private var monitor
    @State private var selection: TaskSection?
    @State private var searchText = ""
    @State private var showingAbout = false
    @State private var showingNewTask = false
    @State private var detailSelection: Int32?
    @State private var columnVisibility: NavigationSplitViewVisibility = .all
    @AppStorage("sidebarCompact") private var sidebarCompact = false

    init() {
        let stored = UserDefaults.standard.string(forKey: "defaultStartPage") ?? TaskSection.processes.rawValue
        _selection = State(initialValue: TaskSection(rawValue: stored) ?? .processes)
    }

    var body: some View {
        NavigationSplitView(columnVisibility: $columnVisibility) {
            Sidebar(selection: $selection, isCompact: sidebarCompact)
            .navigationSplitViewColumnWidth(
                min: sidebarCompact ? 68 : 190,
                ideal: sidebarCompact ? 68 : 210,
                max: sidebarCompact ? 68 : 250
            )
        } detail: {
            Group {
                switch selection ?? .processes {
                case .processes:
                    ProcessesView(searchText: searchText) { process in
                        detailSelection = process.pid
                        selection = .details
                    }
                case .performance:
                    PerformanceView()
                case .history:
                    AppHistoryView(searchText: searchText) { process in
                        detailSelection = process.pid
                        selection = .details
                    }
                case .startup:
                    StartupAppsView()
                case .users:
                    UsersView { process in
                        detailSelection = process.pid
                        selection = .details
                    }
                case .details:
                    DetailsView(searchText: searchText, selection: $detailSelection)
                case .services:
                    ServicesView(searchText: searchText) { process in
                        detailSelection = process.pid
                        selection = .details
                    }
                case .settings:
                    SettingsView()
                }
            }
            .searchable(text: $searchText, placement: .toolbar, prompt: "Type a name, PID, or user")
            .toolbar {
                TaskToolbarContent(showingNewTask: $showingNewTask, showingAbout: $showingAbout)
            }
        }
        .navigationTitle("Task Manager")
        .animation(.snappy(duration: 0.22), value: sidebarCompact)
        .onChange(of: columnVisibility) { _, visibility in
            guard visibility == .detailOnly else { return }
            columnVisibility = .all
            DispatchQueue.main.asyncAfter(deadline: .now() + 0.08) {
                withAnimation(.snappy(duration: 0.22)) { sidebarCompact.toggle() }
            }
        }
        .sheet(isPresented: $showingNewTask) {
            NewTaskView(isPresented: $showingNewTask)
        }
        .alert("Task Manager", isPresented: Binding(
            get: { monitor.errorMessage != nil },
            set: { if !$0 { monitor.errorMessage = nil } }
        )) {
            Button("OK", role: .cancel) { monitor.errorMessage = nil }
        } message: {
            Text(monitor.errorMessage ?? "")
        }
        .alert("Task Manager for macOS", isPresented: $showingAbout) {
            Button("OK", role: .cancel) { }
        } message: {
            Text("A native SwiftUI system monitor inspired by Windows Task Manager.")
        }
        .onAppear {
            DispatchQueue.main.async {
                NSApp.keyWindow?.level = UserDefaults.standard.bool(forKey: "alwaysOnTop") ? .floating : .normal
            }
        }
    }
}

private struct TaskToolbarContent: ToolbarContent {
    @Environment(SystemMonitor.self) private var monitor
    @Binding var showingNewTask: Bool
    @Binding var showingAbout: Bool

    var body: some ToolbarContent {
        @Bindable var monitor = monitor
        ToolbarItemGroup(placement: .primaryAction) {
            Button {
                showingNewTask = true
            } label: {
                Label("Run new task", systemImage: "plus.square")
            }
            .help("Launch an application or executable")

            Button {
                monitor.refresh()
            } label: {
                Label("Refresh", systemImage: "arrow.clockwise")
            }
            .help("Refresh now (⌘R)")

            Menu {
                UpdateSpeedPicker(selection: $monitor.updateSpeed)
                Divider()
                Button("About Task Manager") { showingAbout = true }
            } label: {
                Image(systemName: "ellipsis")
            }
            .menuStyle(.borderlessButton)
        }
    }
}

private struct Sidebar: View {
    @Binding var selection: TaskSection?
    let isCompact: Bool

    var body: some View {
        VStack(spacing: 0) {
            ScrollView {
                VStack(spacing: 4) {
                    ForEach(TaskSection.allCases.filter { $0 != .settings }) { section in
                        Button {
                            selection = section
                        } label: {
                            sidebarLabel(section.rawValue, icon: section.icon)
                                .padding(.horizontal, isCompact ? 0 : 8)
                                .frame(height: 40)
                                .contentShape(Rectangle())
                        }
                        .buttonStyle(.plain)
                        .frame(maxWidth: .infinity)
                        .background(selection == section ? Color.accentColor.opacity(0.18) : .clear)
                        .clipShape(RoundedRectangle(cornerRadius: 7))
                        .help(section.rawValue)
                        .accessibilityLabel(section.rawValue)
                        .accessibilityAddTraits(selection == section ? .isSelected : [])
                    }
                }
                .padding(.horizontal, isCompact ? 8 : 10)
                .padding(.vertical, 8)
            }

            Divider().padding(.horizontal, isCompact ? 12 : 16)

            Button {
                selection = .settings
            } label: {
                sidebarLabel("Settings", icon: "gearshape")
                    .padding(.horizontal, isCompact ? 0 : 8)
                    .frame(height: 40)
                    .contentShape(Rectangle())
            }
            .buttonStyle(.plain)
            .font(.callout)
            .frame(maxWidth: .infinity)
            .background(selection == .settings ? Color.accentColor.opacity(0.18) : .clear)
            .clipShape(RoundedRectangle(cornerRadius: 7))
            .padding(.horizontal, isCompact ? 8 : 10)
            .padding(.vertical, 8)
            .foregroundStyle(selection == .settings ? Color.primary : Color.secondary)
            .help("Settings")
            .accessibilityLabel("Settings")
        }
    }

    private func sidebarLabel(_ title: String, icon: String) -> some View {
        HStack(spacing: 10) {
            Image(systemName: icon)
                .frame(width: 22, height: 20)
            if !isCompact {
                Text(title).lineLimit(1)
                Spacer(minLength: 0)
            }
        }
        .frame(maxWidth: .infinity, alignment: isCompact ? .center : .leading)
    }
}