import SwiftUI
import AppKit

/// The top bar panel shown from the menu bar icon.
struct TopBarView: View {
    @ObservedObject var model: AppListModel

    var body: some View {
        VStack(spacing: 0) {
            header
            Divider()
            ScrollView {
                VStack(alignment: .leading, spacing: 0) {
                    section(title: "Apps", apps: model.regularApps, emptyText: "No apps running")

                    Divider().padding(.vertical, 4)

                    backgroundSection
                }
                .padding(.vertical, 4)
            }
            .frame(maxHeight: 360)

            Divider()
            footer
        }
        .frame(width: 320)
    }

    private var header: some View {
        HStack(spacing: 8) {
            Image(systemName: "menubar.rectangle")
                .foregroundStyle(.secondary)
            Text("SimpleTopBar")
                .font(.headline)
            Spacer()
            Button {
                model.refresh()
            } label: {
                Image(systemName: "arrow.clockwise")
            }
            .buttonStyle(.plain)
            .help("Refresh")
        }
        .padding(.horizontal, 12)
        .padding(.vertical, 8)
    }

    private func section(title: String, apps: [RunningApp], emptyText: String) -> some View {
        VStack(alignment: .leading, spacing: 0) {
            Text(title.uppercased())
                .font(.caption2)
                .fontWeight(.semibold)
                .foregroundStyle(.secondary)
                .padding(.horizontal, 12)
                .padding(.top, 4)
                .padding(.bottom, 2)

            if apps.isEmpty {
                Text(emptyText)
                    .font(.caption)
                    .foregroundStyle(.tertiary)
                    .padding(.horizontal, 12)
                    .padding(.vertical, 4)
            } else {
                ForEach(apps) { app in
                    AppRow(app: app, model: model)
                }
            }
        }
    }

    /// Collapsible dropdown for background apps. When collapsed it is a single
    /// header row; when expanded it reveals a limited number of apps and hides
    /// the overflow behind "Show N more".
    private var backgroundSection: some View {
        VStack(alignment: .leading, spacing: 0) {
            Button {
                model.toggleBackgroundExpanded()
            } label: {
                HStack(spacing: 6) {
                    Image(systemName: model.backgroundExpanded ? "chevron.down" : "chevron.right")
                        .font(.caption2)
                        .foregroundStyle(.secondary)
                        .frame(width: 10)
                    Text("Background Apps")
                        .font(.caption2)
                        .fontWeight(.semibold)
                        .foregroundStyle(.secondary)
                    Spacer()
                    Text("\(model.backgroundApps.count)")
                        .font(.caption2)
                        .foregroundStyle(.tertiary)
                        .padding(.horizontal, 6)
                        .padding(.vertical, 1)
                        .background(Capsule().fill(Color.secondary.opacity(0.15)))
                }
                .contentShape(Rectangle())
            }
            .buttonStyle(.plain)
            .padding(.horizontal, 12)
            .padding(.vertical, 4)
            .help(model.backgroundExpanded ? "Collapse background apps" : "Expand background apps")

            if model.backgroundExpanded {
                if model.backgroundApps.isEmpty {
                    Text("No background apps")
                        .font(.caption)
                        .foregroundStyle(.tertiary)
                        .padding(.horizontal, 12)
                        .padding(.vertical, 4)
                } else {
                    ForEach(model.visibleBackgroundApps) { app in
                        AppRow(app: app, model: model)
                    }

                    if model.canShowMoreBackgroundApps {
                        Button {
                            model.showMoreBackgroundApps()
                        } label: {
                            Label(
                                "Show \(model.hiddenBackgroundCount) more",
                                systemImage: "ellipsis.circle"
                            )
                            .font(.caption)
                        }
                        .buttonStyle(.plain)
                        .foregroundStyle(.secondary)
                        .padding(.horizontal, 12)
                        .padding(.vertical, 4)
                    }
                }
            }
        }
    }

    private var footer: some View {
        HStack(spacing: 8) {
            Text("\(model.regularApps.count) apps · \(model.backgroundApps.count) background")
                .font(.caption2)
                .foregroundStyle(.tertiary)
            Spacer()
            Button(LoginItem.isEnabled ? "Disable Launch at Login" : "Launch at Login") {
                if !LoginItem.toggle() {
                    let alert = NSAlert()
                    alert.messageText = "Could not update Launch at Login"
                    alert.informativeText = "Launch at Login requires a signed app bundle in /Applications. It is not available when running via `swift run`."
                    alert.alertStyle = .warning
                    alert.addButton(withTitle: "OK")
                    alert.runModal()
                }
            }
            .font(.caption2)
            .buttonStyle(.plain)

            Button("Quit") { NSApp.terminate(nil) }
                .font(.caption2)
                .buttonStyle(.plain)
                .keyboardShortcut("q")
        }
        .padding(.horizontal, 12)
        .padding(.vertical, 6)
    }
}

private struct AppRow: View {
    let app: RunningApp
    @ObservedObject var model: AppListModel

    var body: some View {
        Button {
            model.activate(app)
        } label: {
            HStack(spacing: 8) {
                Image(nsImage: app.icon)
                    .resizable()
                    .frame(width: 18, height: 18)
                Text(app.name)
                    .font(.system(size: 12))
                    .lineLimit(1)
                    .truncationMode(.middle)
                if app.isActive {
                    Image(systemName: "circle.fill")
                        .font(.system(size: 5))
                        .foregroundStyle(Color.accentColor)
                }
                Spacer(minLength: 0)
            }
            .contentShape(Rectangle())
            .padding(.horizontal, 12)
            .padding(.vertical, 3)
            .opacity(app.isHidden ? 0.55 : 1)
        }
        .buttonStyle(.plain)
        .help("Activate \(app.name)")
        .contextMenu {
            Button("Activate") { model.activate(app) }
            Button(app.isHidden ? "Unhide" : "Hide") { model.toggleHidden(app) }
            Divider()
            Button("Quit \(app.name)") { model.quit(app) }
        }
    }
}