import SwiftUI
import Combine

/// Top-level view: NavigationSplitView with a CxLLM sidebar.
/// The original WebView surface lives in `WebContentView` and is the
/// default selection so existing behavior is preserved.
struct ContentView: View {
    let webAction: PassthroughSubject<WebView.WebAction, Never>

    @State private var selection: SidebarItem? = .web

    var body: some View {
        NavigationSplitView {
            List(SidebarItem.allCases, selection: $selection) { item in
                Label(item.rawValue, systemImage: item.systemImage)
                    .tag(item)
            }
            .navigationTitle("CxLLM")
            .frame(minWidth: 180)
        } detail: {
            switch selection ?? .web {
            case .web: WebContentView(webAction: webAction)
            case let other: CxLLMSectionView(item: other)
            }
        }
    }
}

struct WebContentView: View {
    @EnvironmentObject var settings: AppSettings
    @StateObject private var health = HealthMonitor()

    @State private var canGoBack = false
    @State private var canGoForward = false
    @State private var isLoading = false
    @State private var pageTitle = ""

    let webAction: PassthroughSubject<WebView.WebAction, Never>

    private var url: URL { URL(string: settings.backendURL) ?? URL(string: "about:blank")! }

    var body: some View {
        VStack(spacing: 0) {
            toolbar
            Divider()
            WebView(
                url: url,
                canGoBack: $canGoBack,
                canGoForward: $canGoForward,
                isLoading: $isLoading,
                pageTitle: $pageTitle,
                developerExtras: settings.developerExtras,
                action: webAction
            )
            Divider()
            statusBar
        }
        .frame(minWidth: 800, minHeight: 600)
        .onAppear { health.start(url: settings.backendURL) }
        .onChange(of: settings.backendURL) { _ in
            health.start(url: settings.backendURL)
        }
    }

    // MARK: -

    private var toolbar: some View {
        HStack(spacing: 8) {
            Button { webAction.send(.back) }    label: { Image(systemName: "chevron.left") }
                .disabled(!canGoBack)
            Button { webAction.send(.forward) } label: { Image(systemName: "chevron.right") }
                .disabled(!canGoForward)
            Button { webAction.send(.reload) }  label: { Image(systemName: "arrow.clockwise") }
            Button { webAction.send(.home) }    label: { Image(systemName: "house") }

            Divider().frame(height: 16)

            statusPill

            Text(settings.backendURL)
                .lineLimit(1)
                .truncationMode(.middle)
                .foregroundStyle(.secondary)
                .font(.system(.caption, design: .monospaced))

            Spacer()

            if isLoading { ProgressView().scaleEffect(0.5).frame(width: 16, height: 16) }

            Button { webAction.send(.copyURL) }      label: { Image(systemName: "doc.on.doc") }
                .help("Copy URL")
            Button { webAction.send(.openInBrowser) } label: { Image(systemName: "safari") }
                .help("Open in default browser")
        }
        .padding(.horizontal, 12)
        .padding(.vertical, 8)
        .buttonStyle(.borderless)
    }

    private var statusPill: some View {
        let (label, color): (String, Color) = {
            switch health.status {
            case .unknown: return ("…",       .gray)
            case .up:      return ("healthy", .green)
            case .down:    return ("down",    .red)
            }
        }()
        return HStack(spacing: 4) {
            Circle().fill(color).frame(width: 8, height: 8)
            Text(label).font(.caption)
        }
        .padding(.horizontal, 8).padding(.vertical, 2)
        .background(.quaternary.opacity(0.6), in: Capsule())
        .help(health.lastError ?? "Backend reachable")
    }

    private var statusBar: some View {
        HStack(spacing: 12) {
            Text(pageTitle.isEmpty ? "CxWebApp" : pageTitle)
                .font(.caption)
                .lineLimit(1)
            Spacer()
            if let t = health.lastChecked {
                Text("checked " + Self.relative(t))
                    .font(.caption2)
                    .foregroundStyle(.secondary)
            }
        }
        .padding(.horizontal, 12)
        .padding(.vertical, 4)
    }

    private static let relativeFmt: RelativeDateTimeFormatter = {
        let f = RelativeDateTimeFormatter(); f.unitsStyle = .short; return f
    }()
    private static func relative(_ d: Date) -> String { relativeFmt.localizedString(for: d, relativeTo: Date()) }
}