import ActivityKit
import SwiftUI
import WidgetKit

/// Lock-screen / Dynamic Island rendering of the aggregate session Activity (UX_IOS §5.3):
/// glance = running count + needs-you count + the most urgent session; tap opens the app
/// (straight to the approval, via the notification-style route). Self-contained colors — the
/// extension doesn't link the app's Theme, so the two palette constants it needs live here
/// (the same teal/amber/blue as `Palette`).
struct SessionLiveActivity: Widget {
    var body: some WidgetConfiguration {
        ActivityConfiguration(for: NucleicSessionAttributes.self) { context in
            // Lock screen banner.
            LockScreenView(state: context.state, hostName: context.attributes.hostName)
                .activityBackgroundTint(Color.black.opacity(0.55))
                .activitySystemActionForegroundColor(.white)
        } dynamicIsland: { context in
            DynamicIsland {
                DynamicIslandExpandedRegion(.leading) {
                    Label("\(context.state.runningCount)", systemImage: "circle.lefthalf.filled")
                        .font(.headline)
                        .foregroundStyle(ActivityPalette.active)
                }
                DynamicIslandExpandedRegion(.trailing) {
                    if context.state.needsYouCount > 0 {
                        Label("\(context.state.needsYouCount)", systemImage: "exclamationmark.triangle.fill")
                            .font(.headline)
                            .foregroundStyle(ActivityPalette.attention)
                    } else {
                        Label("0", systemImage: "checkmark.circle")
                            .font(.headline)
                            .foregroundStyle(.secondary)
                    }
                }
                DynamicIslandExpandedRegion(.bottom) {
                    if let title = context.state.topTitle {
                        HStack(spacing: 6) {
                            Image(systemName: context.state.topNeedsYou
                                ? "exclamationmark.triangle.fill" : "circle.lefthalf.filled")
                                .foregroundStyle(context.state.topNeedsYou
                                    ? ActivityPalette.attention : ActivityPalette.active)
                            Text(title).font(.subheadline.weight(.medium)).lineLimit(1)
                            Spacer()
                            Text(statusLine(context.state))
                                .font(.caption).foregroundStyle(.secondary)
                        }
                    } else {
                        Text(statusLine(context.state))
                            .font(.caption).foregroundStyle(.secondary)
                    }
                }
            } compactLeading: {
                Image(systemName: "circle.lefthalf.filled")
                    .foregroundStyle(ActivityPalette.active)
            } compactTrailing: {
                if context.state.needsYouCount > 0 {
                    Text("\(context.state.needsYouCount)")
                        .font(.caption2.bold())
                        .foregroundStyle(ActivityPalette.attention)
                } else {
                    Text("\(context.state.runningCount)")
                        .font(.caption2.bold())
                        .foregroundStyle(ActivityPalette.active)
                }
            } minimal: {
                Image(systemName: context.state.needsYouCount > 0
                    ? "exclamationmark.triangle.fill" : "circle.lefthalf.filled")
                    .foregroundStyle(context.state.needsYouCount > 0
                        ? ActivityPalette.attention : ActivityPalette.active)
            }
        }
    }

    private func statusLine(_ state: NucleicSessionAttributes.ContentState) -> String {
        var parts: [String] = []
        if state.runningCount > 0 { parts.append("\(state.runningCount) running") }
        if state.needsYouCount > 0 { parts.append("\(state.needsYouCount) need you") }
        return parts.isEmpty ? "Idle" : parts.joined(separator: " · ")
    }
}

private struct LockScreenView: View {
    let state: NucleicSessionAttributes.ContentState
    let hostName: String

    var body: some View {
        HStack(spacing: 12) {
            Image(systemName: state.needsYouCount > 0
                ? "exclamationmark.triangle.fill" : "circle.lefthalf.filled")
                .font(.title2)
                .foregroundStyle(state.needsYouCount > 0
                    ? ActivityPalette.attention : ActivityPalette.active)
            VStack(alignment: .leading, spacing: 2) {
                if let title = state.topTitle {
                    Text(title).font(.headline).lineLimit(1)
                }
                HStack(spacing: 4) {
                    if state.runningCount > 0 {
                        Text("\(state.runningCount) running").foregroundStyle(ActivityPalette.active)
                    }
                    if state.runningCount > 0 && state.needsYouCount > 0 { Text("·") }
                    if state.needsYouCount > 0 {
                        Text("\(state.needsYouCount) waiting for you")
                            .foregroundStyle(ActivityPalette.attention)
                    }
                    if state.runningCount == 0 && state.needsYouCount == 0 {
                        Text("Idle").foregroundStyle(.secondary)
                    }
                }
                .font(.subheadline)
            }
            Spacer()
            Text(hostName)
                .font(.caption2).foregroundStyle(.secondary)
                .lineLimit(1)
        }
        .padding(14)
        .foregroundStyle(.white)
    }
}

/// The two categorical colors the Activity needs — same constants as the app's `Palette`.
private enum ActivityPalette {
    static let active = Color(red: 0.20, green: 0.55, blue: 0.95)     // running blue
    static let attention = Color(red: 1.00, green: 0.65, blue: 0.15)  // needs-you amber
}