import SwiftUI

struct PageHeader<Trailing: View>: View {
    let title: String
    let subtitle: String?
    @ViewBuilder let trailing: () -> Trailing

    init(title: String, subtitle: String? = nil, @ViewBuilder trailing: @escaping () -> Trailing = { EmptyView() }) {
        self.title = title
        self.subtitle = subtitle
        self.trailing = trailing
    }

    var body: some View {
        HStack(alignment: .firstTextBaseline) {
            VStack(alignment: .leading, spacing: 3) {
                Text(title).font(.title.weight(.semibold))
                if let subtitle { Text(subtitle).font(.callout).foregroundStyle(.secondary) }
            }
            Spacer()
            trailing()
        }
        .padding(.horizontal, 20)
        .padding(.top, 18)
        .padding(.bottom, 14)
    }
}

struct ResourceSummaryBar: View {
    let snapshot: SystemSnapshot

    var body: some View {
        HStack(spacing: 22) {
            Label("\(Formatters.percent(snapshot.cpuPercent)) CPU", systemImage: "cpu")
            Label("\(Formatters.percent(snapshot.memoryPercent)) Memory", systemImage: "memorychip")
            Label("\(Formatters.percent(snapshot.diskActivePercent)) Disk activity", systemImage: "internaldrive")
            Label("\(Formatters.rate(snapshot.networkReceiveRate + snapshot.networkSendRate)) Network", systemImage: "network")
            Spacer()
        }
        .font(.callout.weight(.medium))
        .padding(.horizontal, 20)
        .padding(.vertical, 9)
        .background(Color.accentColor.opacity(0.06))
        .overlay(alignment: .bottom) { Divider() }
    }
}

struct UpdateStatus: View {
    @Environment(SystemMonitor.self) private var monitor

    var body: some View {
        HStack(spacing: 6) {
            Circle().fill(monitor.isPaused ? .orange : .green).frame(width: 7, height: 7)
            if monitor.isPaused {
                Text("Updates paused")
            } else if let date = monitor.lastUpdated {
                if Date().timeIntervalSince(date) < 1.5 {
                    Text("Updated now")
                } else {
                    Text("Updated \(date, style: .relative)")
                }
            } else {
                Text("Collecting system data…")
            }
        }
        .font(.caption)
        .foregroundStyle(.secondary)
    }
}

struct EmptyState: View {
    let icon: String
    let title: String
    let message: String

    var body: some View {
        ContentUnavailableView(title, systemImage: icon, description: Text(message))
    }
}

struct UpdateSpeedPicker: View {
    @Binding var selection: UpdateSpeed

    var body: some View {
        Picker("Update speed", selection: $selection) {
            Text("High").tag(UpdateSpeed.high)
            Text("Normal").tag(UpdateSpeed.normal)
            Text("Low").tag(UpdateSpeed.low)
            Text("Paused").tag(UpdateSpeed.paused)
        }
    }
}