import Library
import SkyRenderer
import SwiftUI

struct SystemScreen: View {
    /// Days from now shown by the slider.
    @State private var offsetDays = 0.0
    @State private var playing = false
    @State private var libraryPage: LibraryPage?
    @AppStorage("systemMode") private var mode = "2d"
    @AppStorage("solarScale") private var solarScale = SolarScale.compressed
    @Environment(\.dynamicTypeSize) private var typeSize

    private let ink = Color(red: 0.95, green: 0.95, blue: 0.93)
    private let accent = Color(red: 0.88, green: 0.24, blue: 0.19)
    private let background = Color.black

    private static let start = Date(timeIntervalSince1970: -378_691_200) // 1958-01-01
    private static let end = Date(timeIntervalSince1970: 2_524_608_000) // 2050-01-01
    private var range: ClosedRange<Double> {
        (Self.start.timeIntervalSinceNow / 86_400)...(Self.end.timeIntervalSinceNow / 86_400)
    }
    private var date: Date { .now.addingTimeInterval(offsetDays * 86_400) }

    var body: some View {
        Group {
            if mode == "3d" { threeD } else { twoD }
        }
        .foregroundStyle(ink)
        .background(background.ignoresSafeArea())
        .sheet(item: $libraryPage) { page in
            NavigationStack { LibraryPageView(page: page) }
        }
        .task(id: playing) {
            while playing && !Task.isCancelled {
                try? await Task.sleep(for: .milliseconds(33))
                offsetDays = min(offsetDays + (mode == "3d" ? 2 : 30), range.upperBound)
                if offsetDays >= range.upperBound { playing = false }
            }
        }
    }

    private var modePicker: some View {
        Picker("View", selection: $mode) {
            Text("Map").tag("2d")
            Text("3D").tag("3d")
        }
        .pickerStyle(.segmented)
    }

    private var threeD: some View {
        VStack(alignment: .leading, spacing: 0) {
            VStack(alignment: .leading, spacing: 0) {
                Text("Solar system").font(.title.weight(.medium))
                Rectangle().fill(accent).frame(width: 48, height: 5).padding(.top, 8).padding(.bottom, 12)
                modePicker.padding(.bottom, 8)
                Picker("Scale", selection: $solarScale) {
                    ForEach(SolarScale.allCases) { Text($0.name).tag($0) }
                }
                .pickerStyle(.segmented)
                Text(solarScale == .compressed
                     ? "Distances squeezed and bodies enlarged so everything fits. Drag to turn, pinch to zoom, tap anything. Moons appear as you zoom in to their planet."
                     : "Real distances and sizes: the planets are specks, so circles mark them. Tap one to fly to it.")
                    .font(.caption).dimmed(0.7).padding(.top, 8)
            }
            .padding(.horizontal, 20)
            SolarSystem3DView(date: date, live: abs(offsetDays) < 1, scale: $solarScale, ink: ink, accent: accent) { libraryPage = $0 }
                .frame(maxWidth: .infinity, maxHeight: .infinity)
                .clipped()
                .contentShape(Rectangle())
            timeControls
                .padding(.horizontal, 20)
                .padding(.vertical, 6)
                .background(background)
                .zIndex(1)
        }
    }

    private var timeControls: some View {
        HStack(spacing: 12) {
            Button { playing.toggle() } label: {
                Image(systemName: playing ? "pause.fill" : "play.fill").frame(width: 32, height: 32)
            }
            .accessibilityLabel(playing ? "Pause" : "Play")
            Text(date.formatted(.dateTime.year().month(.abbreviated)))
                .font(.subheadline.weight(.medium).monospacedDigit())
                .fixedSize()
            Slider(value: $offsetDays, in: range).tint(ink)
            Button { playing = false; offsetDays = 0 } label: {
                Text("Today").frame(minWidth: 44, minHeight: 44).contentShape(Rectangle())
            }
            .font(.footnote.weight(.medium))
            .opacity(abs(offsetDays) < 1 ? 0.6 : 1)
        }
    }

    private var twoD: some View {
        ScrollView {
            VStack(alignment: .leading, spacing: 0) {
                Text("Solar system").font(.title.weight(.medium))
                Rectangle().fill(accent).frame(width: 48, height: 5).padding(.top, 8).padding(.bottom, 12)
                Text("The planets, and the five spacecraft travelling out of the solar system, seen from above. Drag the slider or press play to watch them move between 1958 and 2050.")
                    .font(.subheadline).dimmed(0.75).padding(.bottom, 12)
                modePicker.padding(.bottom, 16)

                LiveSection(ink: ink, accent: accent)

                // Labels in this dense diagram stop growing at xxLarge; the table below scales fully.
                OrreryView(date: date, ink: ink, accent: accent)
                    .dynamicTypeSize(...DynamicTypeSize.xxLarge)
                    .accessibilityElement()
                    .accessibilityLabel("Orrery for \(date.formatted(.dateTime.year().month(.wide))). Planets and spacecraft distances are listed below.")

                timeControls.padding(.top, 12)

                Text("Distances beyond 1 AU are drawn on a logarithmic scale. Rings: planet orbits, then 50, 100 and 200 AU.")
                    .font(.caption2).dimmed(0.6).padding(.top, 8)

                section("Spacecraft", note: "How far each probe is from the Sun, and how long its radio signal takes to reach us. Tap one to read about it.") {
                    if typeSize.isAccessibilitySize {
                        VStack(alignment: .leading, spacing: 12) {
                            ForEach(Spacecraft.all) { craft in
                                VStack(alignment: .leading, spacing: 2) {
                                    craftName(craft)
                                    Text(craftDistance(craft)).monospacedDigit().dimmed(0.7)
                                }
                                .font(.subheadline)
                            }
                        }
                    } else {
                        Grid(alignment: .leading, horizontalSpacing: 16, verticalSpacing: 6) {
                            GridRow {
                                Text("").gridColumnAlignment(.leading)
                                Text("From Sun").dimmed(0.6)
                                Text("Light time").dimmed(0.6)
                            }
                            .font(.caption2)
                            ForEach(Spacecraft.all) { craft in
                                GridRow {
                                    craftName(craft)
                                    if let d = craft.distance(at: date) {
                                        Text(String(format: "%.1f AU", d)).monospacedDigit()
                                        Text(lightTime(au: d)).monospacedDigit()
                                    } else {
                                        Text("launch \(craft.launch.prefix(4))").dimmed(0.5)
                                        Text("")
                                    }
                                }
                                .font(.subheadline)
                            }
                        }
                    }
                }
                DSNSection(ink: ink, accent: accent).padding(.top, 24)
                MarsSection().padding(.top, 24)
                Text("Spacecraft positions: NASA/JPL Horizons. Pioneer 10 and 11 positions after contact was lost are predictions.")
                    .font(.caption2).dimmed(0.5).padding(.vertical, 16)
            }
            .padding(.horizontal, 20)
            .readableWidth()
        }
    }

    @ViewBuilder
    private func craftName(_ craft: Spacecraft) -> some View {
        if let page = Library.page(spacecraft: craft.name) {
            Button { libraryPage = page } label: { Text(craft.name).underline().frame(minHeight: 44, alignment: .leading).contentShape(Rectangle()) }.buttonStyle(.plain)
        } else {
            Text(craft.name)
        }
    }

    private func craftDistance(_ craft: Spacecraft) -> String {
        guard let d = craft.distance(at: date) else { return "launch \(craft.launch.prefix(4))" }
        return String(format: "%.1f AU from the Sun · light time %@", d, lightTime(au: d))
    }

    /// One-way light time from the Sun's distance, as hours and minutes.
    private func lightTime(au: Double) -> String {
        let seconds = au * 499.004784
        let h = Int(seconds / 3600), m = Int(seconds.truncatingRemainder(dividingBy: 3600) / 60)
        return h > 0 ? "\(h) h \(m) m" : "\(m) m"
    }

    private func section(_ title: String, note: String? = nil, @ViewBuilder content: () -> some View) -> some View {
        VStack(alignment: .leading, spacing: 10) {
            Text(title).font(.caption2.weight(.medium)).textCase(.uppercase).tracking(0.8).dimmed(0.6)
            if let note { Text(note).font(.footnote).dimmed(0.75) }
            content()
        }
        .padding(.top, 24)
    }
}