// The Live Activity UI (Lock Screen banner + Dynamic Island) for a running session. The app owns
// the Activity's lifecycle (SessionActivityController); this is only its presentation, rendered in
// the widget-extension process from the shared `PunktfunkSessionAttributes`.
//
// The End button runs `EndStreamIntent` (a LiveActivityIntent) IN THE APP's process, which posts
// .punktfunkEndActiveSession → the app disconnects. Elapsed time ticks client-side via
// Text(timerInterval:) — no per-second push.

import ActivityKit
import AppIntents
import SwiftUI
import WidgetKit

import PunktfunkShared

struct PunktfunkSessionLiveActivity: Widget {
    var body: some WidgetConfiguration {
        ActivityConfiguration(for: PunktfunkSessionAttributes.self) { context in
            LockScreenView(context: context)
                .activitySystemActionForegroundColor(.white)
        } dynamicIsland: { context in
            // Island layout (2026-07 rebuild): the EXPANDED island leads with identity (brand
            // glyph + host), keeps the elapsed clock at the trailing edge, and gives the bottom
            // region one purposeful row — session status + the live numbers on the left, the
            // End action on the right. COMPACT shows the one number worth a glance: live
            // latency while streaming (the sparse ~30 s pushes), the disconnect countdown while
            // backgrounded, a state glyph otherwise. Brand purple is the identity accent
            // everywhere `.tint` used to leak system blue.
            DynamicIsland {
                DynamicIslandExpandedRegion(.leading) {
                    HStack(spacing: 6) {
                        Image(systemName: "play.tv.fill")
                            .font(.subheadline)
                            .foregroundStyle(Color.brand)
                        Text(context.attributes.hostName)
                            .font(.subheadline.weight(.semibold))
                            .lineLimit(1)
                    }
                    .padding(.leading, 4)
                    .padding(.top, 2)
                }
                DynamicIslandExpandedRegion(.trailing) {
                    ElapsedClock(startedAt: context.state.startedAt)
                        .font(.subheadline)
                        .foregroundStyle(.secondary)
                        .frame(maxWidth: 64, alignment: .trailing)
                        .padding(.trailing, 4)
                        .padding(.top, 2)
                }
                DynamicIslandExpandedRegion(.center) {
                    if let title = context.attributes.launchTitle {
                        Text(title)
                            .font(.caption)
                            .foregroundStyle(.secondary)
                            .lineLimit(1)
                    }
                }
                DynamicIslandExpandedRegion(.bottom) {
                    // The expanded island's height is there to be used: one info row (status
                    // leading, live numbers trailing — the mode string stays on the Lock
                    // Screen), then the platform-conventional LARGE full-width action button.
                    VStack(spacing: 10) {
                        HStack {
                            StatusLine(state: context.state)
                            Spacer(minLength: 8)
                            StatsLine(state: context.state, showMode: false)
                        }
                        EndButton(fullWidth: true)
                    }
                    .padding(.horizontal, 4)
                    .padding(.top, 6)
                }
            } compactLeading: {
                Image(systemName: "play.tv.fill")
                    .foregroundStyle(Color.brand)
            } compactTrailing: {
                CompactReadout(state: context.state)
            } minimal: {
                Image(systemName: "play.tv.fill")
                    .foregroundStyle(Color.brand)
            }
            .keylineTint(Color.brand)
        }
    }
}

// MARK: - Lock Screen banner

private struct LockScreenView: View {
    let context: ActivityViewContext<PunktfunkSessionAttributes>

    var body: some View {
        HStack(alignment: .top, spacing: 12) {
            Image(systemName: "play.tv.fill")
                .font(.title2)
                .foregroundStyle(Color.brand)
            VStack(alignment: .leading, spacing: 4) {
                HStack {
                    Text(context.attributes.hostName).font(.headline).lineLimit(1)
                    Spacer()
                    ElapsedClock(startedAt: context.state.startedAt)
                        .font(.subheadline)
                        .foregroundStyle(.secondary)
                }
                if let title = context.attributes.launchTitle {
                    Text(title).font(.caption).foregroundStyle(.secondary).lineLimit(1)
                }
                StatusLine(state: context.state)
                StatsLine(state: context.state)
            }
            if context.state.stage == .background {
                EndButton()
            }
        }
        .padding()
    }
}

// MARK: - Shared pieces

/// The ticking elapsed-session clock — client-side via `timerInterval`, no per-second push.
private struct ElapsedClock: View {
    let startedAt: Date
    var body: some View {
        Text(timerInterval: startedAt...Date.distantFuture, countsDown: false)
            .monospacedDigit()
            .multilineTextAlignment(.trailing)
    }
}

/// The session's state as a colored dot + label; while backgrounded with a deadline, the label
/// IS the countdown. One shared truth for the island bottom and the Lock Screen banner.
private struct StatusLine: View {
    let state: PunktfunkSessionAttributes.ContentState

    var body: some View {
        HStack(spacing: 5) {
            Circle()
                .fill(color)
                .frame(width: 6, height: 6)
            label
                .font(.caption2.weight(.medium))
                .foregroundStyle(.secondary)
                .lineLimit(1)
        }
    }

    private var color: Color {
        switch state.stage {
        case .streaming: return .green
        case .background: return .orange
        case .reconnecting: return .yellow
        case .ending: return .secondary
        }
    }

    @ViewBuilder private var label: some View {
        switch state.stage {
        case .streaming:
            Text("Streaming")
        case .background:
            if let deadline = state.backgroundDeadline {
                HStack(spacing: 3) {
                    Text("Background · ends in")
                    Text(timerInterval: Date()...deadline, countsDown: true)
                        .monospacedDigit()
                }
            } else {
                Text("Running in background")
            }
        case .reconnecting:
            Text("Reconnecting…")
        case .ending:
            Text("Session ended")
        }
    }
}

/// The live numbers, one quiet line: latency and bitrate (the sparse ~30 s pushes) ahead of the
/// mode (`showMode` false on the island, where the row shares space with the status line).
/// Anything unreported simply doesn't appear.
private struct StatsLine: View {
    let state: PunktfunkSessionAttributes.ContentState
    var showMode = true

    var body: some View {
        HStack(spacing: 8) {
            if let ms = state.latencyMs {
                stat("bolt.fill", "\(ms) ms")
            }
            if let mbps = state.mbps {
                stat("arrow.down", String(format: "%.0f Mb/s", mbps))
            }
            if showMode {
                Text(state.modeLine)
                    .font(.caption2)
                    .foregroundStyle(.tertiary)
                    .lineLimit(1)
            }
        }
    }

    private func stat(_ icon: String, _ text: String) -> some View {
        HStack(spacing: 3) {
            Image(systemName: icon)
                .font(.system(size: 8, weight: .semibold))
            Text(text)
                .font(.caption2)
                .monospacedDigit()
        }
        .foregroundStyle(.secondary)
    }
}

/// The compact trailing readout — the island's one glanceable number. Streaming: the live
/// latency once the app has reported one, the elapsed clock until then. Backgrounded: the
/// auto-disconnect countdown. Off-nominal stages show a state glyph instead of a number.
private struct CompactReadout: View {
    let state: PunktfunkSessionAttributes.ContentState

    var body: some View {
        switch state.stage {
        case .streaming:
            if let ms = state.latencyMs {
                Text("\(ms) ms")
                    .font(.caption2.weight(.medium))
                    .monospacedDigit()
                    .foregroundStyle(.green)
            } else {
                ElapsedClock(startedAt: state.startedAt)
                    .font(.caption2)
                    .frame(maxWidth: 48)
            }
        case .background:
            if let deadline = state.backgroundDeadline {
                Text(timerInterval: Date()...deadline, countsDown: true)
                    .font(.caption2)
                    .monospacedDigit()
                    .multilineTextAlignment(.trailing)
                    .frame(maxWidth: 48)
                    .foregroundStyle(.orange)
            } else {
                Image(systemName: "moon.fill").foregroundStyle(.orange)
            }
        case .reconnecting:
            Image(systemName: "wifi.exclamationmark").foregroundStyle(.yellow)
        case .ending:
            Image(systemName: "stop.fill").foregroundStyle(.secondary)
        }
    }
}

/// End-stream button — runs EndStreamIntent in the app process (LiveActivityIntent).
/// `fullWidth` is the expanded island's large bottom action (the platform convention there);
/// the compact form remains the Lock Screen banner's trailing button while backgrounded.
private struct EndButton: View {
    var fullWidth = false

    var body: some View {
        if fullWidth {
            Button(intent: EndStreamIntent()) {
                Label("End Session", systemImage: "stop.fill")
                    .font(.subheadline.weight(.semibold))
                    .frame(maxWidth: .infinity)
                    .padding(.vertical, 2)
            }
            .tint(.red)
            .buttonStyle(.bordered)
        } else {
            Button(intent: EndStreamIntent()) {
                Label("End", systemImage: "stop.fill")
                    .font(.caption).bold()
            }
            .tint(.red)
            .buttonStyle(.bordered)
        }
    }
}

// MARK: - Previews (Xcode canvas)
//
// Select the PunktfunkWidgetsExtension scheme and open the canvas (⌥⌘↩) — the activity
// `#Preview(as:using:)` form renders every surface WITHOUT running the app or starting a real
// Activity: `.content` is the Lock Screen banner, `.dynamicIsland(.expanded/.compact/.minimal)`
// the island states (canvas device must be a Dynamic Island phone for those). Each listed
// content state becomes a frame in the canvas timeline strip, so all four session stages are one
// click apart. Sample state lives here (fileprivate), never in PunktfunkShared.

extension PunktfunkSessionAttributes {
    fileprivate static var preview: PunktfunkSessionAttributes {
        PunktfunkSessionAttributes(hostID: UUID(), hostName: "Studio", launchTitle: "Hades II")
    }
}

extension PunktfunkSessionAttributes.ContentState {
    fileprivate static var streaming: Self {
        .init(
            stage: .streaming, startedAt: .now.addingTimeInterval(-754),
            modeLine: "2752×2064 @120 · HEVC · HDR", latencyMs: 8, mbps: 84.2)
    }
    fileprivate static var backgrounded: Self {
        .init(
            stage: .background, startedAt: .now.addingTimeInterval(-1975),
            modeLine: "2752×2064 @120 · HEVC · HDR",
            backgroundDeadline: .now.addingTimeInterval(9 * 60))
    }
    fileprivate static var reconnecting: Self {
        .init(
            stage: .reconnecting, startedAt: .now.addingTimeInterval(-754),
            modeLine: "2752×2064 @120 · HEVC · HDR")
    }
    fileprivate static var ended: Self {
        .init(
            stage: .ending, startedAt: .now.addingTimeInterval(-3541),
            modeLine: "2752×2064 @120 · HEVC · HDR")
    }
}

#Preview("Lock Screen", as: .content, using: PunktfunkSessionAttributes.preview) {
    PunktfunkSessionLiveActivity()
} contentStates: {
    PunktfunkSessionAttributes.ContentState.streaming
    PunktfunkSessionAttributes.ContentState.backgrounded
    PunktfunkSessionAttributes.ContentState.reconnecting
    PunktfunkSessionAttributes.ContentState.ended
}

#Preview(
    "Island expanded", as: .dynamicIsland(.expanded),
    using: PunktfunkSessionAttributes.preview
) {
    PunktfunkSessionLiveActivity()
} contentStates: {
    PunktfunkSessionAttributes.ContentState.streaming
    PunktfunkSessionAttributes.ContentState.backgrounded
}

#Preview(
    "Island compact", as: .dynamicIsland(.compact),
    using: PunktfunkSessionAttributes.preview
) {
    PunktfunkSessionLiveActivity()
} contentStates: {
    PunktfunkSessionAttributes.ContentState.streaming
}

#Preview(
    "Island minimal", as: .dynamicIsland(.minimal),
    using: PunktfunkSessionAttributes.preview
) {
    PunktfunkSessionLiveActivity()
} contentStates: {
    PunktfunkSessionAttributes.ContentState.streaming
}