// FuelBoardLiveActivityView.swift — renders the FuelBoard Live Activity.
//
// Lives in the widget extension (the standard host for ActivityConfiguration).
// Shows the cheapest station for the pinned fuel within the app's chosen
// radius. Tapping anywhere opens Apple Maps directions to that station.

import ActivityKit
import SwiftUI
import WidgetKit

/// The Live Activity itself — registered in the widget bundle alongside the
/// regular price widget. No CarPlay entitlement involved: this renders on the
/// Lock Screen, Dynamic Island, and the car display (CarPlay Ultra, iOS 26+).
/// `.supplementalActivityFamilies([.small])` makes it eligible for the car's
/// small Live Activity slot — display-only there (FuelBoard is not a
/// CarPlay-enabled app, so car-side taps can't launch anything).
struct FuelBoardLiveActivity: Widget {
    var body: some WidgetConfiguration {
        ActivityConfiguration(for: FuelBoardLiveActivityAttributes.self) { context in
            // Lock Screen / banner presentation
            FuelBoardLiveActivityView(context: context)
        } dynamicIsland: { context in
            DynamicIsland {
                DynamicIslandExpandedRegion(.leading) {
                    FuelBoardLiveActivityCompactView(context: context)
                }
                DynamicIslandExpandedRegion(.trailing) {
                    FuelBoardLiveActivityPriceView(context: context)
                }
                DynamicIslandExpandedRegion(.bottom) {
                    FuelBoardLiveActivityStationView(context: context)
                }
            } compactLeading: {
                Image(systemName: "fuelpump.fill")
                    .foregroundStyle(.green)
            } compactTrailing: {
                FuelBoardLiveActivityPriceView(context: context)
            } minimal: {
                Text(context.state.priceText)
                    .font(.caption2.bold().monospacedDigit())
            }
        }
        .supplementalActivityFamilies([.small])
    }
}

/// Lock Screen / banner body — the main presentation.
private struct FuelBoardLiveActivityView: View {
    let context: ActivityViewContext<FuelBoardLiveActivityAttributes>

    var body: some View {
        Link(destination: context.state.mapsURL) {
            HStack(spacing: 12) {
                // LEFT — station brand glyph
                Image(systemName: "fuelpump.circle.fill")
                    .font(.system(size: 32))
                    .foregroundStyle(.green, .white)
                    .frame(width: 40, height: 40)

                // MIDDLE — fuel + station
                VStack(alignment: .leading, spacing: 2) {
                    Text("Cheapest \(context.state.fuel.displayName)")
                        .font(.headline)
                    Text("\(context.state.stationName) · \(context.state.distanceText)")
                        .font(.subheadline)
                        .foregroundStyle(.secondary)
                        .lineLimit(1)
                }
                .frame(maxWidth: .infinity, alignment: .leading)

                // RIGHT — price
                VStack(alignment: .trailing, spacing: 2) {
                    FuelStore.priceTextAttributed(context.state.pricePence,
                                                   style: context.state.priceDisplayStyle,
                                                   size: 22, weight: .bold)
                    Text("Tap for directions")
                        .font(.caption2)
                        .foregroundStyle(.secondary)
                }
            }
            .padding()
        }
    }
}

/// Dynamic Island expanded regions + compact trailing — price only.
private struct FuelBoardLiveActivityPriceView: View {
    let context: ActivityViewContext<FuelBoardLiveActivityAttributes>

    var body: some View {
        FuelStore.priceTextAttributed(context.state.pricePence,
                                      style: context.state.priceDisplayStyle,
                                      size: 17, weight: .bold)
    }
}

/// Dynamic Island expanded — fuel + station name.
private struct FuelBoardLiveActivityCompactView: View {
    let context: ActivityViewContext<FuelBoardLiveActivityAttributes>

    var body: some View {
        VStack(alignment: .leading, spacing: 2) {
            Text("Cheapest \(context.state.fuel.displayName)")
                .font(.caption2)
                .foregroundStyle(.secondary)
            Text(context.state.stationName)
                .font(.caption.bold())
                .lineLimit(1)
        }
    }
}

/// Dynamic Island expanded bottom — station + distance.
private struct FuelBoardLiveActivityStationView: View {
    let context: ActivityViewContext<FuelBoardLiveActivityAttributes>

    var body: some View {
        Text("\(context.state.stationName) · \(context.state.distanceText)")
            .font(.caption)
            .lineLimit(1)
    }
}

// MARK: - ContentState display helpers

extension FuelBoardLiveActivityAttributes.ContentState {
    /// Display distance using the user's chosen unit (miles default).
    var distanceText: String {
        FuelStore.loadDistanceUnit().format(distanceKM)
    }

    /// Price string from pence, in the user's chosen display style
    /// (station sign "129.9" or pounds "£1.29⁹/L"). Uses the style captured
    /// in the state at push time.
    var priceText: String {
        FuelStore.priceText(pricePence, style: priceDisplayStyle)
    }

    /// Apple Maps directions URL to the pinned station.
    var mapsURL: URL {
        URL(string: "maps://?daddr=\(lat),\(lng)&t=d")!
    }
}