// 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.
//
// ADAPTIVE LAYOUT: the Lock Screen body provides two layouts and lets
// ViewThatFits pick by available width, but the narrow `.small` family is NOT
// declared (see note on the config), so iPhone/iPad always render the full
// three-column card (`richBody`) with proper text sizes. `compactBody` is kept
// as a safety fallback should any surface ever hand this view a narrow width.
//
// IMPORTANT: `.supplementalActivityFamilies([.small])` is deliberately absent —
// it made iOS render the squeezed `.small` card on the iPhone Lock Screen.
// CarPlay's small form comes from the Dynamic Island compact closures.

import ActivityKit
import SwiftUI
import WidgetKit

/// The Live Activity itself — registered in the widget bundle alongside the
/// regular price widget. No CarPlay entitlement involved: renders on the
/// Lock Screen (full-width card on iPhone/iPad) and the Dynamic Island
/// (incl. the island's compact form used in the car, display-only — 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 / CarPlay small slot 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(context.state.fuel.tintColor)
            } compactTrailing: {
                FuelBoardLiveActivityPriceView(context: context)
            } minimal: {
                Text(context.state.priceText)
                    .font(.caption2.bold().monospacedDigit())
            }
        }
        .supplementalActivityFamilies([.small])
        // Why `.small` is kept: it lets the SHARED body render a compact form
        // in genuinely small slots (CarPlay small / Apple Watch smart stack)
        // instead of falling back to the Dynamic Island compact closure —
        // which could NOT show the station distance the user wants on CarPlay.
        // The full-width iPhone/iPad card is protected by the `richMinWidth`
        // gate on `richBody` + its flexible, truncating middle column, so
        // iPhone/iPad still get the full card; only truly small space picks
        // the compact strip below.
    }
}

/// Lock Screen / banner / CarPlay body — adaptive.
private struct FuelBoardLiveActivityView: View {
    let context: ActivityViewContext<FuelBoardLiveActivityAttributes>

    /// Below this ACTUAL proposed width we show the compact strip (CarPlay
    /// small / Watch smart stack); at/above it we show the full card. The
    /// decision is made from the real width the system hands the body, read
    /// via a background GeometryReader — NOT ViewThatFits ideal-width
    /// measurement (that's broken for truncating text: a long station name
    /// inflated the "ideal" width past the iPhone Lock Screen and collapsed
    /// the full card).
    private let compactWidthThreshold: CGFloat = 280

    /// Measured slot width (drives the rich-vs-compact branch). Measured in a
    /// background GeometryReader so it does NOT act as the layout container:
    /// a GeometryReader root pins content top-left, and forcing a
    /// maxHeight:.infinity frame on it over-claims the whole proposed height,
    /// centring the content below true vertical centre (bigger gap above) on
    /// the Lock Screen. Measuring behind the scenes keeps the content
    /// intrinsic-sized so the system vertically centres it itself.
    @State private var slotWidth: CGFloat = 400

    var body: some View {
        Link(destination: context.state.mapsURL) {
            Group {
                // Branch on the ACTUAL proposed width. iPhone/iPad offer the
                // full Lock Screen width (>= threshold) → rich card, no matter
                // how long the station name is. Truly small slots (CarPlay /
                // Watch) offer much less → compact strip.
                if slotWidth >= compactWidthThreshold {
                    richBody
                } else {
                    compactBody
                }
            }
            // Fill the card width so the background measure reads the real
            // slot, not the intrinsic content width.
            .frame(maxWidth: .infinity)
            // Side-channel width measurement — never the layout container.
            .background(
                GeometryReader { geo in
                    Color.clear
                        .onAppear { slotWidth = geo.size.width }
                        .onChange(of: geo.size.width) { _, w in slotWidth = w }
                }
            )
        }
    }

    /// Full three-column design (unchanged): brand glyph · fuel+station · price.
    private var richBody: some View {
        HStack(spacing: 12) {
            // LEFT — station brand glyph: the fuel-tinted pump on its own. No
            // background circle behind it (user request).
            Image(systemName: "fuelpump.fill")
                .font(.system(size: 28, weight: .semibold))
                .foregroundStyle(context.state.fuel.tintColor)
                .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)
                    .minimumScaleFactor(0.75)
                    .truncationMode(.tail)
            }
            .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()
    }

    /// Minimal strip for small space (CarPlay small / Watch smart stack):
    /// fuel type + distance + bold price on one line, station name below.
    /// Deliberately no app name and no full address — the watch-sized slot is
    /// too tight, so the second line is reserved for the station name only.
    private var compactBody: some View {
        VStack(alignment: .leading, spacing: 3) {
            HStack(spacing: 5) {
                Text(context.state.fuel.displayName)
                    .font(.caption.bold())
                    .lineLimit(1)
                Spacer(minLength: 4)
                Text(context.state.distanceText)
                    .font(.caption2)
                    .foregroundStyle(.secondary)
                    .lineLimit(1)
                Spacer(minLength: 4)
                FuelStore.priceTextAttributed(context.state.pricePence,
                                               style: context.state.priceDisplayStyle,
                                               size: 15, weight: .bold)
                    .lineLimit(1)
            }
            Text(context.state.stationName)
                .font(.system(size: 10, weight: .medium))
                .foregroundStyle(.secondary)
                .lineLimit(1)
                .minimumScaleFactor(0.75)
                .truncationMode(.tail)
        }
        .padding(8)
    }
}

/// 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")!
    }
}