/// UI-01: the persistent 4-tab shell. Replaces the old push/pop stack rooted at Record.
///
/// One background map, always mounted, shared by every tab -- not four separate map
/// instances. Full opacity and interactive on the Map tab; dimmed and non-interactive
/// (taps pass through to the tab's real content) everywhere else. This is what lets the
/// map survive a tab switch with its camera position and live path intact, and what
/// makes "the map is active on every tab" true without refetching tiles four times over.
///
/// No `AppBar` anywhere in this shell or in any of the four tab roots -- the point of the
/// redesign is showing as much map as possible, and a persistent bottom nav plus zero
/// header chrome is what buys that space back.
library;

import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import 'package:latlong2/latlong.dart' as ll;

import '../app/providers.dart';
import '../domain/models.dart';
import 'components/ride_map.dart';

/// The thin go_router adapter. Kept separate from [ShellScaffold] so tests can drive the
/// actual shell logic (background map, dimming, nav bar) with a plain `currentIndex` and
/// `child`, without needing to construct a real [StatefulNavigationShell] -- which
/// go_router only ever builds internally.
class AppShell extends StatelessWidget {
  const AppShell({super.key, required this.navigationShell});

  final StatefulNavigationShell navigationShell;

  @override
  Widget build(BuildContext context) => ShellScaffold(
    currentIndex: navigationShell.currentIndex,
    onDestinationSelected: (index) => navigationShell.goBranch(
      index,
      // Tapping the already-active tab pops it back to its own root, matching the
      // conventional "tap the active tab to go home" behaviour of a bottom-tab app.
      initialLocation: index == navigationShell.currentIndex,
    ),
    child: navigationShell,
  );
}

class ShellScaffold extends ConsumerWidget {
  const ShellScaffold({
    super.key,
    required this.currentIndex,
    required this.onDestinationSelected,
    required this.child,
  });

  final int currentIndex;
  final ValueChanged<int> onDestinationSelected;
  final Widget child;

  static const mapTabIndex = 0;

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final isMapTab = currentIndex == mapTabIndex;
    // The Settings toggle's whole point (see its own doc comment) is that no tile is
    // ever fetched when off, not merely hidden -- that guarantee must survive this
    // screen becoming a permanent background across every tab, not just apply to the
    // Map tab the way it used to.
    final mapEnabled = ref.watch(mapEnabledProvider);
    final trip = ref.watch(activeTripProvider).valueOrNull;
    final points = trip == null
        ? const <TrackPoint>[]
        : ref.watch(livePointsProvider(trip.id)).valueOrNull ?? const <TrackPoint>[];
    final segments = trip == null
        ? const <Segment>[]
        : ref.watch(liveSegmentsProvider(trip.id)).valueOrNull ?? const <Segment>[];
    // FB-01: only watched while idle, so there's never a duplicate GPS consumer during
    // an active recording -- the moment a trip starts, this stops being watched at all.
    final ambientFix =
        trip == null ? ref.watch(ambientPositionProvider).valueOrNull : null;
    final ambientPosition = ambientFix == null
        ? null
        : ll.LatLng(ambientFix.latitude, ambientFix.longitude);

    return Scaffold(
      // Falls back to the ordinary theme background when the map is disabled -- the
      // per-tab screens are transparent now, relying on this shell to paint something.
      backgroundColor: Theme.of(context).scaffoldBackgroundColor,
      body: Stack(
        children: [
          // The one shared map instance. IgnorePointer rather than a per-tab rebuild:
          // keeping this the same widget across tab switches is what preserves camera
          // position and avoids refetching tiles. Not constructed at all when the map is
          // disabled -- no widget means no tile request can fire, the same real
          // short-circuit `mapEnabledProvider` always guaranteed.
          if (mapEnabled)
            Positioned.fill(
              child: IgnorePointer(
                ignoring: !isMapTab,
                child: RideMap(
                  key: const Key('shell-background-map'),
                  points: points,
                  segments: segments,
                  ambientPosition: ambientPosition,
                  follow: isMapTab,
                  fill: true,
                  showEmptyLabel: false,
                  tileProvider: ref.watch(cachedTileProviderProvider),
                  skeletonMode: ref.watch(mapConnectivityProvider).skeletonMode,
                  // UI-05: only on the Map tab -- a pulsing marker ticking away behind
                  // a scrim on every other tab would be wasted animation no one sees.
                  showLocationMarker: isMapTab,
                ),
              ),
            ),
          // Dims the map behind every tab except Map itself -- decoration there, not a
          // control surface; the scrim also absorbs taps so they can't reach the map.
          if (mapEnabled && !isMapTab)
            const Positioned.fill(
              child: IgnorePointer(
                child: ColoredBox(color: Color(0xB3000000)),
              ),
            ),
          Positioned.fill(child: child),
        ],
      ),
      bottomNavigationBar: _ShellNavBar(
        currentIndex: currentIndex,
        onDestinationSelected: onDestinationSelected,
      ),
    );
  }
}

class _ShellNavBar extends StatelessWidget {
  const _ShellNavBar({required this.currentIndex, required this.onDestinationSelected});

  final int currentIndex;
  final ValueChanged<int> onDestinationSelected;

  @override
  Widget build(BuildContext context) => NavigationBar(
    key: const Key('shell-nav-bar'),
    selectedIndex: currentIndex,
    onDestinationSelected: onDestinationSelected,
    destinations: const [
      NavigationDestination(
        key: Key('nav-map'),
        icon: Icon(Icons.map_outlined),
        selectedIcon: Icon(Icons.map),
        label: 'Map',
      ),
      NavigationDestination(
        key: Key('nav-rides'),
        icon: Icon(Icons.directions_bike_outlined),
        selectedIcon: Icon(Icons.directions_bike),
        label: 'Rides',
      ),
      NavigationDestination(
        key: Key('nav-plan'),
        icon: Icon(Icons.route_outlined),
        selectedIcon: Icon(Icons.route),
        label: 'Plan',
      ),
      NavigationDestination(
        key: Key('nav-settings'),
        icon: Icon(Icons.settings_outlined),
        selectedIcon: Icon(Icons.settings),
        label: 'Settings',
      ),
    ],
  );
}