import 'package:flutter/material.dart';
import 'package:go_router/go_router.dart';

import 'analytics_tabs.dart';
import 'nav_destinations.dart';
import 'top_nav.dart';

/// Below this width the shell falls back to a bottom [NavigationBar]; from here up it is the
/// [TopNav] bar.
const _narrowBreakpoint = 600.0;

/// Adaptive navigation shell around the current route: a bottom [NavigationBar] on narrow
/// surfaces and the [TopNav] bar on wider ones, with the Аналитика tab strip under it while
/// one of the analytics screens is open.
///
/// The top bar shows every destination (the ledger ones behind «Операции»). The bottom bar
/// shows the four primary ones plus «Ещё», which opens the rest in a sheet: twelve
/// destinations in a phone-width bar would leave about 30 px per label, which is not
/// navigation but decoration.
class AppShell extends StatelessWidget {
  const AppShell({required this.location, required this.child, super.key});

  final String location;
  final Widget child;

  int get _selectedIndex {
    // longest prefix wins, so /portfolio/instrument/311 keeps Портфель selected
    var best = -1;
    var bestLength = -1;
    for (var i = 0; i < navDestinations.length; i++) {
      final length = navDestinations[i].matchLength(location);
      if (length > bestLength) {
        best = i;
        bestLength = length;
      }
    }
    return best == -1 || bestLength < 0 ? 0 : best;
  }

  void _onSelect(BuildContext context, int index) {
    if (index != _selectedIndex) context.go(navDestinations[index].path);
  }

  @override
  Widget build(BuildContext context) {
    final width = MediaQuery.sizeOf(context).width;

    if (width < _narrowBreakpoint) {
      final primary = navDestinations.where((d) => d.primary).toList();
      final selected = navDestinations[_selectedIndex];
      final primaryIndex = primary.indexOf(selected);

      return Scaffold(
        body: SafeArea(child: child),
        bottomNavigationBar: NavigationBar(
          // nothing primary matches ⇒ we are inside a screen that lives behind «Ещё»,
          // and «Ещё» is what should look active
          selectedIndex: primaryIndex >= 0 ? primaryIndex : primary.length,
          onDestinationSelected: (i) {
            if (i >= primary.length) {
              _showMore(context, selected);
            } else {
              final target = navDestinations.indexOf(primary[i]);
              _onSelect(context, target);
            }
          },
          destinations: [
            for (final d in primary)
              NavigationDestination(
                icon: Icon(d.icon),
                selectedIcon: Icon(d.selectedIcon),
                label: d.label,
              ),
            NavigationDestination(
              icon: const Icon(Icons.more_horiz),
              selectedIcon: const Icon(Icons.more_horiz),
              label: primaryIndex >= 0 ? 'Ещё' : selected.label,
            ),
          ],
        ),
      );
    }

    return Scaffold(
      body: Column(
        children: [
          TopNav(
            selectedIndex: _selectedIndex,
            onSelect: (i) => _onSelect(context, i),
          ),
          Expanded(
            child: Align(
              alignment: Alignment.topCenter,
              child: ConstrainedBox(
                constraints: const BoxConstraints(maxWidth: kContentMaxWidth),
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.stretch,
                  children: [
                    if (AnalyticsTabs.contains(location))
                      Padding(
                        padding: const EdgeInsets.fromLTRB(16, 16, 16, 0),
                        child: AnalyticsTabs(location: location),
                      ),
                    Expanded(child: child),
                  ],
                ),
              ),
            ),
          ),
        ],
      ),
    );
  }

  /// The non-primary destinations, as a sheet. The currently open one is ticked, so «Ещё»
  /// still answers "where am I".
  void _showMore(BuildContext context, NavDestination current) {
    showModalBottomSheet<void>(
      context: context,
      showDragHandle: true,
      builder: (sheetContext) => SafeArea(
        child: ListView(
          shrinkWrap: true,
          children: [
            for (final d in navDestinations.where((d) => !d.primary))
              ListTile(
                leading: Icon(d == current ? d.selectedIcon : d.icon),
                title: Text(d.label),
                selected: d == current,
                trailing: d == current ? const Icon(Icons.check) : null,
                onTap: () {
                  Navigator.of(sheetContext).pop();
                  if (d != current) context.go(d.path);
                },
              ),
          ],
        ),
      ),
    );
  }
}