import 'package:flutter/material.dart';

import 'panel_header.dart';

/// A navigation item in the NavPanel.
class NavItem {
  const NavItem({
    required this.id,
    required this.label,
    required this.icon,
    this.section,
    this.badge,
  });

  /// Unique identifier for routing.
  final String id;

  /// Display label.
  final String label;

  /// Item icon.
  final IconData icon;

  /// Optional section grouping (e.g., 'Portainer', 'NPM', 'Authentik').
  /// Section headers are shown only when multiple sections exist.
  final String? section;

  /// Optional badge (e.g., item count).
  final String? badge;
}

/// Left-side navigation panel for room-level section navigation.
///
/// Shows a list of items within the current room (e.g., Containers, Networks
/// for Control Room). Items can be grouped into sections with headers.
/// Section headers only appear when multiple sections exist.
///
/// Header content is docked to bottom to accommodate the logo bulge overlay.
///
/// See UI_LAYOUT.md for panel taxonomy and layout specifications.
class NavPanel extends StatelessWidget {
  const NavPanel({
    super.key,
    required this.title,
    required this.icon,
    required this.items,
    required this.selectedId,
    required this.onItemSelected,
    this.width = 280,
    this.trailing,
  });

  /// Panel title displayed in header.
  final String title;

  /// Leading icon for the header.
  final IconData icon;

  /// List of navigation items.
  final List<NavItem> items;

  /// Currently selected item ID.
  final String selectedId;

  /// Callback when an item is tapped.
  final ValueChanged<String> onItemSelected;

  /// Panel width (default 280px per UI_LAYOUT.md spec).
  final double width;

  /// Optional trailing widget below items (e.g., external links).
  final Widget? trailing;

  /// Returns true if section headers should be shown.
  bool get _showSectionHeaders {
    final sections = items.map((i) => i.section).where((s) => s != null).toSet();
    return sections.length > 1;
  }

  /// Groups items by section, preserving order.
  List<(String?, List<NavItem>)> get _groupedItems {
    final groups = <String?, List<NavItem>>{};
    final order = <String?>[];

    for (final item in items) {
      if (!groups.containsKey(item.section)) {
        groups[item.section] = [];
        order.add(item.section);
      }
      groups[item.section]!.add(item);
    }

    return order.map((section) => (section, groups[section]!)).toList();
  }

  @override
  Widget build(BuildContext context) {
    final colorScheme = Theme.of(context).colorScheme;

    return SizedBox(
      width: width,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          PanelHeader(
            title: title,
            icon: icon,
            dockToBottom: true, // Left-side panel
          ),
          Expanded(
            child: ListView(
              padding: const EdgeInsets.symmetric(vertical: 8),
              children: _buildItemList(context),
            ),
          ),
          if (trailing != null) ...[
            Divider(height: 1, color: colorScheme.outlineVariant),
            trailing!,
          ],
        ],
      ),
    );
  }

  List<Widget> _buildItemList(BuildContext context) {
    final widgets = <Widget>[];
    final showHeaders = _showSectionHeaders;

    for (final (section, sectionItems) in _groupedItems) {
      // Add section header if multiple sections exist
      if (showHeaders && section != null) {
        widgets.add(_SectionHeader(title: section));
      }

      // Add items
      for (final item in sectionItems) {
        widgets.add(
          _NavTile(
            item: item,
            isSelected: item.id == selectedId,
            onTap: () => onItemSelected(item.id),
          ),
        );
      }
    }

    return widgets;
  }
}

/// Section header widget with left accent bar.
class _SectionHeader extends StatelessWidget {
  const _SectionHeader({required this.title});

  final String title;

  @override
  Widget build(BuildContext context) {
    final colorScheme = Theme.of(context).colorScheme;
    final textTheme = Theme.of(context).textTheme;

    return Container(
      margin: const EdgeInsets.only(top: 8, bottom: 4),
      padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 6),
      decoration: BoxDecoration(
        color: colorScheme.surfaceContainerHigh,
        border: Border(
          left: BorderSide(
            color: colorScheme.primary,
            width: 2,
          ),
        ),
      ),
      child: Text(
        title.toUpperCase(),
        style: textTheme.labelSmall?.copyWith(
          color: colorScheme.onSurfaceVariant,
          letterSpacing: 0.5,
          fontWeight: FontWeight.w600,
        ),
      ),
    );
  }
}

class _NavTile extends StatelessWidget {
  const _NavTile({
    required this.item,
    required this.isSelected,
    required this.onTap,
  });

  final NavItem item;
  final bool isSelected;
  final VoidCallback onTap;

  @override
  Widget build(BuildContext context) {
    final colorScheme = Theme.of(context).colorScheme;
    final textTheme = Theme.of(context).textTheme;

    return Padding(
      padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 2),
      child: Material(
        color: isSelected
            ? colorScheme.primaryContainer.withValues(alpha: 0.4)
            : Colors.transparent,
        borderRadius: BorderRadius.circular(8),
        child: InkWell(
          onTap: onTap,
          borderRadius: BorderRadius.circular(8),
          child: Padding(
            padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 10),
            child: Row(
              children: [
                Icon(
                  item.icon,
                  size: 20,
                  color: isSelected
                      ? colorScheme.primary
                      : colorScheme.onSurfaceVariant,
                ),
                const SizedBox(width: 12),
                Expanded(
                  child: Text(
                    item.label,
                    style: textTheme.bodyMedium?.copyWith(
                      color: isSelected
                          ? colorScheme.primary
                          : colorScheme.onSurface,
                      fontWeight: isSelected ? FontWeight.w600 : null,
                    ),
                  ),
                ),
                if (item.badge != null)
                  Container(
                    padding: const EdgeInsets.symmetric(
                      horizontal: 8,
                      vertical: 2,
                    ),
                    decoration: BoxDecoration(
                      color: isSelected
                          ? colorScheme.primary.withValues(alpha: 0.2)
                          : colorScheme.surfaceContainerHighest,
                      borderRadius: BorderRadius.circular(12),
                    ),
                    child: Text(
                      item.badge!,
                      style: textTheme.labelSmall?.copyWith(
                        color: isSelected
                            ? colorScheme.primary
                            : colorScheme.onSurfaceVariant,
                      ),
                    ),
                  ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}