import 'package:flutter/material.dart';
import 'package:uto_manager/domain/entities/doctrinal_branch.dart';
import 'package:uto_manager/domain/entities/echelon.dart';
import 'package:uto_manager/domain/entities/unit_node.dart';
import 'package:uuid/uuid.dart';

/// Dialog for creating or editing a [UnitNode].
///
/// Pass [existing] to edit; leave null to create a new unit.
/// Pass [parentUnit] to pre-select the parent and constrain the echelon.
class AddEditUnitDialog extends StatefulWidget {
  const AddEditUnitDialog({
    super.key,
    this.existing,
    this.parentUnit,
    this.availableParents = const [],
  });

  final UnitNode? existing;
  final UnitNode? parentUnit;
  final List<UnitNode> availableParents;

  @override
  State<AddEditUnitDialog> createState() => _AddEditUnitDialogState();
}

class _AddEditUnitDialogState extends State<AddEditUnitDialog> {
  final _formKey = GlobalKey<FormState>();
  late final TextEditingController _nameCtrl;

  late Echelon _echelon;
  late DoctrinalBranch _branch;
  String? _parentUnitId;
  late bool _isKeyLeader;

  bool get _isEditing => widget.existing != null;

  @override
  void initState() {
    super.initState();
    final e = widget.existing;
    _nameCtrl = TextEditingController(text: e?.name ?? '');
    _echelon = e?.echelon ?? _defaultChildEchelon();
    _branch = e?.branch ?? DoctrinalBranch.infantry;
    _parentUnitId = e?.parentUnitId ?? widget.parentUnit?.unitId;
    _isKeyLeader = e?.isKeyLeader ?? false;
  }

  Echelon _defaultChildEchelon() {
    final parent = widget.parentUnit;
    if (parent == null) return Echelon.brigade;
    // Default to one level below parent
    final childLevel = parent.echelon.level + 1;
    return Echelon.values.firstWhere(
      (e) => e.level == childLevel,
      orElse: () => Echelon.team,
    );
  }

  @override
  void dispose() {
    _nameCtrl.dispose();
    super.dispose();
  }

  void _submit() {
    if (!_formKey.currentState!.validate()) return;

    // If no name provided, generate a default from echelon + branch abbreviation
    final rawName = _nameCtrl.text.trim();
    final name = rawName.isEmpty ? '${_echelon.displayName} (${_branch.abbreviation})' : rawName;

    final unit = UnitNode(
      unitId: widget.existing?.unitId ?? const Uuid().v4(),
      echelon: _echelon,
      branch: _branch,
      name: name,
      isKeyLeader: _isKeyLeader,
      parentUnitId: _parentUnitId,
    );

    Navigator.of(context).pop(unit);
  }

  @override
  Widget build(BuildContext context) {
    return AlertDialog(
      title: Row(
        children: [
          Icon(_isEditing ? Icons.edit : Icons.add_box_outlined, size: 20),
          const SizedBox(width: 8),
          Text(_isEditing ? 'Edit Unit' : 'Add Unit'),
        ],
      ),
      content: SizedBox(
        width: 420,
        child: Form(
          key: _formKey,
          child: SingleChildScrollView(
            child: Column(
              mainAxisSize: MainAxisSize.min,
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                // Unit Name
                TextFormField(
                  controller: _nameCtrl,
                  decoration: const InputDecoration(
                    labelText: 'Unit Name / Designation (optional)',
                    hintText: 'e.g. 1-68 AR, Alpha Company, 3rd Platoon',
                    helperText: 'Leave blank to auto-generate from echelon & branch',
                    prefixIcon: Icon(Icons.account_tree_outlined),
                  ),
                  textCapitalization: TextCapitalization.words,
                ),
                const SizedBox(height: 12),

                // Echelon
                DropdownButtonFormField<Echelon>(
                  initialValue: _echelon,
                  decoration: const InputDecoration(
                    labelText: 'Echelon',
                    prefixIcon: Icon(Icons.layers_outlined),
                  ),
                  items: Echelon.values.map((e) {
                    return DropdownMenuItem(
                      value: e,
                      child: Text(e.displayName),
                    );
                  }).toList(),
                  onChanged: (v) => setState(() => _echelon = v!),
                ),
                const SizedBox(height: 12),

                // Branch
                DropdownButtonFormField<DoctrinalBranch>(
                  initialValue: _branch,
                  decoration: const InputDecoration(
                    labelText: 'Branch / Functional Area',
                    prefixIcon: Icon(Icons.category_outlined),
                  ),
                  items: DoctrinalBranch.values.map((b) {
                    return DropdownMenuItem(
                      value: b,
                      child: Text('${b.abbreviation} — ${b.displayName}'),
                    );
                  }).toList(),
                  onChanged: (v) => setState(() => _branch = v!),
                ),
                const SizedBox(height: 12),

                // Parent Unit (optional)
                if (widget.availableParents.isNotEmpty) ...[
                  DropdownButtonFormField<String?>(
                    initialValue: _parentUnitId,
                    decoration: const InputDecoration(
                      labelText: 'Parent Unit (optional)',
                      prefixIcon: Icon(Icons.device_hub_outlined),
                    ),
                    items: [
                      const DropdownMenuItem<String?>(
                        child: Text('— None (root unit) —'),
                      ),
                      ...widget.availableParents.map((u) {
                        return DropdownMenuItem<String?>(
                          value: u.unitId,
                          child: Text('${u.echelon.displayName}: ${u.name}'),
                        );
                      }),
                    ],
                    onChanged: (v) => setState(() => _parentUnitId = v),
                  ),
                  const SizedBox(height: 12),
                ],

                // Key Leader toggle
                SwitchListTile(
                  title: const Text('Key Leader Unit'),
                  subtitle: const Text('Marks this as a command/key leader node'),
                  value: _isKeyLeader,
                  onChanged: (v) => setState(() => _isKeyLeader = v),
                  contentPadding: EdgeInsets.zero,
                  dense: true,
                ),
              ],
            ),
          ),
        ),
      ),
      actions: [
        TextButton(
          onPressed: () => Navigator.of(context).pop(),
          child: const Text('Cancel'),
        ),
        FilledButton.icon(
          icon: Icon(_isEditing ? Icons.save : Icons.add, size: 16),
          label: Text(_isEditing ? 'Save Changes' : 'Add Unit'),
          onPressed: _submit,
        ),
      ],
    );
  }
}