Filament order items relation manager with totals

<?php

namespace App\Filament\Resources\Orders\RelationManagers;

use App\Models\Product;
use Filament\Actions\CreateAction;
use Filament\Actions\DeleteAction;
use Filament\Actions\EditAction;
use Filament\Forms\Components\Select;
use Filament\Forms\Components\TextInput;
use Filament\Resources\RelationManagers\RelationManager;
use Filament\Schemas\Components\Utilities\Get;
use Filament\Schemas\Components\Utilities\Set;
use Filament\Schemas\Schema;
use Filament\Tables\Columns\TextColumn;
use Filament\Tables\Columns\Summarizers\Sum;
use Filament\Tables\Table;

class ItemsRelationManager extends RelationManager
{
    protected static string $relationship = 'items';

    protected static ?string $title = 'Order items';

    // Lines are locked once the order has left "pending".
    public function isReadOnly(): bool
    {
        return $this->getOwnerRecord()->status !== 'pending';
    }

    public function form(Schema $schema): Schema
    {
        return $schema->components([
            Select::make('product_id')
                ->relationship('product', 'name')
                ->searchable()
                ->preload()
                ->required()
                ->live()
                ->afterStateUpdated(fn ($state, Set $set) => $set('unit_price', Product::find($state)?->price ?? 0)),
            TextInput::make('quantity')->numeric()->minValue(1)->default(1)->required()->live(onBlur: true),
            TextInput::make('unit_price')
                ->label('Unit price (cents)')
                ->numeric()
                ->required()
                ->helperText(fn (Get $get) => 'Line total: '.number_format(((int) $get('quantity') * (int) $get('unit_price')) / 100, 2)),
        ]);
    }

    public function table(Table $table): Table
    {
        $recalculate = fn () => $this->getOwnerRecord()->recalculateTotal();

        return $table
            ->recordTitleAttribute('product.name')
            ->columns([
                TextColumn::make('product.name')->label('Product'),
                TextColumn::make('quantity')->summarize(Sum::make()->label('Units')),
                TextColumn::make('unit_price')->money('usd', divideBy: 100),
                TextColumn::make('line_total')
                    ->state(fn ($record) => $record->quantity * $record->unit_price)
                    ->money('usd', divideBy: 100),
            ])
            ->headerActions([CreateAction::make()->after($recalculate)])
            ->recordActions([
                EditAction::make()->after($recalculate),
                DeleteAction::make()->after($recalculate),
            ]);
    }
}