Filament CSV import header action with row validation

<?php

namespace App\Filament\Actions;

use App\Models\Contact;
use Filament\Actions\Action;
use Filament\Forms\Components\FileUpload;
use Filament\Notifications\Notification;
use Illuminate\Support\Facades\Storage;
use Illuminate\Support\Facades\Validator;
use SplFileObject;

class ImportContactsAction
{
    private const REQUIRED_HEADERS = ['name', 'email'];

    public static function make(): Action
    {
        return Action::make('importCsv')
            ->label('Import CSV')
            ->icon('heroicon-o-arrow-up-tray')
            ->modalDescription('First row must be a header with at least: '.implode(', ', self::REQUIRED_HEADERS).'.')
            ->schema([
                FileUpload::make('file')
                    ->disk('local')
                    ->directory('imports')
                    ->acceptedFileTypes(['text/csv', 'text/plain', 'application/vnd.ms-excel'])
                    ->maxSize(5120)
                    ->required(),
            ])
            ->action(function (array $data): void {
                $path = Storage::disk('local')->path($data['file']);
                $result = self::import($path);
                Storage::disk('local')->delete($data['file']);

                Notification::make()
                    ->title("Imported {$result['imported']} rows")
                    ->body($result['skipped'].' skipped'.($result['firstError'] ? ' (first: '.$result['firstError'].')' : ''))
                    ->color($result['skipped'] ? 'warning' : 'success')
                    ->send();
            });
    }

    /** @return array{imported:int, skipped:int, firstError:?string} */
    private static function import(string $path): array
    {
        $file = new SplFileObject($path);
        $file->setFlags(SplFileObject::READ_CSV | SplFileObject::SKIP_EMPTY | SplFileObject::READ_AHEAD | SplFileObject::DROP_NEW_LINE);

        $headers = null;
        $batch = [];
        $imported = $skipped = 0;
        $firstError = null;

        foreach ($file as $line => $cells) {
            if ($headers === null) {
                $headers = array_map(fn ($h) => strtolower(trim((string) $h, "\xEF\xBB\xBF \t")), $cells); // strip BOM
                if (array_diff(self::REQUIRED_HEADERS, $headers)) {
                    return ['imported' => 0, 'skipped' => 0, 'firstError' => 'missing required column'];
                }
                continue;
            }

            $row = array_combine($headers, array_pad(array_slice($cells, 0, count($headers)), count($headers), null));
            $validator = Validator::make($row, ['name' => 'required|max:120', 'email' => 'required|email|max:190']);

            if ($validator->fails()) {
                $skipped++;
                $firstError ??= 'line '.($line + 1).': '.$validator->errors()->first();
                continue;
            }

            $batch[] = ['name' => $row['name'], 'email' => strtolower($row['email'])];

            if (count($batch) === 500) {
                $imported += self::flush($batch);
                $batch = [];
            }
        }

        $imported += self::flush($batch);

        return compact('imported', 'skipped', 'firstError');
    }

    private static function flush(array $batch): int
    {
        if ($batch === []) {
            return 0;
        }

        Contact::upsert($batch, ['email'], ['name']); // idempotent: re-importing updates names

        return count($batch);
    }
}