incr/app/Livewire/Counter.php

<?php

declare(strict_types=1);

namespace App\Livewire;

use App\Models\Tracker;
use Illuminate\Contracts\View\View;
use Livewire\Attributes\Locked;
use Livewire\Attributes\Validate;
use Livewire\Component;

class Counter extends Component
{
    // Ceiling of the unsigned int column backing trackers.count.
    public const MAX_COUNT = 4294967295;

    #[Locked]
    public int $count = 0;

    #[Locked]
    public bool $needsOnboarding = false;

    public bool $editing = false;

    #[Validate('required|integer|min:0|max:'.self::MAX_COUNT)]
    public ?int $value = null;

    public function mount(): void
    {
        $tracker = Tracker::current();

        $this->needsOnboarding = $tracker === null;

        if ($tracker !== null) {
            $this->syncFrom($tracker);
        }
    }

    public function initialise(): void
    {
        $this->validate();

        $tracker = Tracker::current() ?? Tracker::create([
            'label' => 'Counter',
            'unit' => 'units',
            'count' => $this->value,
        ]);

        $this->syncFrom($tracker);
        $this->needsOnboarding = false;
    }

    public function increment(): void
    {
        $tracker = Tracker::current();

        if (! $tracker || $tracker->count >= self::MAX_COUNT) {
            return;
        }

        $tracker->increment('count');

        $this->syncFrom($tracker->refresh());
    }

    public function edit(): void
    {
        $this->value = $this->count;
        $this->resetValidation();
        $this->editing = true;
    }

    public function save(): void
    {
        $this->validate();

        $tracker = Tracker::current();

        if (! $tracker) {
            return;
        }

        $tracker->update(['count' => $this->value]);

        $this->syncFrom($tracker);
        $this->editing = false;
    }

    public function cancel(): void
    {
        $this->value = $this->count;
        $this->resetValidation();
        $this->editing = false;
    }

    /**
     * The tracker is the source of truth; the form input always mirrors it.
     */
    private function syncFrom(Tracker $tracker): void
    {
        $this->count = $tracker->count;
        $this->value = $this->count;
    }

    public function render(): View
    {
        return view('livewire.counter')->layout('layouts.app');
    }
}