breadcrumb-the-shire/core/App/AppContainer.php

<?php

namespace MintyPHP\App;

use RuntimeException;

// Minimal DI container: factories are registered with set() and resolved lazily on first get().
// Each service is instantiated at most once — get() returns the same instance on every call.
final class AppContainer
{
    /** @var array<string, callable(self): mixed> */
    private array $bindings = [];

    /** @var array<string, mixed> */
    private array $instances = [];

    private bool $protectExistingBindings = false;

    public function set(string $id, callable $factory): void
    {
        if ($this->protectExistingBindings && $this->has($id)) {
            throw new RuntimeException('Refusing to overwrite existing service binding: ' . $id);
        }
        $this->bindings[$id] = $factory;
    }

    public function has(string $id): bool
    {
        return array_key_exists($id, $this->instances) || array_key_exists($id, $this->bindings);
    }

    public function get(string $id): mixed
    {
        if (array_key_exists($id, $this->instances)) {
            return $this->instances[$id];
        }

        if (!array_key_exists($id, $this->bindings)) {
            throw new RuntimeException('Service not bound: ' . $id);
        }

        // Resolve, cache, and return — factory receives the container for its own dependencies.
        $this->instances[$id] = ($this->bindings[$id])($this);
        return $this->instances[$id];
    }

    /**
     * Freeze existing bindings/instances: any later overwrite attempt throws.
     */
    public function protectExistingBindings(): void
    {
        $this->protectExistingBindings = true;
    }
}