<?php

namespace Invoker;

use Interop\Container\ContainerInterface;
use Invoker\Exception\NotCallableException;

/**
 * Resolves a callable from a container.
 *
 * @author Matthieu Napoli <matthieu@mnapoli.fr>
 */
class CallableResolver
{
    /**
     * @var ContainerInterface
     */
    private $container;

    public function __construct(ContainerInterface $container)
    {
        $this->container = $container;
    }

    /**
     * Resolve the given callable into a real PHP callable.
     *
     * @param callable|string|array $callable
     *
     * @return callable Real PHP callable.
     *
     * @throws NotCallableException
     */
    public function resolve($callable)
    {
        if (is_string($callable) && strpos($callable, '::') !== false) {
            $callable = explode('::', $callable, 2);
        }

        $callable = $this->resolveFromContainer($callable);

        if (! is_callable($callable)) {
            throw new NotCallableException(sprintf(
                '%s is not a callable',
                is_object($callable) ? 'Instance of ' . get_class($callable) : var_export($callable, true)
            ));
        }

        return $callable;
    }

    /**
     * @param callable|string|array $callable
     * @return callable
     * @throws NotCallableException
     */
    private function resolveFromContainer($callable)
    {
        // Shortcut for a very common use case
        if ($callable instanceof \Closure) {
            return $callable;
        }

        $isStaticCallToNonStaticMethod = false;

        // If it's already a callable there is nothing to do
        if (is_callable($callable)) {
            $isStaticCallToNonStaticMethod = $this->isStaticCallToNonStaticMethod($callable);
            if (! $isStaticCallToNonStaticMethod) {
                return $callable;
            }
        }

        // The callable is a container entry name
        if (is_string($callable)) {
            if ($this->container->has($callable)) {
                return $this->container->get($callable);
            } else {
                throw new NotCallableException(sprintf(
                    '"%s" is neither a callable nor a valid container entry',
                    $callable
                ));
            }
        }

        // The callable is an array whose first item is a container entry name
        // e.g. ['some-container-entry', 'methodToCall']
        if (is_array($callable) && is_string($callable[0])) {
            if ($this->container->has($callable[0])) {
                // Replace the container entry name by the actual object
                $callable[0] = $this->container->get($callable[0]);
                return $callable;
            } elseif ($isStaticCallToNonStaticMethod) {
                throw new NotCallableException(sprintf(
                    'Cannot call %s::%s() because %s() is not a static method and "%s" is not a container entry',
                    $callable[0],
                    $callable[1],
                    $callable[1],
                    $callable[0]
                ));
            } else {
                throw new NotCallableException(sprintf(
                    'Cannot call %s on %s because it is not a class nor a valid container entry',
                    $callable[1],
                    $callable[0]
                ));
            }
        }

        // Unrecognized stuff, we let it fail later
        return $callable;
    }

    /**
     * Check if the callable represents a static call to a non-static method.
     *
     * @param mixed $callable
     * @return bool
     */
    private function isStaticCallToNonStaticMethod($callable)
    {
        if (is_array($callable) && is_string($callable[0])) {
            list($class, $method) = $callable;
            $reflection = new \ReflectionMethod($class, $method);

            return ! $reflection->isStatic();
        }

        return false;
    }
}
