<?php namespace Illuminate\Bus;

use Closure;
use ArrayAccess;
use ReflectionClass;
use RuntimeException;
use ReflectionParameter;
use InvalidArgumentException;
use Illuminate\Pipeline\Pipeline;
use Illuminate\Support\Collection;
use Illuminate\Contracts\Queue\Queue;
use Illuminate\Contracts\Bus\SelfHandling;
use Illuminate\Contracts\Container\Container;
use Illuminate\Contracts\Bus\HandlerResolver;
use Illuminate\Contracts\Queue\ShouldBeQueued;
use Illuminate\Contracts\Bus\QueueingDispatcher;
use Illuminate\Contracts\Bus\Dispatcher as DispatcherContract;

class Dispatcher implements DispatcherContract, QueueingDispatcher, HandlerResolver
{

    /**
     * The container implementation.
     *
     * @var \Illuminate\Contracts\Container\Container
     */
    protected $container;

    /**
     * The pipeline instance for the bus.
     *
     * @var \Illuminate\Pipeline\Pipeline
     */
    protected $pipeline;

    /**
     * The pipes to send commands through before dispatching.
     *
     * @var array
     */
    protected $pipes = [];

    /**
     * The queue resolver callback.
     *
     * @var \Closure|null
     */
    protected $queueResolver;

    /**
     * All of the command-to-handler mappings.
     *
     * @var array
     */
    protected $mappings = [];

    /**
     * The fallback mapping Closure.
     *
     * @var \Closure
     */
    protected $mapper;

    /**
     * Create a new command dispatcher instance.
     *
     * @param  \Illuminate\Contracts\Container\Container $container
     * @param  \Closure|null $queueResolver
     * @return void
     */
    public function __construct(Container $container, Closure $queueResolver = null)
    {
        $this->container = $container;
        $this->queueResolver = $queueResolver;
        $this->pipeline = new Pipeline($container);
    }

    /**
     * Marshal a command and dispatch it to its appropriate handler.
     *
     * @param  mixed $command
     * @param  array $array
     * @return mixed
     */
    public function dispatchFromArray($command, array $array)
    {
        return $this->dispatch($this->marshalFromArray($command, $array));
    }

    /**
     * Marshal a command and dispatch it to its appropriate handler.
     *
     * @param  mixed $command
     * @param  \ArrayAccess $source
     * @param  array $extras
     * @return mixed
     */
    public function dispatchFrom($command, ArrayAccess $source, array $extras = [])
    {
        return $this->dispatch($this->marshal($command, $source, $extras));
    }

    /**
     * Marshal a command from the given array.
     *
     * @param  string $command
     * @param  array $array
     * @return mixed
     */
    protected function marshalFromArray($command, array $array)
    {
        return $this->marshal($command, new Collection, $array);
    }

    /**
     * Marshal a command from the given array accessible object.
     *
     * @param  string $command
     * @param  \ArrayAccess $source
     * @param  array $extras
     * @return mixed
     */
    protected function marshal($command, ArrayAccess $source, array $extras = [])
    {
        $injected = [];

        $reflection = new ReflectionClass($command);

        if ($constructor = $reflection->getConstructor()) {
            $injected = array_map(function ($parameter) use ($command, $source, $extras) {
                return $this->getParameterValueForCommand($command, $source, $parameter, $extras);

            }, $constructor->getParameters());
        }

        return $reflection->newInstanceArgs($injected);
    }

    /**
     * Get a parameter value for a marshaled command.
     *
     * @param  string $command
     * @param  \ArrayAccess $source
     * @param  \ReflectionParameter $parameter
     * @param  array $extras
     * @return mixed
     */
    protected function getParameterValueForCommand($command, ArrayAccess $source,
                                                   ReflectionParameter $parameter, array $extras = array())
    {
        if (array_key_exists($parameter->name, $extras)) {
            return $extras[$parameter->name];
        }

        if (isset($source[$parameter->name])) {
            return $source[$parameter->name];
        }

        if ($parameter->isDefaultValueAvailable()) {
            return $parameter->getDefaultValue();
        }

        MarshalException::whileMapping($command, $parameter);
    }

    /**
     * Dispatch a command to its appropriate handler.
     *
     * @param  mixed $command
     * @param  \Closure|null $afterResolving
     * @return mixed
     */
    public function dispatch($command, Closure $afterResolving = null)
    {
        if ($this->queueResolver && $this->commandShouldBeQueued($command)) {
            return $this->dispatchToQueue($command);
        } else {
            return $this->dispatchNow($command, $afterResolving);
        }
    }

    /**
     * Dispatch a command to its appropriate handler in the current process.
     *
     * @param  mixed $command
     * @param  \Closure|null $afterResolving
     * @return mixed
     */
    public function dispatchNow($command, Closure $afterResolving = null)
    {
        return $this->pipeline->send($command)->through($this->pipes)->then(function ($command) use ($afterResolving) {
            if ($command instanceof SelfHandling) {
                return $this->container->call([$command, 'handle']);
            }

            $handler = $this->resolveHandler($command);

            if ($afterResolving) {
                call_user_func($afterResolving, $handler);
            }

            return call_user_func(
                [$handler, $this->getHandlerMethod($command)], $command
            );
        });

    }

    /**
     * Determine if the given command should be queued.
     *
     * @param  mixed $command
     * @return bool
     */
    protected function commandShouldBeQueued($command)
    {
        if ($command instanceof ShouldBeQueued) {
            return true;
        }

        return (new ReflectionClass($this->getHandlerClass($command)))->implementsInterface(
            'Illuminate\Contracts\Queue\ShouldBeQueued'
        );
    }

    /**
     * Dispatch a command to its appropriate handler behind a queue.
     *
     * @param  mixed $command
     * @return mixed
     *
     * @throws \RuntimeException
     */
    public function dispatchToQueue($command)
    {
        $queue = call_user_func($this->queueResolver);

        if (!$queue instanceof Queue) {
            throw new RuntimeException("Queue resolver did not return a Queue implementation.");
        }

        if (method_exists($command, 'queue')) {
            $command->queue($queue, $command);
        } else {
            $queue->push($command);
        }
    }

    /**
     * Get the handler instance for the given command.
     *
     * @param  mixed $command
     * @return mixed
     */
    public function resolveHandler($command)
    {
        if ($command instanceof SelfHandling) {
            return $command;
        }

        return $this->container->make($this->getHandlerClass($command));
    }

    /**
     * Get the handler class for the given command.
     *
     * @param  mixed $command
     * @return string
     */
    public function getHandlerClass($command)
    {
        if ($command instanceof SelfHandling) {
            return get_class($command);
        }

        return $this->inflectSegment($command, 0);
    }

    /**
     * Get the handler method for the given command.
     *
     * @param  mixed $command
     * @return string
     */
    public function getHandlerMethod($command)
    {
        if ($command instanceof SelfHandling) {
            return 'handle';
        }

        return $this->inflectSegment($command, 1);
    }

    /**
     * Get the given handler segment for the given command.
     *
     * @param  mixed $command
     * @param  int $segment
     * @return string
     */
    protected function inflectSegment($command, $segment)
    {
        $className = get_class($command);

        if (isset($this->mappings[$className])) {
            return $this->getMappingSegment($className, $segment);
        } elseif ($this->mapper) {
            return $this->getMapperSegment($command, $segment);
        }

        throw new InvalidArgumentException("No handler registered for command [{$className}]");
    }

    /**
     * Get the given segment from a given class handler.
     *
     * @param  string $className
     * @param  int $segment
     * @return string
     */
    protected function getMappingSegment($className, $segment)
    {
        return explode('@', $this->mappings[$className])[$segment];
    }

    /**
     * Get the given segment from a given class handler using the custom mapper.
     *
     * @param  mixed $command
     * @param  int $segment
     * @return string
     */
    protected function getMapperSegment($command, $segment)
    {
        return explode('@', call_user_func($this->mapper, $command))[$segment];
    }

    /**
     * Register command-to-handler mappings.
     *
     * @param  array $commands
     * @return void
     */
    public function maps(array $commands)
    {
        $this->mappings = array_merge($this->mappings, $commands);
    }

    /**
     * Register a fallback mapper callback.
     *
     * @param  \Closure $mapper
     * @return void
     */
    public function mapUsing(Closure $mapper)
    {
        $this->mapper = $mapper;
    }

    /**
     * Map the command to a handler within a given root namespace.
     *
     * @param  mixed $command
     * @param  string $commandNamespace
     * @param  string $handlerNamespace
     * @return string
     */
    public static function simpleMapping($command, $commandNamespace, $handlerNamespace)
    {
        $command = str_replace($commandNamespace, '', get_class($command));

        return $handlerNamespace . '\\' . trim($command, '\\') . 'Handler@handle';
    }

    /**
     * Set the pipes through which commands should be piped before dispatching.
     *
     * @param  array $pipes
     * @return $this
     */
    public function pipeThrough(array $pipes)
    {
        $this->pipes = $pipes;

        return $this;
    }

}