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<?php

namespace GuzzleHttp;

use Psr\Http\Message\RequestInterface;

/**

 * Creates a composed Guzzle handler function by stacking middlewares on top of

 * an HTTP handler function.

 */

class HandlerStack

{

    /** @var callable */

    private $handler;

    /** @var array */

    private $stack = [];

    /** @var callable|null */

    private $cached;

    /**

     * Creates a default handler stack that can be used by clients.

     *

     * The returned handler will wrap the provided handler or use the most

     * appropriate default handler for you system. The returned HandlerStack has

     * support for cookies, redirects, HTTP error exceptions, and preparing a body

     * before sending.

     *

     * The returned handler stack can be passed to a client in the "handler"

     * option.

     *

     * @param callable $handler HTTP handler function to use with the stack. If no

     *                          handler is provided, the best handler for your

     *                          system will be utilized.

     *

     * @return HandlerStack

     */

    public static function create(callable $handler = null)

    {

        $stack = new self($handler ?: choose_handler());

        $stack->push(Middleware::httpErrors(), 'http_errors');

        $stack->push(Middleware::redirect(), 'allow_redirects');

        $stack->push(Middleware::cookies(), 'cookies');

        $stack->push(Middleware::prepareBody(), 'prepare_body');

        return $stack;

    }

    /**

     * @param callable $handler Underlying HTTP handler.

     */

    public function __construct(callable $handler = null)

    {

        $this->handler = $handler;

    }

    /**

     * Invokes the handler stack as a composed handler

     *

     * @param RequestInterface $request

     * @param array            $options

     */

    public function __invoke(RequestInterface $request, array $options)

    {

        $handler = $this->resolve();

        return $handler($request, $options);

    }

    /**

     * Dumps a string representation of the stack.

     *

     * @return string

     */

    public function __toString()

    {

        $depth = 0;

        $stack = [];

        if ($this->handler) {

            $stack[] = "0) Handler: " . $this->debugCallable($this->handler);

        }

        $result = '';

        foreach (array_reverse($this->stack) as $tuple) {

            $depth++;

            $str = "{$depth}) Name: '{$tuple[1]}', ";

            $str .= "Function: " . $this->debugCallable($tuple[0]);

            $result = "> {$str}\n{$result}";

            $stack[] = $str;

        }

        foreach (array_keys($stack) as $k) {

            $result .= "< {$stack[$k]}\n";

        }

        return $result;

    }

    /**

     * Set the HTTP handler that actually returns a promise.

     *

     * @param callable $handler Accepts a request and array of options and

     *                          returns a Promise.

     */

    public function setHandler(callable $handler)

    {

        $this->handler = $handler;

        $this->cached = null;

    }

    /**

     * Returns true if the builder has a handler.

     *

     * @return bool

     */

    public function hasHandler()

    {

        return (bool) $this->handler;

    }

    /**

     * Unshift a middleware to the bottom of the stack.

     *

     * @param callable $middleware Middleware function

     * @param string   $name       Name to register for this middleware.

     */

    public function unshift(callable $middleware, $name = null)

    {

        array_unshift($this->stack, [$middleware, $name]);

        $this->cached = null;

    }

    /**

     * Push a middleware to the top of the stack.

     *

     * @param callable $middleware Middleware function

     * @param string   $name       Name to register for this middleware.

     */

    public function push(callable $middleware, $name = '')

    {

        $this->stack[] = [$middleware, $name];

        $this->cached = null;

    }

    /**

     * Add a middleware before another middleware by name.

     *

     * @param string   $findName   Middleware to find

     * @param callable $middleware Middleware function

     * @param string   $withName   Name to register for this middleware.

     */

    public function before($findName, callable $middleware, $withName = '')

    {

        $this->splice($findName, $withName, $middleware, true);

    }

    /**

     * Add a middleware after another middleware by name.

     *

     * @param string   $findName   Middleware to find

     * @param callable $middleware Middleware function

     * @param string   $withName   Name to register for this middleware.

     */

    public function after($findName, callable $middleware, $withName = '')

    {

        $this->splice($findName, $withName, $middleware, false);

    }

    /**

     * Remove a middleware by instance or name from the stack.

     *

     * @param callable|string $remove Middleware to remove by instance or name.

     */

    public function remove($remove)

    {

        $this->cached = null;

        $idx = is_callable($remove) ? 0 : 1;

        $this->stack = array_values(array_filter(

            $this->stack,

            function ($tuple) use ($idx, $remove) {

                return $tuple[$idx] !== $remove;

            }

        ));

    }

    /**

     * Compose the middleware and handler into a single callable function.

     *

     * @return callable

     */

    public function resolve()

    {

        if (!$this->cached) {

            if (!($prev = $this->handler)) {

                throw new \LogicException('No handler has been specified');

            }

            foreach (array_reverse($this->stack) as $fn) {

                $prev = $fn[0]($prev);

            }

            $this->cached = $prev;

        }

        return $this->cached;

    }

    /**

     * @param $name

     * @return int

     */

    private function findByName($name)

    {

        foreach ($this->stack as $k => $v) {

            if ($v[1] === $name) {

                return $k;

            }

        }

        throw new \InvalidArgumentException("Middleware not found: $name");

    }

    /**

     * Splices a function into the middleware list at a specific position.

     *

     * @param          $findName

     * @param          $withName

     * @param callable $middleware

     * @param          $before

     */

    private function splice($findName, $withName, callable $middleware, $before)

    {

        $this->cached = null;

        $idx = $this->findByName($findName);

        $tuple = [$middleware, $withName];

        if ($before) {

            if ($idx === 0) {

                array_unshift($this->stack, $tuple);

            } else {

                $replacement = [$tuple, $this->stack[$idx]];

                array_splice($this->stack, $idx, 1, $replacement);

            }

        } elseif ($idx === count($this->stack) - 1) {

            $this->stack[] = $tuple;

        } else {

            $replacement = [$this->stack[$idx], $tuple];

            array_splice($this->stack, $idx, 1, $replacement);

        }

    }

    /**

     * Provides a debug string for a given callable.

     *

     * @param array|callable $fn Function to write as a string.

     *

     * @return string

     */

    private function debugCallable($fn)

    {

        if (is_string($fn)) {

            return "callable({$fn})";

        }

        if (is_array($fn)) {

            return is_string($fn[0])

                ? "callable({$fn[0]}::{$fn[1]})"

                : "callable(['" . get_class($fn[0]) . "', '{$fn[1]}'])";

        }

        return 'callable(' . spl_object_hash($fn) . ')';

    }

}