<?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) . ')';
}
}
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