text: <?php
  namespace GuzzleHttp\Psr7;
  
  use Psr\Http\Message\StreamInterface;
  
  /**
   * Trait implementing functionality common to requests and responses.
   */
  trait MessageTrait
  {
      /** @var array Map of all registered headers, as original name => array of values */
      private $headers = [];
  
      /** @var array Map of lowercase header name => original name at registration */
      private $headerNames  = [];
  
      /** @var string */
      private $protocol = '1.1';
  
      /** @var StreamInterface */
      private $stream;
  
      public function getProtocolVersion()
      {
          return $this->protocol;
      }
  
      public function withProtocolVersion($version)
      {
          if ($this->protocol === $version) {
              return $this;
          }
  
          $new = clone $this;
          $new->protocol = $version;
          return $new;
      }
  
      public function getHeaders()
      {
          return $this->headers;
      }
  
      public function hasHeader($header)
      {
          return isset($this->headerNames[strtolower($header)]);
      }
  
      public function getHeader($header)
      {
          $header = strtolower($header);
  
          if (!isset($this->headerNames[$header])) {
              return [];
          }
  
          $header = $this->headerNames[$header];
  
          return $this->headers[$header];
      }
  
      public function getHeaderLine($header)
      {
          return implode(', ', $this->getHeader($header));
      }
  
      public function withHeader($header, $value)
      {
          $this->assertHeader($header);
          $value = $this->normalizeHeaderValue($value);
          $normalized = strtolower($header);
  
          $new = clone $this;
          if (isset($new->headerNames[$normalized])) {
              unset($new->headers[$new->headerNames[$normalized]]);
          }
          $new->headerNames[$normalized] = $header;
          $new->headers[$header] = $value;
  
          return $new;
      }
  
      public function withAddedHeader($header, $value)
      {
          $this->assertHeader($header);
          $value = $this->normalizeHeaderValue($value);
          $normalized = strtolower($header);
  
          $new = clone $this;
          if (isset($new->headerNames[$normalized])) {
              $header = $this->headerNames[$normalized];
              $new->headers[$header] = array_merge($this->headers[$header], $value);
          } else {
              $new->headerNames[$normalized] = $header;
              $new->headers[$header] = $value;
          }
  
          return $new;
      }
  
      public function withoutHeader($header)
      {
          $normalized = strtolower($header);
  
          if (!isset($this->headerNames[$normalized])) {
              return $this;
          }
  
          $header = $this->headerNames[$normalized];
  
          $new = clone $this;
          unset($new->headers[$header], $new->headerNames[$normalized]);
  
          return $new;
      }
  
      public function getBody()
      {
          if (!$this->stream) {
              $this->stream = stream_for('');
          }
  
          return $this->stream;
      }
  
      public function withBody(StreamInterface $body)
      {
          if ($body === $this->stream) {
              return $this;
          }
  
          $new = clone $this;
          $new->stream = $body;
          return $new;
      }
  
      private function setHeaders(array $headers)
      {
          $this->headerNames = $this->headers = [];
          foreach ($headers as $header => $value) {
              if (is_int($header)) {
                  // Numeric array keys are converted to int by PHP but having a header name '123' is not forbidden by the spec
                  // and also allowed in withHeader(). So we need to cast it to string again for the following assertion to pass.
                  $header = (string) $header;
              }
              $this->assertHeader($header);
              $value = $this->normalizeHeaderValue($value);
              $normalized = strtolower($header);
              if (isset($this->headerNames[$normalized])) {
                  $header = $this->headerNames[$normalized];
                  $this->headers[$header] = array_merge($this->headers[$header], $value);
              } else {
                  $this->headerNames[$normalized] = $header;
                  $this->headers[$header] = $value;
              }
          }
      }
  
      private function normalizeHeaderValue($value)
      {
          if (!is_array($value)) {
              return $this->trimHeaderValues([$value]);
          }
  
          if (count($value) === 0) {
              throw new \InvalidArgumentException('Header value can not be an empty array.');
          }
  
          return $this->trimHeaderValues($value);
      }
  
      /**
       * Trims whitespace from the header values.
       *
       * Spaces and tabs ought to be excluded by parsers when extracting the field value from a header field.
       *
       * header-field = field-name ":" OWS field-value OWS
       * OWS          = *( SP / HTAB )
       *
       * @param string[] $values Header values
       *
       * @return string[] Trimmed header values
       *
       * @see https://tools.ietf.org/html/rfc7230#section-3.2.4
       */
      private function trimHeaderValues(array $values)
      {
          return array_map(function ($value) {
              if (!is_scalar($value) && null !== $value) {
                  throw new \InvalidArgumentException(sprintf(
                      'Header value must be scalar or null but %s provided.',
                      is_object($value) ? get_class($value) : gettype($value)
                  ));
              }
  
              return trim((string) $value, " \t");
          }, $values);
      }
  
      private function assertHeader($header)
      {
          if (!is_string($header)) {
              throw new \InvalidArgumentException(sprintf(
                  'Header name must be a string but %s provided.',
                  is_object($header) ? get_class($header) : gettype($header)
              ));
          }
  
          if ($header === '') {
              throw new \InvalidArgumentException('Header name can not be empty.');
          }
      }
  }
  