<?php
  
  namespace Masterminds\HTML5\Parser;
  
  use Masterminds\HTML5\Elements;
  use Masterminds\HTML5\InstructionProcessor;
  
  /**
   * Create an HTML5 DOM tree from events.
   *
   * This attempts to create a DOM from events emitted by a parser. This
   * attempts (but does not guarantee) to up-convert older HTML documents
   * to HTML5. It does this by applying HTML5's rules, but it will not
   * change the architecture of the document itself.
   *
   * Many of the error correction and quirks features suggested in the specification
   * are implemented herein; however, not all of them are. Since we do not
   * assume a graphical user agent, no presentation-specific logic is conducted
   * during tree building.
   *
   * FIXME: The present tree builder does not exactly follow the state machine rules
   * for insert modes as outlined in the HTML5 spec. The processor needs to be
   * re-written to accomodate this. See, for example, the Go language HTML5
   * parser.
   */
  class DOMTreeBuilder implements EventHandler
  {
      /**
       * Defined in http://www.w3.org/TR/html51/infrastructure.html#html-namespace-0.
       */
      const NAMESPACE_HTML = 'http://www.w3.org/1999/xhtml';
  
      const NAMESPACE_MATHML = 'http://www.w3.org/1998/Math/MathML';
  
      const NAMESPACE_SVG = 'http://www.w3.org/2000/svg';
  
      const NAMESPACE_XLINK = 'http://www.w3.org/1999/xlink';
  
      const NAMESPACE_XML = 'http://www.w3.org/XML/1998/namespace';
  
      const NAMESPACE_XMLNS = 'http://www.w3.org/2000/xmlns/';
  
      const OPT_DISABLE_HTML_NS = 'disable_html_ns';
  
      const OPT_TARGET_DOC = 'target_document';
  
      const OPT_IMPLICIT_NS = 'implicit_namespaces';
  
      /**
       * Holds the HTML5 element names that causes a namespace switch.
       *
       * @var array
       */
      protected $nsRoots = array(
          'html' => self::NAMESPACE_HTML,
          'svg' => self::NAMESPACE_SVG,
          'math' => self::NAMESPACE_MATHML,
      );
  
      /**
       * Holds the always available namespaces (which does not require the XMLNS declaration).
       *
       * @var array
       */
      protected $implicitNamespaces = array(
          'xml' => self::NAMESPACE_XML,
          'xmlns' => self::NAMESPACE_XMLNS,
          'xlink' => self::NAMESPACE_XLINK,
      );
  
      /**
       * Holds a stack of currently active namespaces.
       *
       * @var array
       */
      protected $nsStack = array();
  
      /**
       * Holds the number of namespaces declared by a node.
       *
       * @var array
       */
      protected $pushes = array();
  
      /**
       * Defined in 8.2.5.
       */
      const IM_INITIAL = 0;
  
      const IM_BEFORE_HTML = 1;
  
      const IM_BEFORE_HEAD = 2;
  
      const IM_IN_HEAD = 3;
  
      const IM_IN_HEAD_NOSCRIPT = 4;
  
      const IM_AFTER_HEAD = 5;
  
      const IM_IN_BODY = 6;
  
      const IM_TEXT = 7;
  
      const IM_IN_TABLE = 8;
  
      const IM_IN_TABLE_TEXT = 9;
  
      const IM_IN_CAPTION = 10;
  
      const IM_IN_COLUMN_GROUP = 11;
  
      const IM_IN_TABLE_BODY = 12;
  
      const IM_IN_ROW = 13;
  
      const IM_IN_CELL = 14;
  
      const IM_IN_SELECT = 15;
  
      const IM_IN_SELECT_IN_TABLE = 16;
  
      const IM_AFTER_BODY = 17;
  
      const IM_IN_FRAMESET = 18;
  
      const IM_AFTER_FRAMESET = 19;
  
      const IM_AFTER_AFTER_BODY = 20;
  
      const IM_AFTER_AFTER_FRAMESET = 21;
  
      const IM_IN_SVG = 22;
  
      const IM_IN_MATHML = 23;
  
      protected $options = array();
  
      protected $stack = array();
  
      protected $current; // Pointer in the tag hierarchy.
      protected $rules;
      protected $doc;
  
      protected $frag;
  
      protected $processor;
  
      protected $insertMode = 0;
  
      /**
       * Track if we are in an element that allows only inline child nodes.
       *
       * @var string|null
       */
      protected $onlyInline;
  
      /**
       * Quirks mode is enabled by default.
       * Any document that is missing the DT will be considered to be in quirks mode.
       */
      protected $quirks = true;
  
      protected $errors = array();
  
      public function __construct($isFragment = false, array $options = array())
      {
          $this->options = $options;
  
          if (isset($options[self::OPT_TARGET_DOC])) {
              $this->doc = $options[self::OPT_TARGET_DOC];
          } else {
              $impl = new \DOMImplementation();
              // XXX:
              // Create the doctype. For now, we are always creating HTML5
              // documents, and attempting to up-convert any older DTDs to HTML5.
              $dt = $impl->createDocumentType('html');
              // $this->doc = \DOMImplementation::createDocument(NULL, 'html', $dt);
              $this->doc = $impl->createDocument(null, '', $dt);
              $this->doc->encoding = !empty($options['encoding']) ? $options['encoding'] : 'UTF-8';
          }
  
          $this->errors = array();
  
          $this->current = $this->doc; // ->documentElement;
  
          // Create a rules engine for tags.
          $this->rules = new TreeBuildingRules();
  
          $implicitNS = array();
          if (isset($this->options[self::OPT_IMPLICIT_NS])) {
              $implicitNS = $this->options[self::OPT_IMPLICIT_NS];
          } elseif (isset($this->options['implicitNamespaces'])) {
              $implicitNS = $this->options['implicitNamespaces'];
          }
  
          // Fill $nsStack with the defalut HTML5 namespaces, plus the "implicitNamespaces" array taken form $options
          array_unshift($this->nsStack, $implicitNS + array('' => self::NAMESPACE_HTML) + $this->implicitNamespaces);
  
          if ($isFragment) {
              $this->insertMode = static::IM_IN_BODY;
              $this->frag = $this->doc->createDocumentFragment();
              $this->current = $this->frag;
          }
      }
  
      /**
       * Get the document.
       */
      public function document()
      {
          return $this->doc;
      }
  
      /**
       * Get the DOM fragment for the body.
       *
       * This returns a DOMNodeList because a fragment may have zero or more
       * DOMNodes at its root.
       *
       * @see http://www.w3.org/TR/2012/CR-html5-20121217/syntax.html#concept-frag-parse-context
       *
       * @return \DOMDocumentFragment
       */
      public function fragment()
      {
          return $this->frag;
      }
  
      /**
       * Provide an instruction processor.
       *
       * This is used for handling Processor Instructions as they are
       * inserted. If omitted, PI's are inserted directly into the DOM tree.
       *
       * @param InstructionProcessor $proc
       */
      public function setInstructionProcessor(InstructionProcessor $proc)
      {
          $this->processor = $proc;
      }
  
      public function doctype($name, $idType = 0, $id = null, $quirks = false)
      {
          // This is used solely for setting quirks mode. Currently we don't
          // try to preserve the inbound DT. We convert it to HTML5.
          $this->quirks = $quirks;
  
          if ($this->insertMode > static::IM_INITIAL) {
              $this->parseError('Illegal placement of DOCTYPE tag. Ignoring: ' . $name);
  
              return;
          }
  
          $this->insertMode = static::IM_BEFORE_HTML;
      }
  
      /**
       * Process the start tag.
       *
       * @todo - XMLNS namespace handling (we need to parse, even if it's not valid)
       *       - XLink, MathML and SVG namespace handling
       *       - Omission rules: 8.1.2.4 Optional tags
       *
       * @param string $name
       * @param array  $attributes
       * @param bool   $selfClosing
       *
       * @return int
       */
      public function startTag($name, $attributes = array(), $selfClosing = false)
      {
          $lname = $this->normalizeTagName($name);
  
          // Make sure we have an html element.
          if (!$this->doc->documentElement && 'html' !== $name && !$this->frag) {
              $this->startTag('html');
          }
  
          // Set quirks mode if we're at IM_INITIAL with no doctype.
          if ($this->insertMode === static::IM_INITIAL) {
              $this->quirks = true;
              $this->parseError('No DOCTYPE specified.');
          }
  
          // SPECIAL TAG HANDLING:
          // Spec says do this, and "don't ask."
          // find the spec where this is defined... looks problematic
          if ('image' === $name && !($this->insertMode === static::IM_IN_SVG || $this->insertMode === static::IM_IN_MATHML)) {
              $name = 'img';
          }
  
          // Autoclose p tags where appropriate.
          if ($this->insertMode >= static::IM_IN_BODY && Elements::isA($name, Elements::AUTOCLOSE_P)) {
              $this->autoclose('p');
          }
  
          // Set insert mode:
          switch ($name) {
              case 'html':
                  $this->insertMode = static::IM_BEFORE_HEAD;
                  break;
              case 'head':
                  if ($this->insertMode > static::IM_BEFORE_HEAD) {
                      $this->parseError('Unexpected head tag outside of head context.');
                  } else {
                      $this->insertMode = static::IM_IN_HEAD;
                  }
                  break;
              case 'body':
                  $this->insertMode = static::IM_IN_BODY;
                  break;
              case 'svg':
                  $this->insertMode = static::IM_IN_SVG;
                  break;
              case 'math':
                  $this->insertMode = static::IM_IN_MATHML;
                  break;
              case 'noscript':
                  if ($this->insertMode === static::IM_IN_HEAD) {
                      $this->insertMode = static::IM_IN_HEAD_NOSCRIPT;
                  }
                  break;
          }
  
          // Special case handling for SVG.
          if ($this->insertMode === static::IM_IN_SVG) {
              $lname = Elements::normalizeSvgElement($lname);
          }
  
          $pushes = 0;
          // when we found a tag thats appears inside $nsRoots, we have to switch the defalut namespace
          if (isset($this->nsRoots[$lname]) && $this->nsStack[0][''] !== $this->nsRoots[$lname]) {
              array_unshift($this->nsStack, array(
                  '' => $this->nsRoots[$lname],
              ) + $this->nsStack[0]);
              ++$pushes;
          }
          $needsWorkaround = false;
          if (isset($this->options['xmlNamespaces']) && $this->options['xmlNamespaces']) {
              // when xmlNamespaces is true a and we found a 'xmlns' or 'xmlns:*' attribute, we should add a new item to the $nsStack
              foreach ($attributes as $aName => $aVal) {
                  if ('xmlns' === $aName) {
                      $needsWorkaround = $aVal;
                      array_unshift($this->nsStack, array(
                          '' => $aVal,
                      ) + $this->nsStack[0]);
                      ++$pushes;
                  } elseif ('xmlns' === (($pos = strpos($aName, ':')) ? substr($aName, 0, $pos) : '')) {
                      array_unshift($this->nsStack, array(
                          substr($aName, $pos + 1) => $aVal,
                      ) + $this->nsStack[0]);
                      ++$pushes;
                  }
              }
          }
  
          if ($this->onlyInline && Elements::isA($lname, Elements::BLOCK_TAG)) {
              $this->autoclose($this->onlyInline);
              $this->onlyInline = null;
          }
  
          try {
              $prefix = ($pos = strpos($lname, ':')) ? substr($lname, 0, $pos) : '';
  
              if (false !== $needsWorkaround) {
                  $xml = "<$lname xmlns=\"$needsWorkaround\" " . (strlen($prefix) && isset($this->nsStack[0][$prefix]) ? ("xmlns:$prefix=\"" . $this->nsStack[0][$prefix] . '"') : '') . '/>';
  
                  $frag = new \DOMDocument('1.0', 'UTF-8');
                  $frag->loadXML($xml);
  
                  $ele = $this->doc->importNode($frag->documentElement, true);
              } else {
                  if (!isset($this->nsStack[0][$prefix]) || ('' === $prefix && isset($this->options[self::OPT_DISABLE_HTML_NS]) && $this->options[self::OPT_DISABLE_HTML_NS])) {
                      $ele = $this->doc->createElement($lname);
                  } else {
                      $ele = $this->doc->createElementNS($this->nsStack[0][$prefix], $lname);
                  }
              }
          } catch (\DOMException $e) {
              $this->parseError("Illegal tag name: <$lname>. Replaced with <invalid>.");
              $ele = $this->doc->createElement('invalid');
          }
  
          if (Elements::isA($lname, Elements::BLOCK_ONLY_INLINE)) {
              $this->onlyInline = $lname;
          }
  
          // When we add some namespacess, we have to track them. Later, when "endElement" is invoked, we have to remove them.
          // When we are on a void tag, we do not need to care about namesapce nesting.
          if ($pushes > 0 && !Elements::isA($name, Elements::VOID_TAG)) {
              // PHP tends to free the memory used by DOM,
              // to avoid spl_object_hash collisions whe have to avoid garbage collection of $ele storing it into $pushes
              // see https://bugs.php.net/bug.php?id=67459
              $this->pushes[spl_object_hash($ele)] = array($pushes, $ele);
          }
  
          foreach ($attributes as $aName => $aVal) {
              // xmlns attributes can't be set
              if ('xmlns' === $aName) {
                  continue;
              }
  
              if ($this->insertMode === static::IM_IN_SVG) {
                  $aName = Elements::normalizeSvgAttribute($aName);
              } elseif ($this->insertMode === static::IM_IN_MATHML) {
                  $aName = Elements::normalizeMathMlAttribute($aName);
              }
  
              $aVal = (string) $aVal;
  
              try {
                  $prefix = ($pos = strpos($aName, ':')) ? substr($aName, 0, $pos) : false;
  
                  if ('xmlns' === $prefix) {
                      $ele->setAttributeNS(self::NAMESPACE_XMLNS, $aName, $aVal);
                  } elseif (false !== $prefix && isset($this->nsStack[0][$prefix])) {
                      $ele->setAttributeNS($this->nsStack[0][$prefix], $aName, $aVal);
                  } else {
                      $ele->setAttribute($aName, $aVal);
                  }
              } catch (\DOMException $e) {
                  $this->parseError("Illegal attribute name for tag $name. Ignoring: $aName");
                  continue;
              }
  
              // This is necessary on a non-DTD schema, like HTML5.
              if ('id' === $aName) {
                  $ele->setIdAttribute('id', true);
              }
          }
  
          if ($this->frag !== $this->current && $this->rules->hasRules($name)) {
              // Some elements have special processing rules. Handle those separately.
              $this->current = $this->rules->evaluate($ele, $this->current);
          } else {
              // Otherwise, it's a standard element.
              $this->current->appendChild($ele);
  
              if (!Elements::isA($name, Elements::VOID_TAG)) {
                  $this->current = $ele;
              }
  
              // Self-closing tags should only be respected on foreign elements
              // (and are implied on void elements)
              // See: https://www.w3.org/TR/html5/syntax.html#start-tags
              if (Elements::isHtml5Element($name)) {
                  $selfClosing = false;
              }
          }
  
          // This is sort of a last-ditch attempt to correct for cases where no head/body
          // elements are provided.
          if ($this->insertMode <= static::IM_BEFORE_HEAD && 'head' !== $name && 'html' !== $name) {
              $this->insertMode = static::IM_IN_BODY;
          }
  
          // When we are on a void tag, we do not need to care about namesapce nesting,
          // but we have to remove the namespaces pushed to $nsStack.
          if ($pushes > 0 && Elements::isA($name, Elements::VOID_TAG)) {
              // remove the namespaced definded by current node
              for ($i = 0; $i < $pushes; ++$i) {
                  array_shift($this->nsStack);
              }
          }
  
          if ($selfClosing) {
              $this->endTag($name);
          }
  
          // Return the element mask, which the tokenizer can then use to set
          // various processing rules.
          return Elements::element($name);
      }
  
      public function endTag($name)
      {
          $lname = $this->normalizeTagName($name);
  
          // Special case within 12.2.6.4.7: An end tag whose tag name is "br" should be treated as an opening tag
          if ('br' === $name) {
              $this->parseError('Closing tag encountered for void element br.');
  
              $this->startTag('br');
          }
          // Ignore closing tags for other unary elements.
          elseif (Elements::isA($name, Elements::VOID_TAG)) {
              return;
          }
  
          if ($this->insertMode <= static::IM_BEFORE_HTML) {
              // 8.2.5.4.2
              if (in_array($name, array(
                  'html',
                  'br',
                  'head',
                  'title',
              ))) {
                  $this->startTag('html');
                  $this->endTag($name);
                  $this->insertMode = static::IM_BEFORE_HEAD;
  
                  return;
              }
  
              // Ignore the tag.
              $this->parseError('Illegal closing tag at global scope.');
  
              return;
          }
  
          // Special case handling for SVG.
          if ($this->insertMode === static::IM_IN_SVG) {
              $lname = Elements::normalizeSvgElement($lname);
          }
  
          $cid = spl_object_hash($this->current);
  
          // XXX: HTML has no parent. What do we do, though,
          // if this element appears in the wrong place?
          if ('html' === $lname) {
              return;
          }
  
          // remove the namespaced definded by current node
          if (isset($this->pushes[$cid])) {
              for ($i = 0; $i < $this->pushes[$cid][0]; ++$i) {
                  array_shift($this->nsStack);
              }
              unset($this->pushes[$cid]);
          }
  
          if (!$this->autoclose($lname)) {
              $this->parseError('Could not find closing tag for ' . $lname);
          }
  
          switch ($lname) {
              case 'head':
                  $this->insertMode = static::IM_AFTER_HEAD;
                  break;
              case 'body':
                  $this->insertMode = static::IM_AFTER_BODY;
                  break;
              case 'svg':
              case 'mathml':
                  $this->insertMode = static::IM_IN_BODY;
                  break;
          }
      }
  
      public function comment($cdata)
      {
          // TODO: Need to handle case where comment appears outside of the HTML tag.
          $node = $this->doc->createComment($cdata);
          $this->current->appendChild($node);
      }
  
      public function text($data)
      {
          // XXX: Hmmm.... should we really be this strict?
          if ($this->insertMode < static::IM_IN_HEAD) {
              // Per '8.2.5.4.3 The "before head" insertion mode' the characters
              // " \t
  \r\f" should be ignored but no mention of a parse error. This is
              // practical as most documents contain these characters. Other text is not
              // expected here so recording a parse error is necessary.
              $dataTmp = trim($data, " \t
  \r\f");
              if (!empty($dataTmp)) {
                  // fprintf(STDOUT, "Unexpected insert mode: %d", $this->insertMode);
                  $this->parseError('Unexpected text. Ignoring: ' . $dataTmp);
              }
  
              return;
          }
          // fprintf(STDOUT, "Appending text %s.", $data);
          $node = $this->doc->createTextNode($data);
          $this->current->appendChild($node);
      }
  
      public function eof()
      {
          // If the $current isn't the $root, do we need to do anything?
      }
  
      public function parseError($msg, $line = 0, $col = 0)
      {
          $this->errors[] = sprintf('Line %d, Col %d: %s', $line, $col, $msg);
      }
  
      public function getErrors()
      {
          return $this->errors;
      }
  
      public function cdata($data)
      {
          $node = $this->doc->createCDATASection($data);
          $this->current->appendChild($node);
      }
  
      public function processingInstruction($name, $data = null)
      {
          // XXX: Ignore initial XML declaration, per the spec.
          if ($this->insertMode === static::IM_INITIAL && 'xml' === strtolower($name)) {
              return;
          }
  
          // Important: The processor may modify the current DOM tree however it sees fit.
          if ($this->processor instanceof InstructionProcessor) {
              $res = $this->processor->process($this->current, $name, $data);
              if (!empty($res)) {
                  $this->current = $res;
              }
  
              return;
          }
  
          // Otherwise, this is just a dumb PI element.
          $node = $this->doc->createProcessingInstruction($name, $data);
  
          $this->current->appendChild($node);
      }
  
      // ==========================================================================
      // UTILITIES
      // ==========================================================================
  
      /**
       * Apply normalization rules to a tag name.
       * See sections 2.9 and 8.1.2.
       *
       * @param string $tagName
       *
       * @return string The normalized tag name.
       */
      protected function normalizeTagName($tagName)
      {
          /*
           * Section 2.9 suggests that we should not do this. if (strpos($name, ':') !== false) { // We know from the grammar that there must be at least one other // char besides :, since : is not a legal tag start. $parts = explode(':', $name); return array_pop($parts); }
           */
          return $tagName;
      }
  
      protected function quirksTreeResolver($name)
      {
          throw new \Exception('Not implemented.');
      }
  
      /**
       * Automatically climb the tree and close the closest node with the matching $tag.
       *
       * @param string $tagName
       *
       * @return bool
       */
      protected function autoclose($tagName)
      {
          $working = $this->current;
          do {
              if (XML_ELEMENT_NODE !== $working->nodeType) {
                  return false;
              }
              if ($working->tagName === $tagName) {
                  $this->current = $working->parentNode;
  
                  return true;
              }
          } while ($working = $working->parentNode);
  
          return false;
      }
  
      /**
       * Checks if the given tagname is an ancestor of the present candidate.
       *
       * If $this->current or anything above $this->current matches the given tag
       * name, this returns true.
       *
       * @param string $tagName
       *
       * @return bool
       */
      protected function isAncestor($tagName)
      {
          $candidate = $this->current;
          while (XML_ELEMENT_NODE === $candidate->nodeType) {
              if ($candidate->tagName === $tagName) {
                  return true;
              }
              $candidate = $candidate->parentNode;
          }
  
          return false;
      }
  
      /**
       * Returns true if the immediate parent element is of the given tagname.
       *
       * @param string $tagName
       *
       * @return bool
       */
      protected function isParent($tagName)
      {
          return $this->current->tagName === $tagName;
      }
  }