path: root/src/HTML5/Parser/DOMTreeBuilder.php

<?php
namespace Masterminds\HTML5\Parser;

use Masterminds\HTML5\Elements;

/**
 * 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 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 $stack = array();

    protected $current; // Pointer in the tag hierarchy.
    protected $doc;

    protected $processor;

    protected $insertMode = 0;

    /**
     * Quirks mode is enabled by default.
     * Any document that is missing the
     * DT will be considered to be in quirks mode.
     */
    protected $quirks = TRUE;

    public $isFragment = FALSE;

    public function __construct($isFragment = FALSE)
    {
        $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, NULL, $dt);
        $this->doc->errors = array();

        // $this->current = $this->doc->documentElement;
        $this->current = $this->doc; // ->documentElement;

        // Create a rules engine for tags.
        $this->rules = new TreeBuildingRules($this->doc);

        if ($isFragment) {
            $this->isFragment = TRUE;
            $this->insertMode = static::IM_IN_BODY;
            $ele = $this->doc->createElement('html');
            $this->doc->appendChild($ele);
            $this->current = $ele;
        }
    }

    /**
     * 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 \DOMFragmentDocumentFragment
     */
    public function fragment()
    {
        $append = $this->doc->documentElement->childNodes;
        $frag = $this->doc->createDocumentFragment();

        // appendChild() modifies the DOMNodeList, so we
        // have to buffer up the items first, then use the
        // array buffer and loop twice.
        $buffer = array();
        foreach ($append as $node) {
            $buffer[] = $node;
        }

        foreach ($buffer as $node) {
            $frag->appendChild($node);
        }

        $frag->errors = $this->doc->errors;

        return $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.
     */
    public function setInstructionProcessor(\Masterminds\HTML5\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
     */
    public function startTag($name, $attributes = array(), $selfClosing = FALSE)
    {
        // fprintf(STDOUT, $name);
        $lname = $this->normalizeTagName($name);

        // Make sure we have an html element.
        if (! $this->doc->documentElement && $name !== 'html') {
            $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."
        if ($name == 'image') {
            $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);
        }

        try {
            $ele = $this->doc->createElement($lname);
        } catch (\DOMException $e) {
            $this->parseError("Illegal tag name: <$lname>. Replaced with <invalid>.");
            $ele = $this->doc->createElement('invalid');
        }

        foreach ($attributes as $aName => $aVal) {

            if ($this->insertMode == static::IM_IN_SVG) {
                $aName = Elements::normalizeSvgAttribute($aName);
            } elseif ($this->insertMode == static::IM_IN_MATHML) {
                $aName = Elements::normalizeMathMlAttribute($aName);
            }

            try {
                $ele->setAttribute($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 ($aName == 'id') {
                $ele->setIdAttribute('id', TRUE);
            }
        }

        // Some elements have special processing rules. Handle those separately.
        if ($this->rules->hasRules($name)) {
            $this->current = $this->rules->evaluate($ele, $this->current);
        }         // Otherwise, it's a standard element.
        else {
            $this->current->appendChild($ele);

            // XXX: Need to handle self-closing tags and unary tags.
            if (! Elements::isA($name, Elements::VOID_TAG)) {
                $this->current = $ele;
            }
        }

        // 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 && $name != 'head' && $name != 'html') {
            $this->insertMode = static::IM_IN_BODY;
        }

        // 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);

        // Ignore closing tags for unary elements.
        if (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);
        }

        // XXX: Not sure whether we need this anymore.
        // if ($name != $lname) {
        // return $this->quirksTreeResolver($lname);
        // }

        // XXX: HTML has no parent. What do we do, though,
        // if this element appears in the wrong place?
        if ($lname == 'html') {
            return;
        }

        // $this->current = $this->current->parentNode;
        if (! $this->autoclose($lname)) {
            $this->parseError('Could not find closing tag for ' . $lname);
        }

        // switch ($this->insertMode) {
        switch ($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\n\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\n\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->doc->errors[] = sprintf("Line %d, Col %d: %s", $line, $col, $msg);
    }

    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 (isset($this->processor)) {
            $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 $name
     *            The tag name.
     * @return string The normalized tag name.
     */
    protected function normalizeTagName($name)
    {
        /*
         * 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 $name;
    }

    protected function quirksTreeResolver($name)
    {
        throw new \Exception("Not implemented.");
    }

    /**
     * Automatically climb the tree and close the closest node with the matching $tag.
     */
    protected function autoclose($tag)
    {
        $working = $this->current;
        do {
            if ($working->nodeType != XML_ELEMENT_NODE) {
                return FALSE;
            }
            if ($working->tagName == $tag) {
                $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 $this->current matches the given tag
     * name, this returns TRUE.
     */
    protected function isAncestor($tagname)
    {
        $candidate = $this->current;
        while ($candidate->nodeType === XML_ELEMENT_NODE) {
            if ($candidate->tagName == $tagname) {
                return TRUE;
            }
            $candidate = $candidate->parentNode;
        }

        return FALSE;
    }

    /**
     * Returns TRUE if the immediate parent element is of the given tagname.
     */
    protected function isParent($tagname)
    {
        return $this->current->tagName == $tagname;
    }
}