<?php
declare(strict_types=1);
namespace Pelago\Emogrifier\HtmlProcessor;
/**
* This HtmlProcessor can convert style HTML attributes to the corresponding other visual HTML attributes,
* e.g. it converts style="width: 100px" to width="100".
*
* It will only add attributes, but leaves the style attribute untouched.
*
* To trigger the conversion, call the convertCssToVisualAttributes method.
*/
class CssToAttributeConverter extends AbstractHtmlProcessor
{
/**
* This multi-level array contains simple mappings of CSS properties to
* HTML attributes. If a mapping only applies to certain HTML nodes or
* only for certain values, the mapping is an object with a whitelist
* of nodes and values.
*
* @var array<string, array{attribute: string, nodes?: array<int, string>, values?: array<int, string>}>
*/
private $cssToHtmlMap = [
'background-color' => [
'attribute' => 'bgcolor',
],
'text-align' => [
'attribute' => 'align',
'nodes' => ['p', 'div', 'td', 'th'],
'values' => ['left', 'right', 'center', 'justify'],
],
'float' => [
'attribute' => 'align',
'nodes' => ['table', 'img'],
'values' => ['left', 'right'],
],
'border-spacing' => [
'attribute' => 'cellspacing',
'nodes' => ['table'],
],
];
/**
* @var array<string, array<string, string>>
*/
private static $parsedCssCache = [];
/**
* Maps the CSS from the style nodes to visual HTML attributes.
*
* @return self fluent interface
*/
public function convertCssToVisualAttributes(): self
{
/** @var \DOMElement $node */
foreach ($this->getAllNodesWithStyleAttribute() as $node) {
$inlineStyleDeclarations = $this->parseCssDeclarationsBlock($node->getAttribute('style'));
$this->mapCssToHtmlAttributes($inlineStyleDeclarations, $node);
}
return $this;
}
/**
* Returns a list with all DOM nodes that have a style attribute.
*
* @return \DOMNodeList
*/
private function getAllNodesWithStyleAttribute(): \DOMNodeList
{
return $this->getXPath()->query('//*[@style]');
}
/**
* Parses a CSS declaration block into property name/value pairs.
*
* Example:
*
* The declaration block
*
* "color: #000; font-weight: bold;"
*
* will be parsed into the following array:
*
* "color" => "#000"
* "font-weight" => "bold"
*
* @param string $cssDeclarationsBlock the CSS declarations block without the curly braces, may be empty
*
* @return array<string, string>
* the CSS declarations with the property names as array keys and the property values as array values
*/
private function parseCssDeclarationsBlock(string $cssDeclarationsBlock): array
{
if (isset(self::$parsedCssCache[$cssDeclarationsBlock])) {
return self::$parsedCssCache[$cssDeclarationsBlock];
}
$properties = [];
foreach (\preg_split('/;(?!base64|charset)/', $cssDeclarationsBlock) as $declaration) {
/** @var array<int, string> $matches */
$matches = [];
if (!\preg_match('/^([A-Za-z\\-]+)\\s*:\\s*(.+)$/s', \trim($declaration), $matches)) {
continue;
}
$propertyName = \strtolower($matches[1]);
$propertyValue = $matches[2];
$properties[$propertyName] = $propertyValue;
}
self::$parsedCssCache[$cssDeclarationsBlock] = $properties;
return $properties;
}
/**
* Applies $styles to $node.
*
* This method maps CSS styles to HTML attributes and adds those to the
* node.
*
* @param array<string, string> $styles the new CSS styles taken from the global styles to be applied to this node
* @param \DOMElement $node node to apply styles to
*/
private function mapCssToHtmlAttributes(array $styles, \DOMElement $node): void
{
foreach ($styles as $property => $value) {
// Strip !important indicator
$value = \trim(\str_replace('!important', '', $value));
$this->mapCssToHtmlAttribute($property, $value, $node);
}
}
/**
* Tries to apply the CSS style to $node as an attribute.
*
* This method maps a CSS rule to HTML attributes and adds those to the node.
*
* @param string $property the name of the CSS property to map
* @param string $value the value of the style rule to map
* @param \DOMElement $node node to apply styles to
*/
private function mapCssToHtmlAttribute(string $property, string $value, \DOMElement $node): void
{
if (!$this->mapSimpleCssProperty($property, $value, $node)) {
$this->mapComplexCssProperty($property, $value, $node);
}
}
/**
* Looks up the CSS property in the mapping table and maps it if it matches the conditions.
*
* @param string $property the name of the CSS property to map
* @param string $value the value of the style rule to map
* @param \DOMElement $node node to apply styles to
*
* @return bool true if the property can be mapped using the simple mapping table
*/
private function mapSimpleCssProperty(string $property, string $value, \DOMElement $node): bool
{
if (!isset($this->cssToHtmlMap[$property])) {
return false;
}
$mapping = $this->cssToHtmlMap[$property];
$nodesMatch = !isset($mapping['nodes']) || \in_array($node->nodeName, $mapping['nodes'], true);
$valuesMatch = !isset($mapping['values']) || \in_array($value, $mapping['values'], true);
$canBeMapped = $nodesMatch && $valuesMatch;
if ($canBeMapped) {
$node->setAttribute($mapping['attribute'], $value);
}
return $canBeMapped;
}
/**
* Maps CSS properties that need special transformation to an HTML attribute.
*
* @param string $property the name of the CSS property to map
* @param string $value the value of the style rule to map
* @param \DOMElement $node node to apply styles to
*/
private function mapComplexCssProperty(string $property, string $value, \DOMElement $node): void
{
switch ($property) {
case 'background':
$this->mapBackgroundProperty($node, $value);
break;
case 'width':
// intentional fall-through
case 'height':
$this->mapWidthOrHeightProperty($node, $value, $property);
break;
case 'margin':
$this->mapMarginProperty($node, $value);
break;
case 'border':
$this->mapBorderProperty($node, $value);
break;
default:
}
}
/**
* @param \DOMElement $node node to apply styles to
* @param string $value the value of the style rule to map
*/
private function mapBackgroundProperty(\DOMElement $node, string $value): void
{
// parse out the color, if any
/** @var array<int, string> $styles */
$styles = \explode(' ', $value, 2);
$first = $styles[0];
if (\is_numeric($first[0]) || \strncmp($first, 'url', 3) === 0) {
return;
}
// as this is not a position or image, assume it's a color
$node->setAttribute('bgcolor', $first);
}
/**
* @param \DOMElement $node node to apply styles to
* @param string $value the value of the style rule to map
* @param string $property the name of the CSS property to map
*/
private function mapWidthOrHeightProperty(\DOMElement $node, string $value, string $property): void
{
// only parse values in px and %, but not values like "auto"
if (!\preg_match('/^(\\d+)(\\.(\\d+))?(px|%)$/', $value)) {
return;
}
$number = \preg_replace('/[^0-9.%]/', '', $value);
$node->setAttribute($property, $number);
}
/**
* @param \DOMElement $node node to apply styles to
* @param string $value the value of the style rule to map
*/
private function mapMarginProperty(\DOMElement $node, string $value): void
{
if (!$this->isTableOrImageNode($node)) {
return;
}
$margins = $this->parseCssShorthandValue($value);
if ($margins['left'] === 'auto' && $margins['right'] === 'auto') {
$node->setAttribute('align', 'center');
}
}
/**
* @param \DOMElement $node node to apply styles to
* @param string $value the value of the style rule to map
*/
private function mapBorderProperty(\DOMElement $node, string $value): void
{
if (!$this->isTableOrImageNode($node)) {
return;
}
if ($value === 'none' || $value === '0') {
$node->setAttribute('border', '0');
}
}
/**
* @param \DOMElement $node
*
* @return bool
*/
private function isTableOrImageNode(\DOMElement $node): bool
{
return $node->nodeName === 'table' || $node->nodeName === 'img';
}
/**
* Parses a shorthand CSS value and splits it into individual values. For example: `padding: 0 auto;` - `0 auto` is
* split into top: 0, left: auto, bottom: 0, right: auto.
*
* @param string $value a CSS property value with 1, 2, 3 or 4 sizes
*
* @return array<string, string>
* an array of values for top, right, bottom and left (using these as associative array keys)
*/
private function parseCssShorthandValue(string $value): array
{
/** @var array<int, string> $values */
$values = \preg_split('/\\s+/', $value);
$css = [];
$css['top'] = $values[0];
$css['right'] = (\count($values) > 1) ? $values[1] : $css['top'];
$css['bottom'] = (\count($values) > 2) ? $values[2] : $css['top'];
$css['left'] = (\count($values) > 3) ? $values[3] : $css['right'];
return $css;
}
}