PhutilRemarkupHexColorCodeRule.php
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PhutilRemarkupHexColorCodeRule.php
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	<?php

	final class PhutilRemarkupHexColorCodeRule
	extends PhabricatorRemarkupCustomInlineRule {

	public function getPriority() {
	return 1000.0;
	}

	public function apply($text) {
	// Match {#FFFFFF}
	if (is_string($text)) {
	return preg_replace_callback(
	'@\B\{(#([0-9a-fA-F]{3}){1,2})\}@',
	array($this, 'markupHexColorCodedText'),
	$text);
	}
	return $text;
	}

	protected function contrastingColor($color_code) {
	$match = ltrim($color_code, '#');
	$colors_hex = str_split($match, strlen($match) / 3);
	list($r, $g, $b) = array_map('hexdec', $colors_hex);
	// Calculation adapted from Myndex, CC BY-SA 4.0
	// https://stackoverflow.com/a/69869976
	$y = pow((double)$r / 255.0, 2.2) * 0.2126 +
	pow((double)$g / 255.0, 2.2) * 0.7152 +
	pow((double)$b / 255.0, 2.2) * 0.0722;

	return ($y < 0.34) ? 'white' : 'black';
	}

	protected function markupHexColorCodedText(array $matches) {
	if ($this->getEngine()->isTextMode()) {
	$result = $matches[1];
	} else {
	if (count($matches) < 2) {
	return $matches[0];
	} else {
	$len = strlen($matches[1]);
	if (7 !== $len && 4 !== $len) {
	return $matches[0];
	}
	}
	$match = $matches[1];
	$fg = $this->contrastingColor($match);
	$result = phutil_tag(
	'tt',
	array(
	'class' => 'remarkup-monospaced',
	'style' => "color: {$fg}; background-color: {$match};",
	),
	$match);
	}

	return $this->getEngine()->storeText($result);
	}

	}