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index.php
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index.php
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<?php
class GitHubMarkdownRender {
const API_URL = 'https://api.github.com/markdown/raw';
const GITHUB_API_VERSION_ACCEPT = 'application/vnd.github.v3+json';
const CONTENT_TYPE = 'text/x-markdown';
const USER_AGENT = 'magnetikonline/ghmarkdownrender 1.0';
const MARKDOWN_EXT = '.md';
const CACHE_SESSION_KEY = 'ghmarkdownrender';
const GITHUB_PERSONAL_ACCESS_TOKEN = 'token';
const DOCUMENT_ROOT = '/path/to/docroot';
public function execute() {
// validate DOCUMENT_ROOT exists
if (!is_dir(self::DOCUMENT_ROOT)) {
$this->renderErrorMessage(
'<p>Given <code>DOCUMENT_ROOT</code> of <code>' . htmlspecialchars(self::DOCUMENT_ROOT) . '</code> is not a valid directory.</p>' .
'<p>Ensure it matches that of your local web server document root.</p>'
);
return;
}
// get requested local markdown page and check file exists
if (($markdownFilePath = $this->getRequestedPageFilePath()) === false) {
$this->renderErrorMessage(
'<p>Unable to determine requested Markdown page.</p>' .
'<p>URI must end with an <code>' . self::MARKDOWN_EXT . '</code> file extension.</p>'
);
return;
}
if (!is_file($markdownFilePath)) {
// can't find markdown file on disk
$this->renderErrorMessage(
'<p>Unable to open <code>' . htmlspecialchars($markdownFilePath) . '</code>.</p>' .
'<p>Ensure <code>DOCUMENT_ROOT</code> matches that of your local web server.</p>'
);
return;
}
// check PHP session for cached markdown response
$html = $this->getMarkdownHtmlFromCache($markdownFilePath);
if ($html !== false) {
// render markdown HTML from cache
echo(
$this->getHtmlPageHeader() .
$html .
$this->getHtmlPageFooter('Rendered from cache')
);
return;
}
// make request to GitHub API passing markdown file source
$response = $this->parseGitHubMarkdownResponse(
$this->doGitHubMarkdownRequest(file_get_contents($markdownFilePath))
);
if (!$response['ok']) {
// error calling API
$this->renderErrorMessage(
'<p>Unable to access GitHub API:</p>' .
'<ul>' .
'<li>Check your <code>GITHUB_PERSONAL_ACCESS_TOKEN</code> is correct (maybe revoked?).</li>' .
'<li>API endpoint <code>' . htmlspecialchars(self::API_URL) . '</code> accessible?</li>' .
'<li>Rate limit exceeded? If so, wait until next hour.</li>' .
'</ul>'
);
return;
}
// save markdown HTML back to cache
$this->setMarkdownHtmlToCache(
$markdownFilePath,
$response['html']
);
// render markdown HTML from API response
echo(
$this->getHtmlPageHeader() .
$response['html'] .
$this->getHtmlPageFooter(
'Rendered from GitHub Markdown API. ' .
'<strong>Rate limit:</strong> ' . $response['rateLimit'] . ' // ' .
'<strong>Rate remain:</strong> ' . $response['rateRemain']
)
);
}
private function getRequestedPageFilePath() {
// get request URI, strip any querystring from end (used to trigger Markdown rendering from web server rewrite rule)
$requestURI = trim($_SERVER['REQUEST_URI']);
$requestURI = preg_replace('/\?.+$/','',$requestURI);
// request URI must end with self::MARKDOWN_EXT
return (preg_match('/\\' . self::MARKDOWN_EXT . '$/',$requestURI))
? self::DOCUMENT_ROOT . $requestURI
: false;
}
private function renderErrorMessage($errorHtml) {
echo(
$this->getHtmlPageHeader() .
'<h1>Error</h1>' .
$errorHtml .
$this->getHtmlPageFooter()
);
}
private function getHtmlPageHeader() {
return <<<EOT
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=Edge" />
<meta name="viewport" content="width=device-width,initial-scale=1" />
<title>GitHub Markdown render</title>
<style>
body {
background: #fff;
color: #333;
font: 16px/1.5 -apple-system,BlinkMacSystemFont,'Segoe UI',Helvetica,Arial,sans-serif,'Apple Color Emoji','Segoe UI Emoji','Segoe UI Symbol';
margin: 20px;
padding: 0;
}
#frame {
border: 1px solid #ddd;
border-radius: 3px;
margin: 0 auto;
width: 978px;
word-wrap: break-word;
}
#markdown {
padding: 45px;
}
#markdown > *:first-child {
margin-top: 0;
}
#markdown > *:last-child {
margin-bottom: 0;
}
h1,h2,h3,h4,h5,h6 {
font-weight: 600;
line-height: 1.25;
margin: 24px 0 16px;
padding: 0;
}
h1,h2 {
padding-bottom: 0.3em;
}
h1 {
border-bottom: 1px solid #eee;
font-size: 2em;
}
h2 {
border-bottom: 1px solid #eee;
font-size: 1.5em;
}
h3 {
font-size: 1.25em;
}
h4 {
font-size: 1em;
}
h5 {
font-size: 0.875em;
}
h6 {
color: #777;
font-size: 0.85em;
}
.anchor {
float: left;
line-height: 1;
margin-left: -20px;
outline: none;
padding-right: 4px;
}
.anchor > .octicon-link {
color: #000;
vertical-align: baseline;
visibility: hidden;
}
.anchor > .octicon-link:before {
content: '\\1f517';
font-size: 16px;
}
h1:hover > .anchor,
h2:hover > .anchor,
h3:hover > .anchor,
h4:hover > .anchor,
h5:hover > .anchor,
h6:hover > .anchor {
text-decoration: none;
}
h1:hover > .anchor > .octicon-link,
h2:hover > .anchor > .octicon-link,
h3:hover > .anchor > .octicon-link,
h4:hover > .anchor > .octicon-link,
h5:hover > .anchor > .octicon-link,
h6:hover > .anchor > .octicon-link {
visibility: visible;
}
a {
color: #0366d6;
text-decoration: none;
}
a:hover {
text-decoration: underline;
}
blockquote,dl,ol,p,pre,table,ul {
margin: 0 0 16px;
padding: 0;
}
blockquote {
border-left: 0.25em solid #ddd;
color: #777;
padding: 0 1em;
}
blockquote > *:first-child {
margin-top: 0;
}
blockquote > *:last-child {
margin-bottom: 0
}
hr {
background: #e1e4e8;
border: 0;
height: 0.25em;
margin: 24px 0;
overflow: hidden;
padding: 0;
}
hr:before,
hr:after {
content: '';
display: table;
}
hr:after {
clear: both;
}
img {
background: #fff;
border: 0;
box-sizing: content-box;
max-width: 100%;
}
kbd {
background: #fafbfc;
border: 1px solid #c6cbd1;
border-bottom-color: #959da5;
border-radius: 3px;
box-shadow: inset 0 -1px 0 #959da5;
color: #444d56;
display: inline-block;
font: 11px/10px 'SFMono-Regular',Consolas,'Liberation Mono',Menlo,Courier,monospace;
padding: 3px 5px;
vertical-align: middle;
}
ol,ul {
padding-left: 2em;
}
ol ol,
ol ul,
ul ol,
ul ul {
margin-bottom: 0;
margin-top: 0;
}
ol ol,
ul ol {
list-style-type: lower-roman;
}
li + li {
margin-top: 0.25em;
}
li > p {
margin-top: 16px;
}
table {
border-collapse: collapse;
border-spacing: 0;
}
table tr {
background: #fff;
border-top: 1px solid #ccc;
}
table tr:nth-child(2n) {
background: #f6f8fa;
}
table th,
table td {
border: 1px solid #ddd;
padding: 6px 13px;
}
table th {
font-weight: bold;
}
code,pre,tt {
font-family: Consolas,'Liberation Mono',Menlo,Courier,monospace;
font-size: 12px;
}
code,tt {
background: rgba(27,31,35,0.05);
border-radius: 3px;
font-size: 85%;
margin: 0;
padding: 0.2em 0;
}
code:before,
code:after,
tt:before,
tt:after {
content: '\\00a0';
letter-spacing: -0.2em;
}
pre {
background: #f6f8fa;
border-radius: 3px;
font-size: 85%;
line-height: 1.45;
overflow: auto;
padding: 16px;
}
pre code,
pre tt {
background: transparent;
border: 0;
margin: 0;
padding: 0;
}
pre > code {
background: transparent;
font-size: 100%;
white-space: pre;
}
pre > code:before,
pre > code:after {
content: normal;
}
h1 code,h1 tt,
h2 code,h2 tt,
h3 code,h3 tt,
h4 code,h4 tt,
h5 code,h5 tt,
h6 code,h6 tt {
font-size: inherit;
}
.highlight { margin-bottom: 16px; }
.pl-ba { color: #586069; }
.pl-bu { color: #b31d28; }
.pl-c { color: #6a737d; }
.pl-c1,.pl-s .pl-v { color: #005cc5; }
.pl-c2 { background-color: #d73a49;color: #fafbfc; }
.pl-corl { color: #032f62;text-decoration: underline; }
.pl-e,.pl-en { color: #6f42c1; }
.pl-ent { color: #22863a; }
.pl-ii { background-color: #b31d28;color: #fafbfc; }
.pl-k { color: #d73a49; }
.pl-mb { color: #24292e;font-weight: bold; }
.pl-mc { background-color: #ffebda;color: #e36209; }
.pl-md { background-color: #ffeef0;color: #b31d28; }
.pl-mdr { color: #6f42c1;font-weight: bold; }
.pl-mh,.pl-mh .pl-en,.pl-ms { color: #005cc5;font-weight: bold; }
.pl-mi { color: #24292e;font-style: italic; }
.pl-mi1 { background-color: #f0fff4;color: #22863a; }
.pl-mi2 { background-color: #005cc5;color: #f6f8fa; }
.pl-ml { color: #735c0f; }
.pl-s,.pl-pds,.pl-s .pl-pse .pl-s1,.pl-sr,.pl-sr .pl-cce,.pl-sr .pl-sre,.pl-sr .pl-sra { color: #032f62; }
.pl-sg { color: #959da5; }
.pl-smi,.pl-s .pl-s1 { color: #24292e; }
.pl-sr .pl-cce { color: #22863a;font-weight: bold; }
.pl-v,.pl-smw { color: #e36209; }
#footer {
color: #777;
font-size: 11px;
margin: 10px auto;
text-align: right;
white-space: nowrap;
width: 978px;
}
</style>
</head>
<body>
<div id="frame"><div id="markdown">
EOT;
}
private function getHtmlPageFooter($footerMessageHtml = false) {
return
'</div></div>' .
(($footerMessageHtml !== false)
? '<p id="footer">' . $footerMessageHtml . '</p>'
: ''
) .
'</body></html>';
}
private function getMarkdownHtmlFromCache($markdownFilePath) {
// start session, look for file path in session space
session_start();
if (!isset($_SESSION[self::CACHE_SESSION_KEY][$markdownFilePath])) {
// file path not found in cache
return false;
}
// file path exists - compare file modification time to that in cache
$cacheData = $_SESSION[self::CACHE_SESSION_KEY][$markdownFilePath];
return ($cacheData['timestamp'] == filemtime($markdownFilePath))
? $cacheData['html']
: false;
}
private function setMarkdownHtmlToCache($markdownFilePath,$html) {
if (!isset($_SESSION[self::CACHE_SESSION_KEY])) {
// create new session cache structure
$_SESSION[self::CACHE_SESSION_KEY] = [];
}
$_SESSION[self::CACHE_SESSION_KEY][$markdownFilePath] = [
'timestamp' => filemtime($markdownFilePath),
'html' => $html
];
}
private function doGitHubMarkdownRequest($markdownSource) {
$curl = curl_init();
curl_setopt_array(
$curl,
[
CURLOPT_HEADER => true,
CURLOPT_HTTPHEADER => [
'Accept: ' . self::GITHUB_API_VERSION_ACCEPT,
'Authorization: token ' . self::GITHUB_PERSONAL_ACCESS_TOKEN,
'Content-Type: ' . self::CONTENT_TYPE,
'User-Agent: ' . self::USER_AGENT
],
CURLOPT_POST => true,
CURLOPT_POSTFIELDS => $markdownSource,
CURLOPT_RETURNTRANSFER => true,
CURLOPT_URL => self::API_URL
]
);
$response = curl_exec($curl);
curl_close($curl);
return $response;
}
private function parseGitHubMarkdownResponse($response) {
$seenHeader = false;
$httpStatusOk = false;
$rateLimit = 0;
$rateRemain = 0;
while (true) {
// seek next CRLF, if not found bail out
$nextEOLpos = strpos($response,"\r\n");
if ($nextEOLpos === false) {
// end of response hit
break;
}
// extract header line and pop off from $response
$headerLine = substr($response,0,$nextEOLpos);
$response = substr($response,$nextEOLpos + 2);
if ($seenHeader && (trim($headerLine) == '')) {
// end of HTTP headers, bail out
break;
}
if (!$seenHeader && preg_match('/^[a-zA-Z-]+:/',$headerLine)) {
// have seen a header item - able to bail out once next blank line detected
$seenHeader = true;
}
if (preg_match('/^Status: (\d+)/',$headerLine,$match)) {
// save HTTP response status, expecting 200 (OK)
$httpStatusOk = (intval($match[1]) == 200);
}
if (preg_match('/^X-RateLimit-Limit: (\d+)$/',$headerLine,$match)) {
// save total allowed request count
$rateLimit = intval($match[1]);
}
if (preg_match('/^X-RateLimit-Remaining: (\d+)$/',$headerLine,$match)) {
// save request count remaining
$rateRemain = intval($match[1]);
}
}
// update id="" values of heading anchor elements from generated Markdown -> HTML
$response = preg_replace(
'/<a id="user-content-([^"]+)" class="anchor" href="/',
'<a id="$1" class="anchor" href="',
$response
);
return [
'ok' => ($httpStatusOk && $rateLimit && $rateRemain),
'rateLimit' => $rateLimit,
'rateRemain' => $rateRemain,
'html' => $response
];
}
}
(new GitHubMarkdownRender())->execute();