scyrizales/lambda.js

## lambda.js
function isBotUserAgent(request) {
    /*VALIDATE request.headers.user-agent*/
    /**
    Facebook: facebookexternalhit/1.1

    Twitter: Twitterbot

    Google: Googlebot

    Slack: Slack

    LinkedIn: LinkedInBot/1.0

    Pinterest: Pinterest
     */
}

exports.handler = (event, context, callback) => {
    const request = event.Records[0].cf.request;
    if (!isBotUserAgent(request)) {
        callback(null, request);
    }

    const uri = request.uri;

    const id = uri.split('/')[2]
    const params = {
        TableName: 'my_table',
        Key: {
            "id": id
        }
    };
    docClient.get(params, (err, data) => {
        if (err) {
            callback(err, null)
        } else if (!data.Item) {
            const errorObj = {
                errorType : "NotFound",
                httpStatus : 404,
                requestId : context.awsRequestId,
                message : "Public tour was not found."
            }
            callback(JSON.stringify(errorObj));
        } else {
            const metaTags = generateMetaTags(data);
            const metaTagTemplate = generateMetaTagTemplate(metaTags);
            /* Generate HTTP response */
            const response = {
                status: '200',
                statusDescription: 'HTTP OK',
                httpVersion: httpVersion,
                body: metaTagTemplate,
                headers: {
                    'cache-control': [{
                        key: 'Cache-Control',
                        value: 'max-age=100'
                    }],
                    'content-type': [{
                        key: 'Content-Type',
                        value: 'text/html'
                    }]
                }
            };
            callback(null, response);
        }
    });
};

## sample.html
<!DOCTYPE html>
   <html>
    <head>
      <!-- COMMON TAGS -->
      <meta charset="utf-8">
      <title>${data.title}</title>
      <!-- Search Engine -->
      <meta name="description" content="${data.description}">
      <meta name="image" content="${data.imgSrc}">
      <!-- Schema.org for Google -->
      <meta itemprop="name" content="${data.title}">
      <meta itemprop="description" content="${data.description}">
      <meta itemprop="image" content="imgSrc">

      <!-- Open Graph general (Facebook, Pinterest & Google+) -->
      <meta prefix="og: http://ogp.me/ns#" name="og:type"             content="website">
      <meta prefix="og: http://ogp.me/ns#" name="og:title" content="${data.title}">
      <meta prefix="og: http://ogp.me/ns#" name="og:description" content="${data.description}">
      <meta prefix="og: http://ogp.me/ns#" name="og:image" content="${agent.includes('LinkedIn') ? data.imgSrc+'.jpg' : data.imgSrc}">
      <meta prefix="og: http://ogp.me/ns#" name="og:url" content="${data.url}">
      <meta prefix="og: http://ogp.me/ns#" name="og:site_name" content="${data.title}">
    </head>
    <body>
      <p>uri: ${uri}</p>
      <p>agent: ${agent}</p>
      <p>name: ${data.title}</p>
      <p>description: ${data.description} </p>
    </body>
 </html>
	function isBotUserAgent(request) {
	/VALIDATE request.headers.user-agent/
	/**
	Facebook: facebookexternalhit/1.1

	Twitter: Twitterbot

	Google: Googlebot

	Slack: Slack

	LinkedIn: LinkedInBot/1.0

	Pinterest: Pinterest
	*/
	}

	exports.handler = (event, context, callback) => {
	const request = event.Records[0].cf.request;
	if (!isBotUserAgent(request)) {
	callback(null, request);
	}

	const uri = request.uri;

	const id = uri.split('/')[2]
	const params = {
	TableName: 'my_table',
	Key: {
	"id": id
	}
	};
	docClient.get(params, (err, data) => {
	if (err) {
	callback(err, null)
	} else if (!data.Item) {
	const errorObj = {
	errorType : "NotFound",
	httpStatus : 404,
	requestId : context.awsRequestId,
	message : "Public tour was not found."
	}
	callback(JSON.stringify(errorObj));
	} else {
	const metaTags = generateMetaTags(data);
	const metaTagTemplate = generateMetaTagTemplate(metaTags);
	/* Generate HTTP response */
	const response = {
	status: '200',
	statusDescription: 'HTTP OK',
	httpVersion: httpVersion,
	body: metaTagTemplate,
	headers: {
	'cache-control': [{
	key: 'Cache-Control',
	value: 'max-age=100'
	}],
	'content-type': [{
	key: 'Content-Type',
	value: 'text/html'
	}]
	}
	};
	callback(null, response);
	}
	});
	};
	<!DOCTYPE html>
	<html>
	<head>
	<!-- COMMON TAGS -->
	<meta charset="utf-8">
	<title>${data.title}</title>
	<!-- Search Engine -->
	<meta name="description" content="${data.description}">
	<meta name="image" content="${data.imgSrc}">
	<!-- Schema.org for Google -->
	<meta itemprop="name" content="${data.title}">
	<meta itemprop="description" content="${data.description}">
	<meta itemprop="image" content="imgSrc">

	<!-- Open Graph general (Facebook, Pinterest & Google+) -->
	<meta prefix="og: http://ogp.me/ns#" name="og:type" content="website">
	<meta prefix="og: http://ogp.me/ns#" name="og:title" content="${data.title}">
	<meta prefix="og: http://ogp.me/ns#" name="og:description" content="${data.description}">
	<meta prefix="og: http://ogp.me/ns#" name="og:image" content="${agent.includes('LinkedIn') ? data.imgSrc+'.jpg' : data.imgSrc}">
	<meta prefix="og: http://ogp.me/ns#" name="og:url" content="${data.url}">
	<meta prefix="og: http://ogp.me/ns#" name="og:site_name" content="${data.title}">
	</head>
	<body>
	<p>uri: ${uri}</p>
	<p>agent: ${agent}</p>
	<p>name: ${data.title}</p>
	<p>description: ${data.description} </p>
	</body>
	</html>