Customizing Newsletter Glue for WordPress post notifications

<?php

class JCH_Newsletter_Glue_Customization_Email_Content {

	protected $logo_url           = null;
	protected $logo_height        = null;
	protected $logo_width         = null;
	protected $twitter_handle     = null;
	protected $permalink          = null;
	protected $twitter_share_url  = null;
	protected $facebook_share_url = null;

	protected $site_config = array(
		'chrishardie.com'      => array(
			'logo_url'       => 'https://chrishardie.com/wp-content/uploads/2018/05/chris-logo-unpadded-480.png',
			'logo_width'     => 480,
			'logo_height'    => 90,
			'twitter_handle' => '@ChrisHardie',
		),
		'tech.chrishardie.com' => array(
			'logo_url'       => 'https://tech.chrishardie.com/wp-content/uploads/2020/06/chris-tech-logo-300x80.png',
			'logo_width'     => 300,
			'logo_height'    => 80,
			'twitter_handle' => '@ChrisHardie',
		),
	);

	public function __construct() {

		$site_domain = wp_parse_url( site_url(), PHP_URL_HOST );

		$this->set_vars( $site_domain );

		add_filter( 'newsletterglue_email_content_header', array( $this, 'generate_header' ), 10, 3 );
		add_filter( 'newsletterglue_email_content_footer', array( $this, 'generate_footer' ), 10, 3 );
	}

	public function set_vars( $site_domain = null ): void {
		if ( ! empty( $site_domain ) && ! empty( $this->site_config[ $site_domain ] ) ) {
			$this->logo_url       = $this->site_config[ $site_domain ]['logo_url'];
			$this->logo_width     = $this->site_config[ $site_domain ]['logo_width'];
			$this->logo_height    = $this->site_config[ $site_domain ]['logo_height'];
			$this->twitter_handle = $this->site_config[ $site_domain ]['twitter_handle'];
		} else {
			$this->set_vars( 'chrishardie.com' );
		}
	}

	public function generate_header( $content, $app, $post ) {
		ob_start();
		include plugin_dir_path( __DIR__ ) . 'partials/header.php';
		$header_content = ob_get_clean();
		$content       .= $header_content;
		return $content;
	}

	public function generate_footer( $content, $app, $post ) {
		$this->set_social_share_links( $post );

		ob_start();
		include plugin_dir_path( __DIR__ ) . 'partials/footer.php';
		$footer_content = ob_get_clean();
		$content       .= $footer_content;
		return $content;
	}

	public function set_social_share_links( $post ) {

		$this->permalink = get_the_permalink( $post );

		$this->twitter_share_url = add_query_arg(
			array(
				'url'  => get_the_permalink( $post ),
				'text' => get_the_title( $post ) . ' by ' . $this->twitter_handle,
			),
			'https://twitter.com/intent/tweet'
		);

		$this->facebook_share_url = add_query_arg(
			array(
				'u' => get_the_permalink( $post ),
			),
			'https://www.facebook.com/sharer/sharer.php'
		);
	}
}
new JCH_Newsletter_Glue_Customization_Email_Content();

<?php

?>

<table style="...">
	<tbody>
		<tr>
			<td style="...">
				<a href="<?php echo esc_url( site_url() ); ?>"><img src="<?php echo esc_url( $this->logo_url ); ?>"
					height="<?php echo esc_attr( $this->logo_height ); ?>"
					width="<?php echo esc_attr( $this->logo_width ); ?>"
					alt="<?php echo esc_html( get_bloginfo( 'name' ) ); ?> Logo"
					class="jch-ng-logo"
					style="..."
				/></a>
			</td>
		</tr>
	</tbody>
</table>
<p style="...">&nbsp;</p>
<table align="left" border="0" cellpadding="0" cellspacing="0" style="...">
	<tbody>
		<tr>
			<td valign="top" style='...'>
				<div>
					<span class="metadata post-date" style='...'>
						<?php echo get_the_date( 'F j, Y', $post ); ?>
					</span>
				</div>
			</td>
		</tr>
	</tbody>
</table>

<?php

?>
<table align="left" border="0" cellpadding="0" cellspacing="0" style="...">
	<tbody>
	<tr>
		<td valign="top" style='...'>
			<ul>
				<li><a href="<?php echo esc_url( $this->permalink ); ?>">Read or comment on this on the web</a></li>
				<li><a href="<?php echo esc_url( $this->facebook_share_url ); ?>">Share on Facebook</a></li>
				<li><a href="<?php echo esc_url( $this->twitter_share_url ); ?>">Share on Twitter</a></li>
			</ul>
			<p>
				Thanks for signing up to get updates from <a href="<?php echo esc_url( site_url() ); ?>"><?php echo esc_html( get_bloginfo( 'name' ) ); ?></a>.
				Don't want to get an email for every new post? <a href="*|UPDATE_PROFILE|*">Update your subscription preferences</a>.
			</p>
		</td>
	</tr>
	</tbody>
</table>