// Shortcode Form
add_shortcode( 'ccom_jetpack_follow', function( $atts ) {
	if( empty( $atts['redirect'] ) ) { return; }
	ob_start();
	?>
	<form method="POST" action="">
		<input type="hidden" name="ccom_jetpack_follow" value= "1" />
		<input type="hidden" name="redirect" value= "<?php echo $atts['redirect']; ?>" />
		<input type="email" name="email" required="required"
			placeholder="Enter your email address" aria-label="Enter your email address" />
		<input type="submit" value="Download the Presentation (PDF)" />
	</form>
	<?php
	return ob_get_clean();
} );

// Submissions
add_action( 'template_redirect', function() {

	// Get Vars
	$action = isset( $_REQUEST['email'] ) ? esc_attr( $_REQUEST['email'] ) : '';
	$email = isset( $_REQUEST['email'] ) ? esc_attr( $_REQUEST['email'] ) : '';
	$redirect = isset( $_REQUEST['redirect'] ) ? esc_attr( $_REQUEST['redirect'] ) : '';

	// Detect Submission
	if( ! $action === 'ccom_jetpack_follow' || ! $email || ! $redirect ) { return; }

	// JetPack Required
	if( ! class_exists( 'Jetpack_Subscriptions' ) ) { return; }

	// Handle Post ID Provided
	if( intval( $redirect ) ) {
		$redirect = wp_get_attachment_url( $redirect );
	}

	// Subscribe To JetPack
	$response = Jetpack_Subscriptions::subscribe( $email, 0, false );

	// Redirect
	wp_redirect( $redirect );
	exit;
} );