share-on-mastodon-example.php

<?php

add_filter( 'share_on_mastodon_status', function( $status, $post ) {
	// Apply `the_content` filters so as to have smart quotes and whatnot.
	$status = apply_filters( 'the_content', $post->post_content );

	// Strip tags and shorten.
	$status = wp_trim_words( $status, 25, ' […]' );
	// Prevent double-encoded entities.
	$status = html_entity_decode( $status, ENT_QUOTES | ENT_HTML5, get_bloginfo( 'charset' ) );

	// Add tags as hashtags.
	$tags = get_the_tags( $post );

	if ( $tags && ! is_wp_error( $tags ) ) {
		$status .= "\n\n";

		foreach ( $tags as $tag ) {
			$tag_name = $tag->name;

			if ( preg_match( '/\s+/', $tag_name ) ) {
				// Try to "CamelCase" multi-word tags.
				$tag_name = preg_replace( '/\s+/', ' ', $tag_name );
				$tag_name = explode( ' ', $tag_name );
				$tag_name = implode( '', array_map( 'ucfirst', $tag_name ) );
			}

			$status .= '#' . $tag_name . ' ';
		}

		// Remove (leading and) trailing spaces.
		$status = trim( $status );
	}

	if ( false === strpos( $status, get_permalink( $post ) ) ) {
		// If the permalink is not somehow already part of `$status`, append it.
		$status .= "\n\n" . get_permalink( $post );
	}

	// That's it!
	return $status;
}, 99, 2 );