WORK IN PROGRESS

jp-infinite-scroll-single.php

<?php

// Plugin name: Jetpack Infinite Scroll for Single Posts

/**
 * Infinite scroll needs to be filtered to function on non-archive pages.
 */
function jisfsp_archive_supported( $supported, $settings ) {
	if ( is_singular( 'post' ) ) {
		return true;
	}
	return $supported;
}
add_filter( 'infinite_scroll_archive_supported', 'jisfsp_archive_supported', 10, 2 );

/**
 * A filter to the infinite scroll settings so we can shove in arbitrary data.
 */
function jisfsp_js_settings( $js_settings ) {
	if ( is_singular( 'post' ) ) {
		$js_settings['id'] = 'main';
		$js_settings['text'] = __( 'Read Next' );
		$js_settings['type'] = 'scroll';

		// mess with $js_settings['query_args'] here!
		$js_settings['query_args']['name'] = null;
		$js_settings['query_args']['post__not_in'][] = get_the_ID();

		// Nip off the page change so the url rewriting won't misparse it.
		$js_settings['history']['path'] = str_replace( 'page/%d/', '', $js_settings['history']['path'] );
	}
	return $js_settings;
}
add_filter( 'infinite_scroll_js_settings', 'jisfsp_js_settings' );

/**
 * Generally infinite scroll won't load if we're on the last page of an archive page.
 *
 * As we're trying to get it to work on single pages,
 */
function jisfsp_is_last_batch( $is_last_batch, $query, $settings ) {
	if ( is_singular( 'post' ) ) {
		return false; // Replace with a check for next post being set
	}
	return $is_last_batch;
}
add_filter( 'infinite_scroll_is_last_batch', 'jisfsp_is_last_batch', 10, 3 );

/**
 * An arbitrary conditional that runs before pages render for any remaining misc bits.
 *
 * As this action runs off WordPress Core actions instead of Infinite Scroll actions we
 * need some extra conditionals to make sure we're not running if IS is disabled.
 */
function jisfsp_all_the_single_posts() {
	if ( ! class_exists( 'Jetpack' ) || ! Jetpack::is_module_active( 'infinite-scroll' ) ) {
		return;
	}

	$settings = The_Neverending_Home_Page::get_settings();

	if ( is_singular( 'post' ) ) {
		wp_register_style( 'jisfsp', null );
		wp_enqueue_style( 'jisfsp' );
		wp_add_inline_style( 'jisfsp', 'nav.post-navigation { display: none; }' );
	}
}
add_action( 'template_redirect', 'jisfsp_all_the_single_posts' );