Add markdown-export plugin for serving posts/pages as markdown

plugins/markdown-export/plugin.php

@@ -0,0 +1,132 @@
+<?php
+/**
+ * Plugin Name: Markdown Export
+ * Description: Adds the ability to respond with markdown version of posts and pages if the requested path ends with .md
+ */
+
+use WordPress\DataLiberation\DataFormatConsumer\BlocksWithMetadata;
+use WordPress\Markdown\MarkdownProducer;
+
+if ( file_exists( __DIR__ . '/php-toolkit.phar' ) ) {
+	// Production – built and installed plugin
+	require_once __DIR__ . '/php-toolkit.phar';
+} else {
+	// Development – plugin mounted in WordPress via Playground CLI mounts
+	require_once __DIR__ . '/../../vendor/autoload.php';
+}
+
+/**
+ * Handle requests for markdown versions of posts and pages.
+ *
+ * This function intercepts requests where the URL path ends with `.md`
+ * and returns the corresponding post/page content in Markdown format.
+ */
+add_action(
+	'template_redirect',
+	function () {
+		// phpcs:ignore WordPress.Security.ValidatedSanitizedInput.InputNotSanitized -- We need the raw URI path; validation below.
+		$request_uri = isset( $_SERVER['REQUEST_URI'] ) ? wp_unslash( $_SERVER['REQUEST_URI'] ) : '';
+
+		// Check if the request ends with .md
+		if ( ! preg_match( '/\.md$/i', $request_uri ) ) {
+			return;
+		}
+
+		// Remove the .md extension to get the actual post slug/path
+		$path = preg_replace( '/\.md$/i', '', $request_uri );
+		$path = strtok( $path, '?' ); // Remove query string if present
+
+		// Try to find the post by path
+		$post = markdown_export_get_post_by_path( $path );
+
+		if ( ! $post ) {
+			status_header( 404 );
+			// phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- Plain text error response.
+			echo 'Post not found';
+			exit;
+		}
+
+		// Convert the post content to markdown
+		$markdown = markdown_export_convert_post_to_markdown( $post );
+
+		/*
+		 * Use text/markdown MIME type as defined in RFC 7763.
+		 * While not universally standardized, it's the most appropriate
+		 * Content-Type for markdown files.
+		 */
+		header( 'Content-Type: text/markdown; charset=utf-8' );
+
+		// Use rawurlencode for RFC 5987 compliant filename in Content-Disposition header.
+		$filename = rawurlencode( sanitize_file_name( $post->post_name ) . '.md' );
+		header( "Content-Disposition: inline; filename*=UTF-8''" . $filename );
+
+		echo $markdown;
+		exit;
+	}
+);
+
+/**
+ * Get a post by its path/slug.
+ *
+ * @param string $path The URL path to find the post for.
+ * @return WP_Post|null The post object or null if not found.
+ */
+function markdown_export_get_post_by_path( $path ) {
+	// Clean up the path
+	$path = trim( $path, '/' );
+
+	if ( empty( $path ) ) {
+		return null;
+	}
+
+	// Try to get by path as a page (hierarchical)
+	$page = get_page_by_path( $path, OBJECT, array( 'page', 'post' ) );
+	if ( $page ) {
+		return $page;
+	}
+
+	// Try to find by slug for non-hierarchical post types
+	$posts = get_posts(
+		array(
+			'name'           => basename( $path ),
+			'post_type'      => array( 'post', 'page' ),
+			'post_status'    => 'publish',
+			'posts_per_page' => 1,
+		)
+	);
+
+	if ( ! empty( $posts ) ) {
+		return $posts[0];
+	}
+
+	return null;
+}
+
+/**
+ * Convert a post to Markdown format using MarkdownProducer.
+ *
+ * @param WP_Post $post The post to convert.
+ * @return string The markdown representation of the post.
+ */
+function markdown_export_convert_post_to_markdown( $post ) {
+	// Prepare metadata for the markdown frontmatter
+	$metadata = array(
+		'post_title' => array( $post->post_title ),
+		'post_date'  => array( $post->post_date ),
+	);
+
+	// Add excerpt if it has content
+	if ( '' !== $post->post_excerpt ) {
+		$metadata['post_excerpt'] = array( $post->post_excerpt );
+	}
+
+	// Create BlocksWithMetadata and convert to markdown
+	$blocks_with_metadata = new BlocksWithMetadata(
+		$post->post_content,
+		$metadata
+	);
+
+	$producer = new MarkdownProducer( $blocks_with_metadata );
+
+	return $producer->produce();
+}