diff --git a/packages/playground/data-liberation/bootstrap.php b/packages/playground/data-liberation/bootstrap.php
index eb6d45c096..4b0a206079 100644
--- a/packages/playground/data-liberation/bootstrap.php
+++ b/packages/playground/data-liberation/bootstrap.php
@@ -55,6 +55,8 @@
 require_once __DIR__ . '/src/import/WP_Attachment_Downloader_Event.php';
 require_once __DIR__ . '/src/import/WP_Stream_Importer.php';
 require_once __DIR__ . '/src/import/WP_Markdown_Importer.php';
+require_once __DIR__ . '/src/import/WP_Logger.php';
+require_once __DIR__ . '/src/import/WP_Topological_Sorter.php';
 
 require_once __DIR__ . '/src/utf8_decoder.php';
 
diff --git a/packages/playground/data-liberation/plugin.php b/packages/playground/data-liberation/plugin.php
index 5f383b4a69..d49d692a85 100644
--- a/packages/playground/data-liberation/plugin.php
+++ b/packages/playground/data-liberation/plugin.php
@@ -27,20 +27,10 @@
 
 add_action('init', function() {
     if ( defined( 'WP_CLI' ) && WP_CLI ) {
-        /**
-         * Import a WXR file.
-         *
-         * <file>
-         * : The WXR file to import.
-         */
-        $command = function ( $args, $assoc_args ) {
-            $file = $args[0];
-            data_liberation_import( $file );
-        };
+        require_once __DIR__ . '/src/cli/WP_Import_Command.php';
 
         // Register the WP-CLI import command.
-		// Example usage: wp data-liberation /path/to/file.xml
-        WP_CLI::add_command( 'data-liberation', $command );
+        WP_CLI::add_command( 'data-liberation', WP_Import_Command::class );
     }
 });
 
diff --git a/packages/playground/data-liberation/src/cli/WP_Import_Command.php b/packages/playground/data-liberation/src/cli/WP_Import_Command.php
new file mode 100644
index 0000000000..fe49ced08e
--- /dev/null
+++ b/packages/playground/data-liberation/src/cli/WP_Import_Command.php
@@ -0,0 +1,173 @@
+<?php
+
+require_once __DIR__ . '/WP_Import_Logger.php';
+
+/**
+ * Implements the `wp data-liberation` command.
+ *
+ * ## EXAMPLES
+ *
+ *     # Import a WXR file.
+ *     wp data-liberation import /path/to/file.xml
+ *
+ *     # Import all files inside a folder.
+ *     wp data-liberation import /path/to/folder
+ *
+ *     # Import a WXR file from a URL.
+ *     wp data-liberation import http://example.com/file.xml
+ *
+ *     Success: Imported data.
+ */
+class WP_Import_Command {
+	/**
+	 * @var bool $dry_run Whether to perform a dry run.
+	 */
+	private $dry_run = false;
+
+	/**
+	 * @var WP_Stream_Importer $importer The importer instance.
+	 */
+	private $importer = null;
+
+	private $wxr_path = '';
+
+	/**
+	 * Import a WXR file.
+	 *
+	 * ## OPTIONS
+	 *
+	 * <path>
+	 * : The path to the WXR file. Either a file, a directory or a URL.
+	 *
+	 * [--dry-run]
+	 * : Perform a dry run if set.
+	 *
+	 * ## EXAMPLES
+	 *
+	 *     wp data-liberation import /path/to/file.xml
+	 *
+	 * @param array $args
+	 * @param array $assoc_args
+	 * @return void
+	 */
+	public function import( $args, $assoc_args ) {
+		$path          = $args[0];
+		$this->dry_run = WP_CLI\Utils\get_flag_value( $assoc_args, 'dry-run', false );
+		$options       = array(
+			'logger' => new WP_Import_logger(),
+		);
+
+		if ( extension_loaded( 'pcntl' ) ) {
+			// Set the signal handler.
+			$this->register_handlers();
+		}
+
+		if ( filter_var( $path, FILTER_VALIDATE_URL ) ) {
+			// Import URL.
+			$this->import_wxr_url( $path, $options );
+		} elseif ( is_dir( $path ) ) {
+			$count = 0;
+			// Get all the WXR files in the directory.
+			foreach ( wp_visit_file_tree( $path ) as $event ) {
+				foreach ( $event->files as $file ) {
+					if ( $file->isFile() && 'xml' === pathinfo( $file->getPathname(), PATHINFO_EXTENSION ) ) {
+						++$count;
+
+						// Import the WXR file.
+						$this->import_wxr_file( $file->getPathname(), $options );
+					}
+				}
+			}
+
+			if ( ! $count ) {
+				WP_CLI::error( WP_CLI::colorize( "No WXR files found in the {$path} directory" ) );
+			}
+		} else {
+			if ( ! is_file( $path ) ) {
+				WP_CLI::error( WP_CLI::colorize( "File not found: %R{$path}%n" ) );
+			}
+
+			// Import the WXR file.
+			$this->import_wxr_file( $path, $options );
+		}
+	}
+
+	/**
+	 * Import a WXR file.
+	 *
+	 * @param string $file_path The path to the WXR file.
+	 * @return void
+	 */
+	private function import_wxr_file( $file_path, $options = array() ) {
+		$this->wxr_path = $file_path;
+		$this->importer = WP_Stream_Importer::create_for_wxr_file( $file_path, $options );
+
+		$this->import_wxr();
+	}
+
+	/**
+	 * Import a WXR file from a URL.
+	 *
+	 * @param string $url The URL to the WXR file.
+	 * @return void
+	 */
+	private function import_wxr_url( $url, $options = array() ) {
+		$this->wxr_path = $url;
+		$this->importer = WP_Stream_Importer::create_for_wxr_url( $url, $options );
+
+		$this->import_wxr();
+	}
+
+	/**
+	 * Import the WXR file.
+	 */
+	private function import_wxr() {
+		if ( ! $this->importer ) {
+			WP_CLI::error( 'Could not create importer' );
+		}
+
+		WP_CLI::line( "Importing {$this->wxr_path}" );
+
+		if ( $this->dry_run ) {
+			WP_CLI::line( 'Dry run enabled.' );
+		} else {
+			while ( $this->importer->next_step() ) {
+				$current_stage = $this->importer->get_current_stage();
+				// WP_CLI::line( "Stage {$current_stage}" );
+			}
+		}
+
+		WP_CLI::success( 'Import finished' );
+	}
+
+	/**
+	 * Callback function registered to `pcntl_signal` to handle signals.
+	 *
+	 * @param int $signal The signal number.
+	 * @return void
+	 */
+	protected function signal_handler( $signal ) {
+		switch ( $signal ) {
+			case SIGINT:
+				WP_CLI::line( 'Received SIGINT signal' );
+				exit( 0 );
+
+			case SIGTERM:
+				WP_CLI::line( 'Received SIGTERM signal' );
+				exit( 0 );
+		}
+	}
+
+	/**
+	 * Register signal handlers for the command.
+	 *
+	 * @return void
+	 */
+	private function register_handlers() {
+		// Handle the Ctrl + C signal to terminate the program.
+		pcntl_signal( SIGINT, array( $this, 'signal_handler' ) );
+
+		// Handle the `kill` command to terminate the program.
+		pcntl_signal( SIGTERM, array( $this, 'signal_handler' ) );
+	}
+}
diff --git a/packages/playground/data-liberation/src/cli/WP_Import_Logger.php b/packages/playground/data-liberation/src/cli/WP_Import_Logger.php
new file mode 100644
index 0000000000..103ab3d9e2
--- /dev/null
+++ b/packages/playground/data-liberation/src/cli/WP_Import_Logger.php
@@ -0,0 +1,51 @@
+<?php
+
+/**
+ * Entity importer logger class.
+ */
+class WP_Import_Logger {
+	/**
+	 * Log a debug message.
+	 *
+	 * @param string $message Message to log
+	 */
+	public function debug( $message ) {
+		WP_CLI::debug( $message );
+	}
+
+	/**
+	 * Log an info message.
+	 *
+	 * @param string $message Message to log
+	 */
+	public function info( $message ) {
+		WP_CLI::log( $message );
+	}
+
+	/**
+	 * Log a warning message.
+	 *
+	 * @param string $message Message to log
+	 */
+	public function warning( $message ) {
+		WP_CLI::warning( $message );
+	}
+
+	/**
+	 * Log an error message.
+	 *
+	 * @param string $message Message to log
+	 */
+	public function error( $message ) {
+		WP_CLI::error( $message, false );
+	}
+
+	/**
+	 * Log a notice message.
+	 *
+	 * @param string $message Message to log
+	 */
+	public function notice( $message ) {
+		WP_CLI::log( $message );
+	}
+}
diff --git a/packages/playground/data-liberation/src/import/WP_Entity_Importer.php b/packages/playground/data-liberation/src/import/WP_Entity_Importer.php
index 0daebac7b4..bbcf394819 100644
--- a/packages/playground/data-liberation/src/import/WP_Entity_Importer.php
+++ b/packages/playground/data-liberation/src/import/WP_Entity_Importer.php
@@ -93,7 +93,7 @@ public function __construct( $options = array() ) {
 		$this->mapping['term_id']   = array();
 		$this->requires_remapping   = $empty_types;
 		$this->exists               = $empty_types;
-		$this->logger               = new Logger();
+		$this->logger               = isset( $options['logger'] ) ? $options['logger'] : new WP_Logger();
 
 		$this->options = wp_parse_args(
 			$options,
@@ -1191,57 +1191,3 @@ public static function sort_comments_by_id( $a, $b ) {
 		return $a['comment_id'] - $b['comment_id'];
 	}
 }
-
-/**
- * @TODO how to treat this? Should this class even exist?
- *       how does WordPress handle different levels? It
- *       seems useful for usage in wp-cli, Blueprints,
- *       and other non-web environments.
- */
-// phpcs:ignore Generic.Files.OneObjectStructurePerFile.MultipleFound
-class Logger {
-	/**
-	 * Log a debug message.
-	 *
-	 * @param string $message Message to log
-	 */
-	public function debug( $message ) {
-		// echo( '[DEBUG] ' . $message );
-	}
-
-	/**
-	 * Log an info message.
-	 *
-	 * @param string $message Message to log
-	 */
-	public function info( $message ) {
-		// echo( '[INFO] ' . $message );
-	}
-
-	/**
-	 * Log a warning message.
-	 *
-	 * @param string $message Message to log
-	 */
-	public function warning( $message ) {
-		echo( '[WARNING] ' . $message );
-	}
-
-	/**
-	 * Log an error message.
-	 *
-	 * @param string $message Message to log
-	 */
-	public function error( $message ) {
-		echo( '[ERROR] ' . $message );
-	}
-
-	/**
-	 * Log a notice message.
-	 *
-	 * @param string $message Message to log
-	 */
-	public function notice( $message ) {
-		// echo( '[NOTICE] ' . $message );
-	}
-}
diff --git a/packages/playground/data-liberation/src/import/WP_Logger.php b/packages/playground/data-liberation/src/import/WP_Logger.php
new file mode 100644
index 0000000000..87605336fe
--- /dev/null
+++ b/packages/playground/data-liberation/src/import/WP_Logger.php
@@ -0,0 +1,51 @@
+<?php
+
+/**
+ * Entity importer logger class.
+ */
+class WP_Logger {
+	/**
+	 * Log a debug message.
+	 *
+	 * @param string $message Message to log
+	 */
+	public function debug( $message ) {
+		// echo( '[DEBUG] ' . $message );
+	}
+
+	/**
+	 * Log an info message.
+	 *
+	 * @param string $message Message to log
+	 */
+	public function info( $message ) {
+		// echo( '[INFO] ' . $message );
+	}
+
+	/**
+	 * Log a warning message.
+	 *
+	 * @param string $message Message to log
+	 */
+	public function warning( $message ) {
+		echo( "[WARNING] {$message}\n" );
+	}
+
+	/**
+	 * Log an error message.
+	 *
+	 * @param string $message Message to log
+	 */
+	public function error( $message ) {
+		echo( "[ERROR] $message\n" );
+	}
+
+	/**
+	 * Log a notice message.
+	 *
+	 * @param string $message Message to log
+	 */
+	public function notice( $message ) {
+		// echo( '[NOTICE] ' . $message );
+	}
+}
diff --git a/packages/playground/data-liberation/src/import/WP_Stream_Importer.php b/packages/playground/data-liberation/src/import/WP_Stream_Importer.php
index a1d625386d..6e24c9d1ca 100644
--- a/packages/playground/data-liberation/src/import/WP_Stream_Importer.php
+++ b/packages/playground/data-liberation/src/import/WP_Stream_Importer.php
@@ -73,6 +73,11 @@ class WP_Stream_Importer {
 	private $active_downloads = array();
 	private $downloader;
 
+	/**
+	 * @var WP_Topological_Sorter
+	 */
+	private $topological_sorter;
+
 	public static function create_for_wxr_file( $wxr_path, $options = array(), $cursor = null ) {
 		return static::create(
 			function ( $cursor = null ) use ( $wxr_path ) {
@@ -241,8 +246,9 @@ private function frontloading_advance_reentrancy_cursor() {
 	 */
 	private function next_frontloading_step() {
 		if ( null === $this->entity_iterator ) {
-			$this->entity_iterator = $this->create_entity_iterator();
-			$this->downloader      = new WP_Attachment_Downloader( $this->options );
+			$this->entity_iterator    = $this->create_entity_iterator();
+			$this->topological_sorter = new WP_Topological_Sorter();
+			$this->downloader         = new WP_Attachment_Downloader( $this->options );
 		}
 
 		$this->frontloading_advance_reentrancy_cursor();
@@ -253,11 +259,15 @@ private function next_frontloading_step() {
 			if ( ! empty( $this->active_downloads ) ) {
 				_doing_it_wrong( __METHOD__, 'Frontloading queue is not empty.', '1.0' );
 			}
-			$this->stage            = self::STAGE_IMPORT_ENTITIES;
-			$this->downloader       = null;
-			$this->active_downloads = array();
-			$this->entity_iterator  = null;
-			$this->resume_at_entity = null;
+
+			print_r( $this->topological_sorter->mapping );
+
+			$this->stage              = self::STAGE_IMPORT_ENTITIES;
+			$this->topological_sorter = null;
+			$this->downloader         = null;
+			$this->active_downloads   = array();
+			$this->entity_iterator    = null;
+			$this->resume_at_entity   = null;
 			return false;
 		}
 
@@ -288,14 +298,22 @@ private function next_frontloading_step() {
 		$cursor                            = $this->entity_iterator->get_reentrancy_cursor();
 		$this->active_downloads[ $cursor ] = array();
 
-		$data = $entity->get_data();
+		$data     = $entity->get_data();
+		$upstream = $this->entity_iterator->get_upstream();
+
 		switch ( $entity->get_type() ) {
+			case 'category':
+			case 'term':
+				$this->topological_sorter->map_term( $upstream, $data );
+				break;
 			case 'site_option':
 				if ( $data['option_name'] === 'home' ) {
 					$this->source_site_url = $data['option_value'];
 				}
 				break;
 			case 'post':
+				$this->topological_sorter->map_post( $upstream, $data );
+
 				if ( isset( $data['post_type'] ) && $data['post_type'] === 'attachment' ) {
 					$this->enqueue_attachment_download( $data['attachment_url'], null );
 				} elseif ( isset( $data['post_content'] ) ) {
diff --git a/packages/playground/data-liberation/src/import/WP_Topological_Sorter.php b/packages/playground/data-liberation/src/import/WP_Topological_Sorter.php
new file mode 100644
index 0000000000..291421aae5
--- /dev/null
+++ b/packages/playground/data-liberation/src/import/WP_Topological_Sorter.php
@@ -0,0 +1,103 @@
+<?php
+
+/**
+ * The topological sorter class.
+ *
+ * We create an in-memory index that contains offsets and lengths of items in the WXR.
+ * The indexer will also topologically sort posts so that the order we iterate over posts
+ * ensures we always get parents before their children.
+ */
+class WP_Topological_Sorter {
+
+	public $unsorted_posts = array();
+	public $terms          = array();
+	public $index          = array();
+
+	/**
+	 * Variable for keeping counts of orphaned posts/attachments, it'll also be assigned as temporarty post ID.
+	 * To prevent duplicate post ID, we'll use negative number.
+	 *
+	 * @var int
+	 */
+	protected $orphan_post_counter = 0;
+
+	/**
+	 * Store the ID of the post ID currently being processed.
+	 * @var int
+	 */
+	protected $last_post_id = 0;
+
+	public function map_term( $upstream, $data ) {
+		if ( empty( $data ) ) {
+			return false;
+		}
+
+		$this->terms[ $data['slug'] ] = array(
+			'upstream' => $upstream,
+			'visited'  => false,
+		);
+	}
+
+	public function map_post( $upstream, $data ) {
+		if ( empty( $data ) ) {
+			return false;
+		}
+
+		// No parent, no need to sort.
+		if ( ! isset( $data['post_type'] ) ) {
+			return false;
+		}
+
+		if ( 'post' === $data['post_type'] || 'page' === $data['post_type'] ) {
+			if ( ! $data['post_id'] ) {
+				$this->last_post_id = $this->orphan_post_counter;
+				--$this->orphan_post_counter;
+			}
+
+			$this->unsorted_posts[ $data['post_id'] ] = array(
+				'upstream' => $upstream,
+				'parent'   => $data['post_parent'],
+				'visited'  => false,
+			);
+		}
+	}
+
+	/**
+	 * Sort posts topologically.
+	 *
+	 * Children posts should not be processed before their parent has been processed.
+	 * This method sorts the posts in the order they should be processed.
+	 *
+	 * Sorted posts will be stored as attachments and posts/pages separately.
+	 */
+	public function sort_posts_topologically() {
+		foreach ( $this->unsorted_posts as $id => $post ) {
+			$this->topological_sort( $id, $post );
+		}
+
+		// Empty the unsorted posts
+		$this->unsorted_posts = array();
+	}
+
+	/**
+	 * Recursive topological sorting.
+	 *
+	 * @param int $id     The id of the post to sort.
+	 * @param array $post The post to sort.
+	 *
+	 * @todo Check for circular dependencies.
+	 */
+	private function topological_sort( $id, $post ) {
+		if ( isset( $this->posts[ $id ]['visited'] ) ) {
+			return;
+		}
+
+		$this->unsorted_posts[ $id ]['visited'] = true;
+
+		if ( isset( $this->posts[ $post['parent'] ] ) ) {
+			$this->topological_sort( $post['parent'], $this->unsorted_posts[ $post['parent'] ] );
+		}
+
+		$this->index[] = $post['upstream'];
+	}
+}
diff --git a/packages/playground/data-liberation/src/wxr/WP_WXR_Reader.php b/packages/playground/data-liberation/src/wxr/WP_WXR_Reader.php
index c37d952714..3b2988457e 100644
--- a/packages/playground/data-liberation/src/wxr/WP_WXR_Reader.php
+++ b/packages/playground/data-liberation/src/wxr/WP_WXR_Reader.php
@@ -389,6 +389,10 @@ protected function __construct( WP_XML_Processor $xml ) {
 		$this->xml = $xml;
 	}
 
+	public function get_upstream() {
+		return $this->entity_byte_offset;
+	}
+
 	public function get_reentrancy_cursor() {
 		/**
 		 * @TODO: Instead of adjusting the XML cursor internals, adjust the get_reentrancy_cursor()