Add the redirect module.

Add the migration to migrate all the redirects.

Also, configure the pathauto for the users.

web/modules/custom/agaric_migration/migrations/redirect.yml

@@ -0,0 +1,41 @@
+id: agaric_redirect
+migration_group: agaric
+label: Agaric Path Redirect
+source:
+  plugin: d7_path_redirect
+  scheme: public
+process:
+  rid: rid
+  uid:
+    - plugin: migration_lookup
+      migration: agaric_user
+      source: uid
+      no_stub: true
+    - # If the user id does not exists then migrate it as anonymous.
+      plugin: default_value
+      default_value: 0
+  redirect_source/path: source
+  redirect_source/query:
+    plugin: d7_redirect_source_query
+    source: source_options
+  redirect_redirect/uri:
+    -
+      plugin: migration_lookup_uri
+      source:
+       - redirect
+       - redirect_options
+    -
+      plugin: d7_path_redirect
+  language:
+    plugin: default_value
+    source: language
+    default_value: und
+  status_code:
+    -
+      plugin: static_map
+      source: status_code
+      map:
+        0: 301
+      bypass: TRUE
+destination:
+  plugin: entity:redirect

web/modules/custom/agaric_migration/src/Plugin/migrate/process/MigrationLookupUri.php

@@ -0,0 +1,102 @@
+<?php
+
+namespace Drupal\agaric_migration\Plugin\migrate\process;
+
+use Drupal\Core\Database\Connection;
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+use Drupal\migrate\MigrateExecutableInterface;
+use Drupal\migrate\ProcessPluginBase;
+use Drupal\migrate\Row;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Update the redirect URIs with the correct ids.
+ *
+ * The nodes and users were migrated and in the new site they have new
+ * ids, so we need to fix the uris before to pass them to the d7_path_redirect
+ * plugin.
+ *
+ * @MigrateProcessPlugin(
+ *   id = "migration_lookup_uri"
+ * )
+ */
+class MigrationLookupUri extends ProcessPluginBase implements ContainerFactoryPluginInterface {
+
+  /**
+   * The database connection.
+   *
+   * @var \Drupal\Core\Database\Connection
+   */
+  protected $connection;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, Connection $database) {
+    parent::__construct($configuration, $plugin_id, $plugin_definition);
+    $this->connection = $database;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    return new static(
+      $configuration,
+      $plugin_id,
+      $plugin_definition,
+      $container->get('database')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
+    $redirect = $value[0];
+    $new_value = [];
+    // We just pass along the $redirect_options.
+    $new_value[1] = $value[1];
+
+    // The entities used in the old agaric sites are: user and node.
+    if (preg_match('/^(user|node)\/([0-9]+)$/', $redirect, $matches)) {
+      $entity_type = $matches[1];
+      $id = $matches[2];
+
+      if ($entity_type == 'node') {
+        $node_migrations = [
+          'migrate_map_agaric_blog',
+          'migrate_map_agaric_page',
+        ];
+        foreach ($node_migrations as $node_migration) {
+          $result = $this->connection->select($node_migration, 'm')
+            ->fields('m')
+            ->condition('sourceid1', $id)
+            ->execute();
+          $row = $result->fetchAssoc();
+          if (!empty($row)) {
+            $new_value[0] = 'node/' . $row['destid1'];
+            break;
+          }
+          $new_value[0] = 'node/' . $row['destid1'];
+        }
+      }
+      elseif ($entity_type == 'user') {
+        $result = $this->connection->select('migrate_map_agaric_user', 'm')
+          ->fields('m')
+          ->condition('sourceid1', $id)
+          ->execute();
+        $row = $result->fetchAssoc();
+        $id = (!empty($row)) ? $row['destid1'] : $id;
+        $new_value[0] = 'user/' . $id;
+      }
+    }
+    else {
+      // Anything different that a redirect to user or node will be ignored.
+      $new_value[0] = $value[0];
+    }
+
+    return $new_value;
+  }
+
+}