feat: add merge fields for Mailchimp

inc/integrations/api/form-response-data.php

@@ -343,6 +343,9 @@ public function set_is_credential_error( $is_credential_error ) {
 	 * @since 2.1.7
 	 */
 	public function process_error_code() {
+		if ( ! $this->has_error() ) {
+			return;
+		}
 		$this->add_reason( self::get_error_code_message( $this->response['code'] ) );
 	}
 

inc/integrations/providers/class-mailchimp.php

@@ -35,6 +35,13 @@ class Mailchimp_Integration implements FormSubscribeServiceInterface {
 	 */
 	protected $server_name = '';
 
+	/**
+	 * The form data.
+	 * 
+	 * @var Form_Data_Request|null
+	 */
+	protected $form_data = null;
+
 
 	/**
 	 * The default constructor.
@@ -110,16 +117,24 @@ function( $item ) {
 	 *
 	 * @param string $email The email address.
 	 * @return array|\WP_Error The response from Mailchimp.
+	 * 
+	 * @see https://mailchimp.com/developer/marketing/api/list-members/add-member-to-list/
 	 */
 	public function make_subscribe_request( $email ) {
 		$user_status = $this->get_new_user_status_mailchimp( $this->list_id );
 
 		$url = 'https://' . $this->server_name . '.api.mailchimp.com/3.0/lists/' . $this->list_id . '/members/' . md5( strtolower( $email ) );
-
+		
 		$payload = array(
 			'email_address' => $email,
 			'status'        => $user_status,
 		);
+
+		$linked_merge_fields = $this->get_linked_merge_fields();
+		if ( ! empty( $linked_merge_fields ) ) {
+			$url                     = add_query_arg( 'skip_merge_validation', 'true', $url );
+			$payload['merge_fields'] = $linked_merge_fields;
+		}
 
 		$args = array(
 			'method'  => 'PUT',
@@ -141,9 +156,10 @@ public function make_subscribe_request( $email ) {
 	 */
 	public function subscribe( $form_data ) {
 
-		$email    = $form_data->get_first_email_from_input_fields();
-		$response = $this->make_subscribe_request( $email );
-		$body     = json_decode( wp_remote_retrieve_body( $response ), true );
+		$this->form_data = $form_data;
+		$email           = $form_data->get_first_email_from_input_fields();
+		$response        = $this->make_subscribe_request( $email );
+		$body            = json_decode( wp_remote_retrieve_body( $response ), true );
 
 		if ( is_wp_error( $response ) || 200 !== wp_remote_retrieve_response_code( $response ) ) {
 
@@ -284,4 +300,99 @@ public function get_information_from_provider( $request ) {
 	private function is_credential_error( $response_code ) {
 		return in_array( $response_code, array( 401, 403, 404, 500 ) );
 	}
+
+	/**
+	 * Get the merge fields from Mailchimp.
+	 *
+	 * @return array An array of merge fields, each containing:
+	 *               - string $tag The merge field's tag
+	 *               - string $type The merge field's type (e.g., 'text')
+	 * @since 2.7.0
+	 * 
+	 * @see https://mailchimp.com/developer/marketing/api/list-merges/list-merge-fields/
+	 */
+	public function get_merge_fields() {
+		$url  = 'https://' . $this->server_name . '.api.mailchimp.com/3.0/lists/' . $this->list_id . '/merge-fields';
+		$args = array(
+			'method'  => 'GET',
+			'headers' => array(
+				'Authorization' => 'Basic ' . base64_encode( 'user:' . $this->api_key ),
+			),
+		);
+
+		if ( function_exists( 'vip_safe_wp_remote_get' ) ) {
+			$response = vip_safe_wp_remote_get( $url, '', 3, 1, 20, $args );
+		} else {
+			$response = wp_remote_get( $url, $args ); // phpcs:ignore WordPressVIPMinimum.Functions.RestrictedFunctions.wp_remote_get_wp_remote_get
+		}
+
+		if ( is_wp_error( $response ) || 200 !== wp_remote_retrieve_response_code( $response ) ) {
+			return array();
+		}
+
+		$body = json_decode( wp_remote_retrieve_body( $response ), true );
+
+		if ( ! isset( $body['merge_fields'] ) || empty( $body['merge_fields'] ) ) {
+			return array();
+		}
+
+		return array_filter(
+			$body['merge_fields'],
+			function( $item ) {
+				return ! empty( $item['tag'] );
+			}
+		);
+	}
+
+	/**
+	 * Link the form fields with their corresponding merge fields.
+	 * 
+	 * @return array The available merge fields to link with the form fields.
+	 * @since 2.7.0
+	 */
+	protected function get_linked_merge_fields() {
+
+		// Check if it is necessary to link the fields.
+		$form_fields = $this->form_data->get_fields();
+		if ( empty( $form_fields ) ) {
+			return array();
+		}
+
+		$available_fields_tags = array();
+
+		foreach ( $form_fields as $field ) {
+			if ( empty( $field['metadata']['mappedName'] ) ) {
+				continue;
+			}
+
+			$available_fields_tags[] = array(
+				'tag'   => strtoupper( $field['metadata']['mappedName'] ),
+				'value' => $field['value'],
+			);
+		}
+
+		if ( empty( $available_fields_tags ) ) {
+			return array();
+		}
+
+
+		$merge_fields = $this->get_merge_fields();
+		if ( empty( $merge_fields ) ) {
+			return array();
+		}
+
+		// Link based on the tag of the merge fields.
+		$linked_fields = array();
+		foreach ( $available_fields_tags as $field ) {
+			foreach ( $merge_fields as $merge_field ) {
+				if ( $field['tag'] !== $merge_field['tag'] ) {
+					continue;
+				}
+
+				$linked_fields[ $merge_field['tag'] ] = $field['value'];
+			}
+		}
+
+		return $linked_fields;
+	}
 }