import { XmlService } from './XmlService';

export abstract class AbstractXmlService<T> extends XmlService<T> {
  serialize(description: T, prettify?: boolean) {
    const serializer = new XMLSerializer();
    let document = this.encode(description);
    if (prettify) { document = this.prettyPrint(document); }
    return serializer.serializeToString(document);
  }

  deserialize(xml: string | Document): T {
    let document: Document;
    if (xml instanceof Document) {
      document = xml;
    } else if (typeof (xml) === 'string') {
      const deserializer = new DOMParser();
      document = deserializer.parseFromString(xml as string, 'application/xml');
    } else {
      return null;
    }
    return this.decode(document);
  }

  protected abstract decode(document: Document): T;

  protected abstract encode(object: T): Document;

  private prettyPrint(source: Document): Document {
    const stylesheet: Document = new DOMParser().parseFromString(
      `<xsl:stylesheet version="1.0"
                           xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
            <xsl:output omit-xml-declaration="yes" indent="yes"/>
            <xsl:template match="node()|@*">
              <xsl:copy>
                <xsl:apply-templates select="node()|@*"/>
              </xsl:copy>
            </xsl:template>
          </xsl:stylesheet>`, 'application/xml');
    const processor = new XSLTProcessor();
    processor.importStylesheet(stylesheet);
    return processor.transformToDocument(source);
  }
}