import type { TransformEngineId } from '../transform/transformTypes';
import { parseXmlDocument } from './xmlValidation';
import type { DiagnosticMessage } from './validationTypes';

const XSLT_NAMESPACE = 'http://www.w3.org/1999/XSL/Transform';

export function validateXslt(
  text: string,
  engine: TransformEngineId = 'native-xsltprocessor'
): DiagnosticMessage[] {
  const { document: stylesheet, diagnostics } = parseXmlDocument(
    text,
    'XSLT stylesheet'
  );

  if (diagnostics.some((diagnostic) => diagnostic.severity === 'error')) {
    return diagnostics;
  }

  const root = stylesheet.documentElement;
  if (!root) {
    return [
      ...diagnostics,
      {
        severity: 'error',
        source: 'XSLT stylesheet',
        message: 'The stylesheet has no document element.',
      },
    ];
  }

  if (
    root.namespaceURI !== XSLT_NAMESPACE ||
    !['stylesheet', 'transform'].includes(root.localName)
  ) {
    diagnostics.push({
      severity: 'error',
      source: 'XSLT stylesheet',
      message:
        'The root element should be xsl:stylesheet or xsl:transform in the XSLT namespace.',
    });
  }

  const version = root.getAttribute('version');
  if (!version) {
    diagnostics.push({
      severity: 'warning',
      source: 'XSLT stylesheet',
      message: 'The stylesheet root should declare a version attribute.',
    });
  }

  if (engine === 'native-xsltprocessor' && version && version !== '1.0') {
    diagnostics.push({
      severity: 'warning',
      source: 'XSLT stylesheet',
      message:
        'The native browser engine usually supports XSLT 1.0 only. XSLT 2.0/3.0 features may fail.',
    });
  }

  return diagnostics;
}