// A webpack loader that returns invalid CSS with a source map.
// The source map points back to the original file, making it clear that the
// loader is responsible for the broken output (not the original source).
module.exports = function (source) {
  // Generate a source map that maps generated lines back to the original source.
  // The original file is valid CSS; the generated output is intentionally broken.
  //
  // Mapping (0-based line numbers):
  //   generated line 0 ("/* Generated by... */") -> original line 0 (".page {")
  //   generated line 1 (".page {")               -> original line 0 (".page {")
  //   generated line 2 ("  color: red")           -> original line 1 ("  color: blue;")
  //   generated line 3 ("  @@@ ...")              -> original line 2 ("  font-size: 16px;")
  //   generated line 4 ("  background: {{{...")   -> original line 1 ("  color: blue;")
  //   generated line 5 ("}")                      -> original line 3 ("}")
  const sourceMap = {
    version: 3,
    sources: [this.resourcePath],
    sourcesContent: [source],
    mappings: 'AAAA;AAAA;AACE;AACA;AADA;AAEF',
    names: [],
  }

  // Return broken CSS that will fail to parse
  const brokenCss = `/* Generated by broken-css-loader */
.page {
  color: red
  @@@ THIS IS NOT VALID CSS @@@;
  background: {{{ invalid
}
`

  this.callback(null, brokenCss, sourceMap)
}