Add raw metadata for IcyInfo

[AlienAsRoger]

[REQUIRED] Use case description

Add ability to extract metadata from ICY on the client implementation.
Currently it's impossible to extract additional information from ICY metadata except title and url. It would be better if you would just pass rawMetadata as additional parameter to IcyInfo, so client will handle extraction on it's own if needed.

Use case is that we are using ads info that is passed along with title, but it's not in "title=", instead it's like adw_ad= or ad|main

Example that we are using:

[StreamTitle='';StreamUrl='';metadata='adswizzContext=fGg6M158cDo2MTkzI3U6ODU3MA%3D%3D';adw_ad='true';durationMilliseconds='30511';adId='54691';insertionType='midroll';]

Proposed solution

@Nullable
  @VisibleForTesting
  /* package */ Metadata decode(String metadata) {
    String name = null;
    String url = null;
    int index = 0;
    Matcher matcher = METADATA_ELEMENT.matcher(metadata);
    while (matcher.find(index)) {
      String key = Util.toLowerInvariant(matcher.group(1));
      String value = matcher.group(2);
      switch (key) {
        case STREAM_KEY_NAME:
          name = value;
          break;
        case STREAM_KEY_URL:
          url = value;
          break;
        default:
          Log.w(TAG, "Unrecognized ICY tag: " + name);
          break;
      }
      index = matcher.end();
    }
    return (name != null || url != null) ? new Metadata(new IcyInfo(name, url, metadata)) : null;
  }

and
  ....
  @Nullable public final String rawMetadata;
  ....

  public IcyInfo(@Nullable String title, @Nullable String url, @Nullable String rawMetadata) {
  ....
    this.rawMetadata = rawMetadata;

Alternatives considered

I know you were thinking about other possible use-cases whether to provide key-value pair, but I think providing just raw String would be sufficient.

[icbaker]

Thanks for the suggestion!

I agree that probably the best we can do is pass through the whole raw string, because it's not really defined what other tags (or separators) are allowed in ICY, so even key-value is tricky.

I think I'll tweak your suggestion to create the IcyInfo even if both title & url end up null, so that any arbitrary text in an ICY context gets passed along to the app to handle.