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package com.launchdarkly.client.files;
import com.google.gson.Gson;
import com.google.gson.JsonElement;
import org.yaml.snakeyaml.Yaml;
import org.yaml.snakeyaml.error.YAMLException;
import java.io.IOException;
import java.io.InputStream;
/**
* Parses a FlagFileRep from a YAML file. Two notes about this implementation:
*
* 1. We already have logic for parsing (and building) flags using Gson, and would rather not repeat
* that logic. So, rather than telling SnakeYAML to parse the file directly into a FlagFileRep object -
* and providing SnakeYAML-specific methods for building flags - we are just parsing the YAML into
* simple Java objects and then feeding that data into the Gson parser. This is admittedly inefficient,
* but it also means that we don't have to worry about any differences between how Gson unmarshals an
* object and how the YAML parser does it. We already know Gson does the right thing for the flag and
* segment classes, because that's what we use in the SDK.
*
* 2. Ideally, it should be possible to have just one parser, since any valid JSON document is supposed
* to also be parseable as YAML. However, at present, that doesn't work:
*
* - SnakeYAML (1.19) rejects many valid JSON documents due to simple things like whitespace.
* Apparently this is due to supporting only YAML 1.1, not YAML 1.2 which has full JSON support.
*
- snakeyaml-engine (https://bitbucket.org/asomov/snakeyaml-engine) says it can handle any JSON,
* but it's only for Java 8 and above.
*
- YamlBeans (https://github.com/EsotericSoftware/yamlbeans) only works right if you're parsing
* directly into a Java bean instance (which FeatureFlag is not). If you try the "parse to simple
* Java types (and then feed them into Gson)" approach, it does not correctly parse non-string types
* (i.e. it treats true as "true"). (https://github.com/EsotericSoftware/yamlbeans/issues/7)
*
*/
final class YamlFlagFileParser extends FlagFileParser {
private static final Yaml yaml = new Yaml();
private static final Gson gson = new Gson();
private static final JsonFlagFileParser jsonFileParser = new JsonFlagFileParser();
@Override
public FlagFileRep parse(InputStream input) throws DataLoaderException, IOException {
Object root;
try {
root = yaml.load(input);
} catch (YAMLException e) {
throw new DataLoaderException("unable to parse YAML", e);
}
JsonElement jsonRoot = gson.toJsonTree(root);
return jsonFileParser.parseJson(jsonRoot);
}
}