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/*
 * Copyright (c) 2014 Red Hat, Inc. and others
 *
 * Red Hat licenses this file to you under the Apache License, version 2.0
 * (the "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at:
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 */

package io.vertx.config.yaml;

import io.vertx.config.spi.ConfigProcessor;
import io.vertx.core.Future;
import io.vertx.core.Vertx;
import io.vertx.core.buffer.Buffer;
import io.vertx.core.impl.ContextInternal;
import io.vertx.core.json.DecodeException;
import io.vertx.core.json.JsonObject;
import org.yaml.snakeyaml.Yaml;
import org.yaml.snakeyaml.constructor.SafeConstructor;

import java.nio.charset.StandardCharsets;
import java.util.Date;
import java.util.Map;

/**
 * A processor using Jackson and SnakeYaml to read Yaml files.
 *
 * @author Clement Escoffier
 */
public class YamlProcessor implements ConfigProcessor {

  @Override
  public String name() {
    return "yaml";
  }

  @Override
  public Future process(Vertx vertx, JsonObject configuration, Buffer input) {
    if (input.length() == 0) {
      // the parser does not support empty files, which should be managed to be homogeneous
      return ((ContextInternal) vertx.getOrCreateContext()).succeededFuture(new JsonObject());
    }

    // Use executeBlocking even if the bytes are in memory
    return vertx.executeBlocking(promise -> {
      try {
        final Yaml yamlMapper = new Yaml(new SafeConstructor());
        Map doc = yamlMapper.load(input.toString(StandardCharsets.UTF_8));
        promise.complete(jsonify(doc));
      } catch (ClassCastException e) {
        promise.fail(new DecodeException("Failed to decode YAML", e));
      } catch (RuntimeException e) {
        promise.fail(e);
      }
    });
  }

  /**
   * Yaml allows map keys of type object, however json always requires key as String,
   * this helper method will ensure we adapt keys to the right type
   *
   * @param yaml yaml map
   * @return json map
   */
  private static JsonObject jsonify(Map yaml) {
    if (yaml == null) {
      return null;
    }

    final JsonObject json = new JsonObject();

    for (Map.Entry kv : yaml.entrySet()) {
      Object value = kv.getValue();
      if (value instanceof Map) {
        value = jsonify((Map) value);
      }
      // snake yaml handles dates as java.util.Date, and JSON does Instant
      if (value instanceof Date) {
        value = ((Date) value).toInstant();
      }
      json.put(kv.getKey().toString(), value);
    }

    return json;
  }

}