/*
 * Copyright (C) 2018 Google Inc.
 *
 * Licensed 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 com.google.cloud.teleport.templates;

import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import org.apache.beam.sdk.io.FileSystems;
import org.apache.beam.sdk.util.StreamUtils;
import org.json.JSONObject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A helper object to parse a JSON on GCS. Usage is to provide A GCS URL and it will return
 * a JSONObject of the file
 */
public class SchemaParser{

  private static final Logger LOG = LoggerFactory.getLogger(SchemaParser.class);

  /**
   * Parses a JSON file and Returns a JSONObject containing the necessary source, sink, and schema
   * information.
   *
   * @param pathToJSON the JSON file location so we can download and parse it
   * @return the parsed JSONObject
   */
  public JSONObject parseSchema(String pathToJSON) throws Exception {

    try {
      ReadableByteChannel readableByteChannel =
          FileSystems.open(FileSystems.matchNewResource(pathToJSON, false));

      String json = new String(
          StreamUtils.getBytesWithoutClosing(Channels.newInputStream(readableByteChannel)));

      return new JSONObject(json);
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }
}