/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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 org.apache.solr.handler.dataimport;

import java.io.*;
import java.lang.invoke.MethodHandles;
import java.nio.charset.StandardCharsets;
import java.util.Properties;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import static org.apache.solr.handler.dataimport.DataImportHandlerException.wrapAndThrow;
import static org.apache.solr.handler.dataimport.DataImportHandlerException.SEVERE;

/**
 * <p>
 * A {@link DataSource} which reads from local files
 * </p>
 * <p>
 * The file is read with the default platform encoding. It can be overriden by
 * specifying the encoding in solrconfig.xml
 * </p>
 * <p>
 * Refer to <a
 * href="http://wiki.apache.org/solr/DataImportHandler">http://wiki.apache.org/solr/DataImportHandler</a>
 * for more details.
 * </p>
 * <p>
 * <b>This API is experimental and may change in the future.</b>
 *
 * @since solr 1.3
 */
public class FileDataSource extends DataSource<Reader> {
  public static final String BASE_PATH = "basePath";

  /**
   * The basePath for this data source
   */
  protected String basePath;

  /**
   * The encoding using which the given file should be read
   */
  protected String encoding = null;

  private static final Logger LOG = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());

  @Override
  public void init(Context context, Properties initProps) {
    basePath = initProps.getProperty(BASE_PATH);
    if (initProps.get(URLDataSource.ENCODING) != null)
      encoding = initProps.getProperty(URLDataSource.ENCODING);
  }

  /**
   * <p>
   * Returns a reader for the given file.
   * </p>
   * <p>
   * If the given file is not absolute, we try to construct an absolute path
   * using basePath configuration. If that fails, then the relative path is
   * tried. If file is not found a RuntimeException is thrown.
   * </p>
   * <p>
   * <b>It is the responsibility of the calling method to properly close the
   * returned Reader</b>
   * </p>
   */
  @Override
  public Reader getData(String query) {
    File f = getFile(basePath,query);
    try {
      return openStream(f);
    } catch (Exception e) {
      wrapAndThrow(SEVERE,e,"Unable to open File : "+f.getAbsolutePath());
      return null;
    }
  }

  static File getFile(String basePath, String query) {
    try {
      File file = new File(query);

      // If it's not an absolute path, try relative from basePath. 
      if (!file.isAbsolute()) {
        // Resolve and correct basePath.
        File basePathFile;
        if (basePath == null) {
          basePathFile = new File(".").getAbsoluteFile(); 
          LOG.warn("FileDataSource.basePath is empty. " +
              "Resolving to: " + basePathFile.getAbsolutePath());
        } else {
          basePathFile = new File(basePath);
          if (!basePathFile.isAbsolute()) {
            basePathFile = basePathFile.getAbsoluteFile();
            LOG.warn("FileDataSource.basePath is not absolute. Resolving to: "
                + basePathFile.getAbsolutePath());
          }
        }

        file = new File(basePathFile, query).getAbsoluteFile();
      }

      if (file.isFile() && file.canRead()) {
        LOG.debug("Accessing File: " + file.getAbsolutePath());
        return file;
      } else {
        throw new FileNotFoundException("Could not find file: " + query + 
            " (resolved to: " + file.getAbsolutePath());
      }
    } catch (FileNotFoundException e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * Open a {@link java.io.Reader} for the given file name
   *
   * @param file a {@link java.io.File} instance
   * @return a Reader on the given file
   * @throws FileNotFoundException if the File does not exist
   * @throws UnsupportedEncodingException if the encoding is unsupported
   * @since solr 1.4
   */
  protected Reader openStream(File file) throws FileNotFoundException,
          UnsupportedEncodingException {
    if (encoding == null) {
      return new InputStreamReader(new FileInputStream(file), StandardCharsets.UTF_8);
    } else {
      return new InputStreamReader(new FileInputStream(file), encoding);
    }
  }

  @Override
  public void close() {

  }
}