/*
    * 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.maven.index.reader;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.text.ParseException;
  import java.util.Date;
  import java.util.Iterator;
  import java.util.Map;
  import java.util.Properties;
  import java.util.UUID;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import org.apache.maven.index.reader.WritableResourceHandler.WritableResource;
  
  import static java.util.Objects.requireNonNull;
  import static org.apache.maven.index.reader.Utils.loadProperties;
  import static org.apache.maven.index.reader.Utils.storeProperties;
  
  /**
   * Maven Index writer that writes chunk and maintains published property file. Instances of this class MUST BE handled
   * as resources (have them closed once done with them), it is user responsibility to close them, ideally in
   * try-with-resource block.
   * <p/>
   * <strong>Currently no incremental update is supported, as the deletion states should be maintained by
   * caller</strong>. Hence, this writer will always produce the "main" chunk only.
   *
   * @since 5.1.2
   */
  public class IndexWriter implements Closeable {
      private static final int INDEX_V1 = 1;
  
      private final AtomicBoolean closed;
  
      private final WritableResourceHandler local;
  
      private final Properties localIndexProperties;
  
      private final boolean incremental;
  
      private final String nextChunkCounter;
  
      private final String nextChunkName;
  
      public IndexWriter(final WritableResourceHandler local, final String indexId, final boolean incrementalSupported)
              throws IOException {
          requireNonNull(local, "local resource handler null");
          requireNonNull(indexId, "indexId null");
          this.closed = new AtomicBoolean(false);
          this.local = local;
          Properties indexProperties = loadProperties(local.locate(Utils.INDEX_FILE_PREFIX + ".properties"));
          if (incrementalSupported && indexProperties != null) {
              this.localIndexProperties = indexProperties;
              // existing index, this is incremental publish, and we will add new chunk
              String localIndexId = localIndexProperties.getProperty("nexus.index.id");
              if (localIndexId == null || !localIndexId.equals(indexId)) {
                  throw new IllegalArgumentException(
                          "index already exists and indexId mismatch or unreadable: " + localIndexId + ", " + indexId);
              }
              this.incremental = true;
              this.nextChunkCounter = calculateNextChunkCounter();
              this.nextChunkName = Utils.INDEX_FILE_PREFIX + "." + nextChunkCounter + ".gz";
          } else {
              // non-existing index, create published index from scratch
              this.localIndexProperties = new Properties();
              this.localIndexProperties.setProperty("nexus.index.id", indexId);
              this.localIndexProperties.setProperty(
                      "nexus.index.chain-id", UUID.randomUUID().toString());
              this.incremental = false;
              this.nextChunkCounter = null;
              this.nextChunkName = Utils.INDEX_FILE_PREFIX + ".gz";
          }
      }
  
      /**
       * Returns the index context ID that published index has set.
       */
      public String getIndexId() {
          return localIndexProperties.getProperty("nexus.index.id");
      }
  
      /**
      * Returns the {@link Date} when index was last published or {@code null} if this is first publishing. In other
      * words,returns {@code null} when {@link #isIncremental()} returns {@code false}. After this writer is closed, the
      * return value is updated to "now" (in {@link #close() method}.
      */
     public Date getPublishedTimestamp() {
         try {
             String timestamp = localIndexProperties.getProperty("nexus.index.timestamp");
             if (timestamp != null) {
                 return Utils.INDEX_DATE_FORMAT.parse(timestamp);
             }
             return null;
         } catch (ParseException e) {
             throw new RuntimeException("Corrupt date", e);
         }
     }
 
     /**
      * Returns {@code true} if incremental publish is about to happen.
      */
     public boolean isIncremental() {
         return incremental;
     }
 
     /**
      * Returns the chain id of published index. If {@link #isIncremental()} is {@code false}, this is the newly
      * generated chain ID.
      */
     public String getChainId() {
         return localIndexProperties.getProperty("nexus.index.chain-id");
     }
 
     /**
      * Returns the next chunk name about to be published.
      */
     public String getNextChunkName() {
         return nextChunkName;
     }
 
     /**
      * Writes out the record iterator and returns the written record count.
      */
     public int writeChunk(final Iterator<Map<String, String>> iterator) throws IOException {
         int written;
 
         try (WritableResource writableResource = local.locate(nextChunkName)) {
             try (ChunkWriter chunkWriter =
                     new ChunkWriter(nextChunkName, writableResource.write(), INDEX_V1, new Date())) {
                 written = chunkWriter.writeChunk(iterator);
             }
             if (incremental) {
                 // TODO: update main gz file
             }
             return written;
         }
     }
 
     /**
      * Closes the underlying {@link ResourceHandler} and synchronizes published index properties, so remote clients
      * becomes able to consume newly published index. If sync is not desired (ie. due to aborted publish), then this
      * method should NOT be invoked, but rather the {@link ResourceHandler} that caller provided in constructor of
      * this class should be closed manually.
      */
     @Override
     public void close() throws IOException {
         if (closed.compareAndSet(false, true)) {
             try {
                 if (incremental) {
                     localIndexProperties.setProperty("nexus.index.last-incremental", nextChunkCounter);
                 }
                 localIndexProperties.setProperty("nexus.index.timestamp", Utils.INDEX_DATE_FORMAT.format(new Date()));
                 storeProperties(local.locate(Utils.INDEX_FILE_PREFIX + ".properties"), localIndexProperties);
             } finally {
                 local.close();
             }
         }
     }
 
     /**
      * Calculates the chunk names that needs to be fetched.
      */
     private String calculateNextChunkCounter() {
         String lastChunkCounter = localIndexProperties.getProperty("nexus.index.last-incremental");
         if (lastChunkCounter != null) {
             return String.valueOf(Integer.parseInt(lastChunkCounter) + 1);
         } else {
             return "1";
         }
     }
 }