content: /*
   * 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.bookkeeper.common.conf;
  
  import static com.google.common.base.Preconditions.checkArgument;
  import static java.nio.charset.StandardCharsets.UTF_8;
  
  import com.google.common.collect.Sets;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.io.PrintStream;
  import java.lang.reflect.Field;
  import java.lang.reflect.Modifier;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.nio.file.StandardOpenOption;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Set;
  import java.util.TreeSet;
  import java.util.stream.Collectors;
  import java.util.stream.IntStream;
  import lombok.Getter;
  import lombok.extern.slf4j.Slf4j;
  import org.apache.commons.configuration2.Configuration;
  import org.apache.commons.lang3.StringUtils;
  
  /**
   * A definition of a configuration instance.
   */
  @Slf4j
  @Getter
  public class ConfigDef {
  
      /**
       * Builder to build a configuration definition.
       */
      public static class Builder {
  
          private final Set<ConfigKeyGroup> groups = new TreeSet<>(ConfigKeyGroup.ORDERING);
          private final Map<String, Set<ConfigKey>> settings = new HashMap<>();
  
          private Builder() {}
  
          /**
           * Add the config key group to the builder.
           *
           * @param group config key group
           * @return builder to build this configuration def
           */
          public Builder withConfigKeyGroup(ConfigKeyGroup group) {
              groups.add(group);
              return this;
          }
  
          /**
           * Add the config key to the builder.
           *
           * @param key the key to add to the builder.
           * @return builder to build this configuration def
           */
          public Builder withConfigKey(ConfigKey key) {
              ConfigKeyGroup group = key.group();
              Set<ConfigKey> keys;
              String groupName;
              if (null == group) {
                  groupName = "";
              } else {
                  groupName = group.name();
                  groups.add(group);
              }
              keys = settings.computeIfAbsent(groupName, name -> new TreeSet<>(ConfigKey.ORDERING));
              keys.add(key);
              return this;
          }
  
          public ConfigDef build() {
              checkArgument(
                  Sets.difference(
                      groups.stream().map(group -> group.name()).collect(Collectors.toSet()),
                      settings.keySet()
                  ).isEmpty(),
                  "Configuration Key Groups doesn't match with keys");
              return new ConfigDef(groups, settings);
          }
  
      }
  
      /**
       * Create a builder to build a config def.
       *
       * @return builder to build a config def.
       */
      public static Builder builder() {
          return new Builder();
      }
  
      private final Set<ConfigKeyGroup> groups;
      private final Map<String, Set<ConfigKey>> settings;
      private final Map<String, ConfigKey> keys;
  
      private ConfigDef(Set<ConfigKeyGroup> groups,
                        Map<String, Set<ConfigKey>> settings) {
          this.groups = groups;
          this.settings = settings;
          this.keys = settings.values()
              .stream()
              .flatMap(keys -> keys.stream())
              .collect(Collectors.toSet())
              .stream()
              .collect(Collectors.toMap(
                  key -> key.name(),
                  key -> key
              ));
      }
  
      /**
       * Validate if the provided <tt>conf</tt> is a valid configuration of this configuration definition.
       *
       * @param conf the configuration to validate
       */
      public void validate(Configuration conf) throws ConfigException {
          for (ConfigKey key : keys.values()) {
              key.validate(conf);
          }
      }
  
      /**
       * Build the config definitation of a config class.
       *
       * @param configClass config class
       * @return config definition.
       */
      @SuppressWarnings("unchecked")
      public static ConfigDef of(Class configClass) {
          ConfigDef.Builder builder = ConfigDef.builder();
  
          Field[] fields = configClass.getDeclaredFields();
          for (Field field : fields) {
              if (Modifier.isStatic(field.getModifiers()) && field.getType().equals(ConfigKey.class)) {
                  field.setAccessible(true);
                  try {
                      builder.withConfigKey((ConfigKey) field.get(null));
                  } catch (IllegalAccessException e) {
                      log.error("Illegal to access {}#{}", configClass.getSimpleName(), field.getName(), e);
                  }
              }
          }
  
          return builder.build();
      }
  
      //
      // Methods to save the configuration to an {@link OutputStream}
      //
  
      private static final int MAX_COLUMN_SIZE = 80;
      private static final String COMMENT_PREFIX = "# ";
  
      public void save(Path path) throws IOException  {
          try (OutputStream stream = Files.newOutputStream(
              path, StandardOpenOption.WRITE, StandardOpenOption.TRUNCATE_EXISTING)) {
              save(stream);
          }
      }
  
      public void save(OutputStream os) throws IOException {
          try (PrintStream ps = new PrintStream(os, false, UTF_8.name())) {
              save(ps);
              ps.flush();
          }
      }
  
      private void writeNSharps(PrintStream stream, int num) {
          IntStream.range(0, num).forEach(ignored -> stream.print("#"));
      }
  
      private void writeConfigKeyGroup(PrintStream stream, ConfigKeyGroup group) {
          int maxLength = Math.min(
              group.description().length() + COMMENT_PREFIX.length(),
              MAX_COLUMN_SIZE
          );
          // "###########"
          writeNSharps(stream, maxLength);
          stream.println();
          // "# Settings of `<group>`
          writeSentence(stream, COMMENT_PREFIX, "Settings of `" + group.name() + "`");
          stream.println("#");
          // "# <group description>"
          writeSentence(stream, COMMENT_PREFIX, group.description());
          // "###########"
          writeNSharps(stream, maxLength);
          stream.println();
      }
  
      private void writeConfigKey(PrintStream stream,
                                  ConfigKey key) {
          // "# <description>"
          // "#"
          if (StringUtils.isNotBlank(key.description())) {
              writeSentence(stream, COMMENT_PREFIX, key.description());
              stream.println("#");
          }
          // "# <documentation>"
          // "#"
          if (StringUtils.isNotBlank(key.documentation())) {
              writeSentence(stream, COMMENT_PREFIX, key.documentation());
              stream.println("#");
          }
          // "# type: <type>, required"
          writeSentence(
              stream,
              COMMENT_PREFIX,
              "TYPE: " + key.type() + ", " + (key.required() ? "required" : "optional"));
          if (null != key.validator() && StringUtils.isNotBlank(key.validator().documentation())) {
              writeSentence(
                  stream, COMMENT_PREFIX,
                  "@constraints : " + key.validator().documentation()
              );
          }
          if (!key.optionValues().isEmpty()) {
              writeSentence(
                  stream, COMMENT_PREFIX, "@options :"
              );
              key.optionValues().forEach(value -> {
                  writeSentence(
                      stream, COMMENT_PREFIX, "  " + value
                  );
              });
          }
          // "#"
          // "# @Since"
          if (StringUtils.isNotBlank(key.since())) {
              stream.println("#");
              writeSentence(stream, COMMENT_PREFIX,
                  "@since " + key.since() + "");
          }
          // "#"
          // "# @Deprecated"
          if (key.deprecated()) {
              stream.println("#");
              writeSentence(stream, COMMENT_PREFIX, getDeprecationDescription(key));
          }
          // <key>=<defaultValue>
          stream.print(key.name());
          stream.print("=");
          if (null != key.defaultValue()) {
              stream.print(key.defaultValue());
          }
          stream.println();
      }
  
      private String getDeprecationDescription(ConfigKey key) {
          StringBuilder sb = new StringBuilder();
          sb.append("@deprecated");
          if (StringUtils.isNotBlank(key.deprecatedSince())) {
              sb.append(" since `")
                .append(key.deprecatedSince())
                .append("`");
          }
          if (StringUtils.isNotBlank(key.deprecatedByConfigKey())) {
              sb.append(" in favor of using `")
                .append(key.deprecatedByConfigKey())
                .append("`");
          }
          return sb.toString();
      }
  
      private void writeSentence(PrintStream stream,
                                 String prefix,
                                 String sentence) {
          int max = MAX_COLUMN_SIZE;
          String[] words = sentence.split(" ");
          int i = 0;
          stream.print(prefix);
          int current = prefix.length();
          while (i < words.length) {
              String word = words[i];
              if (word.length() > max || current + word.length() <= max) {
                  if (i != 0) {
                      stream.print(" ");
                  }
                  stream.print(word);
                  current += (word.length() + 1);
              } else {
                  stream.println();
                  stream.print(prefix);
                  stream.print(word);
                  current = prefix.length() + word.length();
              }
              ++i;
          }
          stream.println();
      }
  
      private void save(PrintStream stream) {
          for (ConfigKeyGroup group : groups) {
              writeConfigKeyGroup(stream, group);
              stream.println();
              Set<ConfigKey> groupKeys = settings.getOrDefault(group.name(), Collections.emptySet());
              groupKeys.forEach(key -> {
                  writeConfigKey(stream, key);
                  stream.println();
              });
          }
      }
  
  
  }
  