/*
 * Copyright 2012-present Facebook, 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.facebook.buck.cli;

import com.google.common.base.Preconditions;
import com.google.common.base.Splitter;
import com.google.common.base.Supplier;
import com.google.common.base.Suppliers;
import com.google.common.collect.ImmutableSet;

import org.kohsuke.args4j.CmdLineException;
import org.kohsuke.args4j.CmdLineParser;
import org.kohsuke.args4j.OptionDef;
import org.kohsuke.args4j.spi.OptionHandler;
import org.kohsuke.args4j.spi.Parameters;
import org.kohsuke.args4j.spi.Setter;

import java.util.Iterator;
import java.util.Set;

/**
 * {@link OptionHandler} that collects multiple arguments passed to an option in a {@link Set}.
 * In a list of command-line arguments:
 * <ul>
 *   <li>The option may be specified multiple times.
 *   <li>When the option is specified, it must have at least one value
 *       (multiple values must be delimited by spaces).
 *   <li>The same value may be specified multiple times for the option.
 *       However, even though a value may be specified more than once, only one instance of it
 *       will be present in the resulting {@link Set}.
 * </ul>
 */
public class StringSetOptionHandler extends OptionHandler<Supplier<ImmutableSet<String>>>{

  private final ImmutableSet.Builder<String> builder = ImmutableSet.builder();
  private final Supplier<ImmutableSet<String>> supplier =
      Suppliers.memoize(new Supplier<ImmutableSet<String>>() {
        @Override
        public ImmutableSet<String> get() {
          return builder.build();
        }
  });

  public StringSetOptionHandler (
      CmdLineParser parser, OptionDef option, Setter<? super Supplier<ImmutableSet<String>>> setter)
          throws CmdLineException {
    super(parser, option, setter);
    setter.addValue(supplier);
  }

  @Override
  public String getDefaultMetaVariable() {
    return "SET<STRING>";
  }

  @Override
  public int parseArguments(Parameters params) throws CmdLineException {
    int counter = 0;
    boolean hasValues = false;

    while (counter < params.size()) {
      String param = params.getParameter(counter);
      if (param.charAt(0) == '-') {
        break;
      }
      Iterator<String> values = Splitter.on(' ')
          .trimResults()
          .omitEmptyStrings()
          .split(param)
          .iterator();
      if (values.hasNext()) {
        hasValues = true;
        builder.addAll(values);
      }

      counter++;
    }

    Preconditions.checkArgument(
        hasValues, "Option \"%s\" takes one or more operands", option);
    return counter;
  }
}