/*
 * Copyright 2015-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.rules.keys;

import com.facebook.buck.rules.AddToRuleKey;
import com.facebook.buck.rules.BuildRule;
import com.google.common.cache.CacheLoader;
import com.google.common.collect.ImmutableCollection;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSortedMap;
import java.lang.reflect.Field;
import java.util.Comparator;

class ReflectiveAlterKeyLoader
    extends CacheLoader<Class<? extends BuildRule>, ImmutableCollection<AlterRuleKey>> {

  private static final Comparator<ValueExtractor> COMPARATOR =
      (o1, o2) -> {
        String name1 = o1.getFullyQualifiedName();
        String name2 = o2.getFullyQualifiedName();
        return name1.compareTo(name2);
      };

  @Override
  public ImmutableCollection<AlterRuleKey> load(Class<? extends BuildRule> key) throws Exception {
    ImmutableList.Builder<AlterRuleKey> builder = ImmutableList.builder();
    for (Class<?> current = key; !Object.class.equals(current); current = current.getSuperclass()) {
      ImmutableSortedMap.Builder<ValueExtractor, AlterRuleKey> sortedExtractors =
          ImmutableSortedMap.orderedBy(COMPARATOR);
      for (final Field field : current.getDeclaredFields()) {
        field.setAccessible(true);
        final AddToRuleKey annotation = field.getAnnotation(AddToRuleKey.class);
        if (annotation != null) {
          ValueExtractor valueExtractor = new FieldValueExtractor(field);
          sortedExtractors.put(valueExtractor, createAlterRuleKey(valueExtractor, annotation));
        }
      }
      builder.addAll(sortedExtractors.build().values());
    }
    return builder.build();
  }

  private AlterRuleKey createAlterRuleKey(ValueExtractor valueExtractor, AddToRuleKey annotation) {
    if (annotation.stringify()) {
      return new StringifyAlterRuleKey(valueExtractor);
    } else {
      return new DefaultAlterRuleKey(valueExtractor);
    }
  }
}