/**
 * 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.search.function;

import org.apache.lucene.search.FieldCache;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.util.BytesRef;
import org.apache.solr.search.MutableValue;
import org.apache.solr.search.MutableValueStr;

import java.io.IOException;

/** Internal class, subject to change.
 *  Serves as base class for DocValues based on StringIndex 
 **/
public abstract class StringIndexDocValues extends DocValues {
    protected final FieldCache.DocTermsIndex termsIndex;
    protected final ValueSource vs;
    protected final MutableValueStr val = new MutableValueStr();

    public StringIndexDocValues(ValueSource vs, IndexReader reader, String field) throws IOException {
      try {
        termsIndex = FieldCache.DEFAULT.getTermsIndex(reader, field);
      } catch (RuntimeException e) {
        throw new StringIndexException(field, e);
      }
      this.vs = vs;
    }
  
    protected abstract String toTerm(String readableValue);

    @Override
    public ValueSourceScorer getRangeScorer(IndexReader reader, String lowerVal, String upperVal, boolean includeLower, boolean includeUpper) {
      // TODO: are lowerVal and upperVal in indexed form or not?
      lowerVal = lowerVal == null ? null : toTerm(lowerVal);
      upperVal = upperVal == null ? null : toTerm(upperVal);

      final BytesRef spare = new BytesRef();

      int lower = Integer.MIN_VALUE;
      if (lowerVal != null) {
        lower = termsIndex.binarySearchLookup(new BytesRef(lowerVal), spare);
        if (lower < 0) {
          lower = -lower-1;
        } else if (!includeLower) {
          lower++;
        }
      }
      
      int upper = Integer.MAX_VALUE;
      if (upperVal != null) {
        upper = termsIndex.binarySearchLookup(new BytesRef(upperVal), spare);
        if (upper < 0) {
          upper = -upper-2;
        } else if (!includeUpper) {
          upper--;
        }
      }

      final int ll = lower;
      final int uu = upper;

      return new ValueSourceScorer(reader, this) {
        @Override
        public boolean matchesValue(int doc) {
          int ord = termsIndex.getOrd(doc);
          return ord >= ll && ord <= uu;
        }
      };
    }

  public String toString(int doc) {
    return vs.description() + '=' + strVal(doc);
  }

  @Override
  public ValueFiller getValueFiller() {
    return new ValueFiller() {
      private final MutableValueStr mval = new MutableValueStr();

      @Override
      public MutableValue getValue() {
        return mval;
      }

      @Override
      public void fillValue(int doc) {
        mval.value = termsIndex.getTerm(doc, val.value);
      }
    };
  }

  public static final class StringIndexException extends RuntimeException {
    public StringIndexException(final String fieldName,
                                final RuntimeException cause) {
      super("Can't initialize StringIndex to generate (function) " +
            "DocValues for field: " + fieldName, cause);
    }
  }


}