/*
 * Copyright (C) 2009 The Guava Authors
 *
 * 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.google.common.escape;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.VisibleForTesting;
import java.util.Collections;
import java.util.Map;

An implementation-specific parameter class suitable for initializing ArrayBasedCharEscaper or ArrayBasedUnicodeEscaper instances. This class should be used when more than one escaper is created using the same character replacement mapping to allow the underlying (implementation specific) data structures to be shared. 
The size of the data structure used by ArrayBasedCharEscaper and ArrayBasedUnicodeEscaper is proportional to the highest valued character that has a replacement. For example a replacement map containing the single character '\u1000' will require approximately 16K of memory. As such sharing this data structure between escaper instances is the primary goal of this class. 
Author:
David Beaumont
Since:
15.0/**
 * An implementation-specific parameter class suitable for initializing {@link
 * ArrayBasedCharEscaper} or {@link ArrayBasedUnicodeEscaper} instances. This class should be used
 * when more than one escaper is created using the same character replacement mapping to allow the
 * underlying (implementation specific) data structures to be shared.
 *
 * <p>The size of the data structure used by ArrayBasedCharEscaper and ArrayBasedUnicodeEscaper is
 * proportional to the highest valued character that has a replacement. For example a replacement
 * map containing the single character '{@literal \}u1000' will require approximately 16K of memory.
 * As such sharing this data structure between escaper instances is the primary goal of this class.
 *
 * @author David Beaumont
 * @since 15.0
 */
@Beta
@GwtCompatible
public final class ArrayBasedEscaperMap {
  
Returns a new ArrayBasedEscaperMap for creating ArrayBasedCharEscaper or
ArrayBasedUnicodeEscaper instances.
Params:
replacements – a map of characters to their escaped representations/**
   * Returns a new ArrayBasedEscaperMap for creating ArrayBasedCharEscaper or
   * ArrayBasedUnicodeEscaper instances.
   *
   * @param replacements a map of characters to their escaped representations
   */
  public static ArrayBasedEscaperMap create(Map<Character, String> replacements) {
    return new ArrayBasedEscaperMap(createReplacementArray(replacements));
  }

  // The underlying replacement array we can share between multiple escaper
  // instances.
  private final char[][] replacementArray;

  private ArrayBasedEscaperMap(char[][] replacementArray) {
    this.replacementArray = replacementArray;
  }

  // Returns the non-null array of replacements for fast lookup.
  char[][] getReplacementArray() {
    return replacementArray;
  }

  // Creates a replacement array from the given map. The returned array is a
  // linear lookup table of replacement character sequences indexed by the
  // original character value.
  @VisibleForTesting
  static char[][] createReplacementArray(Map<Character, String> map) {
    checkNotNull(map); // GWT specific check (do not optimize)
    if (map.isEmpty()) {
      return EMPTY_REPLACEMENT_ARRAY;
    }
    char max = Collections.max(map.keySet());
    char[][] replacements = new char[max + 1][];
    for (char c : map.keySet()) {
      replacements[c] = map.get(c).toCharArray();
    }
    return replacements;
  }

  // Immutable empty array for when there are no replacements.
  private static final char[][] EMPTY_REPLACEMENT_ARRAY = new char[0][0];
}