/*
 * Copyright (C) 2006 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.errorprone.annotations.CanIgnoreReturnValue;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

Simple helper class to build a "sparse" array of objects based on the indexes that were added to
it. The array will be from 0 to the maximum index given. All non-set indexes will contain null
(so it's not really a sparse array, just a pseudo sparse array). The builder can also return a
CharEscaper based on the generated array.
Author:
Sven Mawson
Since:
15.0/**
 * Simple helper class to build a "sparse" array of objects based on the indexes that were added to
 * it. The array will be from 0 to the maximum index given. All non-set indexes will contain null
 * (so it's not really a sparse array, just a pseudo sparse array). The builder can also return a
 * CharEscaper based on the generated array.
 *
 * @author Sven Mawson
 * @since 15.0
 */
@Beta
@GwtCompatible
public final class CharEscaperBuilder {
  
Simple decorator that turns an array of replacement char[]s into a CharEscaper, this results in
a very fast escape method.
/**
   * Simple decorator that turns an array of replacement char[]s into a CharEscaper, this results in
   * a very fast escape method.
   */
  private static class CharArrayDecorator extends CharEscaper {
    private final char[][] replacements;
    private final int replaceLength;

    CharArrayDecorator(char[][] replacements) {
      this.replacements = replacements;
      this.replaceLength = replacements.length;
    }

    /*
     * Overriding escape method to be slightly faster for this decorator. We test the replacements
     * array directly, saving a method call.
     */
    @Override
    public String escape(String s) {
      int slen = s.length();
      for (int index = 0; index < slen; index++) {
        char c = s.charAt(index);
        if (c < replacements.length && replacements[c] != null) {
          return escapeSlow(s, index);
        }
      }
      return s;
    }

    @Override
    protected char[] escape(char c) {
      return c < replaceLength ? replacements[c] : null;
    }
  }

  // Replacement mappings.
  private final Map<Character, String> map;

  // The highest index we've seen so far.
  private int max = -1;

  
Construct a new sparse array builder. /** Construct a new sparse array builder. */
  public CharEscaperBuilder() {
    this.map = new HashMap<>();
  }

  
Add a new mapping from an index to an object to the escaping. /** Add a new mapping from an index to an object to the escaping. */
  @CanIgnoreReturnValue
  public CharEscaperBuilder addEscape(char c, String r) {
    map.put(c, checkNotNull(r));
    if (c > max) {
      max = c;
    }
    return this;
  }

  
Add multiple mappings at once for a particular index. /** Add multiple mappings at once for a particular index. */
  @CanIgnoreReturnValue
  public CharEscaperBuilder addEscapes(char[] cs, String r) {
    checkNotNull(r);
    for (char c : cs) {
      addEscape(c, r);
    }
    return this;
  }

  
Convert this builder into an array of char[]s where the maximum index is the value of the
highest character that has been seen. The array will be sparse in the sense that any unseen
index will default to null.
Returns:
a "sparse" array that holds the replacement mappings./**
   * Convert this builder into an array of char[]s where the maximum index is the value of the
   * highest character that has been seen. The array will be sparse in the sense that any unseen
   * index will default to null.
   *
   * @return a "sparse" array that holds the replacement mappings.
   */
  public char[][] toArray() {
    char[][] result = new char[max + 1][];
    for (Entry<Character, String> entry : map.entrySet()) {
      result[entry.getKey()] = entry.getValue().toCharArray();
    }
    return result;
  }

  
Convert this builder into a char escaper which is just a decorator around the underlying array
of replacement char[]s.
Returns:
an escaper that escapes based on the underlying array./**
   * Convert this builder into a char escaper which is just a decorator around the underlying array
   * of replacement char[]s.
   *
   * @return an escaper that escapes based on the underlying array.
   */
  public Escaper toEscaper() {
    return new CharArrayDecorator(toArray());
  }
}