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/*
 * Copyright 2022 Jeroen Gremmen
 *
 * 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
 *
 *   https://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 de.sayayi.lib.message.util;

import org.jetbrains.annotations.Contract;
import org.jetbrains.annotations.NotNull;

import static java.lang.Character.*;


/**
 * This class contains various methods regarding spaces in strings.
 *
 * @author Jeroen Gremmen
 * @since 0.6.4
 */
public final class SpacesUtil
{
  private SpacesUtil() {}


  /**
   * Determines if the specified character is a Unicode space character. A character is considered
   * to be a space character if and only if it is specified to be a space character by the
   * Unicode Standard. This method returns true if the character's general category type is any of
   * the following:
   * 
   *  {@code SPACE_SEPARATOR}
   * 
 {@code PARAGRAPH_SEPARATOR}
   * 
   *
   * @param ch  the character to be tested
   *
   * @return  {@code true} if the character is a space character,
   *          {@code false} otherwise
   *
   * @see Character#isSpaceChar(char)
   */
  @Contract(pure = true)
  public static boolean isSpaceChar(char ch) {
    return ((((1 << SPACE_SEPARATOR) | (1 << PARAGRAPH_SEPARATOR)) >> getType((int)ch)) & 1) != 0;
  }


  /**
   * Returns a string without leading and trailing spaces. This method differs from
   * {@link String#trim()} in that it doesn't trim newlines.
   *
   * @param s  string to trim, or {@code null}
   *
   * @return  trimmed string, or {@code null} if {@code s} is {@code null}
   *
   * @see #isSpaceChar(char)
   */
  @Contract(value = "null -> null", pure = true)
  @SuppressWarnings("DuplicatedCode")
  public static String trimSpaces(String s)
  {
    if (s == null)
      return null;

    final char[] val = s.toCharArray();
    int endIndex = val.length;
    int startIdx = 0;

    while(startIdx < endIndex && isSpaceChar(val[startIdx]))
      startIdx++;

    while(startIdx < endIndex && isSpaceChar(val[endIndex - 1]))
      endIndex--;

    return startIdx == endIndex
        ? ""
        : startIdx > 0 || endIndex < val.length
            ? new String(val, startIdx, endIndex - startIdx) : s;
  }


  /**
   * Returns the trimmed variant of {@code s}. If {@code s = null} an empty string is returned.
   *
   * @param s  string to trim
   *
   * @return  trimmed string, never {@code null}
   *
   * @see #trimSpaces(String)
   */
  @Contract(pure = true)
  public static @NotNull String trimSpacesNotNull(String s) {
    return s == null ? "" : trimSpaces(s);
  }


  /**
   * Tells if a string is empty.
   * 
   * A string is considered empty if it has zero length or it contains spaces only.
   *
   * @param s  string, not {@code null}
   *
   * @return  {@code true} if the string is empty or contains spaces only, {@code false} otherwise
   *
   * @see #isSpaceChar(char)
   */
  @Contract(pure = true)
  @SuppressWarnings("DuplicatedCode")
  public static boolean isTrimmedEmpty(@NotNull String s)
  {
    final char[] val = s.toCharArray();
    int endIndex = val.length;
    int startIdx = 0;

    while(startIdx < endIndex && isSpaceChar(val[startIdx]))
      startIdx++;

    while(startIdx < endIndex && isSpaceChar(val[endIndex - 1]))
      endIndex--;

    return startIdx == endIndex;
  }


  /**
   * Returns whether string {@code s} is empty or not.
   *
   * @param s  string or {@code null}
   *
   * @return  {@code true} if the string is empty or {@code null}, {@code false} otherwise
   */
  @Contract(value = "null -> true", pure = true)
  public static boolean isEmpty(String s) {
    return s == null || s.isEmpty();
  }
}