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Java Simplified. Extensions and Useful Constructs for the Java Platform. Codeprimate Elements (a.k.a. cp-elements) is a Java library and micro-framework used to simplify the development of software applications written in Java. Elements packages several APIs into one library in order to address various application concerns and aspects of software design and development collectively and conveniently. Elements is a highly simple, yet robust and proven library built on solid OO principles, software design patterns and best practices to effectively solve common and reoccurring problems in software development. Write better Java!

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/*
 * Copyright 2011-Present Author or 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 org.cp.elements.enums;

import java.util.Arrays;
import java.util.Locale;
import java.util.Optional;
import java.util.function.Predicate;

import org.cp.elements.function.FunctionUtils;
import org.cp.elements.lang.StringUtils;
import org.cp.elements.lang.annotation.NotNull;
import org.cp.elements.lang.annotation.Nullable;

/**
 * {@link Enum Enumeration} of length, height or distance measurements.
 *
 * @author John Blum
 * @see java.lang.Enum
 * @see Unit of length
 * @since 1.0.0
 */
public enum LengthUnit {

  YOCTOMETER("ym", Math.pow(10, -24)),
  ZEPTOMETER("zm", Math.pow(10, -21)),
  ATTOMETER("am", Math.pow(10, -18)),
  FEMTOMETER("fm", Math.pow(10, -15)),
  PICOMETER("pm", Math.pow(10, -12)),
  NANOMETER("nm", Math.pow(10, -9)),
  MICROMETER("um", Math.pow(10, -6)),
  MILLIMETER("mm", 0.001d),
  CENTIMETER("cm", 0.01d),
  DECIMETER("dm", 0.10d),
  METER("m", 1.0d),
  DECAMETER("da", 10.0d),
  HECTOMETER("hm", 100.0d),
  KILOMETER("km", 1_000.0d),
  MEGAMETER("MM", 1_000_000d),
  GIGAMETER("GM", 1_000_000_000d),
  TERAMETER("TM", Math.pow(10, 12)),
  PETAMETER("PM", Math.pow(10, 15)),
  EXAMETER("EM", Math.pow(10, 18)),
  ZETAMETER("ZM", Math.pow(10, 21)),
  YOTTAMETER("YM", Math.pow(10, 24)),
  INCH("in", 0.0254d),
  FOOT("ft", 0.3048d),
  YARD("yd", 0.9144),
  MILE("mi", 1609.34),
  LIGHT_YEAR("ly", 9.460528405d * Math.pow(10, 15));

  /**
   * Factory method used to get the default unit of length based in the current, default {@link Locale}.
   * 
   * Returns {@link LengthUnit#FOOT} if this is the {@literal United States of America (USA)},
   * otherwise returns {@link LengthUnit#METER} for all other countries.
   *
   * @return the default {@link LengthUnit} based in the current, default {@link Locale}.
   * @see java.util.Locale#getCountry()
   * @see java.util.Locale#getDefault()
   */
  public static @NotNull LengthUnit getDefault() {

    return Optional.of(Locale.getDefault().getCountry())
      .filter(Locale.US.getCountry()::equals)
      .map(country -> LengthUnit.FOOT)
      .orElse(LengthUnit.METER);
  }

  /**
   * Factory method used to find and match a {@link LengthUnit} by {@link String abbreviation}.
   *
   * @param abbreviation {@link String} containing the {@literal abbreviation} of the {@link LengthUnit} to find.
   * @return the {@link LengthUnit} for the given {@link String abbreviation}, or {@literal null}
   * if no {@link LengthUnit} with the given {@link String abbreviation} exists.
   * @see #valueOf(Predicate)
   * @see #getAbbreviation()
   */
  public static @Nullable LengthUnit valueOfAbbreviation(@Nullable String abbreviation) {
    return valueOf(length -> length.getAbbreviation().equals(abbreviation));
  }

  /**
   * Factory method used to find and match a {@link LengthUnit} by {@link String name}.
   * 
   * This operation is case-insensitive.
   *
   * @param name {@link String} containing the {@literal name} of the {@link LengthUnit} to find.
   * @return the {@link LengthUnit} with the given {@link String name}, or {@literal null}
   * if no {@link LengthUnit} with the given {@link String name} exists.
   * @see #valueOf(Predicate)
   * @see #name()
   */
  public static @Nullable LengthUnit valueOfName(@Nullable String name) {
    return valueOf(length -> length.name().equalsIgnoreCase(name));
  }

  /**
   * Factory method used to find and match a {@link LengthUnit} by the given, required {@link Predicate}.
   *
   * @param predicate {@link Predicate} used to find and match the {@link LengthUnit}; must not be {@literal null}.
   * @return a {@link LengthUnit} matching the given, required {@link Predicate} or {@literal null}
   * if no {@link LengthUnit} is a match for the given, required {@link Predicate}.
   * @see java.util.function.Predicate
   * @see #values()
   */
  private static @Nullable LengthUnit valueOf(@NotNull Predicate predicate) {

    return Arrays.stream(values())
      .filter(FunctionUtils.nullSafePredicateMatchingNone(predicate))
      .findFirst()
      .orElse(null);
  }

  private final double meterConversionFactor;

  private final String abbreviation;

  /**
   * Constructs a new {@link LengthUnit} initialized with the given, required {@link String abbreviation}.
   *
   * @param abbreviation {@link String} containing the abbreviation for {@literal this} {@link LengthUnit}.
   * @param meterConversionFactor {@link Double} conversion factor used to convert measurements
   * in this {@link LengthUnit} to {@link LengthUnit#METER meters}.
   */
  LengthUnit(@NotNull String abbreviation, double meterConversionFactor) {

    this.abbreviation = abbreviation;
    this.meterConversionFactor = meterConversionFactor;
  }

  /**
   * Gets the {@link String abbreviation} for {@literal this} {@link LengthUnit}.
   *
   * @return the {@link String abbreviation} for {@literal this} {@link LengthUnit}.
   * @see java.lang.String
   */
  public @NotNull String getAbbreviation() {
    return this.abbreviation;
  }

  /**
   * Gets the {@link Double} conversion factor used to convert measurements in this {@link LengthUnit}
   * to {@link LengthUnit#METER meters}.
   *
   * @return the {@link Double} conversion factor used to convert measurements in this {@link LengthUnit}
   * to {@link LengthUnit#METER meters}.
   */
  public double getMeterConversionFactor() {
    return this.meterConversionFactor;
  }

  /**
   * Returns the pluralized {@link #name()} of this {@link LengthUnit} enumerated value.
   *
   * @return the pluralized {@link #name()} of this {@link LengthUnit} enumerated value.
   * @see #name()
   */
  public @NotNull String getPluralName() {
    return this == FOOT ? "FEET" : this == INCH ? "INCHES" : name().concat("S");
  }

  /**
   * Returns a {@link String} representation for {@literal this} {@link LengthUnit}.
   *
   * @return a {@link String} describing {@literal this} {@link LengthUnit}.
   * @see java.lang.Object#toString()
   * @see #name()
   */
  @Override
  public String toString() {
    return StringUtils.capitalize(name().toLowerCase());
  }
}