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package com.github.dakusui.valid8j;

import com.github.dakusui.valid8j_pcond.validator.Validator;

import java.util.function.Predicate;

/**
 * A class that offers entry-points for checking "postconditions" with a normal
 * conditional statement of Java language.
 * That is, `if` or ternary operator, not an `assert` statement.
 * This means, the user of your product is not able to disable the checks you
 * write at runtime, unlike ones written using `assert` statements.
 *
 * The author of library thinks these methods should be used in "public facing"
 * methods, when you should claim that the "external" party introduced the bug.
 *
 * The author of library thinks these methods should be used in "public facing"
 * context when the provider of the value to be examined introduced
 * a bug, which makes the condition `false`.
 *
 * For instance, it is an intended use-case, where you call `ensure` at the end of
 * your method in order to express a condition to be satisfied by the value returned
 * from your method.
 */
public enum Ensures {
  ;

  /**
   * Checks if a given value is not `null`.
   * If not an exception will be thrown.
   *
   * @param value A value to be checked.
   * @return The value itself.
   * @param  The type of the `value`.
   */
  public static  T ensureNonNull(T value) {
    return Validator.instance().ensureNonNull(value);
  }

  /**
   * Checks if a given state `value`satisfies a postcondition `cond`.
   * If not an exception will be thrown.
   *
   * @param value A value to be checked.
   * @param cond A condition that checks `value`.
   * @return The `value` itself
   * @param  The type of the `value`.
   */
  public static  T ensureState(T value, Predicate cond) {
    return Validator.instance().ensureState(value, cond);
  }

  /**
   * Checks if a given `value` satisfies a postcondition `cond`.
   * If not an exception will be thrown.
   *
   * @param value A value to be checked.
   * @param cond A condition that checks `value`.
   * @return The `value` itself.
   * @param  The type of the `value`.
   */
  public static  T ensure(T value, Predicate cond) {
    return Validator.instance().ensure(value, cond);
  }
}