/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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.
   */
  
  /*
   * This is not the original file distributed by the Apache Software Foundation
   * It has been modified by the Hipparchus project
   */
  package org.hipparchus.optim;
  
  import org.hipparchus.exception.MathIllegalStateException;
  import org.hipparchus.util.Incrementor;
  
  /**
   * Base class for implementing optimizers.
   * It contains the boiler-plate code for counting the number of evaluations
   * of the objective function and the number of iterations of the algorithm,
   * and storing the convergence checker.
   * <em>It is not a "user" class.</em>
   *
   * @param <P> Type of the point/value pair returned by the optimization
   * algorithm.
   *
   */
  public abstract class BaseOptimizer<P> {
      /** Evaluations counter. */
      protected Incrementor evaluations;
      /** Iterations counter. */
      protected Incrementor iterations;
      /** Convergence checker. */
      private final ConvergenceChecker<P> checker;
  
      /** Simple constructor.
       * @param checker Convergence checker.
       */
      protected BaseOptimizer(ConvergenceChecker<P> checker) {
          this(checker, 0, Integer.MAX_VALUE);
      }
  
      /** Simple constructor.
       * @param checker Convergence checker.
       * @param maxEval Maximum number of objective function evaluations.
       * @param maxIter Maximum number of algorithm iterations.
       */
      protected BaseOptimizer(ConvergenceChecker<P> checker,
                              int maxEval,
                              int maxIter) {
          this.checker = checker;
  
          evaluations = new Incrementor(maxEval);
          iterations  = new Incrementor(maxIter);
      }
  
      /**
       * Gets the maximal number of function evaluations.
       *
       * @return the maximal number of function evaluations.
       */
      public int getMaxEvaluations() {
          return evaluations.getMaximalCount();
      }
  
      /**
       * Gets the number of evaluations of the objective function.
       * The number of evaluations corresponds to the last call to the
       * {@code optimize} method. It is 0 if the method has not been
       * called yet.
       *
       * @return the number of evaluations of the objective function.
       */
      public int getEvaluations() {
          return evaluations.getCount();
      }
  
      /**
       * Gets the maximal number of iterations.
       *
       * @return the maximal number of iterations.
       */
      public int getMaxIterations() {
          return iterations.getMaximalCount();
      }
  
      /**
       * Gets the number of iterations performed by the algorithm.
       * The number iterations corresponds to the last call to the
      * {@code optimize} method. It is 0 if the method has not been
      * called yet.
      *
      * @return the number of evaluations of the objective function.
      */
     public int getIterations() {
         return iterations.getCount();
     }
 
     /**
      * Gets the convergence checker.
      *
      * @return the object used to check for convergence.
      */
     public ConvergenceChecker<P> getConvergenceChecker() {
         return checker;
     }
 
     /**
      * Stores data and performs the optimization.
      * <p>
      * The list of parameters is open-ended so that sub-classes can extend it
      * with arguments specific to their concrete implementations.
      * <p>
      * When the method is called multiple times, instance data is overwritten
      * only when actually present in the list of arguments: when not specified,
      * data set in a previous call is retained (and thus is optional in
      * subsequent calls).
      * <p>
      * Important note: Subclasses <em>must</em> override
      * {@link #parseOptimizationData(OptimizationData[])} if they need to register
      * their own options; but then, they <em>must</em> also call
      * {@code super.parseOptimizationData(optData)} within that method.
      *
      * @param optData Optimization data.
      * This method will register the following data:
      * <ul>
      *  <li>{@link MaxEval}</li>
      *  <li>{@link MaxIter}</li>
      * </ul>
      * @return a point/value pair that satisfies the convergence criteria.
      * @throws MathIllegalStateException if the maximal number of
      * evaluations is exceeded.
      * @throws MathIllegalStateException if the maximal number of
      * iterations is exceeded.
      */
     public P optimize(OptimizationData... optData)
         throws MathIllegalStateException {
         // Parse options.
         parseOptimizationData(optData);
 
         // Reset counters.
         evaluations.reset();
         iterations.reset();
         // Perform optimization.
         return doOptimize();
     }
 
     /**
      * Performs the optimization.
      *
      * @return a point/value pair that satisfies the convergence criteria.
      * @throws MathIllegalStateException if the maximal number of
      * evaluations is exceeded.
      * @throws MathIllegalStateException if the maximal number of
      * iterations is exceeded.
      */
     public P optimize()
         throws MathIllegalStateException {
         // Reset counters.
         evaluations.reset();
         iterations.reset();
         // Perform optimization.
         return doOptimize();
     }
 
     /**
      * Performs the bulk of the optimization algorithm.
      *
      * @return the point/value pair giving the optimal value of the
      * objective function.
      */
     protected abstract P doOptimize();
 
     /**
      * Increment the evaluation count.
      *
      * @throws MathIllegalStateException if the allowed evaluations
      * have been exhausted.
      */
     protected void incrementEvaluationCount()
         throws MathIllegalStateException {
         evaluations.increment();
     }
 
     /**
      * Increment the iteration count.
      *
      * @throws MathIllegalStateException if the allowed iterations
      * have been exhausted.
      */
     protected void incrementIterationCount()
         throws MathIllegalStateException {
         iterations.increment();
     }
 
     /**
      * Scans the list of (required and optional) optimization data that
      * characterize the problem.
      *
      * @param optData Optimization data.
      * The following data will be looked for:
      * <ul>
      *  <li>{@link MaxEval}</li>
      *  <li>{@link MaxIter}</li>
      * </ul>
      */
     protected void parseOptimizationData(OptimizationData... optData) {
         // The existing values (as set by the previous call) are reused if
         // not provided in the argument list.
         for (OptimizationData data : optData) {
             if (data instanceof MaxEval) {
                 evaluations = evaluations.withMaximalCount(((MaxEval) data).getMaxEval());
                 continue;
             }
             if (data instanceof MaxIter) {
                 iterations = iterations.withMaximalCount(((MaxIter) data).getMaxIter());
                 continue;
             }
         }
     }
 }