// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:

// SPDX-FileCopyrightText: Copyright © DUNE Project contributors, see file AUTHORS.md
// SPDX-License-Identifier: LicenseRef-GPL-2.0-only-with-DUNE-exception OR LGPL-3.0-or-later

#include <config.h>

#include <iostream>
#include <memory>
#include <functional>

#include <dune/common/exceptions.hh>
#include <dune/common/parallel/mpihelper.hh>

#include <dune/functions/common/differentiablefunction.hh>
#include <dune/functions/common/differentiablefunctionfromcallables.hh>
#include <dune/functions/common/functionconcepts.hh>

#include <dune/functions/analyticfunctions/polynomial.hh>
#include <dune/functions/analyticfunctions/trigonometricfunction.hh>

//#include "derivativecheck.hh"

bool checkTrue(bool value, std::string error)
{
  if (not(value))
    std::cout << "TEST FAILURE:" << error << std::endl;
  return value;
}

// Check if interface compiles and is implementable by a simple dummy
struct DifferentiableFunctionImplementableTest
{

  template<class F>
  static bool checkWithFunction(F&& f)
  {
    bool passed = true;
    using Dune::Functions::Concept::isFunction;
    using Dune::Functions::Concept::isDifferentiableFunction;
    using Dune::Functions::SignatureTag;

    {
      std::cout << "--------------" << std::endl;

//      passed = passed and DerivativeCheck<QuadraticPolynomial>::checkAllImplementedTrulyDerived(testFunction, 10);

      // Test whether I can evaluate the function somewhere
      std::cout << "Function value at x=5: " << f(5) << std::endl;
      passed = checkTrue(isDifferentiableFunction(f, SignatureTag<double(double)>()), "Raw function f does not satisfy DifferentiableFunction concept");

      std::cout << std::endl << "Check calling derivatives through function object" << std::endl;

      // Test whether I can evaluate the first derivative
      auto df = derivative(f);
      passed = checkTrue(isDifferentiableFunction(df, SignatureTag<double(double)>()), "Raw function df does not satisfy DifferentiableFunction concept");
      std::cout << "Derivative at x=5: " << df(5) << std::endl;

      // Test whether I can evaluate the second derivative through FunctionHandle
      auto ddf = derivative(df);
      passed = checkTrue(isDifferentiableFunction(ddf, SignatureTag<double(double)>()), "Raw function ddf does not satisfy DifferentiableFunction concept");
      std::cout << "Second derivative at x=5: " << ddf(5) << std::endl;

      // Test whether I can evaluate the third derivative through FunctionHandle
      auto dddf = derivative(ddf);
      passed = checkTrue(isFunction(dddf, SignatureTag<double(double)>()), "Raw function dddf does not satisfy Function concept");
      std::cout << "Third derivative at x=5: " << dddf(5) << std::endl;


      std::cout << std::endl << "Check calling derivatives through DifferentiableFunction object" << std::endl;
      Dune::Functions::DifferentiableFunction<double(const double&)> fi = f;
      passed = checkTrue(isDifferentiableFunction(fi, SignatureTag<double(double)>()), "Wrapped function fi does not satisfy DifferentiableFunction concept");

      // Try to reassign wrapper
      fi = f;

      // Try assigning a default constructed wrapper
      Dune::Functions::DifferentiableFunction<double(const double&)> fii;
      passed = checkTrue(isDifferentiableFunction(fii, SignatureTag<double(double)>()), "Wrapped function fii does not satisfy DifferentiableFunction concept");
      fii = fi;

      // Try to copy wrapper
      auto fiii = fii;
      passed = checkTrue(isDifferentiableFunction(fiii, SignatureTag<double(double)>()), "Wrapped function fiii does not satisfy DifferentiableFunction concept");

      std::cout << "Function value at x=5: " << fiii(5) << std::endl;
      // Test whether I can evaluate the first derivative
      auto dfiii = derivative(fiii);
      passed = checkTrue(isDifferentiableFunction(dfiii, SignatureTag<double(double)>()), "Wrapped function dfiii does not satisfy DifferentiableFunction concept");
      std::cout << "Derivative at x=5: " << dfiii(5) << std::endl;

      // Test whether I can evaluate the second derivative through FunctionHandle
      auto ddfiii = derivative(dfiii);
      passed = checkTrue(isDifferentiableFunction(ddfiii, SignatureTag<double(double)>()), "Wrapped function ddfiii does not satisfy DifferentiableFunction concept");
      std::cout << "Second derivative at x=5: " << ddfiii(5) << std::endl;

      // Test whether I can evaluate the third derivative through FunctionHandle
      auto dddfiii = derivative(ddfiii);
      passed = checkTrue(isFunction(dddfiii, SignatureTag<double(double)>()), "Wrapped function dddfiii does not satisfy Function concept");
      std::cout << "Third derivative at x=5: " << dddfiii(5) << std::endl;

      // Wrap as non-differentiable function
      auto g = [=] (const double& x) {return f(x);};
      passed = checkTrue(isFunction(g, SignatureTag<double(double)>()), "Lambda function g does not satisfy Function concept");

      Dune::Functions::DifferentiableFunction<double(const double&)> gg = [=] (const double& x) {return f(x);};
      passed = checkTrue(isFunction(gg, SignatureTag<double(double)>()), "Wrapped function gg does not satisfy DifferentiableFunction concept");
      std::cout << "Function value at x=5: " << gg(5) << std::endl;

      try {
        auto dg = derivative(gg);
        passed = false;
      }
      catch (Dune::NotImplemented& e)
      {
        std::cout << "Obtaining derivative from nondifferentiable function failed expectedly" << std::endl;
        passed = checkTrue(not(isDifferentiableFunction(g, SignatureTag<double(double)>())), "But unwrapped function g does satisfy DifferentiableFunction concept");
      }

    }

    return passed;
  }

  static bool check()
  {
    bool passed = true;

    passed = passed and checkWithFunction(Dune::Functions::Polynomial<double>({1, 2, 3}));
    passed = passed and checkWithFunction(Dune::Functions::TrigonometricFunction<double, 1, 0>());

    auto f = [](double x){ return std::sin(x);};
    auto df = [](double x){ return std::cos(x);};
    auto ddf = [](double x){ return -std::sin(x);};
    auto dddf = [](double x){ return -std::cos(x);};

    auto F = makeDifferentiableFunctionFromCallables(Dune::Functions::SignatureTag<double(double)>(), f, df, ddf, dddf);
    passed = passed and checkWithFunction(F);

    return passed;
  }


};



#if 0
// Check if recursive DerivativeRange definition terminates
// after at most maxRecursionLevel=k derivatives, i.e. if
// the type of the k-th and (k+1)-nd derivative is the same.
template<class D, class R, int maxRecursionLevel>
struct DerivativeRangeTerminationTest
{

  template<class DR, int recursionLevel>
  struct TerminationTest
  {
    static int level()
    {
      std::cout << "Type of " << recursionLevel << "-th derivative is " << Dune::className<DR>() << std::endl;
      typedef typename Dune::Functions::DerivativeTraits<D, DR>::DerivativeRange DDR;
      int upperBound = TerminationTest<DDR, recursionLevel+1>::level();
      if (std::is_same_v<DR, DDR>)
        return recursionLevel;
      else
        return upperBound;
    }
  };

  template<class DR>
  struct TerminationTest<DR, maxRecursionLevel>
  {
    static int level()
    {
      std::cout << "Type of " << maxRecursionLevel << "-th derivative is " << Dune::className<DR>() << std::endl;
      typedef typename Dune::Functions::DerivativeTraits<D, DR>::DerivativeRange DDR;
      if (std::is_same_v<DR, DDR>)
        return maxRecursionLevel;
      else
        return maxRecursionLevel+1;
    }
  };

  static bool check()
  {
    std::cout << "Checking recursion for Domain=" << Dune::className<D>() << " and Range=" << Dune::className<R>() << std::endl;
    int terminationLevel = TerminationTest<R, 0>::level();
    if (terminationLevel <= maxRecursionLevel)
    {
      std::cout << "Recursion terminated after " << terminationLevel << "-th derivative" << std::endl;
      return true;
    }
    else
    {
      std::cout << "Recursion did not terminated after given maxRecursionLevel " << maxRecursionLevel;
      return false;
    }
  }

};
#endif





int main ( int argc, char **argv )
try
{
  Dune::MPIHelper::instance(argc, argv);
  bool passed = true;

  passed = passed and DifferentiableFunctionImplementableTest::check();

#if 0
  passed = passed and DerivativeRangeTerminationTest<double, double, 5>::check();

  passed = passed and DerivativeRangeTerminationTest<Dune::FieldVector<double, 3> , Dune::FieldVector<double, 1>, 5 >::check();

  passed = passed and DerivativeRangeTerminationTest<Dune::FieldVector<double, 1> , Dune::FieldVector<double, 1>, 5 >::check();
#endif


  if (passed)
    std::cout << "All tests passed" << std::endl;


  return passed ? 0: 1;
}
catch( Dune::Exception &e )
{
  std::cerr << "Dune reported error: " << e << std::endl;
  return 1;
}
catch(...)
{
  std::cerr << "Unknown exception thrown!" << std::endl;
  return 1;
}