#include <iostream>
#include <deque>

// This code demonstrates the error that causes the unit test TeuchosParameterList_StringIndexedOrderedValueObjectContainer to fail

// This code fails for optimization level 0 but succeeds for other optimization levels.
// Tested for clang: Apple LLVM version 7.3.0 (clang-703.0.31)

// The bug can be reproduced using a simple command line build with optimization level set to 0
//    build: clang++ -o test test.cpp -O0         Bad! begin() = end() but should be different.
//    build: clang++ -o test test.cpp -O1         OK
//    build: clang++ -o test test.cpp -O2         OK
//    build: clang++ -o test test.cpp -O3         OK
//
// Notable Things
//   Change deque to vector clears all problems
//   Direct read of deque begin() and end() seems ok but reading through templated functions is not ok
//   Checking deque size() always seems ok
//   There are several lines of code which can be added after the 'problem' which then clear the problem. Commented out at the end.
//
// Some spurious things we can remove from this code which also remove the bug
//   The template declaration on the Item class
//   Change the 'itr1.current()' to be 'itr1.current_' 
//   Change the container1 object to have the same template type as container2
//   Remove the container1 object or remove the check on it's begin() and end() which are fine
//   Remove the dummy1 or dummy2 input parameters below
//   Change the inputs to those dummy variables from the current begin() and end() settings

template<class Type> class Filter 
{
public:
  // remove the spurious dummy1 or dummy2 and in the call below and then OK
  Filter( Type current, Type dummy1, Type dummy2 ) : current_(current) {}
  Type current() const { return current_; }
  Type current_;
};

template<class Type> bool operator==(const Filter<Type>& itr1, const Filter<Type>& itr2)
{
  return itr1.current() == itr2.current(); // change first current() to current_ then ok 
}

template<class T> class Item // remove the spurious template parameter and then OK
{
public:
  Item(std::string name) : name_(name) {}
  std::string name_;
};

template<class T> class Container
{
public:  
  typedef Item<T> item_t;
  typedef std::deque<item_t> deque_t;  // change deque to vector and then OK
  typedef Filter<typename deque_t::const_iterator> const_itr;
  
  Container() {}
  void addElement(std::string key) { deque_.push_back(item_t(key)); }
  
  // note the second two parameters are spurious but removing them or changing and then OK
  const_itr begin() const { return const_itr( deque_.begin(),   deque_.begin(), deque_.end() ); }
  const_itr end()   const { return const_itr( deque_.end(),     deque_.begin(), deque_.end() ); }
  deque_t deque_;
};

int main( int argc, char* argv[] )
{
  Container<int> container1; // change template to match other type (double) and then OK
  container1.addElement("AAA");
  if( container1.begin() == container1.end() ) { std::cout << "This never happens and it shouldn't happen..." << std::endl; }  // remove this line and then OK
  
  Container<double> container2; // or change this template to match first (int) and then OK
  container2.addElement("BBB");
  if( container2.begin() == container2.end() ) { std::cout << "Bad! begin() = end() but should be different." << std::endl; return 1; } 
  
  // This will verify direct read is ok
  // if( container2.deque_.begin() != container2.deque_.end() ) { std::cout << "Direct read of container2  begin() and end() is ok - not equal." << std::endl; } 
  
  // This will verify deque size is 1 as it should be
  // std::cout << "deque size is " << container1.deque_.size() << std::endl;

  // Adding any of these lines 'fixes' the above error so it won't happen...
  //   if( container2.deque_.begin() != container2.begin().current() ) { std::cout << "begin() direct does not match begin() through Filter." << std::endl; }
  //   if( container2.deque_.end() != container2.end().current() ) { std::cout << "begin() direct does not match begin() through Filter." << std::endl; } 
  //   container2.end().current();
  //   container2.begin().current();
    
  // Adding any of these lines does not 'fix' the above error
  //   container1.begin();
  //   container1.end();
  //   container2.begin();
  //   container2.end();
  //   container1.end().current();
  //   container1.begin().current();
  
  std::cout << "OK" << std::endl;
  return 0;
}