# ifndef CPPAD_CORE_ADD_EQ_HPP
# define CPPAD_CORE_ADD_EQ_HPP
// SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-or-later
// SPDX-FileCopyrightText: Bradley M. Bell <bradbell@seanet.com>
// SPDX-FileContributor: 2003-24 Bradley M. Bell
// ----------------------------------------------------------------------------

//  BEGIN CppAD namespace
namespace CppAD {

template <class Base>
AD<Base>& AD<Base>::operator += (const AD<Base> &right)
{
   // compute the Base part
   Base left;
   left    = value_;
   value_ += right.value_;

   // check if there is a recording in progress
   local::ADTape<Base>* tape = AD<Base>::tape_ptr();
   if( tape == nullptr )
      return *this;
   tape_id_t tape_id = tape->id_;
   // tape_id cannot match the default value for tape_id_; i.e., 0
   CPPAD_ASSERT_UNKNOWN( tape_id > 0 );

   // check if left and right tapes match
   bool match_left  = tape_id_       == tape_id;
   bool match_right = right.tape_id_ == tape_id;

   // check if left and right are dynamic parameters
   bool dyn_left  = match_left  & (ad_type_ == dynamic_enum);
   bool dyn_right = match_right & (right.ad_type_ == dynamic_enum);

   // check if left and right are variables
   bool var_left  = match_left  & (ad_type_ != dynamic_enum);
   bool var_right = match_right & (right.ad_type_ != dynamic_enum);

   CPPAD_ASSERT_KNOWN(
      tape_id_ == right.tape_id_ || ! match_left || ! match_right ,
      "+= : AD variables or dynamic parameters on different threads."
   );
   if( var_left )
   {  if( var_right )
      {  // this = variable + variable
         CPPAD_ASSERT_UNKNOWN( local::NumRes(local::AddvvOp) == 1 );
         CPPAD_ASSERT_UNKNOWN( local::NumArg(local::AddvvOp) == 2 );

         // put operand addresses in tape
         tape->Rec_.PutArg(taddr_, right.taddr_);
         // put operator in the tape
         taddr_ = tape->Rec_.PutOp(local::AddvvOp);
         // check that this is a variable
         CPPAD_ASSERT_UNKNOWN( tape_id_ == tape_id );
         CPPAD_ASSERT_UNKNOWN( ad_type_ == variable_enum);
      }
      else if( dyn_right | (! IdenticalZero(right.value_) ) )
      {  // this = variable  + parameter
         //      = parameter + variable
         CPPAD_ASSERT_UNKNOWN( local::NumRes(local::AddpvOp) == 1 );
         CPPAD_ASSERT_UNKNOWN( local::NumArg(local::AddpvOp) == 2 );

         // put operand addresses in tape
         addr_t p = right.taddr_;
         if( ! dyn_right )
            p = tape->Rec_.put_con_par(right.value_);
         tape->Rec_.PutArg(p, taddr_);
         // put operator in the tape
         taddr_ = tape->Rec_.PutOp(local::AddpvOp);
         // check that this is a variable
         CPPAD_ASSERT_UNKNOWN( tape_id_ == tape_id );
         CPPAD_ASSERT_UNKNOWN( ad_type_ == variable_enum);
      }
   }
   else if( var_right  )
   {  if( (! dyn_left) && IdenticalZero(left) )
      {  // this = 0 + right
         make_variable(right.tape_id_, right.taddr_);
      }
      else
      {  // this = parameter + variable
         CPPAD_ASSERT_UNKNOWN( local::NumRes(local::AddpvOp) == 1 );
         CPPAD_ASSERT_UNKNOWN( local::NumArg(local::AddpvOp) == 2 );

         // put operand addresses in tape
         addr_t p = taddr_;
         if( ! dyn_left )
            p = tape->Rec_.put_con_par(left);
         tape->Rec_.PutArg(p, right.taddr_);

         // put operator in the tape
         taddr_ = tape->Rec_.PutOp(local::AddpvOp);

         // make this a variable
         tape_id_ = tape_id;
         ad_type_ = variable_enum;
      }
   }
   else if( dyn_left | dyn_right )
   {  if( (! dyn_right) && IdenticalZero(right.value_) )
      {   // this is left += 0, so do nothing
      }
      else if( (! dyn_left) && IdenticalZero(left))
      {   // this is 0 += right
         make_dynamic(right.tape_id_, right.taddr_);
      } 
      else
      {
         addr_t arg0 = taddr_;
         addr_t arg1 = right.taddr_;
         if( ! dyn_left )
         arg0 = tape->Rec_.put_con_par(left);
         if( ! dyn_right )
         arg1 = tape->Rec_.put_con_par(right.value_);
         //
         // parameters with a dynamic parameter results
         taddr_ = tape->Rec_.put_dyn_par(
            value_, local::add_dyn, arg0, arg1
         );
         tape_id_ = tape_id;
         ad_type_ = dynamic_enum;
      }
   }
   return *this;
}

CPPAD_FOLD_ASSIGNMENT_OPERATOR(+=)

} // END CppAD namespace

# endif
