switch_node.h

/* Copyright (C) 2020-2022 Davide Faconti -  All Rights Reserved
*
*   Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"),
*   to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
*   and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
*   The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
*
*   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
*   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
*   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

#pragma once

#include "behaviortree_cpp/control_node.h"

namespace BT
{
/**
 * @brief The SwitchNode is equivalent to a switch statement, where a certain
 * branch (child) is executed according to the value of a blackboard entry.
 *
 * Note that the same behaviour can be achieved with multiple Sequences, Fallbacks and
 * Conditions reading the blackboard, but switch is shorter and more readable.
 *
 * Example usage:
 *

<Switch3 variable="{var}"  case_1="1" case_2="42" case_3="666" >
   <ActionA name="action_when_var_eq_1" />
   <ActionB name="action_when_var_eq_42" />
   <ActionC name="action_when_var_eq_666" />
   <ActionD name="default_action" />
 </Switch3>

When the SwitchNode is executed (Switch3 is a node with 3 cases)
the "variable" will be compared to the cases and execute the correct child
or the default one (last).
 *
 */

namespace details
{

bool CheckStringEquality(const std::string& v1, const std::string& v2,
                         const ScriptingEnumsRegistry* enums);
}

template <size_t NUM_CASES>
class SwitchNode : public ControlNode
{
public:
  SwitchNode(const std::string& name, const BT::NodeConfig& config);

  virtual ~SwitchNode() override = default;

  void halt() override;

  static PortsList providedPorts();

private:
  int running_child_;
  std::vector<std::string> case_keys_;
  virtual BT::NodeStatus tick() override;
};

//-----------------------------------------------
//-----------------------------------------------

template <size_t NUM_CASES>
inline SwitchNode<NUM_CASES>::SwitchNode(const std::string& name,
                                         const NodeConfig& config)
  : ControlNode::ControlNode(name, config), running_child_(-1)
{
  setRegistrationID("Switch");
  for(unsigned i = 1; i <= NUM_CASES; i++)
  {
    case_keys_.push_back(std::string("case_") + std::to_string(i));
  }
}

template <size_t NUM_CASES>
inline void SwitchNode<NUM_CASES>::halt()
{
  running_child_ = -1;
  ControlNode::halt();
}

template <size_t NUM_CASES>
inline PortsList SwitchNode<NUM_CASES>::providedPorts()
{
  static PortsList provided_ports = []() {
    PortsList ports;
    ports.push_back(BT::InputPort<std::string>("variable"));
    for(unsigned i = 1; i <= NUM_CASES; i++)
    {
      auto key = std::string("case_") + std::to_string(i);
      ports.push_back(BT::InputPort<std::string>(key));
    }
    return ports;
  }();

  return provided_ports;
}

template <size_t NUM_CASES>
inline NodeStatus SwitchNode<NUM_CASES>::tick()
{
  if(childrenCount() != NUM_CASES + 1)
  {
    throw LogicError("Wrong number of children in SwitchNode; "
                     "must be (num_cases + default)");
  }

  std::string variable;
  std::string value;
  int match_index = int(NUM_CASES);  // default index;

  // no variable? jump to default
  if(getInput("variable", variable))
  {
    // check each case until you find a match
    for(int index = 0; index < int(NUM_CASES); ++index)
    {
      const std::string& case_key = case_keys_[index];
      if(getInput(case_key, value))
      {
        if(details::CheckStringEquality(variable, value, this->config().enums.get()))
        {
          match_index = index;
          break;
        }
      }
    }
  }

  // if another one was running earlier, halt it
  if(running_child_ != -1 && running_child_ != match_index)
  {
    haltChild(running_child_);
  }

  auto& selected_child = children_nodes_[match_index];
  NodeStatus ret = selected_child->executeTick();
  if(ret == NodeStatus::SKIPPED)
  {
    // if the matching child is SKIPPED, should I jump to default or
    // be SKIPPED myself? Going with the former, for the time being.
    running_child_ = -1;
    return NodeStatus::SKIPPED;
  }
  else if(ret == NodeStatus::RUNNING)
  {
    running_child_ = match_index;
  }
  else
  {
    resetChildren();
    running_child_ = -1;
  }
  return ret;
}

}  // namespace BT