💿🐜 Antkeeper source code
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193 lines
5.2 KiB
193 lines
5.2 KiB
/*
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* Copyright (C) 2021 Christopher J. Howard
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*
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* This file is part of Antkeeper source code.
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*
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* Antkeeper source code is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Antkeeper source code is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Antkeeper source code. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef ANTKEEPER_BEHAVIOR_TREE_HPP
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#define ANTKEEPER_BEHAVIOR_TREE_HPP
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#include <functional>
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#include <list>
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namespace behavior_tree {
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/// Behavior tree node return status enumerations.
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enum class status
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{
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failure, ///< Indicates a node's execution failed.
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success, ///< Indicates a node's execution succeed.
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running ///< Indicates a node's execution has not finished.
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};
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/**
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* Abstract base class for behavior tree nodes.
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*
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* @tparam T Data type on which nodes operate.
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*/
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template <class T>
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struct node
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{
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/// Data type on which nodes operate.
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typedef T context_type;
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/**
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* Executes a node's functionality and returns its status.
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*
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* @param context Context data on which the node will operate.
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*/
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virtual status execute(context_type& context) const = 0;
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};
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/// A node with no children.
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template <class T>
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using leaf_node = node<T>;
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/// A node with exactly one child.
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template <class T>
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struct decorator_node: node<T>
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{
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node* child;
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};
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/// A node that can have one or more children.
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template <class T>
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struct composite_node: node<T>
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{
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std::list<node*> children;
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};
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/// Executes a function on a context and returns the status.
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template <class T>
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struct action: leaf_node<T>
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{
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virtual status execute(context_type& context) const final;
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typedef std::function<status(context_type&)> function_type;
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function_type function;
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};
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/// Evaluates a boolean condition (predicate) and returns either `status::success` or `status::failure`.
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template <class T>
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struct condition: leaf_node<T>
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{
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virtual status execute(context_type& context) const final;
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typedef std::function<status(const context_type&)> predicate_type;
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predicate_type predicate;
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};
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/// Executes a child node and returns its inverted status. If the child returns `status::success`, then `status::failure` will be returned. Otherwise if the child returns `status::failure`, then `status::success` will be returned.
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template <class T>
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struct inverter: decorator_node<T>
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{
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virtual status execute(context_type& context) const final;
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};
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/// Attempts to execute a child node `n` times or until the child fails.
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template <class T>
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struct repeater: decorator_node<T>
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{
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virtual status execute(context_type& context) const final;
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int n;
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};
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/// Executes a child node and returns `status::success` regardless of the child node status.
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template <class T>
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struct succeeder: decorator_node<T>
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{
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virtual status execute(context_type& context) const final;
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};
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/// Attempts to execute each child node sequentially until one fails. If all children are executed successfully, `status::success` will be returned. Otherwise if any children fail, `status::failure` will be returned.
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template <class T>
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struct sequence: composite_node<T>
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{
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virtual status execute(context_type& context) const final;
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};
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/// Attempts to execute each child node sequentially until one succeeds. If a child succeeds, `status::success` will be returned. Otherwise if all children fail, `status::failure` will be returned.
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template <class T>
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struct selector: composite_node<T>
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{
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virtual status execute(context_type& context) const final;
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};
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template <class T>
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status action<T>::execute(context_type& context) const
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{
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return function(context);
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}
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template <class T>
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status condition<T>::execute(context_type& context) const
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{
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return (predicate(context)) ? status::success : status::failure;
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}
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template <class T>
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status inverter<T>::execute(context_type& context) const
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{
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status child_status = child->execute(context);
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return (child_status == status::success) ? status::failure : (child_status == status::failure) ? status::success : child_status;
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}
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template <class T>
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status repeater<T>::execute(context_type& context) const
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{
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status child_status;
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for (int i = 0; i < n; ++i)
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{
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child_status = child->execute(context);
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if (child_status == status::failure)
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break;
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}
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return child_status;
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}
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template <class T>
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status succeeder<T>::execute(context_type& context) const
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{
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child->execute(context);
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return status::success;
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}
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template <class T>
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status sequence<T>::execute(context_type& context) const
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{
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for (const node* child: children)
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{
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status child_status = child->execute(context);
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if (child_status != status::success)
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return child_status;
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}
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return status::success;
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}
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template <class T>
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status selector<T>::execute(context_type& context) const
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{
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for (const node* child: children)
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{
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status child_status = child->execute(context);
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if (child_status != status::failure)
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return child_status;
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}
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return status::failure;
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}
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} // namespace behavior_tree
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#endif // ANTKEEPER_BEHAVIOR_TREE_HPP
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