From 1ddfa176599cb3ab1c190e56e52983872ecddcbb Mon Sep 17 00:00:00 2001
From: Sara <sara@saragerretsen.nl>
Date: Tue, 4 Jun 2024 21:42:09 +0200
Subject: [PATCH] feat: implemented goal oriented action planning

---
 src/goap/action.cpp            |  36 +++---
 src/goap/action.hpp            |  43 +++----
 src/goap/action_db.cpp         |  40 ++++---
 src/goap/action_db.hpp         |  20 ++--
 src/goap/actor_world_state.cpp |   8 ++
 src/goap/actor_world_state.hpp |   3 +
 src/goap/goal.cpp              |  27 +++++
 src/goap/goal.hpp              |   8 +-
 src/goap/planner.cpp           | 209 ++++++++++++++++++++++++++++++---
 src/goap/planner.hpp           |  58 ++++++++-
 src/register_types.cpp         |   8 +-
 11 files changed, 360 insertions(+), 100 deletions(-)
 create mode 100644 src/goap/goal.cpp

diff --git a/src/goap/action.cpp b/src/goap/action.cpp
index 7011195..b9be10a 100644
--- a/src/goap/action.cpp
+++ b/src/goap/action.cpp
@@ -1,11 +1,24 @@
 #include "action.hpp"
 
 namespace goap {
-Action::Action(WorldState &requires, WorldState &effects)
-: requires{requires}, effects{effects} {}
+Action::~Action() {}
+
+bool Action::is_possible(ActorWorldState *context) const {
+    return this->procedural_is_possible(context);
+}
+
+bool Action::is_completed(ActorWorldState *context) const {
+    if(!only_proc_is_completed) {
+        for(WorldProperty const &prop : this->effects) {
+            if(!context->check_property_match(prop))
+                return false;
+        }
+    }
+    return this->procedural_is_completed(context);
+}
 
 WorldState const &Action::get_required() const {
-    return this->requires;
+    return this->required;
 }
 
 WorldState const &Action::get_effects() const {
@@ -16,22 +29,11 @@ ActionID Action::get_id() const {
     return this->id;
 }
 
-ActionData::ActionData(Action *action)
-: data{action} {}
-
-ActionData::~ActionData() {
-    if(this->data != nullptr)
-        delete this->data;
-}
-}
-
-bool TestAction::is_done_for(goap::ActorWorldState *) {
+bool Action::procedural_is_possible(ActorWorldState *context) const {
     return true;
 }
-bool TestAction::is_possible_for(goap::ActorWorldState *) {
+
+bool Action::procedural_is_completed(ActorWorldState *context) const {
     return true;
 }
-goap::State *TestAction::get_apply_state() const {
-    return nullptr;
 }
-
diff --git a/src/goap/action.hpp b/src/goap/action.hpp
index 0c6913a..b3336f8 100644
--- a/src/goap/action.hpp
+++ b/src/goap/action.hpp
@@ -10,7 +10,7 @@
 #define GOAP_ACTION(Name_) \
 public: \
     _FORCE_INLINE_ static gd::String get_static_class() { return #Name_; }\
-    _FORCE_INLINE_ gd::String get_class() const { return #Name_; }\
+    _FORCE_INLINE_ virtual gd::String get_class() const override { return #Name_; }\
 private:
 
 namespace goap {
@@ -22,44 +22,33 @@ typedef int ActionID;
  */
 class Action {
     friend class ActionDB;
-    GOAP_ACTION(Action);
 public:
-    virtual ~Action() = default;
+    static gd::String get_static_class() { return "Action"; }
+    virtual gd::String get_class() const { return "Action"; }
 
-    virtual bool is_possible_for(ActorWorldState *state) = 0;
-    virtual bool is_done_for(ActorWorldState *state) = 0;
+    virtual ~Action();
     virtual State *get_apply_state() const = 0;
 
+    bool is_completed(ActorWorldState *context) const;
+    bool is_possible(ActorWorldState *context) const;
+
     WorldState const &get_required() const;
     WorldState const &get_effects() const;
 
     ActionID get_id() const;
 protected:
     Action() = default;
-    Action(WorldState &requires, WorldState &effects);
-private:
-    WorldState requires{};
-    WorldState effects{};
-    ActionID id{-1};
-};
 
-/* Storage wrapper for managed action class.
- */
-struct ActionData {
-    ActionData() = default;
-    ActionData(Action *action);
-    ~ActionData();
-    Action *data{nullptr};
+    virtual bool procedural_is_possible(ActorWorldState *context) const;
+    virtual bool procedural_is_completed(ActorWorldState *context) const;
+protected:
+    WorldState blocking_required{};
+    WorldState required{};
+    WorldState effects{};
+    bool only_proc_is_completed{false};
+private:
+    ActionID id{-1};
 };
 }
 
-class TestAction : public goap::Action {
-    GOAP_ACTION(TestAction);
-public:
-    TestAction() = default;
-    virtual bool is_done_for(goap::ActorWorldState *) override;
-    virtual bool is_possible_for(goap::ActorWorldState *) override;
-    virtual goap::State *get_apply_state() const override;
-};
-
 #endif // !GOAP_ACTION_HPP
diff --git a/src/goap/action_db.cpp b/src/goap/action_db.cpp
index 70b27fd..a0f03fd 100644
--- a/src/goap/action_db.cpp
+++ b/src/goap/action_db.cpp
@@ -1,36 +1,42 @@
 #include "action_db.hpp"
+#include "godot_cpp/variant/utility_functions.hpp"
 
 namespace goap {
-StaticString::~StaticString() {
-    if(this->ptr != nullptr)
-        delete this->ptr;
+ActionDB::StaticData::~StaticData() {
+    if(this->hint != nullptr)
+        delete this->hint;
+    for(Action *action : this->actions)
+        delete action;
 }
 
-gd::String &StaticString::get() {
-    if(this->ptr == nullptr)
-        this->ptr = new gd::String();
-    return *this->ptr;
+gd::String &ActionDB::StaticData::get_hint() {
+    if(this->hint == nullptr)
+        this->hint = new gd::String();
+    return *this->hint;
 }
 
 ActionID ActionDB::register_action(Action *instance, gd::String name) {
-    instance->id = ActionDB::actions.size();
-    if(!ActionDB::hint.get().is_empty())
-        ActionDB::hint.get() += ",";
-    ActionDB::hint.get() += name;
-    ActionDB::actions.push_back(ActionData(instance));
+    instance->id = ActionDB::data.actions.size();
+    if(!ActionDB::data.get_hint().is_empty())
+        ActionDB::data.get_hint() += ",";
+    ActionDB::data.get_hint() += name;
+    // defer intialization until after emplacement to avoid deleting instance
+    ActionDB::data.actions.push_back(instance);
+    gd::UtilityFunctions::print("registered action ", name);
     return instance->get_id();
 }
 
 Action const *ActionDB::get_action(ActionID index) {
-    if(ActionDB::actions.size() >= index || index < 0)
+    if(ActionDB::data.actions.size() <= index || index < 0) {
+        gd::UtilityFunctions::push_warning("Attempted to get pointer to non-existent Action by ActionID ", index);
         return nullptr;
-    return ActionDB::actions[index].data;
+    }
+    return ActionDB::data.actions[index];
 }
 
 gd::String const &ActionDB::get_enum_hint() {
-    return ActionDB::hint.get();
+    return ActionDB::data.get_hint();
 }
 
-gd::Vector<ActionData> ActionDB::actions{gd::Vector<ActionData>()};
-StaticString ActionDB::hint{};
+ActionDB::StaticData ActionDB::data{};
 }
diff --git a/src/goap/action_db.hpp b/src/goap/action_db.hpp
index 1db4012..1f1e3da 100644
--- a/src/goap/action_db.hpp
+++ b/src/goap/action_db.hpp
@@ -4,15 +4,6 @@
 #include "action.hpp"
 
 namespace goap {
-struct StaticString {
-private:
-    gd::String *ptr{nullptr};
-public:
-    StaticString() = default;
-    ~StaticString();
-    gd::String &get();
-};
-
 /*! Global access to all (registered) Action types.
  *
  * Register them with the `register_action` function from `initialize_gdextension_types()`.
@@ -29,7 +20,13 @@ public:
  * ```
  */
 class ActionDB {
-protected:
+    struct StaticData {
+        StaticData() = default;
+        ~StaticData();
+        gd::String &get_hint();
+        gd::String *hint{nullptr};
+        gd::Vector<Action *> actions{};
+    };
     static ActionID register_action(Action *instance, gd::String name);
 public:
     /*! Get action by ID.
@@ -47,8 +44,7 @@ public:
         return ActionDB::register_action(new TAction(), TAction::get_static_class());
     }
 private:
-    static gd::Vector<ActionData> actions;
-    static StaticString hint;
+    static StaticData data;
 };
 }
 
diff --git a/src/goap/actor_world_state.cpp b/src/goap/actor_world_state.cpp
index de2fba1..8c604f8 100644
--- a/src/goap/actor_world_state.cpp
+++ b/src/goap/actor_world_state.cpp
@@ -4,4 +4,12 @@ namespace goap {
 void ActorWorldState::_bind_methods() {
 #define CLASSNAME ActorWorldState
 }
+
+bool ActorWorldState::check_property_match(WorldProperty const &property) {
+    return this->get_world_property(property.key) == property.value;
+}
+
+gd::Variant ActorWorldState::get_world_property(gd::String world_prop_name) {
+    return this->call("get_" + world_prop_name);
+}
 }
diff --git a/src/goap/actor_world_state.hpp b/src/goap/actor_world_state.hpp
index 3b1a21f..5172fd4 100644
--- a/src/goap/actor_world_state.hpp
+++ b/src/goap/actor_world_state.hpp
@@ -15,6 +15,9 @@ typedef gd::KeyValue<gd::StringName, gd::Variant> WorldProperty;
 class ActorWorldState : public gd::Node {
     GDCLASS(ActorWorldState, gd::Node);
     static void _bind_methods();
+public:
+    bool check_property_match(WorldProperty const &property);
+    gd::Variant get_world_property(gd::String world_prop_name);
 };
 }
 
diff --git a/src/goap/goal.cpp b/src/goap/goal.cpp
new file mode 100644
index 0000000..49d0c3e
--- /dev/null
+++ b/src/goap/goal.cpp
@@ -0,0 +1,27 @@
+#include "goal.hpp"
+#include "utils/godot_macros.hpp"
+#include "utils/util_functions.hpp"
+
+namespace goap {
+void Goal::_bind_methods() {
+#define CLASSNAME Goal
+    GDPROPERTY(requirements_dict, gd::Variant::DICTIONARY);
+    GDPROPERTY(desired_state_dict, gd::Variant::DICTIONARY);
+}
+
+void Goal::set_requirements_dict(gd::Dictionary dict) {
+    this->requirements = utils::dictionary_to_hashmap<gd::StringName, gd::Variant>(dict);
+}
+
+gd::Dictionary Goal::get_requirements_dict() const {
+    return utils::hashmap_to_dictionary(this->requirements);
+}
+
+void Goal::set_desired_state_dict(gd::Dictionary dict) {
+    this->desired_state = utils::dictionary_to_hashmap<gd::StringName, gd::Variant>(dict);
+}
+
+gd::Dictionary Goal::get_desired_state_dict() const {
+    return utils::hashmap_to_dictionary(this->desired_state);
+}
+}
diff --git a/src/goap/goal.hpp b/src/goap/goal.hpp
index 3ca39e3..93498ed 100644
--- a/src/goap/goal.hpp
+++ b/src/goap/goal.hpp
@@ -11,9 +11,11 @@ class Goal : public gd::Resource {
     GDCLASS(Goal, gd::Resource);
     static void _bind_methods();
 public:
-    gd::Dictionary get_desired_state() const;
-    void set_desired_state(gd::Dictionary dict);
-private:
+    void set_requirements_dict(gd::Dictionary dict);
+    gd::Dictionary get_requirements_dict() const;
+    void set_desired_state_dict(gd::Dictionary dict);
+    gd::Dictionary get_desired_state_dict() const;
+public:
     //! Do not select this goal unless all requirements are met.
     WorldState requirements;
     //! The state to find a path to.
diff --git a/src/goap/planner.cpp b/src/goap/planner.cpp
index 4bc61b6..7a86268 100644
--- a/src/goap/planner.cpp
+++ b/src/goap/planner.cpp
@@ -1,34 +1,207 @@
 #include "planner.hpp"
-#include "goap/action_db.hpp"
+#include "action_db.hpp"
+#include "godot_cpp/classes/global_constants.hpp"
+#include "godot_cpp/templates/hashfuncs.hpp"
 #include "utils/godot_macros.hpp"
+#include <cstdint>
+#include <godot_cpp/variant/utility_functions.hpp>
 
 namespace goap {
+WorldStateNode::WorldStateNode(WorldState const &goal, ActorWorldState *context)
+: state{}, open_requirements{goal}, context{context} {}
+
+WorldStateNode::WorldStateNode(WorldStateNode const &last_state, Action const *last_action)
+: state{last_state.state}
+, open_requirements{last_state.open_requirements}
+, last_action{last_action}
+, context{last_state.context} {
+    for(WorldProperty const &req : last_action->get_required())
+        this->open_requirements[req.key] = req.value;
+    for(WorldProperty const &effect : last_action->get_effects())
+        if(this->open_requirements.has(effect.key))
+            this->state[effect.key] = effect.value;
+}
+
+int WorldStateNode::requirements_unmet() const {
+    int requirements = this->open_requirements.size();
+    for(WorldProperty const &req : this->open_requirements) {
+        if(this->state.has(req.key) && this->state[req.key] == req.value) {
+            --requirements;
+        } else if(this->context->check_property_match(req)) {
+            --requirements;
+        }
+    }
+    return requirements;
+}
+
+uint32_t WorldStateNodeHasher::hash(goap::WorldStateNode const &state) {
+    uint32_t hash{1};
+    for(goap::WorldProperty const &prop : state.state) {
+        hash = gd::hash_murmur3_one_32(prop.key.hash(), hash);
+        hash = gd::hash_murmur3_one_32(prop.value.hash(), hash);
+    }
+    return gd::hash_fmix32(hash);
+}
+
+bool operator==(goap::WorldStateNode const &lhs, goap::WorldStateNode const &rhs) {
+    if(lhs.state.size() != rhs.state.size())
+        return false;
+    for(goap::WorldProperty const &prop_lhs : lhs.state) {
+        if((!rhs.state.has(prop_lhs.key)) || rhs.state[prop_lhs.key] != prop_lhs.value)
+            return false;
+    }
+    for(goap::WorldProperty const &prop_rhs : rhs.state) {
+        if((!lhs.state.has(prop_rhs.key)) || lhs.state[prop_rhs.key] != prop_rhs.value)
+            return false;
+    }
+    return true;
+}
+
+bool operator!=(goap::WorldStateNode const &lhs, goap::WorldStateNode const &rhs) {
+    return !(lhs == rhs);
+}
+
+bool operator<(goap::WorldStateNode const &lhs, goap::WorldStateNode const &rhs) {
+    return lhs.state.size() < rhs.state.size();
+}
+
+bool operator<=(goap::WorldStateNode const &lhs, goap::WorldStateNode const &rhs) {
+    return lhs.state.size() <= rhs.state.size();
+}
+
+bool operator>(goap::WorldStateNode const &lhs, goap::WorldStateNode const &rhs) {
+    return lhs.state.size() > rhs.state.size();
+}
+
+bool operator>=(goap::WorldStateNode const &lhs, goap::WorldStateNode const &rhs) {
+    return lhs.state.size() >= rhs.state.size();
+}
+
 void Planner::_bind_methods() {
 #define CLASSNAME Planner
-    GDPROPERTY_HINTED(actions, gd::Variant::PACKED_INT32_ARRAY, gd::PROPERTY_HINT_ENUM, ActionDB::get_enum_hint());
+    GDPROPERTY_HINTED(actions, gd::Variant::ARRAY, gd::PROPERTY_HINT_ARRAY_TYPE, gd::vformat("%s/%s:%s", gd::Variant::INT, gd::PROPERTY_HINT_ENUM, ActionDB::get_enum_hint()));
+    GDPROPERTY_HINTED(test_goal, gd::Variant::OBJECT, gd::PROPERTY_HINT_RESOURCE_TYPE, "Goal");
 }
 
-void Planner::_enter_tree() {
+void Planner::_enter_tree() { GDGAMEONLY();
     this->world_state = this->get_node<ActorWorldState>("../ActorWorldState");
-}
-
-Plan Planner::plan_for_goal(gd::Ref<Goal> goal) {
-    return {};
-}
-
-void Planner::set_actions(gd::PackedInt32Array array) {
-    this->actions.clear();
-    for(int id : array) {
-        Action const *action = ActionDB::get_action(id);
-        if(action != nullptr && !this->actions.has(action))
-            this->actions.push_back(action);
+    if(test_goal.is_valid()) {
+        Plan plan{this->plan_for_goal(test_goal)};
+        gd::UtilityFunctions::print("plan for ", this->test_goal->get_path(), ":");
+        for(Action const *action : plan)
+            gd::UtilityFunctions::print(" ", action->get_class());
     }
 }
 
-gd::PackedInt32Array Planner::get_actions() const {
-    gd::PackedInt32Array array{};
+Plan Planner::plan_for_goal(gd::Ref<Goal> goal) {
+    // exit if goal reference is invalid or goal is already completed
+    if(!goal.is_valid()) {
+        gd::UtilityFunctions::print("goal not valid");
+        return {};
+    }
+    // The node representing the start of the search and the goal of the plan.
+    WorldStateNode goal_node{goal->desired_state, this->world_state};
+    if(goal_node.requirements_unmet() == 0) {
+        gd::UtilityFunctions::print("goal ", goal->get_path(), " already met");
+        return {};
+    }
+    gd::Vector<WorldStateNode> open{goal_node};
+    NodeMap from{};
+    NodeScoreMap best_path_cost{};
+    NodeScoreMap heuristic_cost{};
+
+    best_path_cost.insert(goal_node, 0.f);
+    heuristic_cost.insert(goal_node, goal_node.requirements_unmet());
+
+    WorldStateNode current{goal_node};
+    while(!open.is_empty()) {
+        current = open.get(0);
+        if(current.requirements_unmet() == 0)
+            return this->unroll_plan(current, from);
+        open.remove_at(0);
+        gd::Vector<Action const *> edges{this->get_neighbours(current)};
+        gd::UtilityFunctions::print("found ", edges.size(), " possible actions");
+        for(Action const * action : edges) {
+            WorldStateNode node_through{current, action};
+            float const path_cost{best_path_cost.get(current) + 1.f};
+            gd::UtilityFunctions::print("hashes ", WorldStateNodeHasher::hash(node_through), " ; ", WorldStateNodeHasher::hash(current));
+            gd::UtilityFunctions::print("equiv: ", current == node_through);
+            if(!best_path_cost.has(node_through) || best_path_cost.get(node_through) >= path_cost) {
+                gd::UtilityFunctions::print("node through action ", action->get_class(), " added to open set");
+                best_path_cost[node_through] = path_cost;
+                heuristic_cost[node_through] = path_cost + node_through.requirements_unmet();
+                from[node_through] = current;
+                open.erase(node_through);
+                open.ordered_insert(node_through);
+            } else {
+                gd::UtilityFunctions::print("node through action ", action->get_class(), " scores worse than previous at same state. ", path_cost, " vs ", best_path_cost[node_through]);
+            }
+        }
+    }
+
+    gd::UtilityFunctions::print("failed to find plan for goal ", goal->get_path());
+    return {};
+}
+
+void Planner::set_actions(gd::Array array) {
+    this->actions.clear();
+    for(size_t i = 0; i < array.size(); ++i) {
+        Action const *action = ActionDB::get_action(array[i]);
+        if(action != nullptr && !this->actions.has(action)) {
+            this->actions.push_back(action);
+        }
+    }
+}
+
+gd::Array Planner::get_actions() const {
+    gd::Array array{};
     for(Action const *action : this->actions)
-        action->get_id();
+        array.push_back(action->get_id());
     return array;
 }
+
+void Planner::set_test_goal(gd::Ref<Goal> goal) {
+    this->test_goal = goal;
+}
+
+gd::Ref<Goal> Planner::get_test_goal() const {
+    return this->test_goal;
+}
+
+gd::Vector<Action const *> Planner::get_neighbours(WorldStateNode const &from) const {
+    gd::Vector<Action const *> retval{};
+    for(Action const *action : this->actions) {
+        if(!action->is_possible(from.context)) {
+            gd::UtilityFunctions::print("action ", action->get_class(), " is not possible");
+            continue;
+        }
+        if(!this->does_action_contribute(action, from)) {
+            gd::UtilityFunctions::print("action ", action->get_class(), " does not contribute");
+            continue;
+        }
+        retval.push_back(action);
+    }
+    return retval;
+}
+
+bool Planner::does_action_contribute(Action const *action, WorldStateNode const &node) const {
+    WorldState const &effects = action->get_effects();
+    for(WorldProperty const &goal : node.open_requirements) {
+        if(node.state.has(goal.key) && goal.value == node.state.get(goal.key))
+            continue; // requirement already met, don't count as requiring contribution
+        if(effects.has(goal.key) && effects[goal.key] == goal.value)
+            return true;
+    }
+    return false;
+}
+
+Plan Planner::unroll_plan(WorldStateNode const &start_node, NodeMap const &from) {
+    Plan plan{};
+    WorldStateNode node{start_node};
+    while(node.last_action != nullptr) {
+        plan.push_back(node.last_action);
+        node = from.get(node);
+    }
+    return plan;
+}
 }
diff --git a/src/goap/planner.hpp b/src/goap/planner.hpp
index 41378ed..9db68f3 100644
--- a/src/goap/planner.hpp
+++ b/src/goap/planner.hpp
@@ -4,26 +4,74 @@
 #include "action.hpp"
 #include "actor_world_state.hpp"
 #include "goal.hpp"
-#include "godot_cpp/variant/packed_int32_array.hpp"
-#include <godot_cpp/templates/vector.hpp>
+#include <cstdint>
 #include <godot_cpp/classes/node.hpp>
+#include <godot_cpp/templates/vector.hpp>
+#include <godot_cpp/variant/packed_int32_array.hpp>
 
 namespace gd = godot;
 
 namespace goap {
-typedef gd::Vector<Action> Plan;
+typedef gd::Vector<Action const *> Plan;
 
+/*! Wrapper for WorldState to be used to represent nodes in the A* implementation.
+ * Mainly required to let a HashMap of HashMaps work.
+ */
+struct WorldStateNode {
+    WorldStateNode() = default;
+    //! Root node constructor
+    WorldStateNode(WorldState const &goal, ActorWorldState *context);
+    //! Path node constructor
+    WorldStateNode(WorldStateNode const &last_state, Action const *last_action);
+    ~WorldStateNode() = default;
+    int requirements_unmet() const;
+    WorldState state{};
+    WorldState open_requirements{};
+    Action const *last_action{nullptr};
+    ActorWorldState *context;
+};
+
+struct WorldStateNodeHasher {
+    static uint32_t hash(WorldStateNode const &state);
+};
+
+extern bool operator==(WorldStateNode const &lhs, WorldStateNode const &rhs);
+extern bool operator!=(WorldStateNode const &lhs, WorldStateNode const &rhs);
+extern bool operator<(WorldStateNode const &lhs, WorldStateNode const &rhs);
+extern bool operator<=(WorldStateNode const &lhs, WorldStateNode const &rhs);
+extern bool operator>(WorldStateNode const &lhs, WorldStateNode const &rhs);
+extern bool operator>=(WorldStateNode const &lhs, WorldStateNode const &rhs);
+
+typedef gd::HashMap<WorldStateNode, WorldStateNode, WorldStateNodeHasher> NodeMap;
+typedef gd::HashMap<WorldStateNode, float, WorldStateNodeHasher> NodeScoreMap;
+
+/*! Uses A* to compute `Action` sequences for an actor to achieve `Goal`s.
+ *
+ * Set up available actions from the editor and call plan_for_goal with a desired goal.
+ * Requires a sibling node inheriting from ActorWorldState called "ActorWorldState".
+ */
 class Planner : public gd::Node {
     GDCLASS(Planner, gd::Node);
     static void _bind_methods();
 public:
     virtual void _enter_tree() override;
 
+    //! Compute a plan to achieve the passed `Goal`.
     Plan plan_for_goal(gd::Ref<Goal> goal);
 
-    void set_actions(gd::PackedInt32Array array);
-    gd::PackedInt32Array get_actions() const;
+    void set_actions(gd::Array array);
+    gd::Array get_actions() const;
+    void set_test_goal(gd::Ref<Goal> goal);
+    gd::Ref<Goal> get_test_goal() const;
 private:
+    //! \returns A vector of all actions that satisfy any of the requirements in `unsatisfied`
+    gd::Vector<Action const *> get_neighbours(WorldStateNode const &from) const;
+    //! \returns True if the passed action contributes to any of the open requirements in `node`.
+    bool does_action_contribute(Action const *action, WorldStateNode const &node) const;
+    //! \returns A plan starting with `start_node` traced backwards through the `from` map.
+    Plan unroll_plan(WorldStateNode const &start_node, NodeMap const &from);
+private:
+    gd::Ref<Goal> test_goal{};
     ActorWorldState *world_state{nullptr};
     gd::Vector<Action const *> actions;
 };
diff --git a/src/register_types.cpp b/src/register_types.cpp
index 68eaf35..f8200ae 100644
--- a/src/register_types.cpp
+++ b/src/register_types.cpp
@@ -2,6 +2,7 @@
 #include "goap/action.hpp"
 #include "goap/action_db.hpp"
 #include "goap/actor_world_state.hpp"
+#include "goap/goal.hpp"
 #include "goap/planner.hpp"
 #include "rts_game_mode.hpp"
 #include "rts_player.hpp"
@@ -20,12 +21,17 @@ void initialize_gdextension_types(ModuleInitializationLevel p_level)
         return;
     }
     utils::godot_cpp_utils_register_types();
+
+    // always register actions before classes,
+    // so that ActionDB::get_enum_hint is complete before _bind_methods
+
     ClassDB::register_class<RTSPlayer>();
     ClassDB::register_class<Unit>();
     ClassDB::register_class<RTSGameMode>();
+
     ClassDB::register_class<goap::ActorWorldState>();
+    ClassDB::register_class<goap::Goal>();
     ClassDB::register_class<goap::Planner>();
-    goap::ActionDB::register_action<TestAction>();
 }
 
 extern "C"