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package coffee.liz.ecs;
import coffee.liz.ecs.events.EntityEvent;
import coffee.liz.ecs.model.Component;
import coffee.liz.ecs.model.Entity;
import coffee.liz.ecs.model.Query;
import coffee.liz.ecs.model.QueryBuilder;
import coffee.liz.ecs.model.System;
import coffee.liz.ecs.model.World;
import lombok.extern.log4j.Log4j2;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Consumer;
import java.util.stream.Collectors;
@Log4j2
public class DAGWorld implements World {
private final Set<Entity> entities = Collections.synchronizedSet(new HashSet<>());
private final ComponentCache componentCache = new ComponentCache();
private final Consumer<EntityEvent> entityEventConsumer = componentCache::onEntityEvent;
private final AtomicInteger nextEntityId = new AtomicInteger(0);
protected final Map<Class<? extends System>, System> systems;
private final List<System> systemExecutionOrder;
private final QueryBuilder queryBuilder = new QueryBuilder(this);
private float elapsedTime = 0f;
public DAGWorld(final System... systems) {
this.systems = singletonClazzMap(systems);
this.systemExecutionOrder = buildExecutionOrder(Arrays.asList(systems));
log.info("Executing in order: {}", systemExecutionOrder);
}
@Override
public Entity createEntity() {
final Entity entity = Entity.builder().id(nextEntityId.incrementAndGet()).build();
entity.subscribe(entityEventConsumer);
entities.add(entity);
componentCache.addEntity(entity);
return entity;
}
@Override
public void removeEntity(final Entity entity) {
entity.unsubscribe(entityEventConsumer);
componentCache.removeEntity(entity);
entities.remove(entity);
}
@Override
public Set<Entity> resolve(final Query query) {
final Set<Class<? extends Component>> components = query.queryingComponents();
return switch (query.filter()) {
case ALL_OF -> resolveAllOf(components);
case ANY_OF -> resolveAnyOf(components);
case NONE_OF -> resolveNoneOf(components);
};
}
@Override
public QueryBuilder queryable() {
return queryBuilder;
}
@Override
public void update(final float deltaSeconds) {
elapsedTime += deltaSeconds;
systemExecutionOrder.forEach(system -> system.update(this, deltaSeconds));
}
@Override
public float getTime() {
return elapsedTime;
}
@SuppressWarnings("unchecked")
@Override
public <S extends System> S getSystem(final Class<S> system) {
return (S) systems.get(system);
}
private Set<Entity> resolveAllOf(final Set<Class<? extends Component>> components) {
if (components.isEmpty()) {
return entities;
}
return componentCache.entitiesMatchingAllOf(components);
}
private Set<Entity> resolveAnyOf(final Set<Class<? extends Component>> components) {
if (components.isEmpty()) {
return Collections.emptySet();
}
final Set<Entity> matches = new HashSet<>();
components.forEach(componentType -> matches.addAll(componentCache.entitiesWith(componentType)));
return matches;
}
private Set<Entity> resolveNoneOf(final Set<Class<? extends Component>> components) {
if (components.isEmpty()) {
return entities;
}
final Set<Entity> excluded = new HashSet<>();
components.forEach(componentType -> excluded.addAll(componentCache.entitiesWith(componentType)));
final Set<Entity> result = new HashSet<>();
entities.forEach(entity -> {
if (!excluded.contains(entity)) {
result.add(entity);
}
});
return result;
}
private List<System> buildExecutionOrder(final Collection<System> systems) {
if (systems.isEmpty()) {
return Collections.emptyList();
}
final Map<Class<?>, System> systemMap = systems.stream()
.collect(Collectors.toMap(System::getClass, system -> system, (_sys, b) -> b, LinkedHashMap::new));
final Map<Class<?>, Integer> inDegree = new LinkedHashMap<>();
final Map<Class<?>, Set<Class<?>>> adjacencyList = new LinkedHashMap<>();
systems.forEach(system -> {
inDegree.put(system.getClass(), 0);
adjacencyList.put(system.getClass(), new HashSet<>());
});
systems.forEach(system -> system.getDependencies().forEach(dependency -> {
if (systemMap.containsKey(dependency)) {
adjacencyList.get(dependency).add(system.getClass());
inDegree.merge(system.getClass(), 1, Integer::sum);
}
}));
final List<System> result = new ArrayList<>();
final Queue<Class<?>> queue = new LinkedList<>(
inDegree.entrySet().stream().filter(e -> e.getValue() == 0).map(Map.Entry::getKey).toList());
while (!queue.isEmpty()) {
final Class<?> currentClass = queue.poll();
result.add(systemMap.get(currentClass));
adjacencyList.getOrDefault(currentClass, Collections.emptySet()).forEach(dependent -> {
final int newInDegree = inDegree.get(dependent) - 1;
inDegree.put(dependent, newInDegree);
if (newInDegree == 0) {
queue.add(dependent);
}
});
}
if (result.size() != systems.size()) {
throw new IllegalStateException("Circular dependency detected in systems");
}
return Collections.unmodifiableList(result);
}
@Override
public void dispose() {
systemExecutionOrder.forEach(System::dispose);
entities.forEach(entity -> entity.unsubscribe(entityEventConsumer));
componentCache.clear();
entities.clear();
}
@SuppressWarnings("unchecked")
private static Map<Class<? extends System>, System> singletonClazzMap(final System... singletons) {
final boolean areSingletons = Arrays.stream(singletons)
.map(Object::getClass)
.distinct()
.count() == singletons.length;
if (!areSingletons) {
throw new IllegalArgumentException("Only one instance may be used per clazz");
}
return Arrays.stream(singletons)
.collect(Collectors.toMap(
s -> (Class<? extends System>) s.getClass(),
s -> s));
}
}
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