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using UnityEngine;
using Pathfinding.Util;
#if MODULE_ENTITIES
using Unity.Entities;
#endif
namespace Pathfinding {
/// <summary>
/// Sets the destination of an AI to the position of a specified object.
/// This component should be attached to a GameObject together with a movement script such as AIPath, RichAI or AILerp.
/// This component will then make the AI move towards the <see cref="target"/> set on this component.
///
/// Essentially the only thing this component does is to set the <see cref="Pathfinding.IAstarAI.destination"/> property to the position of the target every frame.
/// There is some additional complexity to make sure that the destination is updated immediately before the AI searches for a path as well, in case the
/// target moved since the last Update. There is also some complexity to reduce the performance impact, by using the <see cref="BatchedEvents"/> system to
/// process all AIDestinationSetter components in a single batch.
///
/// When using ECS, this component is instead added as a managed component to the entity.
/// The destination syncing is then handled by the <see cref="SyncDestinationTransformSystem"/> for better performance.
///
/// See: <see cref="Pathfinding.IAstarAI.destination"/>
///
/// [Open online documentation to see images]
/// </summary>
[UniqueComponent(tag = "ai.destination")]
[AddComponentMenu("Pathfinding/AI/Behaviors/AIDestinationSetter")]
[HelpURL("https://arongranberg.com/astar/documentation/stable/aidestinationsetter.html")]
public class AIDestinationSetter : VersionedMonoBehaviour
#if MODULE_ENTITIES
, IComponentData, IRuntimeBaker
#endif
{
/// <summary>The object that the AI should move to</summary>
public Transform target;
/// <summary>
/// If true, the agent will try to align itself with the rotation of the <see cref="target"/>.
///
/// This can only be used together with the <see cref="FollowerEntity"/> movement script.
/// Other movement scripts will ignore it.
///
/// [Open online documentation to see videos]
///
/// See: <see cref="FollowerEntity.SetDestination"/>
/// </summary>
public bool useRotation;
IAstarAI ai;
#if MODULE_ENTITIES
Entity entity;
World world;
#endif
void OnEnable () {
ai = GetComponent<IAstarAI>();
#if MODULE_ENTITIES
if (ai is FollowerEntity follower) {
// This will call OnCreatedEntity on this component, if the entity has already been created.
follower.RegisterRuntimeBaker(this);
} else
#endif
{
// Update the destination right before searching for a path as well.
// This is enough in theory, but this script will also update the destination every
// frame as the destination is used for debugging and may be used for other things by other
// scripts as well. So it makes sense that it is up to date every frame.
if (ai != null) ai.onSearchPath += UpdateDestination;
// Will make OnUpdate be called once every frame with all components.
// This is significantly faster than letting Unity call the Update method
// on each component.
// See https://blog.unity.com/technology/1k-update-calls
BatchedEvents.Add(this, BatchedEvents.Event.Update, OnUpdate, 0);
}
}
void OnDisable () {
#if MODULE_ENTITIES
if (world != null && world.IsCreated && world.EntityManager.Exists(entity)) {
world.EntityManager.RemoveComponent<AIDestinationSetter>(entity);
}
if (ai != null && !(ai is FollowerEntity)) ai.onSearchPath -= UpdateDestination;
#else
if (ai != null) ai.onSearchPath -= UpdateDestination;
#endif
BatchedEvents.Remove(this);
}
#if MODULE_ENTITIES
void IRuntimeBaker.OnCreatedEntity (World world, Entity entity) {
// Do nothing except add the component. Actual syncing is handled by the SyncDestinationTransformSystem.
this.entity = entity;
this.world = world;
world.EntityManager.AddComponentData<AIDestinationSetter>(entity, this);
}
#endif
/// <summary>Updates the AI's destination every frame</summary>
static void OnUpdate (AIDestinationSetter[] components, int count) {
for (int i = 0; i < count; i++) {
components[i].UpdateDestination();
}
}
/// <summary>Updates the AI's destination immediately</summary>
void UpdateDestination () {
if (target != null && ai != null) ai.destination = target.position;
}
}
}
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