using Sandbox;
using System;

namespace LegacyEntityPack;

/// <summary>
/// A trigger volume that teleports things that touch it. Modern scene-system port of the
/// legacy <c>trigger_teleport</c> entity.
///
/// Put this on a GameObject that has a Collider - it is turned into a trigger automatically.
/// The legacy targetname lookup is replaced by a direct <see cref="Destination"/> reference.
/// </summary>
[Title( "Teleport Volume" )]
[Category( "Triggers" )]
[Icon( "auto_fix_normal" )]
public class TeleportVolume : Component, Component.ITriggerListener
{
	/// <summary>Where touching objects get teleported to.</summary>
	[Property] public GameObject Destination { get; set; }

	/// <summary>
	/// Teleport with an offset based on where the object was inside the trigger (think world
	/// portals). Place the destination accordingly.
	/// </summary>
	[Property] public bool TeleportRelative { get; set; }

	/// <summary>If set, the teleported object keeps its velocity instead of being reset to zero.</summary>
	[Property] public bool KeepVelocity { get; set; }

	/// <summary>Fired with the teleported object, just before it is moved.</summary>
	[Property] public Action<GameObject> OnTriggered { get; set; }

	protected override void OnAwake()
	{
		foreach ( var collider in Components.GetAll<Collider>( FindMode.EverythingInSelfAndDescendants ) )
			collider.IsTrigger = true;
	}

	public void OnTriggerEnter( Collider other )
	{
		if ( !Destination.IsValid() || !other.IsValid() )
			return;

		var body = ResolveBody( other );
		if ( body is null )
			return;

		if ( Networking.IsActive && body.Network.IsProxy )
			return;

		var offset = TeleportRelative ? body.WorldPosition - WorldPosition : Vector3.Zero;

		if ( !KeepVelocity )
			ClearVelocity( body );

		// Fire before moving, so hooked logic can react (e.g. disable the destination's
		// own teleport trigger) before this object lands in it.
		OnTriggered?.Invoke( body );

		TeleportBody( body, Destination.WorldTransform.WithScale( body.WorldScale ), offset );
	}

	/// <summary>Resolve which object to teleport from the touching collider. Defaults to the rigidbody root.</summary>
	protected virtual GameObject ResolveBody( Collider other )
		=> other.Rigidbody.IsValid() ? other.Rigidbody.GameObject : other.GameObject;

	/// <summary>Zero out the body's velocity. Override for custom controllers.</summary>
	protected virtual void ClearVelocity( GameObject body )
	{
		var rb = body.Components.Get<Rigidbody>();
		if ( rb.IsValid() )
			rb.Velocity = Vector3.Zero;

		var controller = body.Components.Get<CharacterController>();
		if ( controller.IsValid() )
			controller.Velocity = Vector3.Zero;
	}

	/// <summary>Move the body to the destination. Override for custom controllers that need extra state updates.</summary>
	protected virtual void TeleportBody( GameObject body, Transform destination, Vector3 offset )
	{
		body.WorldTransform = destination;
		body.WorldPosition += offset;
	}
}