using System;

using UnityEngine;

namespace Framework.Actors {

  /// <summary>Helper methods for head controllers</summary>
  public static class HeadControllerHelper {

    /// <summary>Retrieves the look direction in the global coordinate system</summary>
    /// <param name="headComponent">Component by which the look direction is controlled</param>
    /// <returns>Direction the actor is looking in</returns>
    public static Vector3 GetGlobalLookDirection(this IHeadController headComponent) {
      Quaternion orientation = (
        headComponent.HeadBaseOrientation * headComponent.LocalHeadOrientation
      );
      return orientation * Vector3.forward;
    }

    /// <summary>Sets the look direction in the global coordinate system</summary>
    /// <param name="headController">Component on which the look direction will be set</param>
    /// <param name="direction">Direction the actor will look in</param>
    public static void SetGlobalLookDirection(
      this IHeadController headController, Vector3 direction
    ) {
      Vector3 upwards = headController.HeadBaseOrientation * Vector3.up;
      Quaternion globalOrientation = Quaternion.LookRotation(direction, upwards);

      Quaternion localOrientation = Quaternion.Inverse(
        headController.HeadBaseOrientation
      ) * globalOrientation;

      // This may be outside the head movement range, but that's okay:
      // a head controller is supposed to clamp upon assignment and trigger
      // the ExcessHeadRotation event to apply the clamped-off part to the body.
      headController.LocalHeadOrientation = localOrientation;
    }

  }

} // namespace Framework.Actors