using System;

using UnityEngine;

using Framework.Services;

namespace Framework.Dialogue {

  /// <summary>Manages the active dialogue canvas and canvas placements</summary>
  /// <remarks>
  ///   When the game wants to display dialogue UI, it can use this dialogue manager
  ///   service to find a good placement of the dialogue UI. The dialogue manager
  ///   also tracks the active dialogue canvas so that only one is active at the
  ///   same time.
  /// </remarks>
  [
    ServiceScope(Scope.Scene),
    DefaultBinding(typeof(DialogueManager))
  ]
  public interface IDialogueManager {

    /// <summary>Finds the best dialogue canvas placement on an actor</summary>
    /// <param name="viewer">Viewer for which a placement will be searched</param>
    /// <param name="actor">Actor the placement has to be attached to</param>
    /// <returns>The best dialogue canvas placement for the specified actor</returns>
    DialoguePlacement FindPlacementOnActor(Transform viewer, GameObject actor);

    /// <summary>Finds the best dialogue canvas placement on an actor</summary>
    /// <param name="viewer">Viewer for which a placement will be searched</param>
    /// <param name="actor">Actor the placement has to be attached to</param>
    /// <param name="maximumDistance">
    ///   Maximum distance the placement may have from the viewer
    /// </param>
    /// <returns>The best dialogue canvas placement for the specified actor</returns>
    DialoguePlacement FindPlacementOnActor(
      Transform viewer, GameObject actor, float maximumDistance
    );
    
    /// <summary>Finds the best dialogue canvas placement not attached to an actor</summary>
    /// <param name="viewer">Position of the viewer in the world</param>
    /// <returns>The best dialogue canvas placement not attached to any actor</returns>
    DialoguePlacement FindPlacementInWorld(Transform viewer);

    /// <summary>Displays a new dialogue canvas at a specific location</summary>
    /// <param name="placement">Where the dialogue canvas will be displayed</param>
    IDialogueCanvas ShowDialogue(DialoguePlacement placement);

    /// <summary>Moves the currently active dialoge to a new location</summary>
    /// <param name="newTransform">New location the dialoge should be moved to</param>
    void MoveDialogue(Transform newTransform);

    /// <summary>Kills the currently active dialogue</summary>
    void HideDialogue();

    /// <summary>Currently active dialogue UI</summary>
    IDialogueCanvas ActiveDialogueCanvas { get; }

  }

} // namespace Framework.Dialogue