using System;

using UnityEngine;
using UnityEngine.UI;

using Framework.Services;

namespace Framework.Dialogue2 {

  /// <summary>Dialogue canvas based on UGUI (Unity's new 3D-capable UI system)</summary>
  public class UGuiDialogueCanvas : ScriptComponent, IDialogueCanvas {

    /// <summary>Whether this canvas should auto-destruct when it is closed</summary>
    public bool DestroyWhenClosed = false;

    /// <summary>UGui canvas holding the dialogue controls</summary>
    /// <remarks>
    ///   If this is not set, the game object this component is attached to will be
    ///   searched for a canvas object.
    /// </remarks>
    public Canvas Canvas;

    /// <summary>Triggered when the user confirms speech dialogue or picks a choice</summary>
    public event Action<int> Selected;

    /// <summary>Current visibility state of the canvas</summary>
    public IDialogueCanvasVisibility Visibility {
      get { return null; }
    }

    /// <summary>Current placement of the canvas within the scene</summary>
    public IDialogueCanvasPlacement Placement {
      get { return null; }
    }

    /// <summary>Displays text spoken or thought by a character</summary>
    /// <param name="speech">Text that will be displayed</param>
    public void ShowSpeech(IDialogueText speech) {

    }

    /// <summary>Lets the player make a choice</summary>
    /// <param name="choices">Choices the player can select from</param>
    public void ShowChoices(ArraySegment<IDialogueText> choices) {

    }

    /// <summary>
    ///   Displays text spoken or thought by a character (or the player) and lets
    ///   the player make a choice.
    /// </summary>
    /// <param name="speech">Text that will be displayed</param>
    /// <param name="choices">Choices the player can select from</param>
    public void ShowSpeechAndChoices(IDialogueText speech, ArraySegment<IDialogueText> choices) {

    }

    /// <summary>Hides the dialogue and choice</summary>
    public void Hide() {

    }

    /// <summary>Picks a choice as if the user had clicked on a choice button</summary>
    /// <param name="choiceIndex">Index of the choice that has been selected</param>
    /// <remarks>
    ///   Use this to make the dialogue canvas act as if the user had made
    ///   a choice or clicked the speech panel. The main purpose of this method is to
    ///   support input outside of the UI panel - i.e. keyboard shortcuts or even
    ///   interactions with the game world.
    /// </remarks>
    public void Select(int choiceIndex) {

    }

    /// <summary>Called when the script component gets loaded into a game object</summary>
    protected override void Awake() {
      base.Awake();

      this.dialogueWidgets = CreateWidgetController();
      this.dialogueWidgets.Initialize();
    }

    /// <summary>
    ///   Creates the widget controller the dialogue canvas will use to manage its widgets
    /// </summary>
    /// <returns>A new widget controller for the dialogue canvas' widgets</returns>
    /// <remarks>
    ///   The widgets
    /// </remarks>
    protected virtual UGuiDialogueWidgets CreateWidgetController() {
      if(this.Canvas == null) {
        this.Canvas = GetComponentInChildren<Canvas>();
        if(this.Canvas == null) {
          Debug.LogError(
            "Cannot create widget controller because no canvas was found on " +
            "game object '" + gameObject.name + "'"
          );
          throw new InvalidOperationException("No canvas found on '" + gameObject.name + "'");
        }
      }

      return new UGuiDialogueWidgets(this.Canvas);
    }

    /// <summary>Controller through which the widgets are discovered</summary>
    private UGuiDialogueWidgets dialogueWidgets;

  }

} // namespace Framework.Dialogue2