using System;
using UnityEngine;
using UnityEngine.UIElements;

public class UIManager : MonoBehaviour
{
    /// <summary>
    ///     singleton pattern: define instance field for accessing the singleton elsewhere
    /// </summary>
    public static UIManager Instance;
    
    /// <summary>
    ///     enum for available menus in the game, for use with <c>ShowMenu()</c>
    /// </summary>
    public enum DisplayState
    {
        UnassociatedState,
        Nothing,
        PlayView,
        LeaderboardView,
        AccountView
    }
    
    /// <summary>
    ///     the current display state of the game
    /// </summary>
    [SerializeField] private DisplayState state = DisplayState.UnassociatedState;
    
    /// <summary>
    ///     the visual element object for game ui
    /// </summary>
    public VisualElement UI;

    /// <summary>
    ///     enforces singleton behaviour; sets doesn't destroy on load and checks for multiple instances
    /// </summary>
    private void Awake()
    {
        // check if instance hasn't been set yet
        if (Instance == null)
        {
            Debug.Log("awake as singleton instance, setting self as the forever-alive instance");
            Instance = this;
            DontDestroyOnLoad(gameObject);
        }
        // check if instance is already set and it's not this instance
        else if (Instance != null && Instance != this)
        {
            Debug.Log("awake as non-singleton instance, destroying self");
            Destroy(gameObject);
        }
    }

    private void OnEnable()
    {
        UI = GetComponent<UIDocument>().rootVisualElement;
        SetDisplayState(DisplayState.Nothing);
    }
    
    /// <summary>
    ///     function to show a menu based on the enum passed,
    ///     and any other necessary actions
    /// </summary>
    /// <param name="newDisplayState">the game menu to show</param>
    public void SetDisplayState(DisplayState newDisplayState)
    {
        var currentDisplayState = state;

        // if the new state is the same as the current state, do nothing
        if (currentDisplayState == newDisplayState)
        {
            Debug.Log($"staying at {currentDisplayState} (illogical transition)");
            return;
        }

        Debug.Log($"switching from {currentDisplayState} to {newDisplayState}");

        var gameView = UI.Q<VisualElement>("GameView");
        var leaderboardView = UI.Q<VisualElement>("LeaderboardView");
        var accountView = UI.Q<VisualElement>("AccountView");

        switch (newDisplayState)
        {
            case DisplayState.Nothing:
                gameView.style.display = DisplayStyle.None;
                leaderboardView.style.display = DisplayStyle.None;
                accountView.style.display = DisplayStyle.None;
                break;

            case DisplayState.PlayView:
                gameView.style.display = DisplayStyle.Flex;
                leaderboardView.style.display = DisplayStyle.None;
                accountView.style.display = DisplayStyle.None;
                break;

            case DisplayState.LeaderboardView:
                gameView.style.display = DisplayStyle.None;
                leaderboardView.style.display = DisplayStyle.Flex;
                accountView.style.display = DisplayStyle.None;
                break;

            case DisplayState.AccountView:
                gameView.style.display = DisplayStyle.None;
                leaderboardView.style.display = DisplayStyle.None;
                accountView.style.display = DisplayStyle.Flex;
                break;

            case DisplayState.UnassociatedState:
            default:
                throw new ArgumentOutOfRangeException(nameof(newDisplayState), newDisplayState, null);
        }
    }
}