using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Events;
using UnityEngine.PlayerLoop;

namespace MoreMountains.Tools
{
    /// <summary>
    /// This class lets you define an axis on which to flip a "two sided" UI element (made of two separate and usually aligned objects, effectively turning each side on/off everytime the container's scale goes above/below a certain threshold
    /// </summary>
    [ExecuteAlways]
    public class MMTwoSidedUI : MonoBehaviour
    {
        /// the possible axis on which to flip the double object
        public enum Axis { x, y, z }
        
        [Header("Bindings")]
        /// the object to consider as the "front" of the two sided element. Will be visible if the scale is above the threshold
        public GameObject Front;
        /// the object to consider as the "back" of the two sided element. Will be visible if the scale is below the threshold
        public GameObject Back;
        
        [Header("Axis")]
        /// the axis on which to flip this object
        public Axis FlipAxis;
        /// the scale threshold at which the flip should occur
        public float ScaleThreshold = 0f;

        [Header("Events")]
        /// an event to invoke on flip
        public UnityEvent OnFlip;

        [Header("Debug")] 
        /// whether or not we're in debug mode
        public bool DebugMode;
        /// the value to apply to the scale when in debug mode
        [Range(-1f, 1f)] 
        public float ScaleValue;
        /// whether or not our object is flipped right now
        [MMReadOnly] 
        public bool BackVisible = false;

        protected RectTransform _rectTransform;
        protected bool _initialized = false;

        /// <summary>
        /// On Start we initialize our object
        /// </summary>
        protected virtual void Start()
        {
            Initialization();
        }

        /// <summary>
        /// On init we grab our rect transform and initialize visibility
        /// </summary>
        protected virtual void Initialization()
        {
            _rectTransform = this.gameObject.GetComponent<RectTransform>();
            _initialized = true;
            
            float axis = GetScaleValue();
            BackVisible = (axis < ScaleThreshold);
            
            Front.SetActive(!BackVisible);
            Back.SetActive(BackVisible);
        }
        
        /// <summary>
        /// On Update we update visibility if needed
        /// </summary>
        protected virtual void Update()
        {
            #if UNITY_EDITOR
                IfEditor();
            #endif
            
            float axis = GetScaleValue();

            if ((axis < ScaleThreshold) != BackVisible)
            {
                Front.SetActive(BackVisible);
                Back.SetActive(!BackVisible);
                OnFlip?.Invoke();
            }
            BackVisible = (axis < ScaleThreshold);
        }

        /// <summary>
        /// If in editor, we initialize if needed, and apply the debug scale value if needed
        /// </summary>
        protected virtual void IfEditor()
        {
            if (!_initialized)
            {
                Initialization();
            }

            if (DebugMode)
            {
                switch (FlipAxis)
                {
                    case Axis.x:
                        _rectTransform.localScale = new Vector3(ScaleValue, _rectTransform.localScale.y, _rectTransform.localScale.z);
                        break;
                    case Axis.y:
                        _rectTransform.localScale = new Vector3(_rectTransform.localScale.x, ScaleValue, _rectTransform.localScale.z);
                        break;
                    case Axis.z:
                        _rectTransform.localScale = new Vector3(_rectTransform.localScale.x, _rectTransform.localScale.y, ScaleValue);
                        break;
                }
            }
        }

        /// <summary>
        /// Returns the scale of the selected axis
        /// </summary>
        /// <returns></returns>
        protected virtual float GetScaleValue()
        {
            switch (FlipAxis)
            {
                case Axis.x:
                    return _rectTransform.localScale.x;
                case Axis.y:
                    return _rectTransform.localScale.y;
                case Axis.z:
                    return _rectTransform.localScale.z;
            }

            return 0f;
        }
    }
}