using System;
using System.Text;
using UnityEditor.TerrainTools.UI;
using UnityEngine;
using UnityEngine.TerrainTools;

namespace UnityEditor.TerrainTools
{
    internal class BrushSpacingVariator : BaseBrushVariator, IBrushSpacingController
    {
        private float m_BrushSpacing = 0.0f;

        private bool m_AllowPaint = true;
        private bool m_ThresholdReached = false;
        private float m_DistanceTravelled = 0.0f;
        private Vector3 m_LastBrushPos;

        private float m_defaultBrushSpacing;
        
        public float brushSpacing {
            get { return m_BrushSpacing; }
            set
            {
                m_BrushSpacing = Mathf.Clamp(value, 0f, 100f);
            }
        }
        public bool allowPaint {
            get => m_AllowPaint; set => m_AllowPaint = value; }

        class Styles
        {
            public readonly GUIContent brushSpacing = EditorGUIUtility.TrTextContent("Brush Spacing", "Distance between each brush stamp in a stroke");
        }

        static readonly Styles styles = new Styles();

        public BrushSpacingVariator(string toolName, IBrushEventHandler eventHandler, IBrushTerrainCache terrainCache, float defaultValue = 0.0f) : base(toolName, eventHandler, terrainCache)
        {
            m_defaultBrushSpacing = defaultValue;
        }

        public override void OnEnterToolMode(BrushShortcutHandler<BrushShortcutType> shortcutHandler)
        {
            base.OnEnterToolMode(shortcutHandler);
            m_BrushSpacing = GetEditorPrefs("TerrainBrushSpacing", m_defaultBrushSpacing);
        }

        public override void OnExitToolMode(BrushShortcutHandler<BrushShortcutType> shortcutHandler)
        {
            SetEditorPrefs("TerrainBrushSpacing", m_BrushSpacing);
            base.OnExitToolMode(shortcutHandler);
        }

        public override void OnSceneGUI(Event currentEvent, int controlId, Terrain terrain, IOnSceneGUI editContext)
        {
            //maybe this should be scaled by brush size?
            Vector2 a = new Vector2(m_LastBrushPos.x, m_LastBrushPos.z);
            Vector2 b = new Vector2(editContext.raycastHit.point.x, editContext.raycastHit.point.z);
            float d = Vector2.Distance(a, b);

            float threshold = m_BrushSpacing * 200f; //TODO: make this scalar a user preference?

            base.OnSceneGUI(currentEvent, controlId, terrain, editContext);

            m_DistanceTravelled += d;

            if (m_DistanceTravelled > threshold)
            {
                m_ThresholdReached = true;
                m_LastBrushPos = editContext.raycastHit.point;
                m_DistanceTravelled = 0.0f;
            }
            m_LastBrushPos = editContext.raycastHit.point;

        }

        // for updating condensed slider overlays 
        public static event Action BrushSpacingChanged;
        private float prevBrushSpacing; 
        public override void OnInspectorGUI(Terrain terrain, IOnInspectorGUI editContext)
        {
            base.OnInspectorGUI(terrain, editContext);
            m_BrushSpacing = TerrainToolGUIHelper.PercentSlider(styles.brushSpacing, m_BrushSpacing, 0.0f, 1.0f);
            if (!Mathf.Approximately(m_BrushSpacing, prevBrushSpacing) && BrushSpacingChanged != null)
            {
                BrushSpacingChanged();
                prevBrushSpacing = m_BrushSpacing;
            }
        }

        public override bool OnPaint(Terrain terrain, IOnPaint editContext)
        {
            base.OnPaint(terrain, editContext);

            m_AllowPaint = m_ThresholdReached;
            if (m_AllowPaint)
            {
                m_ThresholdReached = false;
            }


            return true;
        }

        public override void AppendBrushInfo(Terrain terrain, IOnSceneGUI editContext, StringBuilder builder)
        {
            base.AppendBrushInfo(terrain, editContext, builder);
            builder.AppendLine($"Spacing = {m_BrushSpacing:F3}");
        }
    }
}