using System; 
using System.Text;
using UnityEngine;
using UnityEngine.TerrainTools;

namespace UnityEditor.TerrainTools
{
    internal class BrushScatterVariator : BaseBrushVariator, IBrushScatterController
    {

        private float m_BrushScatter;
        
        public float brushScatter {
            get { return m_BrushScatter; }
            set
            {
                m_BrushScatter = Mathf.Clamp(value, 0f, 100f);
            }
        }

        private bool m_UseNewRandomValue;
        private Vector2 m_RandomValues;
        
        private float m_defaultBrushScatter;

        public Vector2 ScatterBrushStamp(Vector2 uv, float brushSize)
        {
            float scatterRadius = 0.5f * m_BrushScatter;
            Vector2 r = scatterRadius * m_RandomValues;

            return r + uv;
        }

        class Styles
        {
            public readonly GUIContent brushScatter = EditorGUIUtility.TrTextContent("Brush Scatter", "Randomized scattering perpendicular to the stroke direction");
        }

        static readonly Styles styles = new Styles();

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

        public void RequestRandomisation()
        {
            m_UseNewRandomValue = true;
        }

        public override void OnEnterToolMode(BrushShortcutHandler<BrushShortcutType> shortcutHandler)
        {
            base.OnEnterToolMode(shortcutHandler);
            m_BrushScatter = GetEditorPrefs("TerrainBrushScatter", m_defaultBrushScatter);
        }

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

        public override void OnSceneGUI(Event currentEvent, int controlId, Terrain terrain, IOnSceneGUI editContext)
        {
            if (m_UseNewRandomValue)
            {
                m_RandomValues = UnityEngine.Random.insideUnitCircle;
                m_UseNewRandomValue = false;
            }

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

        // for updating condensed slider overlays 
        public static event Action BrushScatterChanged;
        private float prevBrushScatter; 
        public override void OnInspectorGUI(Terrain terrain, IOnInspectorGUI editContext)
        {
            base.OnInspectorGUI(terrain, editContext);

            m_BrushScatter = TerrainToolGUIHelper.PercentSlider(styles.brushScatter, m_BrushScatter, 0.0f, 1.0f);
            if (!Mathf.Approximately(m_BrushScatter, prevBrushScatter) && BrushScatterChanged != null)
            {
                BrushScatterChanged();
                prevBrushScatter = m_BrushScatter; 
            }
        }

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