using System;
using System.Collections.Generic;
using System.Linq;
using UnityEngine;
using Object = UnityEngine.Object;

namespace UnityEditor.Tilemaps
{
    /// <summary>
    /// GridPaintingState controls the state of objects for painting with a Tile Palette.
    /// </summary>
    /// <remarks>
    /// Utilize this class to get and set the current painting target and brush for painting
    /// with the Tile Palette.
    /// </remarks>
    public class GridPaintingState : ScriptableSingleton<GridPaintingState>
    {
        [SerializeField] private GameObject m_EditModeScenePaintTarget; // Which GameObject in scene was the last painting target in EditMode
        [SerializeField] private GameObject m_ScenePaintTarget; // Which GameObject in scene is considered as painting target
        [SerializeField] private GridBrushBase m_Brush; // Which brush will handle painting callbacks
        [SerializeField] private PaintableGrid m_ActiveGrid; // Grid that has painting focus (can be palette, too)
        [SerializeField] private PaintableGrid m_LastActiveGrid; // Grid that last had painting focus (can be palette, too)
        [SerializeField] private HashSet<Object> m_InterestedPainters = new HashSet<Object>(); // A list of objects that can paint using the GridPaintingState

        private GameObject[] m_CachedPaintTargets;
        private bool m_FlushPaintTargetCache;
        private Editor m_CachedEditor;
        private bool m_SavingPalette;

        /// <summary>
        /// Callback when the Tile Palette's active target has changed
        /// </summary>
        public static event Action<GameObject> scenePaintTargetChanged;
        /// <summary>
        /// Callback when the Tile Palette's active brush has changed.
        /// </summary>
        public static event Action<GridBrushBase> brushChanged;
        /// <summary>
        /// Callback when the Tile Palette's active palette GameObject has changed.
        /// </summary>
        public static event Action<GameObject> paletteChanged;

        private void OnEnable()
        {
            EditorApplication.hierarchyChanged += HierarchyChanged;
            EditorApplication.playModeStateChanged += PlayModeStateChanged;
            Selection.selectionChanged += OnSelectionChange;
            m_FlushPaintTargetCache = true;
        }

        private void OnDisable()
        {
            m_InterestedPainters.Clear();
            EditorApplication.hierarchyChanged -= HierarchyChanged;
            EditorApplication.playModeStateChanged -= PlayModeStateChanged;
            Selection.selectionChanged -= OnSelectionChange;
            FlushCache();
        }

        private void OnSelectionChange()
        {
            if (hasInterestedPainters && ValidatePaintTarget(Selection.activeGameObject))
            {
                scenePaintTarget = Selection.activeGameObject;
            }
        }

        private void PlayModeStateChanged(PlayModeStateChange state)
        {
            if (state == PlayModeStateChange.ExitingEditMode)
            {
                m_EditModeScenePaintTarget = scenePaintTarget;
            }
            else if (state == PlayModeStateChange.EnteredEditMode)
            {
                if (GridPaintActiveTargetsPreferences.restoreEditModeSelection && m_EditModeScenePaintTarget != null)
                {
                    scenePaintTarget = m_EditModeScenePaintTarget;
                }
            }
        }

        private void HierarchyChanged()
        {
            if (hasInterestedPainters)
            {
                m_FlushPaintTargetCache = true;
                if (validTargets == null || validTargets.Length == 0 || !validTargets.Contains(scenePaintTarget))
                {
                    // case 1102618: Try to use current Selection as scene paint target if possible
                    if (Selection.activeGameObject != null && hasInterestedPainters && ValidatePaintTarget(Selection.activeGameObject))
                    {
                        scenePaintTarget = Selection.activeGameObject;
                    }
                    else
                    {
                        AutoSelectPaintTarget();
                    }
                }
            }
        }

        private GameObject[] GetValidTargets()
        {
            if (m_FlushPaintTargetCache)
            {
                m_CachedPaintTargets = null;
                if (activeBrushEditor != null)
                    m_CachedPaintTargets = activeBrushEditor.validTargets;
                if (m_CachedPaintTargets == null || m_CachedPaintTargets.Length == 0)
                    scenePaintTarget = null;
                else
                {
                    var comparer = GridPaintActiveTargetsPreferences.GetTargetComparer();
                    if (comparer != null)
                        Array.Sort(m_CachedPaintTargets, comparer);
                }

                m_FlushPaintTargetCache = false;
            }
            return m_CachedPaintTargets;
        }

        internal static void AutoSelectPaintTarget()
        {
            if (activeBrushEditor != null)
            {
                if (validTargets != null && validTargets.Length > 0)
                {
                    scenePaintTarget = validTargets[0];
                }
            }
        }

        /// <summary>
        /// The currently active target for the Tile Palette
        /// </summary>
        public static GameObject scenePaintTarget
        {
            get { return instance.m_ScenePaintTarget; }
            set
            {
                if (value != instance.m_ScenePaintTarget)
                {
                    instance.m_ScenePaintTarget = value;
                    if (scenePaintTargetChanged != null)
                        scenePaintTargetChanged(instance.m_ScenePaintTarget);
                    RepaintGridPaintPaletteWindow();
                }
            }
        }

        /// <summary>
        /// The currently active brush for the Tile Palette
        /// </summary>
        public static GridBrushBase gridBrush
        {
            get
            {
                if (instance.m_Brush == null)
                    instance.m_Brush = GridPaletteBrushes.instance.GetLastUsedBrush();

                return instance.m_Brush;
            }
            set
            {
                if (instance.m_Brush != value)
                {
                    instance.m_Brush = value;
                    instance.m_FlushPaintTargetCache = true;

                    if (value != null)
                        GridPaletteBrushes.instance.StoreLastUsedBrush(value);

                    // Ensure that current scenePaintTarget is still a valid target after a brush change
                    if (scenePaintTarget != null && !ValidatePaintTarget(scenePaintTarget))
                        scenePaintTarget = null;

                    // Use Selection if previous scenePaintTarget was not valid
                    if (scenePaintTarget == null)
                        scenePaintTarget = ValidatePaintTarget(Selection.activeGameObject) ? Selection.activeGameObject : null;

                    // Auto select a valid target if there is still no scenePaintTarget
                    if (scenePaintTarget == null)
                        AutoSelectPaintTarget();

                    if (null != brushChanged)
                        brushChanged(value);

                    RepaintGridPaintPaletteWindow();
                }
            }
        }

        /// <summary>
        ///  Returns all available brushes for the Tile Palette
        /// </summary>
        public static IList<GridBrushBase> brushes
        {
            get { return GridPaletteBrushes.brushes; }
        }

        internal static GridBrush defaultBrush
        {
            get { return gridBrush as GridBrush; }
            set { gridBrush = value; }
        }

        /// <summary>
        /// The currently active palette GameObject for the Tile Palette
        /// </summary>
        public static GameObject palette
        {
            get
            {
                if (GridPaintPaletteWindow.instances.Count > 0)
                    return GridPaintPaletteWindow.instances[0].palette;
                return null;
            }
            set
            {
                if (value == null || !GridPalettes.palettes.Contains(value))
                    throw new ArgumentException(L10n.Tr("Unable to set invalid palette"));
                if (GridPaintPaletteWindow.instances.Count > 0 && GridPaintPaletteWindow.instances[0].palette != value)
                {
                    GridPaintPaletteWindow.instances[0].palette = value;
                }
            }
        }

        /// <summary>
        /// Checks if target GameObject is part of the active Palette.
        /// </summary>
        /// <param name="target">GameObject to check.</param>
        /// <returns>True if the target GameObject is part of the active palette. False if not.</returns>
        public static bool IsPartOfActivePalette(GameObject target)
        {
            if (GridPaintPaletteWindow.instances.Count > 0 && target == GridPaintPaletteWindow.instances[0].paletteInstance)
                return true;
            if (target == palette)
                return true;
            var parent = target.transform.parent;
            return parent != null && IsPartOfActivePalette(parent.gameObject);
        }

        /// <summary>
        /// Returns all available Palette GameObjects for the Tile Palette
        /// </summary>
        public static IList<GameObject> palettes
        {
            get { return GridPalettes.palettes; }
        }

        /// <summary>
        /// The currently active editor for the active brush for the Tile Palette
        /// </summary>
        public static GridBrushEditorBase activeBrushEditor
        {
            get
            {
                Editor.CreateCachedEditor(gridBrush, null, ref instance.m_CachedEditor);
                GridBrushEditorBase baseEditor = instance.m_CachedEditor as GridBrushEditorBase;
                return baseEditor;
            }
        }

        internal static Editor fallbackEditor
        {
            get
            {
                Editor.CreateCachedEditor(gridBrush, null, ref instance.m_CachedEditor);
                return instance.m_CachedEditor;
            }
        }

        internal static PaintableGrid activeGrid
        {
            get { return instance.m_ActiveGrid; }
            set
            {
                instance.m_ActiveGrid = value;
                if (instance.m_ActiveGrid != null)
                    instance.m_LastActiveGrid = value;
            }
        }

        internal static PaintableGrid lastActiveGrid
        {
            get { return instance.m_LastActiveGrid; }
        }

        private static bool ValidatePaintTarget(GameObject candidate)
        {
            if (candidate == null || candidate.GetComponentInParent<Grid>() == null && candidate.GetComponent<Grid>() == null)
                return false;

            if (validTargets != null && validTargets.Length > 0 && !validTargets.Contains(candidate))
                return false;

            return true;
        }

        internal static void FlushCache()
        {
            if (instance.m_CachedEditor != null)
            {
                DestroyImmediate(instance.m_CachedEditor);
                instance.m_CachedEditor = null;
            }
            instance.m_FlushPaintTargetCache = true;
        }

        /// <summary>
        /// A list of all valid targets that can be set as an active target for the Tile Palette
        /// </summary>
        public static GameObject[] validTargets
        {
            get { return instance.GetValidTargets(); }
        }

        internal static bool savingPalette
        {
            get { return instance.m_SavingPalette; }
            set { instance.m_SavingPalette = value; }
        }

        internal static void OnPaletteChanged(GameObject palette)
        {
            if (null != paletteChanged)
                paletteChanged(palette);
        }

        internal static void UpdateActiveGridPalette()
        {
            if (GridPaintPaletteWindow.instances.Count > 0)
                GridPaintPaletteWindow.instances[0].DelayedResetPreviewInstance();
        }

        internal static void RepaintGridPaintPaletteWindow()
        {
            if (GridPaintPaletteWindow.instances.Count > 0)
                GridPaintPaletteWindow.instances[0].Repaint();
        }

        internal static void UnlockGridPaintPaletteClipboardForEditing()
        {
            if (GridPaintPaletteWindow.instances.Count > 0)
                GridPaintPaletteWindow.instances[0].clipboardView.UnlockAndEdit();
        }

        internal static void RegisterPainterInterest(Object painter)
        {
            instance.m_InterestedPainters.Add(painter);
        }

        internal static void UnregisterPainterInterest(Object painter)
        {
            instance.m_InterestedPainters.Remove(painter);
        }

        private bool hasInterestedPainters
        {
            get { return m_InterestedPainters.Count > 0; }
        }
    }
}