// Copyright (c) 2012-2020 Wojciech Figat. All rights reserved.

using System;
using System.Collections.Generic;
using System.Linq;
using FlaxEditor.Actions;
using FlaxEditor.SceneGraph;
using FlaxEngine;

namespace FlaxEditor.Modules
{
    /// <summary>
    /// Editing scenes module. Manages scene objects selection and editing modes.
    /// </summary>
    /// <seealso cref="FlaxEditor.Modules.EditorModule" />
    public sealed class SceneEditingModule : EditorModule
    {
        /// <summary>
        /// The selected objects.
        /// </summary>
        public readonly List<SceneGraphNode> Selection = new List<SceneGraphNode>(64);

        /// <summary>
        /// Gets the amount of the selected objects.
        /// </summary>
        public int SelectionCount => Selection.Count;

        /// <summary>
        /// Gets a value indicating whether any object is selected.
        /// </summary>
        public bool HasSthSelected => Selection.Count > 0;

        /// <summary>
        /// Occurs when selected objects collection gets changed.
        /// </summary>
        public event Action SelectionChanged;

        /// <summary>
        /// Occurs before spawning actor to game action.
        /// </summary>
        public event Action SpawnBegin;

        /// <summary>
        /// Occurs after spawning actor to game action.
        /// </summary>
        public event Action SpawnEnd;

        /// <summary>
        /// Occurs before selection delete action.
        /// </summary>
        public event Action SelectionDeleteBegin;

        /// <summary>
        /// Occurs after selection delete action.
        /// </summary>
        public event Action SelectionDeleteEnd;

        internal SceneEditingModule(Editor editor)
        : base(editor)
        {
        }

        /// <summary>
        /// Selects all scenes.
        /// </summary>
        public void SelectAllScenes()
        {
            // Select all scenes (linked to the root node)
            Select(Editor.Scene.Root.ChildNodes);
        }

        /// <summary>
        /// Selects the specified actor (finds it's scene graph node).
        /// </summary>
        /// <param name="actor">The actor.</param>
        public void Select(Actor actor)
        {
            var node = Editor.Scene.GetActorNode(actor);
            if (node != null)
                Select(node);
        }

        /// <summary>
        /// Selects the specified collection of objects.
        /// </summary>
        /// <param name="selection">The selection.</param>
        /// <param name="additive">if set to <c>true</c> will use additive mode, otherwise will clear previous selection.</param>
        public void Select(List<SceneGraphNode> selection, bool additive = false)
        {
            if (selection == null)
                throw new ArgumentNullException();

            // Prevent from selecting null nodes
            selection.RemoveAll(x => x == null);

            // Check if won't change
            if (!additive && Selection.Count == selection.Count && Selection.SequenceEqual(selection))
                return;

            var before = Selection.ToArray();
            if (!additive)
                Selection.Clear();
            Selection.AddRange(selection);

            SelectionChange(before);
        }

        /// <summary>
        /// Selects the specified collection of objects.
        /// </summary>
        /// <param name="selection">The selection.</param>
        /// <param name="additive">if set to <c>true</c> will use additive mode, otherwise will clear previous selection.</param>
        public void Select(SceneGraphNode[] selection, bool additive = false)
        {
            if (selection == null)
                throw new ArgumentNullException();

            Select(selection.ToList(), additive);
        }

        /// <summary>
        /// Selects the specified object.
        /// </summary>
        /// <param name="selection">The selection.</param>
        /// <param name="additive">if set to <c>true</c> will use additive mode, otherwise will clear previous selection.</param>
        public void Select(SceneGraphNode selection, bool additive = false)
        {
            if (selection == null)
                throw new ArgumentNullException();

            // Check if won't change
            if (!additive && Selection.Count == 1 && Selection[0] == selection)
                return;
            if (additive && Selection.Contains(selection))
                return;

            var before = Selection.ToArray();
            if (!additive)
                Selection.Clear();
            Selection.Add(selection);

            SelectionChange(before);
        }

        /// <summary>
        /// Deselects given object.
        /// </summary>
        public void Deselect(SceneGraphNode node)
        {
            if (!Selection.Contains(node))
                return;

            var before = Selection.ToArray();
            Selection.Remove(node);

            SelectionChange(before);
        }

        /// <summary>
        /// Clears selected objects collection.
        /// </summary>
        public void Deselect()
        {
            // Check if won't change
            if (Selection.Count == 0)
                return;

            var before = Selection.ToArray();
            Selection.Clear();

            SelectionChange(before);
        }

        private void SelectionChange(SceneGraphNode[] before)
        {
            Undo.AddAction(new SelectionChangeAction(before, Selection.ToArray(), OnSelectionUndo));

            OnSelectionChanged();
        }

        private void OnSelectionUndo(SceneGraphNode[] toSelect)
        {
            Selection.Clear();
            if (toSelect != null)
            {
                for (int i = 0; i < toSelect.Length; i++)
                {
                    if (toSelect[i] != null)
                        Selection.Add(toSelect[i]);
                    else
                        Editor.LogWarning("Null scene graph node to select");
                }
            }

            OnSelectionChanged();
        }

        /// <summary>
        /// Spawns the specified actor to the game (with undo).
        /// </summary>
        /// <param name="actor">The actor.</param>
        /// <param name="parent">The parent actor. Set null as default.</param>
        public void Spawn(Actor actor, Actor parent = null)
        {
            bool isPlayMode = Editor.StateMachine.IsPlayMode;

            if (Level.IsAnySceneLoaded == false)
                throw new InvalidOperationException("Cannot spawn actor when no scene is loaded.");

            SpawnBegin?.Invoke();

            // Add it
            Level.SpawnActor(actor, parent);

            // Peek spawned node
            var actorNode = Editor.Instance.Scene.GetActorNode(actor);
            if (actorNode == null)
                throw new InvalidOperationException("Failed to create scene node for the spawned actor.");

            // During play in editor mode spawned actors should be dynamic (user can move them)
            if (isPlayMode)
                actor.StaticFlags = StaticFlags.None;

            // Call post spawn action (can possibly setup custom default values)
            actorNode.PostSpawn();

            // Create undo action
            var action = new DeleteActorsAction(new List<SceneGraphNode>(1) { actorNode }, true);
            Undo.AddAction(action);

            // Mark scene as dirty
            Editor.Scene.MarkSceneEdited(actor.Scene);

            SpawnEnd?.Invoke();

            var options = Editor.Options.Options;

            // Auto CSG mesh rebuild
            if (!isPlayMode && options.General.AutoRebuildCSG)
            {
                if (actor is BoxBrush && actor.Scene)
                    actor.Scene.BuildCSG(options.General.AutoRebuildCSGTimeoutMs);
            }

            // Auto NavMesh rebuild
            if (!isPlayMode && options.General.AutoRebuildNavMesh && actor.Scene && (actor.StaticFlags & StaticFlags.Navigation) == StaticFlags.Navigation)
            {
                var bounds = actor.BoxWithChildren;
                Navigation.BuildNavMesh(actor.Scene, bounds, options.General.AutoRebuildNavMeshTimeoutMs);
            }
        }

        /// <summary>
        /// Deletes the selected objects. Supports undo/redo.
        /// </summary>
        public void Delete()
        {
            // Peek things that can be removed
            var objects = Selection.Where(x => x.CanDelete).ToList().BuildAllNodes().Where(x => x.CanDelete).ToList();
            if (objects.Count == 0)
                return;

            bool isPlayMode = Editor.StateMachine.IsPlayMode;

            SelectionDeleteBegin?.Invoke();

            // Change selection
            var action1 = new SelectionChangeAction(Selection.ToArray(), new SceneGraphNode[0], OnSelectionUndo);

            // Delete objects
            var action2 = new DeleteActorsAction(objects);

            // Merge two actions and perform them
            var action = new MultiUndoAction(new IUndoAction[]
            {
                action1,
                action2
            }, action2.ActionString);
            action.Do();
            Undo.AddAction(action);

            SelectionDeleteEnd?.Invoke();

            var options = Editor.Options.Options;

            // Auto CSG mesh rebuild
            if (!isPlayMode && options.General.AutoRebuildCSG)
            {
                foreach (var obj in objects)
                {
                    if (obj is ActorNode node && node.Actor is BoxBrush)
                        node.Actor.Scene.BuildCSG(options.General.AutoRebuildCSGTimeoutMs);
                }
            }

            // Auto NavMesh rebuild
            if (!isPlayMode && options.General.AutoRebuildNavMesh)
            {
                foreach (var obj in objects)
                {
                    if (obj is ActorNode node && node.Actor.Scene && (node.Actor.StaticFlags & StaticFlags.Navigation) == StaticFlags.Navigation)
                    {
                        var bounds = node.Actor.BoxWithChildren;
                        Navigation.BuildNavMesh(node.Actor.Scene, bounds, options.General.AutoRebuildNavMeshTimeoutMs);
                    }
                }
            }
        }

        /// <summary>
        /// Copies the selected objects.
        /// </summary>
        public void Copy()
        {
            // Peek things that can be copied (copy all actors)
            var objects = Selection.Where(x => x.CanCopyPaste).ToList().BuildAllNodes().Where(x => x.CanCopyPaste && x is ActorNode).ToList();
            if (objects.Count == 0)
                return;

            // Serialize actors
            var actors = objects.ConvertAll(x => ((ActorNode)x).Actor);
            var data = Actor.ToBytes(actors.ToArray());
            if (data == null)
            {
                Editor.LogError("Failed to copy actors data.");
                return;
            }

            // Copy data
            Clipboard.RawData = data;
        }


        /// <summary>
        /// Pastes the copied objects. Supports undo/redo.
        /// </summary>
        public void Paste()
        {
            Paste(null);
        }

        /// <summary>
        /// Pastes the copied objects. Supports undo/redo.
        /// </summary>
        /// <param name="pasteTargetActor">The target actor to paste copied data.</param>
        public void Paste(Actor pasteTargetActor)
        {
            // Get clipboard data
            var data = Clipboard.RawData;

            // Set paste target if only one actor is selected and no target provided
            if (pasteTargetActor == null && SelectionCount == 1 && Selection[0] is ActorNode actorNode)
            {
                pasteTargetActor = actorNode.Actor;
            }

            // Create paste action
            var pasteAction = PasteActorsAction.Paste(data, pasteTargetActor?.ID ?? Guid.Empty);
            if (pasteAction != null)
            {
                OnPasteAction(pasteAction);
            }
        }

        /// <summary>
        /// Cuts the selected objects. Supports undo/redo.
        /// </summary>
        public void Cut()
        {
            Copy();
            Delete();
        }

        /// <summary>
        /// Duplicates the selected objects. Supports undo/redo.
        /// </summary>
        public void Duplicate()
        {
            // Peek things that can be copied (copy all actors)
            var objects = Selection.Where(x => x.CanCopyPaste).ToList().BuildAllNodes().Where(x => x.CanCopyPaste && x is ActorNode).ToList();
            if (objects.Count == 0)
                return;

            // Serialize actors
            var actors = objects.ConvertAll(x => ((ActorNode)x).Actor);
            var data = Actor.ToBytes(actors.ToArray());
            if (data == null)
            {
                Editor.LogError("Failed to copy actors data.");
                return;
            }

            // Create paste action (with selecting spawned objects)
            var pasteAction = PasteActorsAction.Duplicate(data, Guid.Empty);
            if (pasteAction != null)
            {
                OnPasteAction(pasteAction);
            }
        }

        private void OnPasteAction(PasteActorsAction pasteAction)
        {
            pasteAction.Do(out _, out var nodeParents);

            // Select spawned objects
            var selectAction = new SelectionChangeAction(Selection.ToArray(), nodeParents.Cast<SceneGraphNode>().ToArray(), OnSelectionUndo);
            selectAction.Do();

            Undo.AddAction(new MultiUndoAction(pasteAction, selectAction));
            OnSelectionChanged();
        }

        /// <summary>
        /// Called when selection gets changed. Invokes the other events and updates editor. Call it when you manually modify selected objects collection.
        /// </summary>
        public void OnSelectionChanged()
        {
            SelectionChanged?.Invoke();
        }

        /// <inheritdoc />
        public override void OnInit()
        {
            // Deselect actors on remove (and actor child nodes)
            Editor.Scene.ActorRemoved += Deselect;
            Editor.Scene.Root.ActorChildNodesDispose += OnActorChildNodesDispose;
        }

        private void OnActorChildNodesDispose(ActorNode node)
        {
            // TODO: cache if selection contains any actor child node and skip this loop if no need to iterate

            // Deselect child nodes
            for (int i = 0; i < node.ChildNodes.Count; i++)
            {
                if (Selection.Contains(node.ChildNodes[i]))
                {
                    Deselect();
                    return;
                }
            }
        }
    }
}