// Animancer // Copyright 2020 Kybernetik //

#if UNITY_EDITOR

#pragma warning disable IDE0041 // Use 'is null' check.

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

namespace Animancer.Editor
{
    /// <summary>[Editor-Only] Draws the Inspector GUI for an <see cref="AnimancerState"/>.</summary>
    public class AnimancerStateDrawer<T> : AnimancerNodeDrawer<T> where T : AnimancerState
    {
        /************************************************************************************************************************/

        /// <summary>
        /// Constructs a new <see cref="AnimancerStateDrawer{T}"/> to manage the Inspector GUI for the `target`.
        /// </summary>
        public AnimancerStateDrawer(T target)
        {
            Target = target;
        }

        /************************************************************************************************************************/

        /// <summary>The <see cref="GUIStyle"/> used for the area encompassing this drawer. Null.</summary>
        protected override GUIStyle RegionStyle { get { return null; } }

        /************************************************************************************************************************/

        /// <summary>
        /// Draws the state's main label: an <see cref="Object"/> field if it has a
        /// <see cref="AnimancerState.MainObject"/>, otherwise just a simple text label.
        /// <para></para>
        /// Also shows a bar to indicate its progress.
        /// </summary>
        protected override void DoLabelGUI(Rect area)
        {
            var key = Target.Key;
            var mainObject = Target.MainObject;
            var isAssetUsedAsKey = key == null || ReferenceEquals(key, mainObject);

            string label;
            if (isAssetUsedAsKey)
            {
                label = "";
            }
            else
            {
                if (key is string)
                    label = "\"" + key + "\"";
                else
                    label = key.ToString();
            }

            HandleLabelClick(area);

            AnimancerGUI.DoWeightLabel(ref area, Target.Weight);

            if (!ReferenceEquals(mainObject, null))
            {
                EditorGUI.BeginChangeCheck();

                mainObject = EditorGUI.ObjectField(area, label, mainObject, typeof(Object), false);

                if (EditorGUI.EndChangeCheck())
                    Target.MainObject = mainObject;
            }
            else
            {
                EditorGUI.LabelField(area, label, Target.ToString());
            }

            // Highlight a section of the label based on the time like a loading bar.
            if (Target.IsPlaying || Target.Time != 0)
            {
                var color = GUI.color;

                // Green = Playing, Yelow = Paused.
                GUI.color = Target.IsPlaying ? new Color(0.15f, 0.7f, 0.15f, 0.35f) : new Color(0.7f, 0.7f, 0.15f, 0.35f);

                area.xMin += AnimancerGUI.IndentSize;
                area.width -= 18;

                float length;
                var wrappedTime = GetWrappedTime(out length);
                if (length > 0)
                    area.width *= Mathf.Clamp01(wrappedTime / length);

                GUI.DrawTexture(area, Texture2D.whiteTexture);

                GUI.color = color;
            }
        }

        /************************************************************************************************************************/

        /// <summary>
        /// Handles Ctrl + Click on the label to CrossFade the animation.
        /// <para></para>
        /// If Shift is also held, the effect will be queued until after the previous animation finishes.
        /// </summary>
        private void HandleLabelClick(Rect area)
        {
            var currentEvent = Event.current;
            if (currentEvent.type != EventType.MouseUp ||
                !currentEvent.control ||
                !area.Contains(currentEvent.mousePosition))
                return;

            currentEvent.Use();

            if (currentEvent.shift)
            {
                AnimationQueue.CrossFadeQueued(Target);
                return;
            }

            AnimationQueue.ClearQueue(Target.Layer);

            Target.Root.UnpauseGraph();
            var fadeDuration = Target.CalculateEditorFadeDuration(AnimancerPlayable.DefaultFadeDuration);
            Target.Root.Play(Target, fadeDuration);
        }

        /************************************************************************************************************************/

        /// <summary>Draws a foldout arrow to expand/collapse the state details.</summary>
        protected override void DoFoldoutGUI(Rect area)
        {
            var key = Target.Key;
            var isAssetUsedAsKey = key == null || ReferenceEquals(key, Target.MainObject);

            float foldoutWidth;
            if (isAssetUsedAsKey)
            {
                foldoutWidth = EditorGUI.indentLevel * AnimancerGUI.IndentSize;
            }
            else
            {
                foldoutWidth = EditorGUIUtility.labelWidth;
            }

            area.xMin -= 2;
            area.width = foldoutWidth;

            var hierarchyMode = EditorGUIUtility.hierarchyMode;
            EditorGUIUtility.hierarchyMode = true;

            IsExpanded = EditorGUI.Foldout(area, IsExpanded, GUIContent.none, true);

            EditorGUIUtility.hierarchyMode = hierarchyMode;
        }

        /************************************************************************************************************************/

        /// <summary>
        /// Manages the playing of animations in sequence.
        /// </summary>
        private sealed class AnimationQueue
        {
            /************************************************************************************************************************/

            private static readonly Dictionary<AnimancerLayer, AnimationQueue>
                PlayableToQueue = new Dictionary<AnimancerLayer, AnimationQueue>();

            private readonly List<AnimancerState>
                Queue = new List<AnimancerState>();

            /************************************************************************************************************************/

            private AnimationQueue() { }

            public static void CrossFadeQueued(AnimancerState state)
            {
                CleanUp();

                var layer = state.Layer;

                // If the layer has no current state, just play the animation immediately.
                if (!layer.CurrentState.IsValid() || layer.CurrentState.Weight == 0)
                {
                    var fadeDuration = state.CalculateEditorFadeDuration(AnimancerPlayable.DefaultFadeDuration);
                    layer.Play(state, fadeDuration);
                    return;
                }

                AnimationQueue queue;
                if (!PlayableToQueue.TryGetValue(layer, out queue))
                {
                    queue = new AnimationQueue();
                    PlayableToQueue.Add(layer, queue);
                }

                queue.Queue.Add(state);

                layer.CurrentState.Events.OnEnd -= queue.PlayNext;
                layer.CurrentState.Events.OnEnd += queue.PlayNext;
            }

            /************************************************************************************************************************/

            public static void ClearQueue(AnimancerLayer layer)
            {
                PlayableToQueue.Remove(layer);
            }

            /************************************************************************************************************************/

            private static readonly List<AnimancerLayer>
                OldQueues = new List<AnimancerLayer>();

            /// <summary>
            /// Clear out any playables that have been destroyed.
            /// </summary>
            private static void CleanUp()
            {
                OldQueues.Clear();

                foreach (var layer in PlayableToQueue.Keys)
                {
                    if (!layer.IsValid)
                        OldQueues.Add(layer);
                }

                for (int i = 0; i < OldQueues.Count; i++)
                {
                    PlayableToQueue.Remove(OldQueues[i]);
                }
            }

            /************************************************************************************************************************/

            private void PlayNext()
            {
                if (Queue.Count == 0)
                    return;

                var state = Queue[0];
                Queue.RemoveAt(0);
                if (!state.IsValid())
                {
                    PlayNext();
                    return;
                }

                var fadeDuration = state.CalculateEditorFadeDuration(AnimancerPlayable.DefaultFadeDuration);
                state.Layer.Play(state, fadeDuration);
                state.Events.OnEnd = PlayNext;
            }

            /************************************************************************************************************************/
        }

        /************************************************************************************************************************/

        /// <summary>
        /// Gets the current <see cref="AnimancerState.Time"/>.
        /// If the state is looping, the value is modulo by the <see cref="AnimancerState.Length"/>.
        /// </summary>
        private float GetWrappedTime(out float length)
        {
            var time = Target.Time;
            length = Target.Length;

            var wrappedTime = time;

            if (Target.IsLooping)
            {
                wrappedTime = Mathf.Repeat(wrappedTime, length);
                if (wrappedTime == 0 && time != 0)
                    wrappedTime = length;
            }

            return wrappedTime;
        }

        /************************************************************************************************************************/

        /// <summary> Draws the details of the target state in the GUI.</summary>
        protected override void DoDetailsGUI(IAnimancerComponent owner)
        {
            if (!IsExpanded)
                return;

            EditorGUI.indentLevel++;
            DoTimeSliderGUI();
            DoNodeDetailsGUI();
            DoOnEndGUI();
            EditorGUI.indentLevel--;
        }

        /************************************************************************************************************************/

        /// <summary>Draws a slider for controlling the current <see cref="AnimancerState.Time"/>.</summary>
        private void DoTimeSliderGUI()
        {
            if (Target.Length <= 0)
                return;

            float length;
            var time = GetWrappedTime(out length);

            if (length == 0)
                return;

            var area = AnimancerGUI.LayoutSingleLineRect(AnimancerGUI.SpacingMode.Before);

            var normalized = DoNormalizedTimeToggle(ref area);

            string label;
            float max;
            if (normalized)
            {
                label = "Normalized Time";
                time /= length;
                max = 1;
            }
            else
            {
                label = "Time";
                max = length;
            }

            DoLoopCounterGUI(ref area, length);

            EditorGUI.BeginChangeCheck();
            label = AnimancerGUI.BeginTightLabel(label);
            time = EditorGUI.Slider(area, label, time, 0, max);
            AnimancerGUI.EndTightLabel();
            if (AnimancerGUI.TryUseClickEvent(area, 2))
                time = 0;
            if (EditorGUI.EndChangeCheck())
            {
                if (normalized)
                    Target.NormalizedTime = time;
                else
                    Target.Time = time;
            }
        }

        /************************************************************************************************************************/

        private static readonly BoolPref UseNormalizedTimeSliders = new BoolPref("Inspector", "UseNormalizedTimeSliders", false);
        private static readonly GUIElementWidth UseNormalizedTimeSlidersWidth = new GUIElementWidth();

        private bool DoNormalizedTimeToggle(ref Rect area)
        {
            var content = AnimancerGUI.TempContent("N");
            var style = AnimancerGUI.MiniButton;

            var width = UseNormalizedTimeSlidersWidth.GetWidth(style, content.text);
            var toggleArea = AnimancerGUI.StealFromRight(ref area, width);

            UseNormalizedTimeSliders.Value = GUI.Toggle(toggleArea, UseNormalizedTimeSliders, content, style);
            return UseNormalizedTimeSliders;
        }

        /************************************************************************************************************************/

        private static ConversionCache<int, string> _LoopCounterCache;

        private void DoLoopCounterGUI(ref Rect area, float length)
        {
            if (_LoopCounterCache == null)
                _LoopCounterCache = new ConversionCache<int, string>((x) => "x" + x);

            string label;
            var normalizedTime = Target.Time / length;
            if (float.IsNaN(normalizedTime))
            {
                label = "NaN";
            }
            else
            {
                var loops = (int)Math.Abs(Target.Time / length);
                label = _LoopCounterCache.Convert(loops);
            }

            var width = AnimancerGUI.CalculateLabelWidth(label);

            var labelArea = AnimancerGUI.StealFromRight(ref area, width);

            GUI.Label(labelArea, label);
        }

        /************************************************************************************************************************/

        private void DoOnEndGUI()
        {
            if (Target.Events.OnEnd == null)
                return;

            var area = AnimancerGUI.LayoutSingleLineRect(AnimancerGUI.SpacingMode.Before);

            EditorGUI.LabelField(area, "OnEnd: " + Target.Events.OnEnd.Method);
        }

        /************************************************************************************************************************/
        #region Context Menu
        /************************************************************************************************************************/

        /// <summary>Adds functions relevant to the <see cref="AnimancerNodeDrawer{T}.Target"/>.</summary>
        protected override void PopulateContextMenu(GenericMenu menu)
        {
            AddContextMenuFunctions(menu);

            AnimancerEditorUtilities.AddMenuItem(menu, "Play",
                !Target.IsPlaying || Target.Weight != 1,
                () =>
                {
                    Target.Root.UnpauseGraph();
                    Target.Root.Play(Target);
                });

            AnimancerEditorUtilities.AddFadeFunction(menu, "Cross Fade (Ctrl + Click)",
                Target.Weight != 1,
                Target, (duration) =>
                {
                    Target.Root.UnpauseGraph();
                    Target.Root.Play(Target, duration);
                });

            AnimancerEditorUtilities.AddFadeFunction(menu, "Cross Fade Queued (Ctrl + Shift + Click)",
                Target.Weight != 1,
                Target, (duration) =>
                {
                    AnimationQueue.CrossFadeQueued(Target);
                });

            menu.AddSeparator("");
            menu.AddItem(new GUIContent("Destroy State"), false, () => Target.Destroy());

            menu.AddSeparator("");
            AnimancerEditorUtilities.AddDocumentationLink(menu, "State Documentation", "/docs/manual/states");
        }

        /************************************************************************************************************************/

        /// <summary>[Editor-Only]
        /// Adds the details of this state to the menu.
        /// By default, that means a single item showing the path of the <see cref="AnimancerState.MainObject"/>.
        /// </summary>
        protected virtual void AddContextMenuFunctions(GenericMenu menu)
        {
            menu.AddDisabledItem(new GUIContent(DetailsPrefix + "Key: " + Target.Key));

            var length = Target.Length;
            if (!float.IsNaN(length))
                menu.AddDisabledItem(new GUIContent(DetailsPrefix + "Length: " + length));

            menu.AddDisabledItem(new GUIContent(DetailsPrefix + "Playable Path: " + Target.GetPath()));

            var mainAsset = Target.MainObject;
            if (mainAsset != null)
            {
                var assetPath = AssetDatabase.GetAssetPath(mainAsset);
                if (assetPath != null)
                    menu.AddDisabledItem(new GUIContent(DetailsPrefix + "Asset Path: " + assetPath.Replace("/", "->")));
            }

            const string OnEndPrefix = "End Event/";
            {
                var endEvent = Target.Events.endEvent;
                menu.AddDisabledItem(new GUIContent(OnEndPrefix + "NormalizedTime: " + endEvent.normalizedTime));

                if (endEvent.callback == null)
                {
                    menu.AddDisabledItem(new GUIContent(OnEndPrefix + "Callback: null"));
                }
                else
                {
                    var label = OnEndPrefix +
                        (endEvent.callback.Target != null ? ("Target: " + endEvent.callback.Target) : "Target: null");

                    var targetObject = endEvent.callback.Target as Object;
                    AnimancerEditorUtilities.AddMenuItem(menu, label,
                        targetObject != null,
                        () => Selection.activeObject = targetObject);

                    menu.AddDisabledItem(new GUIContent(
                        OnEndPrefix + "Declaring Type: " + endEvent.callback.Method.DeclaringType.FullName));

                    menu.AddDisabledItem(new GUIContent(
                        OnEndPrefix + "Method: " + endEvent.callback.Method));
                }

                AnimancerEditorUtilities.AddMenuItem(menu, OnEndPrefix + "Clear",
                    !float.IsNaN(endEvent.normalizedTime) || endEvent.callback != null,
                    () => Target.Events.endEvent = new AnimancerEvent(float.NaN, null));

                AnimancerEditorUtilities.AddMenuItem(menu, OnEndPrefix + "Invoke",
                    endEvent.callback != null,
                    () => Target.Events.endEvent.Invoke(Target));
            }
        }

        /************************************************************************************************************************/
        #endregion
        /************************************************************************************************************************/
    }
}

#endif