using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using UnityEditor;
using UnityEngine;

namespace FullscreenEditor {
    /// <summary>The window that will be shown in the place of the original view when creating a fullscreen container.</summary>
    public class PlaceholderWindow : EditorWindow {

        private const float PREVIEW_FRAMERATE = 24f;

        private static class Styles {

            public static readonly GUIStyle textStyle = new GUIStyle("BoldLabel");
            public static readonly GUIStyle backgroundShadow = new GUIStyle("InnerShadowBg");
            public static readonly GUIStyle buttonStyle = new GUIStyle("LargeButton");

            static Styles() {
                textStyle.wordWrap = true;
                textStyle.alignment = TextAnchor.MiddleCenter;
            }

        }

        [SerializeField] private Vector2 m_scroll;
        [SerializeField] private FullscreenContainer m_fullscreenContainer;
        [SerializeField] private bool m_containerForcefullyClosed;

        private double m_nextUpdate;
        private RenderTexture m_previewRT;

        private FullscreenContainer FullscreenContainer {
            get {
                if (m_containerForcefullyClosed)
                    return null;
                if (!m_fullscreenContainer)
                    m_fullscreenContainer = FullscreenUtility.GetRef<FullscreenContainer>(name);
                if (!m_fullscreenContainer)
                    m_containerForcefullyClosed = true;

                return m_fullscreenContainer;
            }
            set { m_fullscreenContainer = value; }
        }

        private bool PreviewSupported {
            get {
                return FullscreenContainer &&
                    !FullscreenContainer.Rect.Overlaps(position) &&
                    FullscreenContainer.m_dst.View &&
                    FullscreenContainer.m_src.Window &&
                    FullscreenContainer.m_dst.View.HasMethod("GrabPixels");
            }
        }

        private void Update() {
            if (EditorApplication.timeSinceStartup < m_nextUpdate)
                return;

            m_nextUpdate = EditorApplication.timeSinceStartup + (1f / PREVIEW_FRAMERATE);
            RenderTexture.ReleaseTemporary(m_previewRT);
            m_previewRT = null;

            if (!PreviewSupported || m_containerForcefullyClosed)
                return;

            var view = FullscreenContainer ? FullscreenContainer.m_dst.View : null;
            var width = (int)FullscreenContainer.Rect.width;
            var height = (int)FullscreenContainer.Rect.height;

            if (!view || width < 10 || height < 10)
                return;

            m_previewRT = RenderTexture.GetTemporary(width, height, 0);
            view.InvokeMethod("GrabPixels", m_previewRT, new Rect(0f, 0f, width, height));
            Repaint();
        }

        private void OnDisable() {
            RenderTexture.ReleaseTemporary(m_previewRT);
        }

        private void OnGUI() {

            using(var scrollScope = new EditorGUILayout.ScrollViewScope(m_scroll))
            using(var mainScope = new EditorGUILayout.VerticalScope(Styles.backgroundShadow)) {

                m_scroll = scrollScope.scrollPosition;

                using(new GUIColor(Color.white, 0.1f))
                if (m_previewRT) {
                    var rtRect = SystemInfo.graphicsUVStartsAtTop ?
                        Rect.MinMaxRect(0f, 1f, 1f, 0f) : // Direct3D like
                        Rect.MinMaxRect(0f, 0f, 1f, 1f); // OpenGL like

                    GUI.DrawTextureWithTexCoords(mainScope.rect, m_previewRT, rtRect);
                }

                using(new GUIColor(Styles.textStyle.normal.textColor * 0.05f))
                GUI.DrawTexture(mainScope.rect, FullscreenUtility.FullscreenIcon, ScaleMode.ScaleAndCrop);

                GUILayout.FlexibleSpace();

                using(new EditorGUILayout.HorizontalScope()) {
                    GUILayout.FlexibleSpace();

                    using(new GUIContentColor(Styles.textStyle.normal.textColor))
                    GUILayout.Label(FullscreenUtility.FullscreenIcon, Styles.textStyle);

                    using(new EditorGUILayout.VerticalScope()) {
                        if (FullscreenContainer && FullscreenContainer.ActualViewPyramid.Container) {
                            GUILayout.Label("The view that lives here is in fullscreen mode", Styles.textStyle);
                            GUILayout.Label("Don't close this placeholder", Styles.textStyle);
                        } else {
                            GUILayout.Label("The view that lived here was forcefully closed while in fullscreen, restore is not available", Styles.textStyle);
                            GUILayout.Label("Consider using the shortcuts to exit fullscreen", Styles.textStyle);
                            GUILayout.Label("You may close this placeholder", Styles.textStyle);
                        }

                    }
                    GUILayout.FlexibleSpace();
                }

                using(new EditorGUILayout.HorizontalScope()) {
                    GUILayout.FlexibleSpace();

                    if (FullscreenContainer && FullscreenContainer.ActualViewPyramid.Container) {
                        if (GUILayout.Button("Restore View", Styles.buttonStyle))
                            FullscreenContainer.Close();
                    } else if (GUILayout.Button("Close Placeholder", Styles.buttonStyle))
                        Close();
                    GUILayout.FlexibleSpace();
                }

                GUILayout.FlexibleSpace();

                // This GUI may be called after "this" has been destroyed, that causes a NullReference for the "name" getter
                // Not sure why this happens tho
                EditorGUILayout.LabelField(SafeObjToString(() => name));
                EditorGUILayout.Space();

                if (FullscreenUtility.DebugModeEnabled) {
                    EditorGUILayout.LabelField("Forcefully Closed", SafeObjToString(() => m_containerForcefullyClosed));

                    EditorGUILayout.LabelField("Container", SafeObjToString(() => FullscreenContainer));
                    EditorGUILayout.LabelField("Rect", SafeObjToString(() => FullscreenContainer.Rect));

                    EditorGUILayout.LabelField("SRC Window", SafeObjToString(() => FullscreenContainer.m_src.Window));
                    EditorGUILayout.LabelField("SRC View", SafeObjToString(() => FullscreenContainer.m_src.View));
                    EditorGUILayout.LabelField("SRC Container", SafeObjToString(() => FullscreenContainer.m_src.Container));

                    EditorGUILayout.LabelField("DST Window", SafeObjToString(() => FullscreenContainer.m_dst.Window));
                    EditorGUILayout.LabelField("DST View", SafeObjToString(() => FullscreenContainer.m_dst.View));
                    EditorGUILayout.LabelField("DST Container", SafeObjToString(() => FullscreenContainer.m_dst.Container));

                    EditorGUILayout.Space();
                }

            }
        }

        private string SafeObjToString<T>(Func<T> obj) {
            try {
                var i = obj();
                return i == null? "null": i.ToString();
            } catch {
                return "invalid";
            }
        }

    }
}