using System;
using System.Collections.Generic;
using System.Linq;
using Luneraria.View;
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.UIElements;

namespace Luneraria.UI
{
    /// <summary>
    /// Portraits from the real game models (port of components/portrait_cache.gd). An offscreen
    /// camera renders one model at a time with the same orthographic three-quarter view, the same
    /// key, fill and rim light and a transparent background; every model is framed from its own
    /// bounds, so small creatures and the Schlundkrone fill the card alike. Each portrait is
    /// rendered once and kept, so cards never hold live views. Requests are queued and rendered a
    /// few per frame (Godot: one per frame).
    /// </summary>
    public sealed class LunePortraits : MonoBehaviour
    {
        public const int Small = 160;
        public const int Large = 400;
        const float Yaw = .42f;
        const float Pitch = .2f;
        /// <summary>Layer of the portrait stage; the portrait camera renders nothing else.</summary>
        public const int Layer = 31;
        const int PerFrame = 3;

        public static LunePortraits Shared { get; private set; }
        public event Action<string> PortraitReady;
        public LuneUnitLibrary Library;
        /// <summary>Portraits rendered so far (tests and the performance log).</summary>
        public int Rendered { get; private set; }

        readonly Dictionary<string, Texture> _textures = new Dictionary<string, Texture>();
        readonly List<string> _queue = new List<string>();
        Camera _camera;
        readonly Light[] _lights = new Light[3];

        public static string KeyFor(string modelId, bool large = false)
        {
            return modelId + (large ? "@L" : "");
        }

        public static LunePortraits Create(LuneUnitLibrary library)
        {
            if (Shared != null)
            {
                Shared.Library = library;
                return Shared;
            }
            var host = new GameObject("LunePortraits");
            host.transform.position = new Vector3(0f, -2000f, 0f);
            var portraits = host.AddComponent<LunePortraits>();
            portraits.Library = library;
            return portraits;
        }

        void Awake()
        {
            Shared = this;
            var cameraObject = new GameObject("PortraitCamera");
            cameraObject.transform.SetParent(transform, false);
            _camera = cameraObject.AddComponent<Camera>();
            _camera.enabled = false;
            _camera.orthographic = true;
            _camera.clearFlags = CameraClearFlags.SolidColor;
            _camera.backgroundColor = new Color(0f, 0f, 0f, 0f);
            _camera.cullingMask = 1 << Layer;
            _camera.allowMSAA = true;
            _camera.allowHDR = false;
            var data = cameraObject.AddComponent<UnityEngine.Rendering.Universal.UniversalAdditionalCameraData>();
            data.renderPostProcessing = false;
            data.renderShadows = false;
            // Key, fill and rim light of the reference. Godot rotation_degrees (x, y) with the light along
            // -Z (YXZ order) become Unity Euler (-x, 180 - y) with the light along +Z and x mirrored.
            Vector3[] angles = { new Vector3(38f, 212f, 0f), new Vector3(18f, 30f, 0f), new Vector3(8f, 140f, 0f) };
            Color[] colors = { LuneUiTheme.Hex("ffe2bc"), LuneUiTheme.Hex("9fc4ff"), LuneUiTheme.Hex("c8d4e4") };
            float[] energies = { 1.75f, .9f, .35f };
            for (int index = 0; index < 3; index++)
            {
                var lightObject = new GameObject("PortraitLight" + index);
                lightObject.transform.SetParent(transform, false);
                lightObject.transform.rotation = Quaternion.Euler(angles[index]);
                Light light = lightObject.AddComponent<Light>();
                light.type = LightType.Directional;
                light.color = colors[index];
                light.intensity = energies[index];
                light.shadows = LightShadows.None;
                light.cullingMask = 1 << Layer;
                light.enabled = false;
                _lights[index] = light;
            }
        }

        void OnDestroy()
        {
            if (Shared == this)
                Shared = null;
            foreach (Texture texture in _textures.Values)
            {
                if (texture is RenderTexture target)
                    target.Release();
            }
        }

        /// <summary>The cached portrait, or null while it is queued (PortraitReady follows).</summary>
        public Texture Portrait(string modelId, bool large = false)
        {
            if (string.IsNullOrEmpty(modelId))
                return null;
            string key = KeyFor(modelId, large);
            if (_textures.TryGetValue(key, out Texture texture))
                return texture;
            if (!_queue.Contains(key))
                _queue.Add(key);
            return null;
        }

        public int Pending { get { return _queue.Count; } }

        void LateUpdate()
        {
            for (int count = 0; count < PerFrame && _queue.Count > 0; count++)
            {
                string key = _queue[0];
                _queue.RemoveAt(0);
                RenderNow(key);
            }
        }

        /// <summary>Renders every queued portrait now (tests, captures).</summary>
        public void Flush()
        {
            while (_queue.Count > 0)
            {
                string key = _queue[0];
                _queue.RemoveAt(0);
                RenderNow(key);
            }
        }

        void RenderNow(string key)
        {
            bool large = key.EndsWith("@L", StringComparison.Ordinal);
            string modelId = large ? key.Substring(0, key.Length - 2) : key;
            int edge = large ? Large : Small;
            GameObject model = Instantiate(modelId);
            if (model == null)
            {
                _textures[key] = null;
                PortraitReady?.Invoke(key);
                return;
            }
            var target = new RenderTexture(edge, edge, 24, RenderTextureFormat.ARGB32) { antiAliasing = 4, name = "Portrait " + key };
            Frame(model);
            // Only the portrait lights shine; the scene's lights and ambient come back afterwards.
            List<Light> others = FindObjectsByType<Light>(FindObjectsSortMode.None).Where(l => l.enabled && Array.IndexOf(_lights, l) < 0).ToList();
            foreach (Light light in others)
                light.enabled = false;
            foreach (Light light in _lights)
                light.enabled = true;
            SphericalHarmonicsL2 ambient = RenderSettings.ambientProbe;
            var probe = new SphericalHarmonicsL2();
            probe.AddAmbientLight(LuneUiTheme.Hex("a8b4c8").linear * .62f);
            RenderSettings.ambientProbe = probe;
            bool fog = RenderSettings.fog;
            RenderSettings.fog = false;
            _camera.targetTexture = target;
            _camera.Render();
            _camera.targetTexture = null;
            RenderSettings.fog = fog;
            RenderSettings.ambientProbe = ambient;
            foreach (Light light in _lights)
                light.enabled = false;
            foreach (Light light in others)
                light.enabled = true;
            // Destroy takes effect at the end of the frame: hide the model now, or the next portrait
            // of the same frame would show it too.
            model.SetActive(false);
            Destroy(model);
            _textures[key] = target;
            Rendered++;
            PortraitReady?.Invoke(key);
        }

        GameObject Instantiate(string modelId)
        {
            if (Library == null)
                return null;
            LuneUnitLibrary.UnitModel entry = Library.Find(modelId);
            if (entry == null || entry.Prefab == null)
                return null;
            GameObject model = UnityEngine.Object.Instantiate(entry.Prefab, transform, false);
            model.SetActive(true);
            foreach (Transform node in model.GetComponentsInChildren<Transform>(true))
                node.gameObject.layer = Layer;
            Library.Materials?.Dress(model, 2);
            // Skinned figures stand in their idle pose (Godot preview("idle", .4)).
            if (entry.Controller != null)
            {
                AnimationClip idle = entry.Controller.animationClips.FirstOrDefault(c => c.name == "idle") ?? entry.Controller.animationClips.FirstOrDefault();
                Animator animator = model.GetComponentInChildren<Animator>();
                if (idle != null)
                    idle.SampleAnimation(animator != null ? animator.gameObject : model, Mathf.Min(.4f, idle.length));
            }
            return model;
        }

        /// <summary>Frames the model's bounds: the same view direction for every portrait, size from bounds.</summary>
        void Frame(GameObject model)
        {
            Bounds box = BoundsOf(model);
            Vector3 center = box.center;
            float radius = Mathf.Max(.3f, box.size.magnitude * .5f);
            // Godot view direction (sin yaw cos pitch, sin pitch, cos yaw cos pitch) in Unity's frame (x mirrored).
            var direction = new Vector3(-Mathf.Sin(Yaw) * Mathf.Cos(Pitch), Mathf.Sin(Pitch), Mathf.Cos(Yaw) * Mathf.Cos(Pitch));
            float size = Mathf.Max(box.size.y, Mathf.Max(box.size.x, box.size.z) * .92f) * 1.12f;
            _camera.orthographicSize = size * .5f;
            _camera.nearClipPlane = .05f;
            _camera.farClipPlane = radius * 8f + 10f;
            _camera.transform.position = center + direction * (radius * 3f + 2f);
            _camera.transform.LookAt(center, Vector3.up);
        }

        static Bounds BoundsOf(GameObject model)
        {
            Renderer[] renderers = model.GetComponentsInChildren<Renderer>(true);
            if (renderers.Length == 0)
                return new Bounds(model.transform.position + Vector3.up * .8f, new Vector3(1f, 1.6f, 1f));
            Bounds result = renderers[0].bounds;
            foreach (Renderer renderer in renderers)
                result.Encapsulate(renderer.bounds);
            return result;
        }
    }

    /// <summary>
    /// A real-model portrait on the neutral card background (dark slate gradient, soft floor;
    /// Godot LunePortraitRect). It asks LunePortraits for the texture and fills in when the
    /// render is done. Options: dimmed, a coloured ring, diagonal hatching (attack champions),
    /// a red cross (fallen units).
    /// </summary>
    public sealed class LunePortraitElement : VisualElement
    {
        public string ModelId { get; private set; } = "";
        public bool Large { get; private set; }
        readonly VisualElement _image;
        readonly VisualElement _overlay;
        Texture _texture;
        bool _dimmed;
        Color _ring;
        Color _hatch;
        bool _crossed;
        bool _listening;

        public LunePortraitElement()
        {
            pickingMode = PickingMode.Ignore;
            style.overflow = Overflow.Hidden;
            style.flexShrink = 0f;
            generateVisualContent += DrawBackground;
            _image = new VisualElement { pickingMode = PickingMode.Ignore };
            _image.style.position = Position.Absolute;
            Add(_image);
            _overlay = new VisualElement { pickingMode = PickingMode.Ignore };
            _overlay.style.position = Position.Absolute;
            _overlay.style.left = 0f;
            _overlay.style.top = 0f;
            _overlay.style.right = 0f;
            _overlay.style.bottom = 0f;
            _overlay.generateVisualContent += DrawOverlay;
            Add(_overlay);
            RegisterCallback<GeometryChangedEvent>(_ => PlaceImage());
            RegisterCallback<DetachFromPanelEvent>(_ => Unlisten());
        }

        public bool HasPortrait { get { return _texture != null; } }

        public void ShowModel(string id, bool large = false)
        {
            if (id == ModelId && large == Large && _texture != null)
                return;
            ModelId = id ?? "";
            Large = large;
            LunePortraits cache = LunePortraits.Shared;
            _texture = cache != null ? cache.Portrait(ModelId, large) : null;
            if (_texture == null && cache != null && !_listening)
            {
                cache.PortraitReady += OnReady;
                _listening = true;
            }
            ApplyTexture();
        }

        void OnReady(string key)
        {
            if (key != LunePortraits.KeyFor(ModelId, Large) || LunePortraits.Shared == null)
                return;
            _texture = LunePortraits.Shared.Portrait(ModelId, Large);
            ApplyTexture();
            Unlisten();
        }

        void Unlisten()
        {
            if (_listening && LunePortraits.Shared != null)
                LunePortraits.Shared.PortraitReady -= OnReady;
            _listening = false;
        }

        void ApplyTexture()
        {
            if (_texture is RenderTexture target)
                _image.style.backgroundImage = new StyleBackground(Background.FromRenderTexture(target));
            else if (_texture is Texture2D texture)
                _image.style.backgroundImage = new StyleBackground(texture);
            else
                _image.style.backgroundImage = StyleKeyword.None;
            _image.style.unityBackgroundImageTintColor = _dimmed ? new Color(1f, 1f, 1f, .45f) : Color.white;
            MarkDirtyRepaint();
        }

        void PlaceImage()
        {
            float edge = Mathf.Min(layout.width, layout.height);
            if (float.IsNaN(edge))
                return;
            _image.style.left = (layout.width - edge) * .5f;
            _image.style.top = (layout.height - edge) * .5f;
            _image.style.width = edge;
            _image.style.height = edge;
        }

        public bool Dimmed
        {
            get { return _dimmed; }
            set
            {
                if (value == _dimmed)
                    return;
                _dimmed = value;
                ApplyTexture();
            }
        }

        public Color Ring
        {
            get { return _ring; }
            set
            {
                if (value == _ring)
                    return;
                _ring = value;
                _overlay.MarkDirtyRepaint();
            }
        }

        /// <summary>Diagonal hatching over the background (attack champions: temporary units).</summary>
        public Color Hatch
        {
            get { return _hatch; }
            set
            {
                if (value == _hatch)
                    return;
                _hatch = value;
                MarkDirtyRepaint();
            }
        }

        /// <summary>Fallen units: a red cross over the portrait.</summary>
        public bool Crossed
        {
            get { return _crossed; }
            set
            {
                if (value == _crossed)
                    return;
                _crossed = value;
                _overlay.MarkDirtyRepaint();
            }
        }

        void DrawBackground(MeshGenerationContext context)
        {
            var rect = new Rect(0f, 0f, layout.width, layout.height);
            if (rect.width <= 0f || rect.height <= 0f)
                return;
            LunePlates.Gradient(context, LuneHpBar.Corners(rect), rect, LuneUiTheme.Hex("202b37"), LuneUiTheme.Hex("0d1218"));
            Painter2D painter = context.painter2D;
            var floor = new Vector2[20];
            for (int index = 0; index < 20; index++)
            {
                float angle = Mathf.PI * 2f * index / 20f;
                floor[index] = new Vector2(rect.width * .5f + Mathf.Cos(angle) * rect.width * .36f, rect.height * .88f + Mathf.Sin(angle) * rect.height * .06f);
            }
            LunePlates.Polygon(painter, floor, new Color(0f, 0f, 0f, .35f));
            if (_hatch.a > 0f)
            {
                for (float x = -rect.height; x < rect.width; x += 9f)
                {
                    var from = new Vector2(Mathf.Max(x, 0f), Mathf.Max(0f, -x));
                    var to = new Vector2(Mathf.Min(x + rect.height, rect.width), Mathf.Min(rect.height, rect.width - x));
                    LunePlates.Line(painter, from, to, _hatch, 2f);
                }
            }
            if (_texture == null)
            {
                float inset = Mathf.Min(rect.width, rect.height) * .22f;
                LuneGlyphs.Draw(painter, "human", new Rect(inset, inset, rect.width - inset * 2f, rect.height - inset * 2f), new Color(1f, 1f, 1f, .08f));
            }
        }

        void DrawOverlay(MeshGenerationContext context)
        {
            Painter2D painter = context.painter2D;
            float width = _overlay.layout.width;
            float height = _overlay.layout.height;
            if (_ring.a > 0f)
                LunePlates.Outline(painter, LuneHpBar.Corners(new Rect(1f, 1f, width - 2f, height - 2f)), _ring, 2f);
            if (_crossed)
            {
                float inset = Mathf.Min(width, height) * .22f;
                var color = new Color(1f, .42f, .36f, .85f);
                LunePlates.Line(painter, new Vector2(inset, inset), new Vector2(width - inset, height - inset), color, 2f);
                LunePlates.Line(painter, new Vector2(width - inset, inset), new Vector2(inset, height - inset), color, 2f);
            }
        }
    }
}