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

namespace UnityEditor.Rendering
{
    using IProvider = FilterWindow.IProvider;
    using Element = FilterWindow.Element;
    using GroupElement = FilterWindow.GroupElement;

    class VolumeComponentProvider : IProvider
    {
        class VolumeComponentElement : Element
        {
            public Type type;

            public VolumeComponentElement(int level, string label, Type type)
            {
                this.level = level;
                this.type = type;
                // TODO: Add support for custom icons
                content = new GUIContent(label);
            }
        }

        class PathNode : IComparable<PathNode>
        {
            public List<PathNode> nodes = new List<PathNode>();
            public string name;
            public Type type;

            public int CompareTo(PathNode other)
            {
                return name.CompareTo(other.name);
            }
        }

        public Vector2 position { get; set; }

        VolumeProfile m_Target;
        VolumeComponentListEditor m_TargetEditor;

        public VolumeComponentProvider(VolumeProfile target, VolumeComponentListEditor targetEditor)
        {
            m_Target = target;
            m_TargetEditor = targetEditor;
        }

        static readonly Dictionary<Type, List<(string, Type)>> s_SupportedVolumeComponentsForRenderPipeline = new();

        static List<(string, Type)> GetSupportedVolumeComponents(Type currentPipelineType)
        {
            if (s_SupportedVolumeComponentsForRenderPipeline.TryGetValue(currentPipelineType,
                out var supportedVolumeComponents))
                return supportedVolumeComponents;

            supportedVolumeComponents = FilterVolumeComponentTypes(
                VolumeManager.instance.baseComponentTypeArray, currentPipelineType);
            s_SupportedVolumeComponentsForRenderPipeline[currentPipelineType] = supportedVolumeComponents;

            return supportedVolumeComponents;
        }

        static List<(string, Type)> FilterVolumeComponentTypes(Type[] types, Type currentPipelineType)
        {
            var volumes = new List<(string, Type)>();
            foreach (var t in types)
            {
                string path = string.Empty;

                var attrs = t.GetCustomAttributes(false);

                bool skipComponent = false;

                // Look for the attributes of this volume component and decide how is added and if it needs to be skipped
                foreach (var attr in attrs)
                {
                    switch (attr)
                    {
                        case VolumeComponentMenu attrMenu:
                        {
                            path = attrMenu.menu;
                            if (attrMenu is VolumeComponentMenuForRenderPipeline supportedOn)
                                skipComponent |= !supportedOn.pipelineTypes.Contains(currentPipelineType);
                            break;
                        }
                        case HideInInspector attrHide:
                        case ObsoleteAttribute attrDeprecated:
                            skipComponent = true;
                            break;
                    }
                }

                if (skipComponent)
                    continue;

                // If no attribute or in case something went wrong when grabbing it, fallback to a
                // beautified class name
                if (string.IsNullOrEmpty(path))
                    path = ObjectNames.NicifyVariableName(t.Name);

                volumes.Add((path, t));
            }

            return volumes;
        }

        public void CreateComponentTree(List<Element> tree)
        {
            var currentPipeline = RenderPipelineManager.currentPipeline;
            if (currentPipeline == null)
            {
                tree.Add(new GroupElement(0, "No SRP in use"));
                return;
            }

            tree.Add(new GroupElement(0, "Volume Overrides"));

            var volumeComponentTypesFiltered =
                GetSupportedVolumeComponents(currentPipeline.GetType());

            if (volumeComponentTypesFiltered.Any())
            {
                var rootNode = new PathNode();

                foreach (var (path, t) in volumeComponentTypesFiltered)
                {
                    // Skip components that have already been added to the volume
                    if (m_Target.Has(t))
                        continue;

                    // Prep the categories & types tree
                    AddNode(rootNode, path, t);
                }

                // Recursively add all elements to the tree
                Traverse(rootNode, 1, tree);
            }
        }

        public bool GoToChild(Element element, bool addIfComponent)
        {
            if (element is VolumeComponentElement volumeComponentElement)
            {
                m_TargetEditor.AddComponent(volumeComponentElement.type);
                return true;
            }

            return false;
        }

        void AddNode(PathNode root, string path, Type type)
        {
            var current = root;
            var parts = path.Split(new[] { '/' }, StringSplitOptions.RemoveEmptyEntries);

            foreach (var part in parts)
            {
                var child = current.nodes.Find(x => x.name == part);

                if (child == null)
                {
                    child = new PathNode { name = part, type = type };
                    current.nodes.Add(child);
                }

                current = child;
            }
        }

        void Traverse(PathNode node, int depth, List<Element> tree)
        {
            node.nodes.Sort();

            foreach (var n in node.nodes)
            {
                if (n.nodes.Count > 0) // Group
                {
                    tree.Add(new GroupElement(depth, n.name));
                    Traverse(n, depth + 1, tree);
                }
                else // Element
                {
                    tree.Add(new VolumeComponentElement(depth, n.name, n.type));
                }
            }
        }
    }
}