using System;
using System.Collections.Generic;
#if UNITY_EDITOR
using UnityEditor;
#endif
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;
using UnityEngine.XR;

namespace Golems
{
    /// <summary>
    /// Creates a bunch of named RenderTexture for the camera that can then be used by other
    /// render passes.
    /// The textures can be used, for example, as a temporary texture when operating on the
    /// camera colour texture and then copying it back - saving the pass having to create
    /// its own texture. Another example is that the textures can be used to pass result between
    /// passes - since these temporary textures will be around from the time they are created to
    /// the end of the render pipeline.
    ///
    /// Other passes should access the textures via the static interface this class
    /// provides.
    ///
    /// NOTE: names are converted to integer hashes to save doing string operations every frame.
    /// </summary>
    public class TemporaryCameraCopyTextureRenderFeature : ScriptableRendererFeature
    {
        [SerializeField]
        private RenderPassEvent m_WhenToAdd = RenderPassEvent.BeforeRendering;

        [SerializeField]
        private List<string> m_TextureNames;
        
        private TemporaryCameraTextureRenderPass m_Pass;

        private readonly Dictionary<int, RenderTargetIdentifier> m_NameHashToTargetIdentifierMap =
            new Dictionary<int, RenderTargetIdentifier>();

        private readonly List<NameHashShaderIdPair> m_NameHashesAndIds = new List<NameHashShaderIdPair>();

        public struct NameHashShaderIdPair
        {
            public int m_NameHash;
            public int m_ShaderId;
        }
        
        public override void Create()
        {
            if (s_HasInstance && s_Instance != null)
            {
                return;
            }

            s_HasInstance = true;
            s_Instance = this;
            
            //
            // Create the name hashes
            //
            m_NameHashesAndIds.Clear();
            for (int i = 0; i < m_TextureNames.Count; i++)
            {
                m_NameHashesAndIds.Add( new NameHashShaderIdPair()
                {
                    m_NameHash = GetNameHash(m_TextureNames[i]),
                    m_ShaderId = Shader.PropertyToID(m_TextureNames[i]),
                });
            }
            
            m_Pass = new TemporaryCameraTextureRenderPass();
        }

        public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData)
        {
            if (m_Pass == null)
            {
                return;
            }
            
#if ENABLE_VR
            var isXR = XRSettings.enabled;
            m_Pass.Setup(m_WhenToAdd, isXR, m_NameHashesAndIds, SetupTempTargetIdentifier, ClearTempTargetIdentifiers);
#else
            m_Pass.Setup(m_WhenToAdd, false, m_NameHashesAndIds, SetupTempTargetIdentifier, ClearTempTargetIdentifiers);
#endif
            renderer.EnqueuePass(m_Pass);
            
            
        }

        protected override void Dispose(bool disposing)
        {
            if (s_Instance == this)
            {
                s_HasInstance = false;
                s_Instance = null;
            }
            base.Dispose(disposing);
        }


        private bool InternalTryGetTempTextureIdentifier(int nameHash, out RenderTargetIdentifier outTargetIdentifier)
        {
            return m_NameHashToTargetIdentifierMap.TryGetValue(nameHash, out outTargetIdentifier);
        }

        private void InternalClearTempTargetIdentifiers()
        {
            m_NameHashToTargetIdentifierMap.Clear();
        }

        private void InternalSetupTempTargetIdentifier(int nameHash, RenderTargetIdentifier identifier)
        {
            m_NameHashToTargetIdentifierMap[nameHash] = identifier;
        }

        //
        //
        // Static interface
        //
        //
        public const int k_InvalidNameHash = -1;
        private static bool s_HasInstance;
        private static TemporaryCameraCopyTextureRenderFeature s_Instance;

        /// <summary>
        /// Used by passes to ask for a named texture by its name hash.
        /// NOTE: hashes are used to avoid having a dictionary keyed by strings.
        /// </summary>
        /// <param name="nameHash"></param>
        /// <param name="outTargetIdentifier"></param>
        /// <returns>true if the texture is available, false otherwise</returns>
        public static bool TryGetTempTextureIdentifier(int nameHash, out RenderTargetIdentifier outTargetIdentifier)
        {
            if (!s_HasInstance)
            {
                outTargetIdentifier = default;
                return false;
            }

            return s_Instance.InternalTryGetTempTextureIdentifier(nameHash, out outTargetIdentifier);
        }

        /// <summary>
        /// Given a name, this returns the hash of that name.
        /// </summary>
        public static int GetNameHash(string name)
        {
            if (string.IsNullOrEmpty(name))
            {
                return k_InvalidNameHash;
            }

            return name.GetHashCode();
        }

        private static void SetupTempTargetIdentifier(int nameHash, RenderTargetIdentifier identifier)
        {
            if (!s_HasInstance)
            {
                return;
            }

            s_Instance.InternalSetupTempTargetIdentifier(nameHash, identifier);
        }

        private static void ClearTempTargetIdentifiers()
        {
            if (!s_HasInstance)
            {
                return;
            }
            
            s_Instance.InternalClearTempTargetIdentifiers();
        }
                
#if UNITY_EDITOR
        private bool m_EditorNameHashToTargetIdentifierMapFoldout;
        private bool m_EditorNameHashesAndIdsFoldout;
        protected virtual void EditorOnInspectorGUIAfterBase()
        {
            EditorGUILayout.LabelField("Info", EditorStyles.boldLabel);
            
            var origIndent = EditorGUI.indentLevel;
            EditorGUI.indentLevel += 1;
#if false
            //
            // NOTE:
            // m_NameHashToTargetIdentifierMap gets cleared every frame so no useful info
            //
            m_EditorNameHashToTargetIdentifierMapFoldout = EditorGUILayout.Foldout(m_EditorNameHashToTargetIdentifierMapFoldout, "Name hash to identifier map");
            if (m_EditorNameHashToTargetIdentifierMapFoldout)
            {

                foreach (var nameHashIdentifier in m_NameHashToTargetIdentifierMap)
                {
                    EditorGUILayout.LabelField(
                        $"Name hash: {nameHashIdentifier.Key}, identifier {nameHashIdentifier.Value}");
                }
            }
#endif
            m_EditorNameHashesAndIdsFoldout = EditorGUILayout.Foldout(m_EditorNameHashesAndIdsFoldout, "Name hash to shader id map");
            if (m_EditorNameHashesAndIdsFoldout)
            {
                foreach (var nameHashIds in m_NameHashesAndIds)
                {
                    EditorGUILayout.LabelField(
                        $"Name hash: {nameHashIds.m_NameHash}, identifier {nameHashIds.m_ShaderId}");
                }
            }
            
            EditorGUI.BeginDisabledGroup(true);
            EditorGUILayout.ObjectField("Instance", s_Instance, typeof(TemporaryCameraCopyTextureRenderFeature), false);
            EditorGUI.EndDisabledGroup();

            EditorGUI.indentLevel = origIndent;

            EditorGUILayout.LabelField("Controls", EditorStyles.boldLabel);
        }

        private static void EditorTextureNameAndHash(string label, string namedTemporaryName, int namedTemporaryNameHash)
        {
            EditorGUILayout.TextField(label);
            EditorGUI.indentLevel += 1;
            if (!string.IsNullOrEmpty(namedTemporaryName))
            {
                EditorGUILayout.IntField(namedTemporaryName, namedTemporaryNameHash);
            }
            else
            {
                EditorGUILayout.IntField("null name", namedTemporaryNameHash);
            }
            EditorGUI.indentLevel -= 1;
        }

        [CustomEditor(typeof(TemporaryCameraCopyTextureRenderFeature))]
        private class TemporaryCameraCopyTextureRenderFeatureEditor : Editor
        {
            public override void OnInspectorGUI()
            {
                base.OnInspectorGUI();

                var me = target as TemporaryCameraCopyTextureRenderFeature;
                if (me != null)
                {
                    me.EditorOnInspectorGUIAfterBase();
                }
            }
        }
#endif

    }

    /// <summary>
    /// This is the pass that creates the named textures.
    /// </summary>
    public class TemporaryCameraTextureRenderPass : ScriptableRenderPass
    {
        private bool m_IsXR;
        private List<TemporaryCameraCopyTextureRenderFeature.NameHashShaderIdPair> m_NameHashesAndIds;
        private Action<int, RenderTargetIdentifier> m_SetIdentifierAction;
        private Action m_ClearIdentifiersAction;

        public void Setup(RenderPassEvent whenToRender, bool isXR,
            List<TemporaryCameraCopyTextureRenderFeature.NameHashShaderIdPair> nameHashesAndIds, Action<int, RenderTargetIdentifier> setIdentifierAction,
            Action clearIdentifiersAction)
        {
            renderPassEvent = whenToRender;
            m_IsXR = isXR;
            m_NameHashesAndIds = nameHashesAndIds;
            m_SetIdentifierAction = setIdentifierAction;
            m_ClearIdentifiersAction = clearIdentifiersAction;
        }

        public override void OnCameraSetup(CommandBuffer cmd, ref RenderingData renderingData)
        {
            //
            // Create the temporary textures
            //
#if UNITY_SWITCH
            var renderTextureDescriptor = renderingData.cameraData.cameraTargetDescriptor;
            var width = 1280;
            var height = 720;
#elif ENABLE_VR
            var renderTextureDescriptor = m_IsXR ? XRSettings.eyeTextureDesc : renderingData.cameraData.cameraTargetDescriptor;
#else
            var renderTextureDescriptor = renderingData.cameraData.cameraTargetDescriptor;
#endif
            for (int i = 0; i < m_NameHashesAndIds.Count; i++)
            {
                #if UNITY_SWITCH
                cmd.GetTemporaryRT(m_NameHashesAndIds[i].m_ShaderId, width,height,renderTextureDescriptor.depthBufferBits,FilterMode.Bilinear,renderTextureDescriptor.colorFormat);
                #else
                cmd.GetTemporaryRT(m_NameHashesAndIds[i].m_ShaderId, renderTextureDescriptor);
                #endif
                m_SetIdentifierAction?.Invoke(m_NameHashesAndIds[i].m_NameHash, new RenderTargetIdentifier(m_NameHashesAndIds[i].m_ShaderId));
            }
        }

        public override void OnCameraCleanup(CommandBuffer cmd)
        {
            m_ClearIdentifiersAction?.Invoke();
        }

        public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
        {
        }
    }
}