using System;
using System.Collections.Generic;
using XCEngine;

namespace XCEngine.Rendering
{
    internal enum RenderGraphRasterPassExecutionKind
    {
        None = 0,
        ColorScaleFullscreen = 1,
        ShaderVectorFullscreen = 2
    }

    public sealed class RenderGraphRasterPassBuilder
    {
        private readonly ScriptableRenderContext m_context;
        private readonly string m_passName;
        private readonly List<RenderGraphTextureHandle> m_readTextures =
            new List<RenderGraphTextureHandle>();
        private readonly List<RenderGraphTextureHandle> m_colorAttachments =
            new List<RenderGraphTextureHandle>();
        private RenderGraphTextureHandle m_sourceColorTexture;
        private Vector4 m_vectorPayload;
        private string m_shaderPath = string.Empty;
        private string m_shaderPassName = string.Empty;
        private RenderGraphRasterPassExecutionKind m_executionKind;
        private bool m_finalized;

        internal RenderGraphRasterPassBuilder(
            ScriptableRenderContext context,
            string passName)
        {
            if (context == null)
            {
                throw new ArgumentNullException(nameof(context));
            }

            if (string.IsNullOrEmpty(passName))
            {
                throw new ArgumentException(
                    "Render graph raster pass name cannot be null or empty.",
                    nameof(passName));
            }

            m_context = context;
            m_passName = passName;
        }

        public RenderGraphRasterPassBuilder UseColorSource(
            RenderGraphTextureHandle texture)
        {
            m_sourceColorTexture = texture;
            return this;
        }

        public RenderGraphRasterPassBuilder UseTexture(
            RenderGraphTextureHandle texture)
        {
            if (texture.isValid)
            {
                m_readTextures.Add(texture);
            }

            return this;
        }

        public RenderGraphRasterPassBuilder SetColorAttachment(
            RenderGraphTextureHandle texture,
            int index = 0)
        {
            if (index < 0)
            {
                throw new ArgumentOutOfRangeException(
                    nameof(index),
                    "Render graph color attachment index cannot be negative.");
            }

            while (m_colorAttachments.Count <= index)
            {
                m_colorAttachments.Add(default);
            }

            m_colorAttachments[index] = texture;
            return this;
        }

        public RenderGraphRasterPassBuilder
        SetColorScaleFullscreenExecution(
            Vector4 colorScale)
        {
            m_executionKind =
                RenderGraphRasterPassExecutionKind
                    .ColorScaleFullscreen;
            m_vectorPayload = colorScale;
            m_shaderPath = string.Empty;
            m_shaderPassName = string.Empty;
            return this;
        }

        public RenderGraphRasterPassBuilder
        SetShaderVectorFullscreenExecution(
            string shaderPath,
            Vector4 vectorPayload,
            string shaderPassName = null)
        {
            if (string.IsNullOrEmpty(shaderPath))
            {
                throw new ArgumentException(
                    "Fullscreen shader path cannot be null or empty.",
                    nameof(shaderPath));
            }

            m_executionKind =
                RenderGraphRasterPassExecutionKind
                    .ShaderVectorFullscreen;
            m_vectorPayload = vectorPayload;
            m_shaderPath = shaderPath;
            m_shaderPassName = shaderPassName ?? string.Empty;
            return this;
        }

        public bool Commit()
        {
            if (m_finalized ||
                !HasExecutionConfigured() ||
                !HasAnyColorAttachment())
            {
                return false;
            }

            m_finalized = true;

            ulong nativePassHandle =
                InternalCalls
                    .Rendering_ScriptableRenderContext_BeginRasterPass(
                        m_context.nativeHandle,
                        m_passName);
            if (nativePassHandle == 0ul)
            {
                return false;
            }

            if (m_sourceColorTexture.isValid &&
                !InternalCalls
                    .Rendering_ScriptableRenderContext_SetRasterPassSourceColorTexture(
                        m_context.nativeHandle,
                        nativePassHandle,
                        m_sourceColorTexture.nativeIndex))
            {
                return false;
            }

            for (int i = 0; i < m_readTextures.Count; ++i)
            {
                RenderGraphTextureHandle readTexture =
                    m_readTextures[i];
                if (!readTexture.isValid)
                {
                    continue;
                }

                if (!InternalCalls
                        .Rendering_ScriptableRenderContext_AddRasterPassReadTexture(
                            m_context.nativeHandle,
                            nativePassHandle,
                            readTexture.nativeIndex))
                {
                    return false;
                }
            }

            for (int i = 0; i < m_colorAttachments.Count; ++i)
            {
                RenderGraphTextureHandle colorAttachment =
                    m_colorAttachments[i];
                if (!colorAttachment.isValid)
                {
                    continue;
                }

                if (!InternalCalls
                        .Rendering_ScriptableRenderContext_SetRasterPassColorAttachment(
                            m_context.nativeHandle,
                            nativePassHandle,
                            i,
                            colorAttachment.nativeIndex))
                {
                    return false;
                }
            }

            bool configuredExecution;
            switch (m_executionKind)
            {
                case RenderGraphRasterPassExecutionKind
                    .ColorScaleFullscreen:
                    configuredExecution =
                        InternalCalls
                            .Rendering_ScriptableRenderContext_SetRasterPassColorScaleFullscreenExecution(
                                m_context.nativeHandle,
                                nativePassHandle,
                                ref m_vectorPayload);
                    break;
                case RenderGraphRasterPassExecutionKind
                    .ShaderVectorFullscreen:
                    configuredExecution =
                        InternalCalls
                            .Rendering_ScriptableRenderContext_SetRasterPassShaderVectorFullscreenExecution(
                                m_context.nativeHandle,
                                nativePassHandle,
                                m_shaderPath,
                                m_shaderPassName,
                                ref m_vectorPayload);
                    break;
                default:
                    configuredExecution = false;
                    break;
            }

            return configuredExecution &&
                   InternalCalls
                       .Rendering_ScriptableRenderContext_CommitRasterPass(
                           m_context.nativeHandle,
                           nativePassHandle);
        }

        private bool HasExecutionConfigured()
        {
            return m_executionKind !=
                RenderGraphRasterPassExecutionKind.None;
        }

        private bool HasAnyColorAttachment()
        {
            for (int i = 0; i < m_colorAttachments.Count; ++i)
            {
                if (m_colorAttachments[i].isValid)
                {
                    return true;
                }
            }

            return false;
        }
    }
}