#include "../../../include/RenderBackend/OpenGL/ShaderProgram.hpp"
#include "../../../include/RenderBackend/OpenGL/opengl.hpp"
#include "../../../include/RenderBackend/OpenGL/CompiledShader.hpp"

using namespace std;

namespace amalgine
{
    ShaderProgramUsedBeforeBuilt::ShaderProgramUsedBeforeBuilt() : 
        runtime_error("Shader program was used before it was built")
    {
        
    }
    
    ShaderProgram::ShaderProgram() : built(false)
    {
        shaderProgramId = glCreateProgram();
    }
    
    ShaderProgram::~ShaderProgram()
    {
        GLint numAttachedShaders;
        glGetProgramiv(shaderProgramId, GL_ATTACHED_SHADERS, &numAttachedShaders);
        
        GLuint *attachedShaders = new GLuint[numAttachedShaders];
        glGetAttachedShaders(shaderProgramId, numAttachedShaders, nullptr, attachedShaders);
        
        for(int i = 0; i < numAttachedShaders; ++i)
        {
            GLuint attachedShaderId = attachedShaders[i];
            glDetachShader(shaderProgramId, attachedShaderId);
        }
        
        glDeleteProgram(shaderProgramId);
    }
    
    // TODO: Before adding shader to program, check if it has already been added
    
    bool ShaderProgram::setVertexShader(CompiledVertexShader *vertexShader)
    {
        if(!vertexShader) return false;
        
        // TODO: Do not allow adding shader if the program has already been built
        glAttachShader(shaderProgramId, vertexShader->getShaderId());
        return true;
    }
    
    bool ShaderProgram::setPixelShader(CompiledPixelShader *pixelShader)
    {
        if(!pixelShader) return false;
        
        // TODO: Do not allow adding shader if the program has already been built
        glAttachShader(shaderProgramId, pixelShader->getShaderId());
        
        const auto &pixelAttributes = pixelShader->getPixelAttributes();
        for(const auto &pixelAttribute : pixelAttributes)
        {
            const string &attributeName = pixelAttribute.first;
            i32 attributeLocation = pixelAttribute.second;
            glBindFragDataLocation(shaderProgramId, attributeLocation, attributeName.c_str());
        }
        
        return true;
    }
    
    Result<bool> ShaderProgram::build()
    {
        if(built)
            return Result<bool>::Err("Shader program already built");
        
        glLinkProgram(shaderProgramId);
        built = true;
        return Result<bool>::Ok(true);
    }
    
    void ShaderProgram::use()
    {
        if(built)
        {
            glUseProgram(shaderProgramId);
        }
        else
        {
            throw ShaderProgramUsedBeforeBuilt();
        }
    }
}