//
// Created by lukas on 03.02.22.
//

#include "Shader.h"

#define GL_GLEXT_PROTOTYPES

#include <GL/gl.h>
#include <GL/glcorearb.h>
#include <string>
#include <fstream>
#include <vector>
#include <sstream>

unsigned int Shader::compileShader(const char *source, unsigned int type) const {
    unsigned int shaderid = glCreateShader(type);

    // Compile Shader
    glShaderSource(shaderid, 1, &source, NULL);
    glCompileShader(shaderid);

    // Check Shader
    int Result = GL_FALSE;
    int InfoLogLength;

    glGetShaderiv(shaderid, GL_COMPILE_STATUS, &Result);
    glGetShaderiv(shaderid, GL_INFO_LOG_LENGTH, &InfoLogLength);
    if (InfoLogLength > 0) {
        std::vector<char> VertexShaderErrorMessage(InfoLogLength + 1);
        glGetShaderInfoLog(shaderid, InfoLogLength, NULL, &VertexShaderErrorMessage[0]);
        printf("%s\n", &VertexShaderErrorMessage[0]);

        return 0;
    }

    return shaderid;
}

void Shader::Bind() const {
    glUseProgram(mProgHandle);
}

unsigned Shader::getHandle() const {
    return mProgHandle;
}

unsigned Shader::getUniformHandle(std::string name) {
    if (uniformhandles.find(name) != uniformhandles.end()) {
        return uniformhandles[name];
    } else {
        const unsigned id = glGetUniformLocation(mProgHandle, name.c_str());
        uniformhandles[name] = id;
        return id;
    }
}

std::string Shader::readFile(std::string path) {
    // Read the Vertex Shader code from the file
    std::string VertexShaderCode;
    std::ifstream VertexShaderStream(path, std::ios::in);
    if (VertexShaderStream.is_open()) {
        std::stringstream sstr;
        sstr << VertexShaderStream.rdbuf();
        VertexShaderCode = sstr.str();
        VertexShaderStream.close();
    } else {
        printf("Impossible to open %s. Are you in the right directory ? Don't forget to read the FAQ !\n", path.c_str());
        getchar();
        return "";
    }
    return VertexShaderCode;
}

unsigned int Shader::loadShaderFromFile(const std::string vertex_file_path, const std::string geometry_file_path, const std::string fragment_file_path) {
    // Read the Vertex Shader code from the file
    std::string VertexShaderCode = readFile(vertex_file_path);
    std::string FragmentShaderCode = readFile(fragment_file_path);
    std::string GeometryShaderCode = readFile("../geometry.shader");

    return loadShader(VertexShaderCode, GeometryShaderCode, FragmentShaderCode);
}

unsigned int Shader::loadShader(const std::string vertex_src, const std::string geometry_src, const std::string fragment_src) {
    uint VertexShaderID;
    uint GeometryShaderID;
    uint FragmentShaderID;

    if (!vertex_src.empty()) {
        // Compile Vertex Shader
        printf("Compiling vertex shader\n");
        VertexShaderID = compileShader(vertex_src.c_str(), GL_VERTEX_SHADER);
        if (VertexShaderID == 0) {
            printf("Error Compiling vertex shader\n");
            return 0;
        }
    }


    if (!geometry_src.empty()) {
        printf("Compiling geometry shader\n");
        GeometryShaderID = compileShader(geometry_src.c_str(), GL_GEOMETRY_SHADER);
        if (GeometryShaderID == 0) {
            printf("Error Compiling shader\n");
            return 0;
        }
    }

    if (!fragment_src.empty()) {
        printf("Compiling fragment shader\n");
        FragmentShaderID = compileShader(fragment_src.c_str(), GL_FRAGMENT_SHADER);
        if (FragmentShaderID == 0) {
            printf("Error Compiling shader\n");
            return 0;
        }
    }


    // Link the program
    GLint Result = GL_FALSE;
    int InfoLogLength;

    printf("Linking shader program\n");
    GLuint ProgramID = glCreateProgram();
    if (!vertex_src.empty()) {
        glAttachShader(ProgramID, VertexShaderID);
    }
    if (!geometry_src.empty()) {
        glAttachShader(ProgramID, GeometryShaderID);
    }
    if (!fragment_src.empty()) {
        glAttachShader(ProgramID, FragmentShaderID);
    }

    glLinkProgram(ProgramID);

    // Check the program
    glGetProgramiv(ProgramID, GL_LINK_STATUS, &Result);
    glGetProgramiv(ProgramID, GL_INFO_LOG_LENGTH, &InfoLogLength);
    if (InfoLogLength > 0) {
        std::vector<char> ProgramErrorMessage(InfoLogLength + 1);
        glGetProgramInfoLog(ProgramID, InfoLogLength, NULL, &ProgramErrorMessage[0]);
        printf("%s\n", &ProgramErrorMessage[0]);
    }

    // cleanup shaders
    if (!vertex_src.empty()){
        glDetachShader(ProgramID, VertexShaderID);
        glDeleteShader(VertexShaderID);
    }

    if (!geometry_src.empty()){
        glDetachShader(ProgramID, GeometryShaderID);
        glDeleteShader(GeometryShaderID);
    }

    if (!fragment_src.empty()){
        glDetachShader(ProgramID, FragmentShaderID);
        glDeleteShader(FragmentShaderID);
    }

    mProgHandle = ProgramID;
    return ProgramID;
}