#include <GL/glew.h>

#include <fstream>
#include <iostream>
#include <cstring>
using namespace std;

//Adapted from Edward Angels InitShader code

// Create a NULL-terminated string by reading the provided file
static char* readShaderSource(const char* shaderFile)
{
    ifstream ifs(shaderFile, ios::in | ios::binary | ios::ate);
    if (ifs.is_open())
    {
        unsigned int filesize = static_cast<unsigned int>(ifs.tellg());
        ifs.seekg(0, ios::beg);
        char* bytes = new char[filesize + 1];
        memset(bytes, 0, filesize + 1);
        ifs.read(bytes, filesize);
        ifs.close();
        return bytes;
    }
    return NULL;
}

void printShaderCompileError(GLuint shader)
{
    GLint  logSize;
    glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &logSize);
    char* logMsg = new char[logSize];
    glGetShaderInfoLog(shader, logSize, NULL, logMsg);
    std::cerr << logMsg << std::endl;
    delete[] logMsg;

}

void printProgramLinkError(GLuint program)
{
    GLint  logSize;
    glGetProgramiv(program, GL_INFO_LOG_LENGTH, &logSize);
    char* logMsg = new char[logSize];
    glGetProgramInfoLog(program, logSize, NULL, logMsg);
    std::cerr << logMsg << std::endl;
    delete[] logMsg;
}

GLuint InitShader(const char* computeShaderFile)
{
    bool error = false;
    struct Shader
    {
        const char*  filename;
        GLenum       type;
        GLchar*      source;
    }  shaders[1] =
    {
        { computeShaderFile, GL_COMPUTE_SHADER, NULL }
    };

    GLuint program = glCreateProgram();

    for (int i = 0; i < 1; ++i)
    {
        Shader& s = shaders[i];
        s.source = readShaderSource(s.filename);
        if (shaders[i].source == NULL)
        {
            std::cerr << "Failed to read " << s.filename << std::endl;
            error = true;
        }

        GLuint shader = glCreateShader(s.type);
        glShaderSource(shader, 1, (const GLchar**)&s.source, NULL);
        glCompileShader(shader);

        GLint  compiled;
        glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
        if (!compiled)
        {
            std::cerr << s.filename << " failed to compile:" << std::endl;
            printShaderCompileError(shader);
            error = true;
        }

        delete[] s.source;

        glAttachShader(program, shader);
    }

    /* link  and error check */
    glLinkProgram(program);

    GLint  linked;
    glGetProgramiv(program, GL_LINK_STATUS, &linked);
    if (!linked)
    {
        std::cerr << "Shader program failed to link" << std::endl;
        printProgramLinkError(program);

        error = true;
    }

    if (error == true)
    {
        return -1;
    }

    /* use program object */
    glUseProgram(program);

    return program;
}


// Create a GLSL program object from vertex and fragment shader files
GLuint InitShader(const char* vShaderFile, const char* fShaderFile)
{

    bool error = false;
    struct Shader
    {
        const char*  filename;
        GLenum       type;
        GLchar*      source;
    }  shaders[2] =
    {
        { vShaderFile, GL_VERTEX_SHADER, NULL },
        { fShaderFile, GL_FRAGMENT_SHADER, NULL }
    };

    GLuint program = glCreateProgram();

    for (int i = 0; i < 2; ++i)
    {
        Shader& s = shaders[i];
        s.source = readShaderSource(s.filename);
        if (shaders[i].source == NULL)
        {
            std::cerr << "Failed to read " << s.filename << std::endl;
            error = true;
        }

        GLuint shader = glCreateShader(s.type);
        glShaderSource(shader, 1, (const GLchar**)&s.source, NULL);
        glCompileShader(shader);

        GLint  compiled;
        glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
        if (!compiled)
        {
            std::cerr << s.filename << " failed to compile:" << std::endl;
            printShaderCompileError(shader);
            error = true;
        }

        delete[] s.source;

        glAttachShader(program, shader);
    }

    //set shader attrib locations
    const int posLoc = 0;
    const int texCoordLoc = 1;
    const int normalLoc = 2;

    glBindAttribLocation(program, posLoc, "posAttrib");
    glBindAttribLocation(program, texCoordLoc, "texCoordAttrib");
    glBindAttribLocation(program, normalLoc, "normalAttrib");

    /* link  and error check */
    glLinkProgram(program);

    GLint  linked;
    glGetProgramiv(program, GL_LINK_STATUS, &linked);
    if (!linked)
    {
        std::cerr << "Shader program failed to link" << std::endl;
        printProgramLinkError(program);

        error = true;
    }

    if (error == true)
    {
        return -1;
    }

    /* use program object */
    glUseProgram(program);
    return program;
}

// Create a GLSL program object from vertex and fragment shader files
GLuint InitShader(const char* vShaderFile, const char* gShaderFile, const char* fShaderFile)
{
    bool error = false;
    struct Shader
    {
        const char*  filename;
        GLenum       type;
        GLchar*      source;
    }  shaders[3] =
    {
        { vShaderFile, GL_VERTEX_SHADER, NULL },
        { gShaderFile, GL_GEOMETRY_SHADER, NULL },
        { fShaderFile, GL_FRAGMENT_SHADER, NULL }
    };

    GLuint program = glCreateProgram();

    for (int i = 0; i < 3; ++i)
    {
        Shader& s = shaders[i];
        s.source = readShaderSource(s.filename);
        if (shaders[i].source == NULL)
        {
            std::cerr << "Failed to read " << s.filename << std::endl;
            error = true;
        }

        GLuint shader = glCreateShader(s.type);
        glShaderSource(shader, 1, (const GLchar**)&s.source, NULL);
        glCompileShader(shader);

        GLint  compiled;
        glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
        if (!compiled)
        {
            std::cerr << s.filename << " failed to compile:" << std::endl;
            printShaderCompileError(shader);
            error = true;
        }

        delete[] s.source;

        glAttachShader(program, shader);
    }

    //set shader attrib locations
    const int posLoc = 0;
    const int texCoordLoc = 1;
    const int normalLoc = 2;

    glBindAttribLocation(program, posLoc, "posAttrib");
    glBindAttribLocation(program, texCoordLoc, "texCoordAttrib");
    glBindAttribLocation(program, normalLoc, "normalAttrib");

    /* link  and error check */
    glLinkProgram(program);

    GLint  linked;
    glGetProgramiv(program, GL_LINK_STATUS, &linked);
    if (!linked)
    {
        std::cerr << "Shader program failed to link" << std::endl;
        printProgramLinkError(program);

        error = true;
    }

    if (error == true)
    {
        return -1;
    }

    /* use program object */
    glUseProgram(program);

    return program;
}

GLuint InitShader( const char* vShaderFile, const char* tcShader, const char* teShader, const char* fShaderFile )
{
    bool error = false;
    struct Shader 
    {
        const char*  filename;
        GLenum       type;
        std::string  source;
    }  shaders[4] = 
    {
        { vShaderFile, GL_VERTEX_SHADER, "" },
        { tcShader, GL_TESS_CONTROL_SHADER, "" },
        { teShader, GL_TESS_EVALUATION_SHADER, "" },
        { fShaderFile, GL_FRAGMENT_SHADER, "" }
    };

    GLuint program = glCreateProgram();
    
    for ( int i = 0; i < 4; ++i ) 
    {
        Shader& s = shaders[i];
        s.source = readShaderSource(s.filename);
        if ( shaders[i].source.length() == 0 ) 
        {
            std::cerr << "Failed to read " << s.filename << std::endl;
            error = true;
        }

        GLuint shader = glCreateShader( s.type );
        const char *c_str = s.source.c_str();
        glShaderSource(shader, 1, (const GLchar**)&c_str, NULL);
        glCompileShader( shader );

        GLint  compiled;
        glGetShaderiv( shader, GL_COMPILE_STATUS, &compiled );
        if ( !compiled ) 
        {
            std::cerr << s.filename << " failed to compile:" << std::endl;
            printShaderCompileError(shader);
            error = true;
        }

        glAttachShader( program, shader );
    }

    //set shader attrib locations
    const int posLoc = 0;
    const int texCoordLoc = 1;

    glBindAttribLocation(program, posLoc, "posAttrib");
    glBindAttribLocation(program, texCoordLoc, "texCoordAttrib");

    /* link  and error check */
    glLinkProgram(program);

    GLint  linked;
    glGetProgramiv( program, GL_LINK_STATUS, &linked );
    if ( !linked ) 
    {
        std::cerr << "Shader program failed to link" << std::endl;
        printProgramLinkError(program);

        error = true;
    }

    if(error == true)
    {
        return -1;
    }

    /* use program object */
    glUseProgram(program);

    return program;
}

GLuint InitShader( const char* vShaderFile, const char* tcShader, const char* teShader, const char* gShaderFile, const char* fShaderFile )
{
    bool error = false;
    struct Shader 
    {
        const char*  filename;
        GLenum       type;
        std::string      source;
    }  shaders[5] = 
    {
        { vShaderFile, GL_VERTEX_SHADER, "" },
        { tcShader, GL_TESS_CONTROL_SHADER, "" },
        { teShader, GL_TESS_EVALUATION_SHADER, "" },
        { gShaderFile, GL_GEOMETRY_SHADER, "" },
        { fShaderFile, GL_FRAGMENT_SHADER, "" }
    };

    GLuint program = glCreateProgram();
        
    for ( int i = 0; i < 5; ++i ) 
    {
        Shader& s = shaders[i];
        s.source = readShaderSource(s.filename);
        if ( shaders[i].source.length() == 0 ) 
        {
            std::cerr << "Failed to read " << s.filename << std::endl;
            error = true;
        }

        GLuint shader = glCreateShader( s.type );
        const char *c_str = s.source.c_str();
        glShaderSource( shader, 1, (const GLchar**) &c_str, NULL );
        glCompileShader( shader );

        GLint  compiled;
        glGetShaderiv( shader, GL_COMPILE_STATUS, &compiled );
        if ( !compiled ) 
        {
            std::cerr << s.filename << " failed to compile:" << std::endl;
            printShaderCompileError(shader);
            error = true;
        }

        glAttachShader( program, shader );
    }

    /* link  and error check */
    glLinkProgram(program);

    GLint  linked;
    glGetProgramiv( program, GL_LINK_STATUS, &linked );
    if ( !linked ) 
    {
        std::cerr << "Shader program failed to link" << std::endl;
        printProgramLinkError(program);

        error = true;
    }

    if(error == true)
    {
        return -1;
    }

    /* use program object */
    glUseProgram(program);

    return program;
}