#pragma once

#include <stdexcept>

#include <GL/glew.h>

namespace ugly{

/**
 * \brief Builder class for OpenGL shader and programs.
 * 
 * On initialization, creates a new OpenGL program. Attach and compile shader
 * sources using `attachFrom*`. Link and get the program with `link()`. User is
 * responsible of managing returned program's lifetime, including destroying it.
 */
class ShaderProgramBuilder {
private:
    GLuint mProgram;
    
public:
    ShaderProgramBuilder();
    ~ShaderProgramBuilder();
    /**
     * \brief Deletes program and starts from scratch.
     */
    void reset();
    /**
     * \brief Creates, compiles, and attaches a shader.
     * \param type Specifies the type of shader to be created. Must be one of
     *             \c GL_VERTEX_SHADER, \c GL_GEOMETRY_SHADER or
     *             \c GL_FRAGMENT_SHADER .
     * \param string Shader source code.
     * \param length Bytes to read from \p string, \c 0 reads until NUL byte.
     * \returns *this
     */
    ShaderProgramBuilder &attachFromMemory(GLenum type, const GLchar *string, GLint length = 0);
    /**
     * \brief Creates, compiles, and attaches a shader. Reads source from file.
     * \param type Specifies the type of shader to be created. Must be one of
     *             \c GL_VERTEX_SHADER, \c GL_GEOMETRY_SHADER or
     *             \c GL_FRAGMENT_SHADER .
     * \param filename Shader source code file.
     * \returns \c *this
     */
    ShaderProgramBuilder &attachFromFile(GLenum type, const char *filename);
    /**
     * \brief Links OpenGL program after attaching sources.
     * 
     * After this function is called the builder object is reset.
     * \return OpenGL object name. User is reponsible for managing it.
     */
    [[nodiscard]] GLuint link();
};

}