drawing_gl 0.8.0

use std::ffi::{CStr, CString};

pub struct Shader {
    id: gl::types::GLuint,
}

impl Shader {
    pub fn from_source(source: &CStr, kind: gl::types::GLenum) -> Result<Shader, String> {
        let id = shader_from_source(source, kind)?;
        Ok(Shader { id })
    }

    pub fn from_vert_str(src: &str) -> Result<Shader, String> {
        Shader::from_source(&CString::new(src).unwrap(), gl::VERTEX_SHADER)
    }

    pub fn from_frag_str(src: &str) -> Result<Shader, String> {
        Shader::from_source(&CString::new(src).unwrap(), gl::FRAGMENT_SHADER)
    }

    pub fn id(&self) -> gl::types::GLuint {
        self.id
    }
}

impl Drop for Shader {
    fn drop(&mut self) {
        unsafe {
            gl::DeleteShader(self.id);
        }
    }
}

fn shader_from_source(source: &CStr, kind: gl::types::GLenum) -> Result<gl::types::GLuint, String> {
    let id = unsafe { gl::CreateShader(kind) };
    unsafe {
        gl::ShaderSource(id, 1, &source.as_ptr(), std::ptr::null());
        gl::CompileShader(id);
    }

    let mut success: gl::types::GLint = gl::FALSE as gl::types::GLint;
    unsafe {
        gl::GetShaderiv(id, gl::COMPILE_STATUS, &mut success);
    }

    if success != (gl::TRUE as gl::types::GLint) {
        let mut len: gl::types::GLint = 0;
        unsafe {
            gl::GetShaderiv(id, gl::INFO_LOG_LENGTH, &mut len);
        }

        let error = crate::utils::ffi_utils::create_whitespace_cstring_with_len(len as usize);

        unsafe {
            gl::GetShaderInfoLog(
                id,
                len,
                std::ptr::null_mut(),
                error.as_ptr() as *mut gl::types::GLchar,
            );
        }

        return Err(error.to_string_lossy().into_owned());
    }

    Ok(id)
}