#![allow(unsafe_code)]
use crate::misc_util::glow_debug_print;
use glow::HasContext;
use std::convert::TryInto;

#[derive(Copy, Clone, Debug, PartialEq, Eq)]
#[allow(dead_code)]
pub(crate) enum ShaderVersion {
    Gl120,
    Gl140,
    Es100,
    Es300,
}

impl ShaderVersion {
    pub(crate) fn get(gl: &glow::Context) -> Self {
        let shading_lang = unsafe { gl.get_parameter_string(glow::SHADING_LANGUAGE_VERSION) };
        glow_debug_print(&shading_lang);
        Self::parse(&shading_lang)
    }

    #[inline]
    pub(crate) fn parse(glsl_ver: &str) -> Self {
        let start = glsl_ver.find(|c| char::is_ascii_digit(&c)).unwrap();
        let es = glsl_ver[..start].contains(" ES ");
        let ver = glsl_ver[start..].splitn(2, ' ').next().unwrap();
        let [maj, min]: [u8; 2] = ver
            .splitn(3, '.')
            .take(2)
            .map(|x| x.parse().unwrap_or_default())
            .collect::<Vec<u8>>()
            .try_into()
            .unwrap();
        if es {
            if maj >= 3 {
                Self::Es300
            } else {
                Self::Es100
            }
        } else if maj > 1 || (maj == 1 && min >= 40) {
            Self::Gl140
        } else {
            Self::Gl120
        }
    }

    pub(crate) fn version(&self) -> &'static str {
        match self {
            Self::Gl120 => "#version 120\n",
            Self::Gl140 => "#version 140\n",
            Self::Es100 => "#version 100\n",
            Self::Es300 => "#version 300 es\n",
        }
    }
    pub(crate) fn is_new_shader_interface(&self) -> &'static str {
        match self {
            ShaderVersion::Es300 | ShaderVersion::Gl140 => "#define NEW_SHADER_INTERFACE\n",
            _ => "",
        }
    }
}

#[test]
fn test_shader_version() {
    use ShaderVersion::{Es100, Es300, Gl120, Gl140};
    for (s, v) in [
        ("1.2 OpenGL foo bar", Gl120),
        ("3.0", Gl140),
        ("0.0", Gl120),
        ("OpenGL ES GLSL 3.00 (WebGL2)", Es300),
        ("OpenGL ES GLSL 1.00 (WebGL)", Es100),
        ("OpenGL ES GLSL ES 1.00 foo bar", Es100),
        ("WebGL GLSL ES 3.00 foo bar", Es300),
        ("WebGL GLSL ES 3.00", Es300),
        ("WebGL GLSL ES 1.0 foo bar", Es100),
    ] {
        assert_eq!(ShaderVersion::parse(s), v);
    }
}