use std::ffi::OsStr;
use std::fs::File;
use std::io::Write;
use std::path::Path;
use std::process::Command;

fn main() -> std::io::Result<()> {
    println!("building shaders...");
    //shaders path
    let shaders = Path::new("./src/shaders");
    //shader target path
    Command::new("mkdir").arg("target/shaders/").status()?;

    let shader_target = Path::new("./target/shaders/");
    //compile all glsl shaders
    for entry in shaders.read_dir().expect("reading shader directory failed") {
        if let Ok(entry) = entry {
            let shader_path = entry.path();
            println!("cargo:warning=compiling shader: {:?}", shader_path);
            let shader_path_string: String = "./target/shaders/".to_string()
                + shader_path.file_name().unwrap().to_str().unwrap()
                + ".spv";
            println!(
                "cargo:warning=compiling destination: {:?}",
                shader_path_string
            );
            let shader_file: &OsStr = OsStr::new::<str>(shader_path_string.as_str());
            Command::new("glslc")
                .arg("-c")
                .arg(shader_path)
                .arg("-o")
                .arg(shader_file)
                .status()?;
        }
    }
    //include all compiled shaders in shaders.rs file in src dir
    let mut txt = "use ash::vk::ShaderStageFlags;\n\n".to_string()
        + "pub fn shaders() -> Vec<(Vec<u8>, ShaderStageFlags)> {\nvec![\n";
    for entry in shader_target
        .read_dir()
        .expect("reading compiled shader target directory failed")
    {
        if let Ok(entry) = entry {
            let bin_path = entry.path();
            let bin_path_string = bin_path.file_name().unwrap().to_str().unwrap().to_string();

            let shader_type = (match bin_path_string.split(".").nth(1).unwrap() {
                "vert" => "VERTEX",
                "frag" => "FRAGMENT",
                "comp" => "COMPUTE",
                "tesc" => "TESSELLATION_CONTROL",
                "tese" => "TESSELLATION_EVALUATION",
                "geom" => "GEOMETRY",
                _ => panic!("unknown shader type"),
            })
            .to_string();
            txt += &("(include_bytes!(\"../target/shaders/".to_owned()
                + &bin_path_string
                + "\").to_vec(), ShaderStageFlags::"
                + &shader_type
                + "),\n");
        }
    }
    txt += "]}";
    let mut file = File::create("./src/shaders.rs")?;
    file.write_all(txt.as_bytes())?;
    Ok(())
}