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use proc_macro::TokenStream;
use quote::quote;
use serde::Deserialize;

#[derive(Deserialize)]
struct ExerciseInfo {
    name: String,
    dir: String,
}

#[derive(Deserialize)]
struct InfoFile {
    exercises: Vec<ExerciseInfo>,
}

#[proc_macro]
pub fn include_files(_: TokenStream) -> TokenStream {
    let info_file = include_str!("../info.toml");
    let exercises = toml_edit::de::from_str::<InfoFile>(info_file)
        .expect("Failed to parse `info.toml`")
        .exercises;

    let exercise_files = exercises
        .iter()
        .map(|exercise| format!("../exercises/{}/{}.rs", exercise.dir, exercise.name));
    let solution_files = exercises
        .iter()
        .map(|exercise| format!("../solutions/{}/{}.rs", exercise.dir, exercise.name));

    let mut dirs = Vec::with_capacity(32);
    let mut dir_inds = vec![0; exercises.len()];

    for (exercise, dir_ind) in exercises.iter().zip(&mut dir_inds) {
        // The directory is often the last one inserted.
        if let Some(ind) = dirs.iter().rev().position(|dir| *dir == exercise.dir) {
            *dir_ind = dirs.len() - 1 - ind;
            continue;
        }

        dirs.push(exercise.dir.as_str());
        *dir_ind = dirs.len() - 1;
    }

    let readmes = dirs
        .iter()
        .map(|dir| format!("../exercises/{dir}/README.md"));

    quote! {
        EmbeddedFiles {
            info_file: #info_file,
            exercise_files: &[#(ExerciseFiles { exercise: include_bytes!(#exercise_files), solution: include_bytes!(#solution_files), dir_ind: #dir_inds }),*],
            exercise_dirs: &[#(ExerciseDir { name: #dirs, readme: include_bytes!(#readmes) }),*]
        }
    }
    .into()
}