use std::{env, fs, path::PathBuf};

fn main() {
    println!("cargo:rerun-if-changed=lang");

    let manifest_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR"));
    let lang_dir = manifest_dir.join("lang");
    let mut files = fs::read_dir(&lang_dir)
        .unwrap_or_else(|error| panic!("failed to read {}: {error}", lang_dir.display()))
        .filter_map(Result::ok)
        .map(|entry| entry.path())
        .filter(|path| path.extension().and_then(|value| value.to_str()) == Some("json"))
        .collect::<Vec<_>>();
    files.sort();

    if files.is_empty() {
        panic!("lang directory must contain at least one .json language file");
    }

    let mut generated = String::from("pub const EMBEDDED_LANGUAGE_FILES: &[(&str, &str)] = &[\n");
    for path in files {
        let name = path
            .file_name()
            .and_then(|value| value.to_str())
            .expect("language filename must be valid UTF-8");
        println!("cargo:rerun-if-changed=lang/{name}");
        generated.push_str(&format!(
            "    ({name:?}, include_str!(concat!(env!(\"CARGO_MANIFEST_DIR\"), \"/lang/{name}\"))),\n"
        ));
    }
    generated.push_str("];\n");

    let out_dir = PathBuf::from(env::var("OUT_DIR").expect("OUT_DIR"));
    fs::write(out_dir.join("languages.rs"), generated).expect("failed to generate embedded languages");
}