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

fn main() {
    if !cfg!(feature = "dynamic") {
        // do nothing if the `dynamic` feature is disabled
        return;
    }
    if env::var_os("SKIP_BINDGEN").is_some() {
        return;
    }

    let crate_dir = env::var("CARGO_MANIFEST_DIR").unwrap();
    let out_dir = Path::new("generated");
    fs::create_dir_all(out_dir).unwrap();
    let out_file_path = out_dir.join("alumet-api.h");
    // let sym_file_path = out_dir.join("alumet-symbols.txt");

    // Configure cbindgen for C
    let mut cbindgen_config = cbindgen::Config {
        language: cbindgen::Language::C,
        ..Default::default()
    };

    // Avoid conflicts between enumeration values
    cbindgen_config.enumeration.prefix_with_name = true;

    // Add a PLUGIN_API macro to only export the symbols of the plugin api
    cbindgen_config.after_includes = Some("#define PLUGIN_API __attribute__((visibility(\"default\")))".to_owned());

    // Wrap all the declarations in #ifndef
    cbindgen_config.header = Some("#ifndef __ALUMET_API_H\n#define __ALUMET_API_H".to_owned());
    cbindgen_config.trailer = Some("#endif".to_owned());
    cbindgen_config.parse.expand.crates.push(String::from("alumet"));

    // Generate the bindings
    // TEMPORARILY DISABLED FOR PUBLISHING (build.rs not allowed to modify source dirs)
    // let bindings = with_rustc_bootstrap(|| {
    //     cbindgen::Builder::new()
    //         .with_crate(crate_dir)
    //         .with_config(cbindgen_config)
    //         .generate()
    //         .expect("Unable to generate C bindings for the plugin API")
    // });

    // Write the list of symbols for the linker (useful during the compilation of `app-agent`)
    // DISABLED HERE (cannot publish to crates.io with git dependency, and need
    // https://github.com/mozilla/cbindgen/pull/916 to be merged to run the script)
    // bindings.generate_symfile(sym_file_path);

    // Write the C bindings.
    // bindings.write_to_file(out_file_path);

    println!("C-compatible API generated");
}

/// Enable flag RUSTC_BOOTSTRAP, which allows to use nightly API on the stable compiler.
/// This is necessary to expand macros, see:
/// - https://github.com/dtolnay/cargo-expand/pull/183/files
/// - https://github.com/rust-lang/rust/issues/43364
fn with_rustc_bootstrap<R>(f: impl FnOnce() -> R) -> R {
    let previous_bootstrap = env::var("RUSTC_BOOTSTRAP").ok();
    env::set_var("RUSTC_BOOTSTRAP", "1");

    let res = f();

    if let Some(prev) = previous_bootstrap {
        env::set_var("RUSTC_BOOTSTRAP", prev);
    } else {
        env::remove_var("RUSTC_BOOTSTRAP");
    }

    res
}