use std::env;
use std::path::PathBuf;

fn main() {
	let callee_root = env::var("CALLEE_PATH").expect("Callee path variable must be available");
	let lean_root = env::var("LEAN_ROOT").expect("Lean root must exist");
	let output_path = PathBuf::from(env::var("OUT_DIR").unwrap());
	let input = format!("{lean_root}/include/lean/lean.h");
	println!("cargo:rustc-link-search={callee_root}");
	println!("cargo:rustc-link-search={lean_root}/lib/lean");

	let bindings = bindgen::Builder::default()
		.header(&input)
		// Tell cargo to invalidate the built crate whenever any of the
		// included header files changed.
		.parse_callbacks(Box::new(bindgen::CargoCallbacks::new()))
		// The following is specific to `lean.h`: There are a lot of static
		// function
		.wrap_static_fns(true)
		// but some functions use `_Atomic(int)` types that bindgen cannot handle,
		// so they are blocklisted. The types which use `_Atomic` are treated as
		// opaque.
		.blocklist_function("lean_get_rc_mt_addr")
		.opaque_type("lean_thunk_object")
		.opaque_type("lean_task_object")
		.generate()
		.expect("Unable to generate bindings");

	bindings
		.write_to_file(output_path.join("lean.rs"))
		.expect("Couldn't write bindings!");

	let extern_src_path = env::temp_dir().join("bindgen").join("extern.c");
	let extern_obj_path = env::temp_dir().join("bindgen").join("extern.o");

	// This is the path to the static library file.
	let lib_path = output_path.join("libextern.a");

	// Compile the generated wrappers into an object file.
	let clang_output = std::process::Command::new("clang")
		.arg("-O")
		.arg("-c")
		.arg("-o")
		.arg(&extern_obj_path)
		.arg(&extern_src_path)
		.arg("-include")
		.arg(&input)
		.arg("-I")
		.arg(format!("{lean_root}/include"))
		.output()
		.unwrap();
	if !clang_output.status.success() {
		panic!(
			"Could not compile object file:\n{}",
			String::from_utf8_lossy(&clang_output.stderr)
		);
	}

	// Turn the object file into a static library
	#[cfg(not(target_os = "windows"))]
	let lib_output = std::process::Command::new("ar")
		.arg("rcs")
		.arg(output_path.join(&lib_path))
		.arg(&extern_obj_path)
		.output()
		.unwrap();
	#[cfg(target_os = "windows")]
	let lib_output = std::process::Command::new("LIB")
		.arg(obj_path)
		.arg(format!(
			"/OUT:{}",
			output_path.join("libextern.lib").display()
		))
		.output()
		.unwrap();
	if !lib_output.status.success() {
		panic!(
			"Could not emit library file:\n{}",
			String::from_utf8_lossy(&lib_output.stderr)
		);
	}

	// Statically link against the generated lib
	println!("cargo:rustc-link-search={}", output_path.display());
	println!("cargo:rustc-link-lib=static=extern");
}