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

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let manifest_dir = PathBuf::from(std::env::var("CARGO_MANIFEST_DIR")?);
    let proto_dir = manifest_dir.join("proto");
    let out_dir = PathBuf::from(std::env::var("OUT_DIR")?);

    fs::create_dir_all(&out_dir)?;
    clean_generated_files(&out_dir)?;

    let protos = proto_files(&proto_dir)?;
    for proto in &protos {
        println!("cargo:rerun-if-changed={}", proto.display());
    }
    println!("cargo:rerun-if-changed={}", proto_dir.display());
    println!("cargo:rerun-if-changed=build.rs");

    tonic_prost_build::configure()
        .build_client(true)
        .build_server(true)
        .emit_rerun_if_changed(false)
        .out_dir(&out_dir)
        .compile_protos(&protos, &[proto_dir])?;

    Ok(())
}

fn proto_files(proto_dir: &Path) -> Result<Vec<PathBuf>, Box<dyn std::error::Error>> {
    let mut files = fs::read_dir(proto_dir)?
        .map(|entry| entry.map(|entry| entry.path()))
        .collect::<Result<Vec<_>, _>>()?;

    files.retain(|path| path.extension().is_some_and(|ext| ext == "proto"));
    files.sort();
    Ok(files)
}

fn clean_generated_files(out_dir: &Path) -> Result<(), Box<dyn std::error::Error>> {
    for entry in fs::read_dir(out_dir)? {
        let path = entry?.path();
        let is_generated_rs = path.extension().is_some_and(|ext| ext == "rs")
            && path.file_name().is_some_and(|name| name != "mod.rs");

        if is_generated_rs {
            fs::remove_file(path)?;
        }
    }

    Ok(())
}