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

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

    println!("cargo:rerun-if-changed=build.rs");
    if !proto_root.is_dir() {
        println!("cargo:warning=proto 目录不存在，跳过协议生成");
        return Ok(());
    }
    println!("cargo:rerun-if-changed={}", proto_root.display());

    let sources = collect_protos(&proto_root)?;
    if sources.is_empty() {
        println!("cargo:warning=proto 下没有 .proto 文件，跳过协议生成");
        return Ok(());
    }

    let cwd = env::current_dir()?;
    let include_root = relative_path(&cwd, &proto_root);
    let protos: Vec<PathBuf> = sources
        .iter()
        .map(|path| relative_path(&cwd, path))
        .collect();

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

    Ok(())
}

fn collect_protos(dir: &Path) -> std::io::Result<Vec<PathBuf>> {
    let mut found = Vec::new();
    let mut stack = vec![dir.to_path_buf()];
    while let Some(dir) = stack.pop() {
        for entry in fs::read_dir(&dir)? {
            let path = entry?.path();
            if path.is_dir() {
                stack.push(path);
            } else if path.extension().is_some_and(|ext| ext == "proto") {
                found.push(path);
            }
        }
    }
    found.sort();
    Ok(found)
}

fn relative_path(base: &Path, target: &Path) -> PathBuf {
    let base: Vec<_> = base.components().collect();
    let target: Vec<_> = target.components().collect();
    let common = base
        .iter()
        .zip(target.iter())
        .take_while(|(a, b)| a == b)
        .count();
    if common == 0 {
        return target.iter().collect();
    }

    let mut rel = PathBuf::new();
    for _ in common..base.len() {
        rel.push("..");
    }
    rel.extend(target[common..].iter().map(|c| c.as_os_str()));
    rel
}