use std::path::PathBuf;

fn main() {
    // Capture the absolute C compiler path at build time so the binary is self-contained.
    // This is critical for Nix builds where cc/gcc live in /nix/store paths.
    let cc_path = std::env::var("CC").ok()
        .filter(|s| !s.is_empty())
        .and_then(|s| resolve_absolute(&s))
        .or_else(|| find_in_path("cc"))
        .or_else(|| find_in_path("gcc"))
        .or_else(|| find_in_path("clang"))
        .unwrap_or_default();

    println!("cargo:rustc-env=LUX_CC_PATH={}", cc_path);
    println!("cargo:rerun-if-env-changed=CC");
    println!("cargo:rerun-if-env-changed=PATH");
}

/// Resolve a command name to its absolute path by searching PATH.
fn find_in_path(cmd: &str) -> Option<String> {
    let path_var = std::env::var("PATH").ok()?;
    for dir in path_var.split(':') {
        let candidate = PathBuf::from(dir).join(cmd);
        if candidate.is_file() {
            return Some(candidate.to_string_lossy().into_owned());
        }
    }
    None
}

/// If the path is already absolute and exists, return it. Otherwise search PATH.
fn resolve_absolute(cmd: &str) -> Option<String> {
    let p = PathBuf::from(cmd);
    if p.is_absolute() && p.is_file() {
        return Some(cmd.to_string());
    }
    find_in_path(cmd)
}