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

use gethostname::gethostname;

/// Detect which console/beamline we're running on based on the short hostname.
pub fn detect_beamline() -> Result<String, String> {
    let hostname = gethostname().to_string_lossy().into_owned();
    if hostname.starts_with("x10sa") {
        Ok("x10sa".to_string())
    } else if hostname.starts_with("x06da") {
        Ok("x06da".to_string())
    } else if hostname.starts_with("x0sda") {
        Ok("x06sa".to_string())
    } else {
        Err(format!(
            "Error: unrecognized hostname '{hostname}' — cannot determine beamline"
        ))
    }
}

/// Detect the Python virtual environments directly inside `dir`.
///
/// A subdirectory is treated as a virtualenv when it contains a `pyvenv.cfg`
/// file — the marker written by both `python -m venv` and `uv venv`. The
/// returned paths are the venv directories, sorted by name.
pub fn detect_venvs(dir: &Path) -> Result<Vec<PathBuf>, String> {
    let entries =
        fs::read_dir(dir).map_err(|e| format!("cannot read directory '{}': {e}", dir.display()))?;

    let mut venvs: Vec<PathBuf> = entries
        .filter_map(|entry| entry.ok().map(|entry| entry.path()))
        .filter(|path| is_venv(path))
        .collect();

    venvs.sort();
    Ok(venvs)
}

/// Whether `path` is a Python virtualenv, i.e. a directory holding a
/// `pyvenv.cfg` marker file.
fn is_venv(path: &Path) -> bool {
    path.is_dir() && path.join("pyvenv.cfg").is_file()
}