fleetcom 0.8.0

A fleet-view supervisor for arbitrary shell commands.
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//! Filesystem-independent path helpers for display and session resolution.

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

/// Shorten a path for display: `$HOME` collapses to `~`. Everything else stays
/// absolute, so two directories never render as the same label.
pub fn abbreviate(path: &Path) -> String {
    let s = path.to_string_lossy();
    if let Ok(home) = std::env::var("HOME")
        && !home.is_empty()
        && let Some(rest) = s.strip_prefix(&home)
    {
        if rest.is_empty() {
            return "~".to_string();
        } else if rest.starts_with('/') {
            return format!("~{rest}");
        }
    }
    s.into_owned()
}

/// Expand a leading `~` (alone or `~/…`) to `$HOME`.
fn expand_tilde(s: &str) -> String {
    if let Some(rest) = s.strip_prefix('~')
        && (rest.is_empty() || rest.starts_with('/'))
        && let Ok(home) = std::env::var("HOME")
    {
        return format!("{home}{rest}");
    }
    s.to_string()
}

/// Collapse `.` and `..` without resolving symlinks: `/a/b/../c` becomes `/a/c`.
fn lexical_clean(p: &Path) -> PathBuf {
    let mut out = PathBuf::new();
    for comp in p.components() {
        match comp {
            Component::CurDir => {}
            Component::ParentDir => match out.components().next_back() {
                Some(Component::Normal(_)) => {
                    out.pop();
                }
                Some(Component::RootDir) => {}       // `/..` stays `/`
                _ => out.push(Component::ParentDir), // leading `..` in a relative path
            },
            other => out.push(other.as_os_str()),
        }
    }
    if out.as_os_str().is_empty() {
        out.push(".");
    }
    out
}

/// Resolve `~` and relative paths against `base`, then clean them lexically.
pub fn resolve(base: &Path, s: &str) -> PathBuf {
    let expanded = expand_tilde(s);
    let p = if expanded.is_empty() {
        base.to_path_buf()
    } else if Path::new(&expanded).is_absolute() {
        PathBuf::from(expanded)
    } else {
        base.join(expanded)
    };
    lexical_clean(&p)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn resolve_normalizes_trailing_slash() {
        let base = Path::new("/base");
        assert_eq!(resolve(base, "/tmp/"), PathBuf::from("/tmp"));
        assert_eq!(resolve(base, "/tmp"), PathBuf::from("/tmp"));
    }

    #[test]
    fn resolve_collapses_dotdot() {
        let base = Path::new("/base");
        assert_eq!(resolve(base, "/a/b/../c"), PathBuf::from("/a/c"));
        assert_eq!(resolve(base, "/a/b/../../c"), PathBuf::from("/c"));
        assert_eq!(resolve(base, "/../x"), PathBuf::from("/x")); // can't climb past root
        assert_eq!(
            resolve(base, "/Users/x/Code/Rust/fleetcom/../imessage-exporter"),
            PathBuf::from("/Users/x/Code/Rust/imessage-exporter")
        );
        // relative input resolves against base, then collapses
        assert_eq!(resolve(base, "sub/.."), PathBuf::from("/base"));
    }
}