starship/src/modules/directory.rs

use super::Segment;
use std::env;
use std::path::PathBuf;
use ansi_term::{Color, Style};
use clap::ArgMatches;
use dirs;
use git2::Repository;

/// Creates a segment with the current directory
/// 
/// Will perform path contraction and truncation.
/// **Contraction**
///     - Paths begining with the home directory will be contracted to `~`
///     - Paths containing a git repo will contract to begin at the repo root
/// 
/// **Truncation**
/// Paths will be limited in length to `3` path components by default.
pub fn segment(_: &ArgMatches) -> Segment {
    const COLOR_DIR: Color = Color::Cyan;
    const DIR_TRUNCATION_LENGTH: usize = 3;
    const HOME_SYMBOL: &str = "~";

    let current_path = env::current_dir()
        .expect("Unable to identify current directory")
        .canonicalize()
        .expect("Unable to canonicalize current directory");

    let dir_string;
    if let Ok(repo) = git2::Repository::discover(&current_path) {
        // Contract the path to the git repo root
        let repo_root = get_repo_root(repo);

        let repo_folder_name = repo_root
            .components()
            .last()
            .unwrap()
            .as_os_str()
            .to_str()
            .unwrap();

        dir_string = contract_path(&current_path, &repo_root, &repo_folder_name);
    } else {
        // Contract the path to the home directory
        let home_dir = dirs::home_dir().unwrap();
        dir_string = contract_path(&current_path, &home_dir, HOME_SYMBOL);
    }

    // Truncate the dir string to the maximum number of path components
    let truncated_dir_string = truncate(dir_string, DIR_TRUNCATION_LENGTH);

    Segment {
        value: truncated_dir_string,
        style: Style::from(COLOR_DIR).bold(),
        ..Default::default()
    }
}

/// Get the root directory of a git repo
fn get_repo_root(repo: Repository) -> PathBuf {
    if repo.is_bare() {
        // Bare repos will return the repo root
        repo.path().to_path_buf()
    } else {
        // Non-bare repos will return the path of `.git`
        repo.path().parent().unwrap().to_path_buf()
    }
}

/// Contract the root component of a path
fn contract_path(full_path: &PathBuf, top_level_path: &PathBuf, top_level_replacement: &str) -> String {
    if !full_path.starts_with(top_level_path) {
        return full_path.to_str().unwrap().to_string();
    }

    if full_path == top_level_path {
        return top_level_replacement.to_string();
    }

    let top_level_path_depth = top_level_path.components().count();

    format!(
        "{replacement}{separator}{path}",
        replacement = top_level_replacement,
        separator = std::path::MAIN_SEPARATOR,
        path = full_path
            .iter()
            .skip(top_level_path_depth)
            .collect::<PathBuf>()
            .to_str()
            .unwrap()
    )
}

/// Truncate a path to only have a set number of path components
fn truncate(dir_string: String, length: usize) -> String {
    if length == 0 {
        return dir_string;
    }

    let components = dir_string.split(std::path::MAIN_SEPARATOR).collect::<Vec<&str>>();
    if components.len() < length {
        return dir_string;
    }

    let truncated_components = &components[..length];
    truncated_components.join(&std::path::MAIN_SEPARATOR.to_string())
}

#[cfg(test)]
mod tests {
    // TODO: Look into stubbing `env` so that tests can be run in parallel
    use super::*;
    use clap::{App, Arg};
    use std::path::Path;

    #[test]
    fn truncate_home_dir() {
        let args = App::new("starship")
            .arg(Arg::with_name("status_code"))
            .get_matches_from(vec!["starship", "0"]);

        let home_dir = dirs::home_dir().unwrap();
        env::set_current_dir(&home_dir).unwrap();

        let segment = segment(&args);
        assert_eq!(segment.value, "~");
    }

    #[test]
    fn dont_truncate_non_home_dir() {
        let args = App::new("starship")
            .arg(Arg::with_name("status_code"))
            .get_matches_from(vec!["starship", "0"]);

        let root_dir = Path::new("/");
        env::set_current_dir(&root_dir).unwrap();

        let segment = segment(&args);
        assert_eq!(segment.value, "/");
    }
}