use std::env;
use std::os::unix::process::ExitStatusExt;
use std::process::{ExitStatus, Output};

/// cd
///
/// The builtin `cd` command. Used to change directories. This must be
/// implemented by the shell, since the `pwd` is context sensitive within a
/// process. If no arguments are given, `cd` will take the user back to their
/// home directory (i.e. `~`).
///
/// # Shell Example
/// ```sh
/// cd ~/.config # Change into /home/<user>/.config
/// ```
pub fn incant(clause: &Option<Vec<String>>, uerr: bool) -> Output {
    let status;
    let out: Vec<u8> = Vec::new();
    let mut err: Vec<u8> = Vec::new();
    let path = match clause {
        Some(path) => path[0].to_string(),
        None => match env::var("HOME") {
            Ok(val) => val,
            Err(_) => {
                status = 1;
                if uerr {
                    err.append(&mut "cd: unknown home, staying in pwd\n".as_bytes().to_vec());
                } else {
                    eprintln!("cd: unknown home, staying in pwd");
                }
                return Output {
                    status: ExitStatus::from_raw(status),
                    stdout: out,
                    stderr: err,
                };
            }
        },
    };

    status = match std::env::set_current_dir(&path) {
        Ok(_) => 0,
        Err(e) => {
            if uerr {
                err.append(
                    &mut format!(
                        "cd: unable to change into {}: {}\n",
                        path,
                        e.to_string().to_lowercase()
                    )
                    .as_bytes()
                    .to_vec(),
                );
            } else {
                eprintln!(
                    "cd: unable to change into {}: {}",
                    path,
                    e.to_string().to_lowercase()
                );
            }
            1
        }
    };

    Output {
        status: ExitStatus::from_raw(status),
        stdout: out,
        stderr: err,
    }
}