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

/// export
///
/// The builtin `export` command. Used to set global environment
/// variables for the current instance of the shell.
///
/// # Aliases
/// * export
/// * set
///
/// # Shell Examples
/// ```sh
/// export FOO=BAR
/// ```
pub fn incant(clause: &Option<Vec<String>>, uout: bool) -> Output {
    let status = 0;
    let mut out: Vec<u8> = Vec::new();
    let err: Vec<u8> = Vec::new();
    match clause {
        Some(clause) => {
            for stanza in clause {
                let (key, val) = match stanza.split_once("=") {
                    Some((key, val)) => (key, val),
                    None => continue,
                };
                env::set_var(key, val);
            }
        }
        None => {
            let mut lines = Vec::new();
            let sorted: BTreeMap<_, _> = env::vars().into_iter().collect();
            for (key, val) in sorted {
                lines.push(format!("{}={}", key, val));
            }

            if uout {
                out.append(&mut format!("{}\n", lines.join("\n")).as_bytes().to_vec());
            } else {
                println!("{}", lines.join("\n"));
            }
        }
    }

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

/// unset
///
/// The builtin `unset` command. Used to remove global environment variables
/// from the current instance of the shell, since `export` may be called with
/// an empty string as the value.
///
/// # Shell Examples
/// ```sh
/// unset FOO
/// ```
pub fn unincant(clause: &Option<Vec<String>>, uerr: bool) -> Output {
    let mut status = 0;
    let out: Vec<u8> = Vec::new();
    let mut err: Vec<u8> = Vec::new();
    match clause {
        Some(clause) => {
            for stanza in clause {
                env::remove_var(stanza);
            }
        }
        None => {
            status = 1;
            if uerr {
                err.append(&mut "unset: not enough arguments\n".as_bytes().to_vec());
            } else {
                eprintln!("unset: not enough arguments");
            }
        }
    }

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