pub fn compile_script(&self) -> String {

        self.script.replace("{alias}", &self.alias)

    }

    pub fn new(alias: String, script: String) -> Self {

        Shell { alias, script }

    }

pub fn initialize(alias: String, hint: &Option<String>) -> Result<Shell, &'static str> {

    let shell = match hint {

        Some(hint) => hint.clone(),

        None => match detect() {

            Some(shell) => shell,

            None => return Err("No hint given and SHELL environment variable not found."),

    match shell.as_str() {

        s if s.contains("bash") => Ok(Shell::new(alias, bash::SCRIPT.to_string())),

        s if s.contains("fish") => Ok(Shell::new(alias, fish::SCRIPT.to_string())),

        s if s.contains("powershell") => Ok(Shell::new(alias, pwsh::SCRIPT.to_string())),

        s if s.contains("pwsh") => Ok(Shell::new(alias, pwsh::SCRIPT.to_string())),

        s if s.contains("zsh") => Ok(Shell::new(alias, zsh::SCRIPT.to_string())),

        _ => Ok(Shell::new(alias, bash::SCRIPT.to_string())),

}

    if let Ok(shell) = env::var("SHELL") {

        Some(shell)

        None

}

            let hint = Some($value.to_string());

            // WHEN trying to initialize the hinted shell

            let alias = String::from("up");

            let actual = initialize(alias, &hint);

            // THEN we should get the initialization function for the expected

            // shell

            let expected = format!("init {}", &hint.unwrap());

            assert!(actual.unwrap().compile_script().contains(&expected))

        }

    #[test]

    fn initialize_from_env() {

        // GIVEN non-existing shell

        env::set_var("SHELL", "radish");

        // WHEN trying initialize without a hint

        let alias = String::from("up");

        let actual = initialize(alias, &None);

        // THEN we should get the initialization function for the default shell

        let expected = "init bash";

        assert!(actual.unwrap().compile_script().contains(&expected))

    }

    #[test]

    fn initialize_non_existant() {

        // GIVEN empty SHELL variable

        env::remove_var("SHELL");

        // WHEN trying initialize without a hint

        let alias = String::from("up");

        let actual = initialize(alias, &None);

        // THEN we should get an error

        let expected = Err("No hint given and SHELL environment variable not found.");

        assert_eq!(actual, expected);

    }

    initialize_shell! {

        initialize_bash: ("bash"),

        initialize_fish: ("fish"),

        initialize_pwsh: ("pwsh"),

        initialize_zsh: ("zsh"),

    }