use crate::command_runner::CommandRunner;
use crate::symbols::Symbol;
use async_trait::async_trait;
use once_cell::sync::Lazy;
use std::error::Error;
use tokio::sync::Semaphore;

pub type Wait = Lazy<Semaphore>;
static WAIT: Wait = Lazy::new(|| Semaphore::new(1));

#[derive(Debug)]
pub struct User<U, C> {
  user_name: U,
  command_runner: C,
}

impl<U, C> User<U, C> {
  pub const fn new(user_name: U, command_runner: C) -> Self {
    Self {
      user_name,
      command_runner,
    }
  }
}

#[async_trait(?Send)]
impl<U: AsRef<str>, C: CommandRunner> Symbol for User<U, C> {
  async fn target_reached(&self) -> Result<bool, Box<dyn Error>> {
    let output = self
      .command_runner
      .run_with_args("getent", args!["passwd", self.user_name.as_ref()])
      .await?;
    match output.status.code() {
      Some(2) => Ok(false),
      Some(0) => Ok(true),
      _ => Err("Unknown error".into()),
    }
  }

  async fn execute(&self) -> Result<(), Box<dyn Error>> {
    // adduser is not reentrant because finding the next uid
    // and creating the account is not an atomic operation
    let wait = WAIT.acquire().await;
    let res = self
      .command_runner
      .run_successfully(
        "adduser",
        args![
          // "-m", // Necessary for Fedora, not accepted in Debian
          "--system",
          self.user_name.as_ref(),
        ],
      )
      .await;
    drop(wait);
    res
  }
}

#[cfg(test)]
mod test {
  use crate::async_utils::run;
  use crate::command_runner::StdCommandRunner;
  use crate::symbols::user::User;
  use crate::symbols::Symbol;

  #[test]
  fn test_target_reached_nonexisting() {
    let symbol = User {
      user_name: "nonexisting",
      command_runner: StdCommandRunner,
    };
    assert_eq!(run(symbol.target_reached()).unwrap(), false);
  }

  #[test]
  fn test_target_reached_root() {
    let symbol = User {
      user_name: "root",
      command_runner: StdCommandRunner,
    };
    assert_eq!(run(symbol.target_reached()).unwrap(), true);
  }
}