use std::borrow::Cow;
use std::error::Error;
use std::ffi::OsStr;
use std::fmt;
use std::io;
use std::path::Path;
use std::path::PathBuf;
use std::process::Output;
use std::thread::sleep;
use std::time::Duration;

use command_runner::{CommandRunner, SetuidCommandRunner};
use resources::Resource;
use symbols::file::File as FileSymbol;
use symbols::{Action, OwnedSymbolAction, Symbol, SymbolAction, SymbolRunner};

#[derive(Debug)]
pub enum UserServiceError<E: Error> {
  ActivationFailed(io::Result<Output>),
  ExecError(E),
  GenericError,
}

impl From<io::Error> for UserServiceError<io::Error> {
  fn from(err: io::Error) -> Self {
    Self::ExecError(err)
  }
}

impl<E: Error> Error for UserServiceError<E> {
  fn description(&self) -> &str {
    match self {
      UserServiceError::ExecError(ref e) => e.description(),
      UserServiceError::GenericError => "Generic error",
      UserServiceError::ActivationFailed(_) => "Activation of service failed",
    }
  }
  fn cause(&self) -> Option<&dyn Error> {
    match self {
      UserServiceError::ExecError(ref e) => Some(e),
      _ => None,
    }
  }
}

impl<E: Error> fmt::Display for UserServiceError<E> {
  fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
    write!(f, "{}", self.description())?;
    if let UserServiceError::ActivationFailed(Ok(ref log)) = self {
      write!(f, ": {:?}", log)?;
    };
    Ok(())
  }
}

pub struct UserService<'a, C: AsRef<str>, R: CommandRunner> {
  socket_path: Cow<'a, Path>,
  service_name: &'a str,
  user_name: Cow<'a, str>,
  command_runner: R,
  config: FileSymbol<C, PathBuf>,
}

impl<'a, R: CommandRunner> UserService<'a, String, SetuidCommandRunner<'a, Cow<'a, str>, R>> {
  pub fn new_nodejs(
    home: Cow<'a, Path>,
    user_name: Cow<'a, str>,
    service_name: &'a str,
    path: Cow<'a, Path>,
    command_runner: &'a R,
    socket_path: Cow<'a, Path>,
  ) -> Self {
    let content = format!(
      "[Service]
Environment=NODE_ENV=production
Environment=PORT={1}
ExecStartPre=/bin/rm -f {1}
ExecStart=/usr/bin/nodejs {0}
ExecStartPost=/bin/sh -c 'sleep 1 && chmod 666 {1}'

# FIXME: This only works if the nodejs path is a directory
WorkingDirectory={0}
#RuntimeDirectory=service
#RuntimeDirectoryMode=766
Restart=always

[Install]
WantedBy=default.target
",
      path.to_str().unwrap(),
      socket_path.to_str().unwrap()
    );
    UserService::new(
      socket_path,
      home,
      user_name,
      service_name,
      command_runner,
      content,
    )
  }

  pub fn new(
    socket_path: Cow<'a, Path>,
    home: Cow<'a, Path>,
    user_name: Cow<'a, str>,
    service_name: &'a str,
    command_runner: &'a R,
    content: String,
  ) -> Self {
    let config_path: PathBuf = [
      home.as_ref(),
      format!(".config/systemd/user/{}.service", service_name).as_ref(),
    ]
    .iter()
    .collect();

    UserService {
      socket_path,
      service_name,
      user_name: user_name.clone(),
      command_runner: SetuidCommandRunner::new(user_name, command_runner),
      config: FileSymbol::new(config_path, content),
    }
  }
}

impl<'a, C: AsRef<str>, R: CommandRunner> UserService<'a, C, R> {
  fn systemctl_wait_for_dbus(&self, args: &[&OsStr]) -> Result<String, Box<dyn Error>> {
    let mut tries = 5;
    loop {
      let result = self.command_runner.run_with_args("systemctl", args)?;
      if !result.status.success() {
        let raw_stderr = String::from_utf8(result.stderr)?;
        let stderr = raw_stderr.trim_end();
        if stderr != "Failed to connect to bus: No such file or directory" {
          return Err(stderr.into());
        }
      } else {
        return Ok(String::from_utf8(result.stdout)?.trim_end().to_string());
      }
      tries -= 1;
      if tries == 0 {
        return Err("Gave up waiting for dbus to appear".to_string().into());
      }
      sleep(Duration::from_millis(500));
    }
  }

  fn check_if_service(&self) -> Result<bool, Box<dyn Error>> {
    loop {
      let active_state = self.systemctl_wait_for_dbus(args![
        "--user",
        "show",
        "--property",
        "ActiveState",
        self.service_name,
      ])?;
      match active_state.as_ref() {
        "ActiveState=activating" => sleep(Duration::from_millis(500)),
        "ActiveState=active" => return Ok(true),
        "ActiveState=failed" => {
          return Err(Box::new(
            UserServiceError::ActivationFailed(self.command_runner.run_with_args(
              "journalctl",
              args!["--user", format!("--user-unit={}", self.service_name)],
            )) as UserServiceError<io::Error>,
          ))
        }
        _ => return Ok(false),
      }
    }
  }
}

impl<'a, C: AsRef<str>, R: CommandRunner> Symbol for UserService<'a, C, R> {
  fn target_reached(&self) -> Result<bool, Box<dyn Error>> {
    if !(self.config.target_reached()?) {
      return Ok(false);
    }
    self.check_if_service()
  }

  fn execute(&self) -> Result<(), Box<dyn Error>> {
    self.config.execute()?;
    self.systemctl_wait_for_dbus(args!["--user", "enable", self.service_name])?;
    self.systemctl_wait_for_dbus(args!["--user", "restart", self.service_name])?;

    loop {
      if !(self.check_if_service()?) {
        return Err(Box::new(
          UserServiceError::GenericError as UserServiceError<io::Error>,
        ));
      }

      if self.socket_path.exists() {
        return Ok(());
      }
      sleep(Duration::from_millis(500));
    }
  }

  fn get_prerequisites(&self) -> Vec<Resource> {
    let mut r = vec![Resource::new(
      "file",
      format!("/var/lib/systemd/linger/{}", self.user_name),
    )];
    r.extend(self.config.get_prerequisites().into_iter());
    r
  }

  fn as_action<'b>(&'b self, runner: &'b dyn SymbolRunner) -> Box<dyn Action + 'b> {
    Box::new(SymbolAction::new(runner, self))
  }

  fn into_action<'b>(self: Box<Self>, runner: &'b dyn SymbolRunner) -> Box<dyn Action + 'b>
  where
    Self: 'b,
  {
    Box::new(OwnedSymbolAction::new(runner, *self))
  }
}

impl<'a, C: AsRef<str>, R: CommandRunner> fmt::Display for UserService<'a, C, R> {
  fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
    write!(f, "Systemd user service unit for {}", self.service_name)
  }
}