use std::error::Error;
use std::fmt;
use std::fs;
use std::io;
use std::ops::Deref;
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) -> UserServiceError<io::Error> {
    UserServiceError::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> {
    try!(write!(f, "{}", self.description()));
    if let UserServiceError::ActivationFailed(Ok(ref log)) = self {
      try!(write!(f, ": {:?}", log));
    };
    Ok(())
  }
}

pub struct UserService<'a, C, R>
where
  C: Deref<Target = str>,
  R: CommandRunner,
{
  service_name: &'a str,
  user_name: &'a str,
  command_runner: R,
  file: FileSymbol<C, String>,
}

impl<'a, R> UserService<'a, String, SetuidCommandRunner<'a, R>>
where
  R: CommandRunner,
{
  pub fn new_nodejs(
    home: &'a str,
    user_name: &'a str,
    service_name: &'a str,
    path: &'a str,
    command_runner: &'a R,
  ) -> Self {
    let port = format!("/var/tmp/{}-{}.socket", user_name, service_name);
    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, port
    );
    UserService::new(home, user_name, service_name, command_runner, content)
  }

  pub fn new(
    home: &'a str,
    user_name: &'a str,
    service_name: &'a str,
    command_runner: &'a R,
    content: String,
  ) -> Self {
    let file_path = format!(
      "{}/.config/systemd/user/{}.service",
      home.trim_end(),
      service_name
    );

    UserService {
      service_name,
      user_name,
      command_runner: SetuidCommandRunner::new(user_name, command_runner),
      file: FileSymbol::new(file_path, content),
    }
  }
}

impl<'a, C, R> UserService<'a, C, R>
where
  C: Deref<Target = str>,
  R: CommandRunner,
{
  fn systemctl_wait_for_dbus(&self, args: &[&str]) -> Result<String, Box<dyn Error>> {
    let mut tries = 5;
    loop {
      let result = try!(self.command_runner.run_with_args("systemctl", args));
      if !result.status.success() {
        let raw_stderr = try!(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(
          try!(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 = try!(self.systemctl_wait_for_dbus(&[
        "--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",
              &["--user", &format!("--user-unit={}", self.service_name)],
            )) as UserServiceError<io::Error>,
          ))
        }
        _ => return Ok(false),
      }
    }
  }
}

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

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

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

    let file_name = format!("/var/tmp/{}-{}.socket", self.user_name, self.service_name);
    fs::metadata(&file_name)
      .map(|_| ())
      .map_err(|e| Box::new(e) as Box<dyn Error>)
  }

  fn get_prerequisites(&self) -> Vec<Resource> {
    let mut r = vec![Resource::new(
      "file",
      format!("/var/lib/systemd/linger/{}", self.user_name),
    )];
    r.extend(self.file.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, R> fmt::Display for UserService<'a, C, R>
where
  C: Deref<Target = str>,
  R: CommandRunner,
{
  fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
    write!(f, "Systemd user service unit for {}", self.service_name)
  }
}