use std::error::Error;
use std::fmt;
use std::io;
use std::path::Path;
use std::thread::sleep;
use std::time::Duration;
use std::ops::Deref;

use command_runner::CommandRunner;
use symbols::Symbol;
use symbols::file::File as FileSymbol;

#[derive(Debug)]
pub enum NodeJsSystemdUserServiceError<E: Error> {
  ExecError(E),
  GenericError
}

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

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

impl<E: Error> fmt::Display for NodeJsSystemdUserServiceError<E> {
  fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
    write!(f, "{}", self.description())
  }
}

pub struct NodeJsSystemdUserService<'a, P, C> where P: AsRef<str> + fmt::Display, C: Deref<Target=str> {
  name: &'a str,
  path: P,
  command_runner: &'a CommandRunner,
  file: FileSymbol<C, Cow<'a, str>>
}

use std::borrow::Cow;

impl<'a> NodeJsSystemdUserService<'a, Cow<'a, str>, String> {
  pub fn new(name: &'a str, path: &'a str, command_runner: &'a CommandRunner) -> Self {
    let home = String::from_utf8(command_runner.run_with_args("sh", &["-c", "echo \"$HOME\""]).unwrap().stdout).unwrap();
    let file_path: Cow<str> = Cow::from(String::from(home.trim_right()) + "/.config/systemd/user/" + name + ".service");

    let content = format!("[Service]
ExecStart=/usr/bin/nodejs {}
Restart=always
Environment=NODE_ENV=production
Environment=PORT={}/var/service.socket

[Install]
WantedBy=default.target
", path, home);
    NodeJsSystemdUserService {
      name: name,
      path: file_path.clone(),
      command_runner: command_runner,
      file: FileSymbol::new(file_path, content)
    }
  }
}

impl<'a, P, C> Symbol for NodeJsSystemdUserService<'a, P, C> where P: AsRef<str> + fmt::Display, C: Deref<Target=str> {
  type Error = NodeJsSystemdUserServiceError<io::Error>;
  fn target_reached(&self) -> Result<bool, Self::Error> {
    match self.file.target_reached() {
      Ok(false) => return Ok(false),
      Ok(true) => {},
      Err(e) => return Err(NodeJsSystemdUserServiceError::GenericError)
    }
/*
    if !(try!(self.file.target_reached())) {
      return Ok(false)
    }
*/
    loop {
      // Check if service is registered
      let active_state = try!(self.command_runner.run_with_args("systemctl", &["--user", "show", "--property", "ActiveState", self.name]));
      if !active_state.status.success() {
        return Ok(false);
      }
      // Check if service is running
      match String::from_utf8(active_state.stdout).unwrap().trim_right() {
        "ActiveState=activating" => sleep(Duration::from_millis(500)),
        "ActiveState=active" => return Ok(true),
        _ => return Ok(false)
      }
    }
  }

  fn execute(&self) -> Result<(), Self::Error> {
    try!(self.command_runner.run_with_args("mkdir", &["-p", Path::new(self.path.as_ref()).parent().unwrap().to_str().unwrap()]));
    // FIXME: Permissions
    //    try!(create_dir_all(Path::new(&path).parent().unwrap()));
    match self.file.execute() {
      Ok(_) => {},
      Err(e) => return Err(NodeJsSystemdUserServiceError::GenericError)
    }
    try!(self.command_runner.run_with_args("systemctl", &["--user", "enable", self.name]));
    try!(self.command_runner.run_with_args("systemctl", &["--user", "start", self.name]));
    Ok(())
  }
}

impl<'a, P, C> fmt::Display for NodeJsSystemdUserService<'a, P, C> where P: AsRef<str> + fmt::Display, C: Deref<Target=str> {
  fn fmt(&self, f: &mut fmt::Formatter) -> Result<(),fmt::Error>{
    write!(f, "Systemd Node.js user service unit for {}", self.path)
  }
}