use std::fs;
use std::os::linux::fs::MetadataExt;
use std::os::unix::prelude::PermissionsExt;
use std::time::SystemTime;
use nix::unistd;
use serde_json::Value;

const PERSIST_TIME:         u64 = 60 * 3;

pub fn get_persist(user: &str) -> bool {
  let json = match get_terminal_config() {
      Some(data) => data,
      None => return false
  };
  let timestamp = match json[user].as_u64() {
      Some(data) => data,
      None => return false
  };
  return now() - timestamp < PERSIST_TIME && timestamp < now();
}

pub fn set_persist(user: &str) {
  let mut json = match get_terminal_config() {
      Some(data) => data,
      None => return
  };
  json[user] = Value::from(now());
  let id = match get_terminal_process() {
      Some(data) => data,
      None => return
  };
  match write_terminal_config(&id, &json.to_string()) {
      Ok(_) => {},
      Err(e) => {
          eprintln!("Internal Error: {}", e)
      }
  };
}

fn get_terminal_process() -> Option<i32> {
  let id: i32 = match std::process::id().try_into() {
      Ok(data) => data,
      Err(_) => return None
  };
  let stat = match procinfo::pid::stat(id) {
      Ok(data) => data,
      Err(_) => return None
  };
  Some(stat.session)
}

fn get_terminal_config() -> Option<Value> {
  let id = match get_terminal_process() {
      Some(data) => data,
      None => return None
  };
  if !is_file_root(&path(&id)) {
      return None;
  }
  let data = match std::fs::read_to_string(path(&id)) {
      Ok(data) => data,
      Err(_) => "{}".to_string()
  };
  let json: Value = match serde_json::from_str(&data) {
      Ok(data) => data,
      Err(_) => return None
  };
  Some(json)
}

fn write_terminal_config(id: &i32, data: &str) -> Result<(), Box<dyn std::error::Error>> {
  std::fs::create_dir_all("/var/run/crab")?;
  make_file_root("/var/run/crab")?;
  std::fs::write(path(&id), "")?;
  make_file_root(&path(&id))?;
  std::fs::write(path(&id), data)?;
  Ok(())
}

fn make_file_root(path: &str) -> Result<(), Box<dyn std::error::Error>> {
  unistd::chown(std::path::Path::new(path), Some(unistd::Uid::from(0)), Some(unistd::Gid::from(0)))?;
  let metadata = std::fs::metadata(path)?;
  let mut perms = metadata.permissions();
  perms.set_mode(0o100600);
  fs::set_permissions(path, perms)?;
  Ok(())
}

fn is_file_root(path: &str) -> bool {
  let metadata = match std::fs::metadata(path) {
      Ok(data) => data,
      Err(e) => {
          if let Some(err) = e.raw_os_error() {
              return err == 2;
          }
          return true
      }
  };
  let perms = metadata.permissions();
  return perms.mode() == 0o100600 && metadata.st_uid() == 0 && metadata.st_gid() == 0;
}

fn now() -> u64 {
  return SystemTime::now().duration_since(SystemTime::UNIX_EPOCH).unwrap().as_secs();
}

fn path(id: &i32) -> String {
  return format!("/var/run/crab/{}", id);
}