tab-daemon 0.5.4

the daemon module for the tab terminal multiplexer
Documentation 
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use log::{debug, error, warn};
use std::{
    fs::File,
    io::{BufReader, BufWriter},
    path::{Path, PathBuf},
};
use tab_api::config::{daemon_file, is_running, load_daemon_file, DaemonConfig};
use thiserror::Error;

#[derive(Error, Debug)]
pub enum DaemonConfigError {
    #[error("the daemon is already running")]
    AlreadyRunning,
}

/// The runtime wrapper over `~/.tab/daemon-pid.yml`.  Creates and deletes the daemonfile.
pub struct DaemonFile {
    pid: i32,
    path: PathBuf,
}

impl DaemonFile {
    pub fn new(config: &DaemonConfig) -> anyhow::Result<DaemonFile> {
        let daemon_file = daemon_file()?;

        if daemon_file.exists() {
            debug!("daemon_file already exists");
            let stored = load_daemon_file()?;
            if let Some(stored) = stored {
                debug!("retrieved stored daemon_file: {:?}", stored);

                if is_running(&stored) {
                    debug!("daemon running at pid {}, terminating.", stored.pid);
                    return Err(DaemonConfigError::AlreadyRunning.into());
                } else {
                    debug!("daemon not running at pid {}, replacing.", stored.pid);
                }
            }
        } else {
            debug!("daemonfile does not exist at {:?}", daemon_file);
        }

        std::fs::create_dir_all(daemon_file.parent().unwrap())?;
        let file = File::create(daemon_file.as_path())?;

        let buf_writer = BufWriter::new(file);
        serde_yaml::to_writer(buf_writer, config)?;

        Self::set_mode(daemon_file.as_path())?;

        let daemon_file = DaemonFile {
            pid: config.pid,
            path: daemon_file,
        };

        Ok(daemon_file)
    }

    /// Deletes the daemonfile, if the serialized pid matches this pid.
    pub fn try_drop(&mut self) -> anyhow::Result<()> {
        let config = self.reload_config()?;

        if config.pid == self.pid {
            debug!("removing pidfile: {}", self.path.display());
            std::fs::remove_file(self.path.as_path())?;
        } else {
            warn!(
                "not removing pidfile - does not contain my pid: {}",
                self.path.display()
            );
        }

        Ok(())
    }

    fn reload_config(&self) -> anyhow::Result<DaemonConfig> {
        let file = File::open(self.path.as_path())?;
        let buf_reader = BufReader::new(file);
        let config: DaemonConfig = serde_yaml::from_reader(buf_reader)?;
        Ok(config)
    }

    #[cfg(target_family = "unix")]
    fn set_mode(path: &Path) -> anyhow::Result<()> {
        use std::os::unix::fs::PermissionsExt;

        let metadata = path.metadata()?;
        let mut permissions = metadata.permissions();
        permissions.set_mode(0o600);

        std::fs::set_permissions(path, permissions)?;

        Ok(())
    }

    #[cfg(not(target_family = "unix"))]
    fn set_mode(path: &Path) -> anyhow::Result<()> {
        Ok(())
    }
}

impl Drop for DaemonFile {
    fn drop(&mut self) {
        let result = self.try_drop();
        if let Err(e) = result {
            if e.to_string().starts_with("No such file or directory") {
                return;
            }

            error!("failed to drop pidfile: {}", e);
        }
    }
}