// [[file:../remote.note::fed8a9d3][fed8a9d3]]
use super::*;
// fed8a9d3 ends here

// [[file:../remote.note::50e6ed5a][50e6ed5a]]
/// Represents a computational job inputted by user.
#[derive(Debug, Clone, Deserialize, Serialize)]
#[serde(default)]
pub struct Job {
    // FIXME: remove pub
    /// The content of running script
    pub(crate) script: String,

    /// A unique random name
    name: String,

    /// Path to a file for saving output stream of computation.
    pub out_file: PathBuf,

    /// Path to a file for saving error stream of computation.
    pub err_file: PathBuf,

    /// Path to a script file that defining how to start computation
    pub run_file: PathBuf,
}

impl Default for Job {
    fn default() -> Self {
        Self {
            script: "pwd".into(),
            name: random_name(),
            out_file: "job.out".into(),
            err_file: "job.err".into(),
            run_file: "run".into(),
        }
    }
}

impl Job {
    /// Construct a Job running shell script.
    ///
    /// # Parameters
    ///
    /// * script: the content of the script for running the job.
    ///
    pub fn new(script: impl Into<String>) -> Self {
        Self {
            script: script.into(),
            ..Default::default()
        }
    }

    /// Set job name.
    pub fn with_name(mut self, name: &str) -> Self {
        self.name = name.into();
        self
    }

    /// Return the job name
    pub fn name(&self) -> String {
        self.name.clone()
    }
}

fn random_name() -> String {
    use rand::distributions::Alphanumeric;
    use rand::Rng;

    let mut rng = rand::thread_rng();
    std::iter::repeat(())
        .map(|()| rng.sample(Alphanumeric))
        .map(char::from)
        .take(6)
        .collect()
}
// 50e6ed5a ends here

// [[file:../remote.note::769262a8][769262a8]]
mod node {
    use super::*;
    use crossbeam_channel::{unbounded, Receiver, Sender};

    /// Represents a remote node for computation
    #[derive(Debug, Clone, Deserialize, Serialize)]
    pub struct Node {
        name: String,
    }

    impl Node {
        /// Return the name of remote node
        pub fn name(&self) -> &str {
            &self.name
        }
    }

    impl<T: Into<String>> From<T> for Node {
        fn from(node: T) -> Self {
            let name = node.into();
            assert!(!name.is_empty(), "node name cannot be empty!");
            Self { name }
        }
    }

    impl std::fmt::Display for Node {
        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
            let name = &self.name;
            write!(f, "{name}")
        }
    }

    /// Represents a list of remote nodes allocated for computation
    #[derive(Clone)]
    pub struct Nodes {
        rx: Receiver<Node>,
        tx: Sender<Node>,
    }

    impl Nodes {
        /// Construct `Nodes` from a list of nodes.
        pub fn new<T: Into<Node>>(nodes: impl IntoIterator<Item = T>) -> Self {
            let (tx, rx) = unbounded();
            let nodes = nodes.into_iter().collect_vec();
            let n = nodes.len();
            info!("We have {n} nodes in totoal for computation.");
            for node in nodes {
                tx.send(node.into()).unwrap();
            }
            Self { rx, tx }
        }

        /// Return the number of nodes
        pub fn len(&self) -> usize {
            self.rx.len()
        }

        /// Borrow one node from `Nodes`
        pub fn borrow_node(&self) -> Result<Node> {
            let node = self.rx.recv()?;
            let name = &node.name;
            info!("client borrowed one node: {name:?}");
            Ok(node)
        }

        /// Return one `node` to `Nodes`
        pub fn return_node(&self, node: Node) -> Result<()> {
            let name = &node.name;
            info!("client returned node {name:?}");
            self.tx.send(node)?;
            Ok(())
        }
    }
}
// 769262a8 ends here

// [[file:../remote.note::e19bce71][e19bce71]]
use std::path::{Path, PathBuf};

use gosh_runner::prelude::SpawnSessionExt;
use gosh_runner::process::Session;

use tempfile::TempDir;
// e19bce71 ends here

// [[file:../remote.note::955c926a][955c926a]]
/// Computation represents a submitted `Job`
pub struct Computation {
    job: Job,

    /// command session. The drop order is above Tempdir
    session: Option<Session<tokio::process::Child>>,

    /// The working directory of computation
    wrk_dir: TempDir,
}
// 955c926a ends here

// [[file:../remote.note::a65e6dae][a65e6dae]]
impl Computation {
    /// The full path to the working directory for running the job.
    fn wrk_dir(&self) -> &Path {
        self.wrk_dir.path()
    }

    /// The full path to computation output file (stdout).
    fn out_file(&self) -> PathBuf {
        self.wrk_dir().join(&self.job.out_file)
    }

    /// The full path to computation error file (stderr).
    fn err_file(&self) -> PathBuf {
        self.wrk_dir().join(&self.job.err_file)
    }

    /// The full path to the script for running the job.
    fn run_file(&self) -> PathBuf {
        self.wrk_dir().join(&self.job.run_file)
    }
}
// a65e6dae ends here

// [[file:../remote.note::f8672e0c][f8672e0c]]
impl Job {
    /// Submit the job and turn it into Computation.
    pub fn submit(self) -> Result<Computation> {
        Computation::try_run(self)
    }
}

impl Computation {
    /// create run file and make sure it executable later
    fn create_run_file(&self) -> Result<()> {
        let run_file = &self.run_file();
        gut::fs::write_script_file(run_file, &self.job.script)?;
        LockFile::wait(&run_file, 2.0)?;

        Ok(())
    }

    /// Construct `Computation` of user inputted `Job`.
    fn try_run(job: Job) -> Result<Self> {
        // create working directory in scratch space.
        let wdir = tempfile::TempDir::new_in(".").expect("temp dir");
        let session = Self {
            job,
            wrk_dir: wdir.into(),
            session: None,
        };

        session.create_run_file()?;

        Ok(session)
    }

    /// Wait for background command to complete.
    async fn wait(&mut self) -> Result<()> {
        if let Some(s) = self.session.as_mut() {
            let ecode = s.child.wait().await?;
            info!("job session exited: {}", ecode);
            if !ecode.success() {
                error!("job exited unsuccessfully!");
                let txt = gut::fs::read_file(self.run_file())?;
                let run = format!("run file: {txt:?}");
                let txt = gut::fs::read_file(self.err_file())?;
                let err = format!("stderr: {txt:?}");
                bail!("Job failed with error:\n{run:?}{err:?}");
            }
            Ok(())
        } else {
            bail!("Job not started yet.");
        }
    }

    /// Run command in background.
    async fn start(&mut self) -> Result<()> {
        let program = self.run_file();
        let wdir = self.wrk_dir();
        trace!("job work direcotry: {}", wdir.display());

        let mut session = tokio::process::Command::new(&program)
            .current_dir(wdir)
            .stdout(std::process::Stdio::piped())
            .stderr(std::process::Stdio::piped())
            .spawn_session()?;

        let mut stdout = session
            .child
            .stdout
            .take()
            .expect("child did not have a handle to stdout");
        let mut stderr = session
            .child
            .stderr
            .take()
            .expect("child did not have a handle to stderr");

        // redirect stdout and stderr to files for user inspection.
        let mut fout = tokio::fs::File::create(self.out_file()).await?;
        let mut ferr = tokio::fs::File::create(self.err_file()).await?;
        tokio::io::copy(&mut stdout, &mut fout).await?;
        tokio::io::copy(&mut stderr, &mut ferr).await?;

        let sid = session.handler().id();
        debug!("command running in session {:?}", sid);
        self.session = session.into();

        Ok(())
    }

    /// Start computation, and wait and return its standard output
    pub async fn wait_for_output(&mut self) -> Result<String> {
        self.start().await?;
        self.wait().await?;
        let txt = gut::fs::read_file(self.out_file())?;
        Ok(txt)
    }
}
// f8672e0c ends here

// [[file:../remote.note::9b7911ae][9b7911ae]]
/// A singleton pattern based on file locking
#[derive(Debug)]
pub struct LockFile {
    file: std::fs::File,
    path: PathBuf,
}

impl LockFile {
    fn create(path: &Path) -> Result<LockFile> {
        use fs2::*;

        let file = std::fs::OpenOptions::new()
            .create(true)
            .write(true)
            .open(&path)
            .context("Could not create ID file")?;

        // https://docs.rs/fs2/0.4.3/fs2/trait.FileExt.html
        file.try_lock_exclusive()
            .context("Could not lock lock file; Is the instance already running?")?;

        Ok(LockFile {
            file,
            path: path.to_owned(),
        })
    }

    fn write_msg(&mut self, msg: &str) -> Result<()> {
        writeln!(&mut self.file, "{msg}").context("Could not write lock file")?;
        self.file.flush().context("Could not flush lock file")
    }

    /// Create a lockfile contains text `msg`
    pub fn new(path: &Path, msg: impl std::fmt::Display) -> Result<Self> {
        let mut lockfile = Self::create(path)?;
        lockfile.write_msg(&msg.to_string())?;
        Ok(lockfile)
    }

    /// Wait until file `f` available for max time of `timeout`.
    ///
    /// # Parameters
    /// * timeout: timeout in seconds
    /// * f: the file to wait for available
    pub fn wait(f: &std::path::Path, timeout: f64) -> Result<()> {
        use gut::utils::sleep;

        // wait a moment for socke file ready
        let interval = 0.1;
        let mut t = 0.0;
        loop {
            if f.exists() {
                trace!("Elapsed time during waiting: {:.2} seconds ", t);
                return Ok(());
            }
            t += interval;
            sleep(interval);

            if t > timeout {
                bail!("file {:?} doest exist for {} seconds", f, timeout);
            }
        }
    }
}

impl Drop for LockFile {
    fn drop(&mut self) {
        let _ = std::fs::remove_file(&self.path);
    }
}
// 9b7911ae ends here

// [[file:../remote.note::4a28f1b7][4a28f1b7]]
pub use node::{Node, Nodes};
// 4a28f1b7 ends here

// [[file:../remote.note::f725ca9b][f725ca9b]]
#[test]
fn test_node() {
    let localhost: Node = "localhost".into();
    assert_eq!(localhost.name(), "localhost");
}
// f725ca9b ends here