From b94f8e694bf01f5dba9ce2c01f589463a3dfbc69 Mon Sep 17 00:00:00 2001
From: Toby Vincent <tobyv@tobyvin.dev>
Date: Wed, 9 Oct 2024 18:23:58 -0500
Subject: feat!: rewrite to use traits and streams

---
 src/service/command.rs | 128 +++++++++++++++++++++++++++++++------------------
 1 file changed, 81 insertions(+), 47 deletions(-)

(limited to 'src/service/command.rs')

diff --git a/src/service/command.rs b/src/service/command.rs
index 41a79b3..3535ee2 100644
--- a/src/service/command.rs
+++ b/src/service/command.rs
@@ -1,79 +1,113 @@
 use std::{process::Stdio, time::Duration};
 
+use async_stream::stream;
+use futures::{Stream, StreamExt};
 use serde::Deserialize;
-use tokio::{
-    io::{AsyncBufReadExt, BufReader},
-    sync::watch::Sender,
-};
+use tokio::io::{AsyncBufReadExt, BufReader};
 
-use crate::{Error, Status};
+use super::IntoService;
 
-use super::ServiceSpawner;
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    #[error("IO error: {0}")]
+    Io(#[from] std::io::Error),
+    #[error("Exited with status code: {code}\n{stderr}")]
+    ExitCode { code: i32, stderr: String },
+    #[error("Process terminated by signal")]
+    Signal,
+    #[error("Serialization error: {0}")]
+    Serialization(#[from] serde_json::error::Error),
+    #[error("{0}")]
+    Stderr(String),
+    #[error("{0}")]
+    Output(String),
+    #[error("Exited with status code: {0}")]
+    PersistExitCode(i32),
+    #[error("Failed to get stderr of child process")]
+    NoStderr,
+    #[error("Failed to get stdout of child process")]
+    NoStdout,
+}
 
 #[derive(Debug, Clone, Deserialize)]
 pub struct Command {
     pub command: String,
     pub args: Vec<String>,
-    pub interval: Option<Duration>,
+    #[serde(default)]
+    pub persist: bool,
+    #[serde(default = "super::default_interval")]
+    pub interval: Duration,
 }
 
 impl Command {
-    async fn spawn_interval(
+    #[tracing::instrument]
+    fn persist(
+        mut interval: tokio::time::Interval,
         mut command: tokio::process::Command,
-        period: Duration,
-        tx: Sender<Status>,
-    ) -> Result<(), Error> {
-        let mut interval = tokio::time::interval(period);
-        loop {
-            interval.tick().await;
+    ) -> impl Stream<Item = Result<(), Error>> {
+        stream! {
+            loop {
+                interval.tick().await;
+
+                let mut child = command
+                    .stdout(Stdio::piped())
+                    .stderr(Stdio::piped())
+                    .spawn()?;
 
-            let status = command.output().await.map_or_else(Into::into, |o| {
-                if o.status.success() {
-                    Status::Ok
-                } else {
-                    let stdout = String::from_utf8_lossy(&o.stdout).trim().to_string();
-                    Status::Error(Some(format!("Service state: {}", stdout)))
+                let mut stdout_reader =
+                    BufReader::new(child.stdout.take().ok_or(Error::NoStdout)?).lines();
+
+                while let Some(line) = stdout_reader.next_line().await? {
+                    if "Ok" == line {
+                        yield Ok(());
+                    } else {
+                        yield Err(Error::Output(line))
+                    }
                 }
-            });
 
-            tx.send_if_modified(|s| s.update(status));
+                match child.wait().await?.code() {
+                    Some(0) => yield Ok(()),
+                    Some(code) => yield Err(Error::PersistExitCode(code)),
+                    None => yield Err(Error::Signal),
+                };
+            }
         }
     }
 
-    async fn spawn_persist(
+    #[tracing::instrument]
+    fn interval(
+        mut interval: tokio::time::Interval,
         mut command: tokio::process::Command,
-        tx: Sender<Status>,
-    ) -> Result<(), Error> {
-        let mut child = command.stdout(Stdio::piped()).spawn()?;
-        let mut stdout = BufReader::new(child.stdout.take().unwrap()).lines();
-
-        while let Some(line) = stdout.next_line().await? {
-            let status: Status = serde_json::from_str(&line)
-                .unwrap_or_else(|err| Status::Error(Some(format!("Serialization error: {err}"))));
-            tx.send_if_modified(|s| s.update(status));
+    ) -> impl Stream<Item = Result<(), Error>> {
+        stream! {
+            loop {
+                interval.tick().await;
+                let output = command.output().await?;
+                match output.status.code() {
+                    Some(0) => yield Ok(()),
+                    Some(code) => {
+                        let stderr = String::from_utf8_lossy(&output.stderr).to_string();
+                        yield Err(Error::ExitCode { code, stderr })
+                    }
+                    None => yield Err(Error::Signal),
+                }
+            }
         }
-
-        let exit_status = child.wait().await?;
-        let status = match exit_status.code() {
-            Some(0) => Status::Ok,
-            Some(code) => Status::Error(Some(format!("Exited with status code: {code}"))),
-            None => Status::Error(Some("Process terminated by signal".to_string())),
-        };
-
-        tx.send_if_modified(|s| s.update(status));
-        Ok(())
     }
 }
 
-impl ServiceSpawner for Command {
-    async fn spawn(self, tx: Sender<Status>) -> Result<(), Error> {
+impl IntoService for Command {
+    type Error = Error;
+
+    fn into_service(self) -> impl Stream<Item = Result<(), Self::Error>> {
+        let interval = tokio::time::interval(self.interval);
         let mut command = tokio::process::Command::new(self.command);
         command.args(self.args);
 
-        if let Some(period) = self.interval {
-            Self::spawn_interval(command, period, tx).await
+        if self.persist {
+            Self::persist(interval, command).boxed()
         } else {
-            Self::spawn_persist(command, tx).await
+            Self::interval(interval, command).boxed()
         }
     }
 }
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