adds log querying (#401)

* adds log querying

* Apply suggestions from code review

Co-authored-by: Aiden McClelland <3732071+dr-bonez@users.noreply.github.com>

* formatting

Co-authored-by: Aiden McClelland <3732071+dr-bonez@users.noreply.github.com>

appmgr/src/error.rs

@@ -49,6 +49,7 @@ pub enum ErrorKind {
     ParseNetAddress = 41,
     ParseSshKey = 42,
     SoundError = 43,
+    ParseTimestamp = 44,
 }
 impl ErrorKind {
     pub fn as_str(&self) -> &'static str {
@@ -97,6 +98,7 @@ impl ErrorKind {
             ParseNetAddress => "Net Address Parsing Error",
             ParseSshKey => "SSH Key Parsing Error",
             SoundError => "Sound Interface Error",
+            ParseTimestamp => "Timestamp Parsing Error",
         }
     }
 }

appmgr/src/lib.rs

@@ -38,6 +38,7 @@ pub mod s9pk;
 pub mod sound;
 pub mod ssh;
 pub mod status;
+pub mod system;
 pub mod util;
 pub mod version;
 pub mod volume;

appmgr/src/system.rs

@@ -0,0 +1,65 @@
+use chrono::{DateTime, Utc};
+use clap::ArgMatches;
+use rpc_toolkit::command;
+use tokio::process::Command;
+
+use crate::context::RpcContext;
+use crate::{Error, ErrorKind, ResultExt};
+
+pub const SYSTEMD_UNIT: &'static str = "embassyd";
+
+fn parse_datetime(text: &str, _matches: &ArgMatches) -> Result<DateTime<Utc>, Error> {
+    text.parse().with_kind(ErrorKind::ParseTimestamp)
+}
+
+#[command(rpc_only)]
+pub async fn logs(
+    #[context] _ctx: RpcContext,
+    #[arg(parse(crate::system::parse_datetime))] before: Option<DateTime<Utc>>,
+    #[arg] limit: Option<usize>,
+) -> Result<Vec<(String, String)>, Error> {
+    let before = before.unwrap_or(Utc::now());
+    let limit = limit.unwrap_or(50);
+    // Journalctl has unexpected behavior where "until" does not play well with "lines" unless the output is reversed.
+    // Keep this in mind if you are changing the code below
+    let out = Command::new("journalctl")
+        .args(&[
+            "-u",
+            SYSTEMD_UNIT,
+            &format!(
+                "-U\"{} {} UTC\"",
+                before.date().naive_utc(),
+                before.time().format("%H:%M:%S")
+            ),
+            "--output=short-iso",
+            "--no-hostname",
+            "--utc",
+            "--reverse",
+            &format!("-n{}", limit),
+        ])
+        .output()
+        .await?
+        .stdout;
+    let out_string = String::from_utf8(out)?;
+    let lines = out_string.lines();
+    let mut split_lines = lines
+        .skip(1) // ditch the journalctl header
+        .map(|s| {
+            // split the timestamp off from the log line
+            let (ts, l) = s.split_once(" ").unwrap();
+            (ts.to_owned(), l.to_owned())
+        })
+        .collect::<Vec<(String, String)>>();
+    // reverse output again because we reversed it above
+    split_lines.reverse();
+    Ok(split_lines)
+}
+
+#[test]
+pub fn test_output() {
+    println!(
+        "{} {} UTC",
+        Utc::now().date().naive_utc(),
+        Utc::now().time().format("%H:%M:%S")
+    )
+}