feat: file logging on client, logs command to fetch last N lines

crates/client/src/logger.rs

@@ -0,0 +1,59 @@
+/// File logger — writes structured log lines alongside the pretty terminal output.
+use std::fs::{File, OpenOptions};
+use std::io::Write;
+use std::sync::{Mutex, OnceLock};
+
+static LOG_FILE: OnceLock<Mutex<File>> = OnceLock::new();
+static LOG_PATH: OnceLock<String> = OnceLock::new();
+
+pub fn init() {
+    let path = log_path();
+    // Create parent dir if needed
+    if let Some(parent) = std::path::Path::new(&path).parent() {
+        let _ = std::fs::create_dir_all(parent);
+    }
+    match OpenOptions::new().create(true).append(true).open(&path) {
+        Ok(f) => {
+            LOG_PATH.set(path.clone()).ok();
+            LOG_FILE.set(Mutex::new(f)).ok();
+            write_line("INFO", "helios-remote started");
+        }
+        Err(e) => eprintln!("[logger] Failed to open log file {path}: {e}"),
+    }
+}
+
+fn log_path() -> String {
+    #[cfg(windows)]
+    {
+        let base = std::env::var("LOCALAPPDATA")
+            .unwrap_or_else(|_| "C:\\Temp".to_string());
+        format!("{base}\\helios-remote\\helios-remote.log")
+    }
+    #[cfg(not(windows))]
+    {
+        "/tmp/helios-remote.log".to_string()
+    }
+}
+
+pub fn get_log_path() -> String {
+    LOG_PATH.get().cloned().unwrap_or_else(log_path)
+}
+
+pub fn write_line(level: &str, msg: &str) {
+    let now = chrono::Local::now().format("%Y-%m-%d %H:%M:%S");
+    let line = format!("{now} [{level:<5}] {msg}\n");
+    if let Some(mutex) = LOG_FILE.get() {
+        if let Ok(mut f) = mutex.lock() {
+            let _ = f.write_all(line.as_bytes());
+        }
+    }
+}
+
+/// Read the last `n` lines from the log file.
+pub fn tail(n: u32) -> String {
+    let path = get_log_path();
+    let content = std::fs::read_to_string(&path).unwrap_or_default();
+    let lines: Vec<&str> = content.lines().collect();
+    let start = lines.len().saturating_sub(n as usize);
+    lines[start..].join("\n")
+}