par-term 0.32.1

//! System resource monitor for the status bar.
//!
//! Polls CPU, memory, and network usage on a background thread using `sysinfo`.
//! Data is shared via `Arc<parking_lot::Mutex<...>>` for lock-free reads from
//! the render thread.

use std::time::Instant;

// ============================================================================
// Shared types (always compiled)
// ============================================================================

/// Snapshot of system resource usage.
#[derive(Debug, Clone, Default)]
pub struct SystemMonitorData {
    /// Global CPU usage percentage (0.0 - 100.0)
    pub cpu_usage: f32,
    /// Memory currently in use (bytes)
    pub memory_used: u64,
    /// Total physical memory (bytes)
    pub memory_total: u64,
    /// Network receive rate (bytes/sec)
    pub network_rx_rate: u64,
    /// Network transmit rate (bytes/sec)
    pub network_tx_rate: u64,
    /// When this data was last updated
    pub last_update: Option<Instant>,
}

// ============================================================================
// Full implementation (feature enabled)
// ============================================================================

#[cfg(feature = "system-monitor")]
mod inner {
    use std::sync::Arc;
    use std::sync::atomic::{AtomicBool, Ordering};
    use std::thread::JoinHandle;
    use std::time::{Duration, Instant};

    use parking_lot::Mutex;

    use super::SystemMonitorData;

    /// Background system resource monitor.
    ///
    /// Spawns a polling thread that periodically refreshes CPU, memory, and
    /// network statistics via `sysinfo`.
    pub struct SystemMonitor {
        data: Arc<Mutex<SystemMonitorData>>,
        running: Arc<AtomicBool>,
        thread: Mutex<Option<JoinHandle<()>>>,
    }

    impl SystemMonitor {
        /// Create a new (stopped) system monitor.
        pub fn new() -> Self {
            Self {
                data: Arc::new(Mutex::new(SystemMonitorData::default())),
                running: Arc::new(AtomicBool::new(false)),
                thread: Mutex::new(None),
            }
        }

        /// Start the polling thread.
        ///
        /// If the monitor is already running, this is a no-op.
        pub fn start(&self, poll_interval_secs: f32) {
            if self
                .running
                .compare_exchange(false, true, Ordering::SeqCst, Ordering::SeqCst)
                .is_err()
            {
                return;
            }

            let data = Arc::clone(&self.data);
            let running = Arc::clone(&self.running);
            let interval = Duration::from_secs_f32(poll_interval_secs.max(0.5));

            let handle = std::thread::Builder::new()
                .name("status-bar-sysmon".to_string())
                .spawn(move || {
                    use sysinfo::{CpuRefreshKind, MemoryRefreshKind, RefreshKind, System};

                    let mut sys = System::new_with_specifics(
                        RefreshKind::nothing()
                            .with_cpu(CpuRefreshKind::everything())
                            .with_memory(MemoryRefreshKind::everything()),
                    );
                    let mut networks = sysinfo::Networks::new_with_refreshed_list();

                    // First CPU poll is always 0% — need two samples.
                    sys.refresh_cpu_all();
                    std::thread::sleep(Duration::from_millis(200));

                    let mut prev_rx: u64 = 0;
                    let mut prev_tx: u64 = 0;
                    let mut first_net = true;

                    while running.load(Ordering::SeqCst) {
                        sys.refresh_cpu_all();
                        sys.refresh_memory();
                        networks.refresh(true);

                        // Network totals
                        let (mut total_rx, mut total_tx) = (0u64, 0u64);
                        for (_name, net) in networks.iter() {
                            total_rx = total_rx.saturating_add(net.total_received());
                            total_tx = total_tx.saturating_add(net.total_transmitted());
                        }

                        let (rx_rate, tx_rate) = if first_net {
                            first_net = false;
                            (0, 0)
                        } else {
                            let secs = interval.as_secs_f64();
                            let rx_delta = total_rx.saturating_sub(prev_rx);
                            let tx_delta = total_tx.saturating_sub(prev_tx);
                            (
                                (rx_delta as f64 / secs) as u64,
                                (tx_delta as f64 / secs) as u64,
                            )
                        };
                        prev_rx = total_rx;
                        prev_tx = total_tx;

                        {
                            let mut d = data.lock();
                            d.cpu_usage = sys.global_cpu_usage();
                            d.memory_used = sys.used_memory();
                            d.memory_total = sys.total_memory();
                            d.network_rx_rate = rx_rate;
                            d.network_tx_rate = tx_rate;
                            d.last_update = Some(Instant::now());
                        }

                        // Sleep in short increments so stop() returns quickly
                        let deadline = Instant::now() + interval;
                        while Instant::now() < deadline && running.load(Ordering::Relaxed) {
                            std::thread::sleep(Duration::from_millis(50));
                        }
                    }
                });

            match handle {
                Ok(h) => *self.thread.lock() = Some(h),
                Err(e) => {
                    // Thread spawn failed (e.g. OS out of resources); reset the
                    // running flag so start() can be retried and degrade gracefully
                    // without crashing the terminal session.
                    self.running.store(false, Ordering::SeqCst);
                    crate::debug_error!("SESSION_LOGGER", "failed to spawn sysmon thread: {:?}", e);
                }
            }
        }

        /// Signal the polling thread to stop without waiting for it to finish.
        pub fn signal_stop(&self) {
            self.running.store(false, Ordering::SeqCst);
        }

        /// Stop the polling thread and wait for it to finish.
        pub fn stop(&self) {
            self.signal_stop();
            if let Some(handle) = self.thread.lock().take() {
                let _ = handle.join();
            }
        }

        /// Whether the polling thread is currently running.
        pub fn is_running(&self) -> bool {
            self.running.load(Ordering::SeqCst)
        }

        /// Get a clone of the current data snapshot.
        pub fn data(&self) -> SystemMonitorData {
            self.data.lock().clone()
        }
    }

    impl Default for SystemMonitor {
        fn default() -> Self {
            Self::new()
        }
    }

    impl Drop for SystemMonitor {
        fn drop(&mut self) {
            self.stop();
        }
    }
}

#[cfg(feature = "system-monitor")]
pub use inner::SystemMonitor;

// ============================================================================
// Stub implementation (feature disabled)
// ============================================================================

#[cfg(not(feature = "system-monitor"))]
mod inner {
    use super::SystemMonitorData;

    /// Stub system resource monitor (sysinfo feature disabled).
    ///
    /// Provides the same public API as the full implementation but all methods
    /// are no-ops. This allows callers in `StatusBarUI` to compile without
    /// changes when the `system-monitor` feature is disabled.
    pub struct SystemMonitor;

    impl SystemMonitor {
        /// Create a new (stopped) system monitor stub.
        pub fn new() -> Self {
            Self
        }

        /// No-op — the monitor is never started.
        pub fn start(&self, _poll_interval_secs: f32) {}

        /// No-op — nothing to signal.
        pub fn signal_stop(&self) {}

        /// No-op — nothing to stop.
        pub fn stop(&self) {}

        /// Always returns `false` (never running).
        pub fn is_running(&self) -> bool {
            false
        }

        /// Returns a default (all-zero) data snapshot.
        pub fn data(&self) -> SystemMonitorData {
            SystemMonitorData::default()
        }
    }

    impl Default for SystemMonitor {
        fn default() -> Self {
            Self::new()
        }
    }
}

#[cfg(not(feature = "system-monitor"))]
pub use inner::SystemMonitor;

// ============================================================================
// Formatting helpers
// ============================================================================

/// Format bytes-per-second into a fixed-width human-readable string.
///
/// Output is always 10 characters wide (e.g. `"  1.0 KB/s"`) so the
/// status bar doesn't jump around when values change.
pub fn format_bytes_per_sec(bytes: u64) -> String {
    const KB: u64 = 1024;
    const MB: u64 = 1024 * 1024;
    const GB: u64 = 1024 * 1024 * 1024;

    if bytes >= GB {
        format!("{:>5.1} GB/s", bytes as f64 / GB as f64)
    } else if bytes >= MB {
        format!("{:>5.1} MB/s", bytes as f64 / MB as f64)
    } else if bytes >= KB {
        format!("{:>5.1} KB/s", bytes as f64 / KB as f64)
    } else {
        // Extra space before "B" so width matches "KB", "MB", "GB"
        format!("{:>5}  B/s", bytes)
    }
}

/// Format memory usage (used / total) into a human-readable string.
///
/// Each side is fixed-width (7 chars, e.g. `"  4.0 GB"`) so the status
/// bar doesn't jump when values change.
pub fn format_memory(used: u64, total: u64) -> String {
    fn human(bytes: u64) -> String {
        const KB: u64 = 1024;
        const MB: u64 = 1024 * 1024;
        const GB: u64 = 1024 * 1024 * 1024;

        if bytes >= GB {
            format!("{:>5.1} GB", bytes as f64 / GB as f64)
        } else if bytes >= MB {
            format!("{:>5.1} MB", bytes as f64 / MB as f64)
        } else if bytes >= KB {
            format!("{:>5.1} KB", bytes as f64 / KB as f64)
        } else {
            format!("{:>5}  B", bytes)
        }
    }

    format!("{} / {}", human(used), human(total))
}

// ============================================================================
// Tests
// ============================================================================

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_system_monitor_data_default() {
        let d = SystemMonitorData::default();
        assert_eq!(d.cpu_usage, 0.0);
        assert_eq!(d.memory_used, 0);
        assert_eq!(d.memory_total, 0);
        assert_eq!(d.network_rx_rate, 0);
        assert_eq!(d.network_tx_rate, 0);
        assert!(d.last_update.is_none());
    }

    #[test]
    fn test_format_bytes_per_sec() {
        assert_eq!(format_bytes_per_sec(0), "    0  B/s");
        assert_eq!(format_bytes_per_sec(512), "  512  B/s");
        assert_eq!(format_bytes_per_sec(1024), "  1.0 KB/s");
        assert_eq!(format_bytes_per_sec(1536), "  1.5 KB/s");
        assert_eq!(format_bytes_per_sec(1_048_576), "  1.0 MB/s");
        assert_eq!(format_bytes_per_sec(1_073_741_824), "  1.0 GB/s");
        // All outputs have same width
        assert_eq!(
            format_bytes_per_sec(0).len(),
            format_bytes_per_sec(1024).len()
        );
        assert_eq!(
            format_bytes_per_sec(1024).len(),
            format_bytes_per_sec(1_048_576).len()
        );
    }

    #[test]
    fn test_format_memory() {
        assert_eq!(format_memory(0, 0), "    0  B /     0  B");
        // 1 GB used / 8 GB total
        assert_eq!(
            format_memory(1_073_741_824, 8_589_934_592),
            "  1.0 GB /   8.0 GB"
        );
        // 512 MB / 1 GB
        assert_eq!(
            format_memory(536_870_912, 1_073_741_824),
            "512.0 MB /   1.0 GB"
        );
    }

    #[cfg(feature = "system-monitor")]
    #[test]
    fn test_system_monitor_start_stop() {
        use std::time::Duration;

        let monitor = SystemMonitor::new();
        assert!(!monitor.is_running());

        monitor.start(1.0);
        assert!(monitor.is_running());

        // Give the thread a moment to do an initial poll
        std::thread::sleep(Duration::from_millis(500));

        let data = monitor.data();
        // After starting, last_update should be set (thread had 200ms init + sleep)
        assert!(data.last_update.is_some());

        monitor.stop();
        assert!(!monitor.is_running());
    }
}