feat: process list

this is unnacceptably unperformant;
I think I've reached the point at which sysinfo doesn't do what I want,
which is keep track of a table of processes efficiently enough.

src/sysinfo_snapshot.rs

@@ -1,7 +1,20 @@
 use std::time::Duration;
 
+pub fn refreshes() -> sysinfo::RefreshKind {
+    sysinfo::RefreshKind::nothing()
+        .with_memory(sysinfo::MemoryRefreshKind::everything())
+        .with_cpu(sysinfo::CpuRefreshKind::nothing().with_cpu_usage())
+        .with_processes(
+            sysinfo::ProcessRefreshKind::nothing()
+                .with_cpu()
+                .with_cmd(sysinfo::UpdateKind::OnlyIfNotSet)
+                .with_exe(sysinfo::UpdateKind::OnlyIfNotSet),
+        )
+}
+
 #[derive(Clone, Debug, serde::Serialize, serde::Deserialize)]
 pub struct SysinfoSnapshot {
+    /// in seconds
     uptime: u64,
 
     pub cpu_total: f32,
@@ -11,6 +24,8 @@ pub struct SysinfoSnapshot {
     pub memory_total: u64,
     pub swap: u64,
     pub swap_total: u64,
+
+    pub processes: Vec<ProcessSnapshot>,
 }
 impl SysinfoSnapshot {
     #[cfg_attr(not(feature = "app"), allow(dead_code))]
@@ -31,6 +46,42 @@ impl From<&sysinfo::System> for SysinfoSnapshot {
             memory_total: value.total_memory(),
             swap: value.used_swap(),
             swap_total: value.total_swap(),
+
+            processes: value
+                .processes()
+                .iter()
+                .map(|(_pid, process)| ProcessSnapshot::from(process))
+                .collect(),
+        }
+    }
+}
+
+#[derive(Clone, Debug, serde::Serialize, serde::Deserialize)]
+pub struct ProcessSnapshot {
+    pub pid: usize,
+
+    /// in CPU-milliseconds
+    accumulated_cpu_time: u64,
+
+    /// note: it's by core, and can be up to eg 1600 on a 16-core device
+    pub cpu_usage: f32,
+
+    pub name: String,
+}
+impl ProcessSnapshot {
+    pub fn cpu_time(&self) -> Duration {
+        Duration::from_millis(self.accumulated_cpu_time)
+    }
+}
+
+impl From<&sysinfo::Process> for ProcessSnapshot {
+    fn from(value: &sysinfo::Process) -> Self {
+        Self {
+            pid: value.pid().into(),
+            accumulated_cpu_time: value.accumulated_cpu_time(),
+            cpu_usage: value.cpu_usage(),
+
+            name: value.name().to_string_lossy().into_owned(),
         }
     }
 }