Expand pk;stats functionality

PluralKit.Bot/Services/CpuStatService.cs

@@ -0,0 +1,47 @@
+using System.Diagnostics;
+using System.Threading.Tasks;
+
+using Serilog;
+
+namespace PluralKit.Bot
+{
+    public class CpuStatService
+    {
+        private ILogger _logger;
+        
+        public double LastCpuMeasure { get; private set; }
+
+        public CpuStatService(ILogger logger)
+        {
+            _logger = logger;
+        }
+
+        /// <summary>
+        /// Gets the current CPU usage. Estimation takes ~5 seconds (of mostly sleeping).
+        /// </summary>
+        public async Task<double> EstimateCpuUsage()
+        {
+            // We get the current processor time, wait 5 seconds, then compare
+            // https://medium.com/@jackwild/getting-cpu-usage-in-net-core-7ef825831b8b
+            
+            _logger.Information("Estimating CPU usage...");
+            var stopwatch = new Stopwatch();
+            
+            stopwatch.Start();
+            var cpuTimeBefore = Process.GetCurrentProcess().TotalProcessorTime;
+            
+            await Task.Delay(5000);
+            
+            stopwatch.Stop();
+            var cpuTimeAfter = Process.GetCurrentProcess().TotalProcessorTime;
+
+            var cpuTimePassed = cpuTimeAfter - cpuTimeBefore;
+            var timePassed = stopwatch.Elapsed;
+
+            var percent = cpuTimePassed / timePassed;
+            _logger.Information("CPU usage measured as {Percent:P}", percent);
+            LastCpuMeasure = percent;
+            return percent;
+        }
+    }
+}