Add enhancements to progress widget

* Adds TransferSpeedColumn
* Adds DownloadedColumn
* Adds ElapsedTimeColumn
* Minor enhancements to existing columns

src/Spectre.Console/Internal/FileSize.cs

@@ -0,0 +1,89 @@
+using System;
+using System.Globalization;
+
+namespace Spectre.Console.Internal
+{
+    internal struct FileSize
+    {
+        public double Bytes { get; }
+        public FileSizeUnit Unit { get; }
+        public string Suffix => GetSuffix();
+
+        public FileSize(double bytes)
+        {
+            Bytes = bytes;
+            Unit = Detect(bytes);
+        }
+
+        public FileSize(double bytes, FileSizeUnit unit)
+        {
+            Bytes = bytes;
+            Unit = unit;
+        }
+
+        public string Format(CultureInfo? culture = null)
+        {
+            var @base = GetBase(Unit);
+            if (@base == 0)
+            {
+                @base = 1;
+            }
+
+            var bytes = Bytes / @base;
+
+            return Unit == FileSizeUnit.Bytes
+                ? ((int)bytes).ToString(culture ?? CultureInfo.InvariantCulture)
+                : bytes.ToString("F1", culture ?? CultureInfo.InvariantCulture);
+        }
+
+        public override string ToString()
+        {
+            return ToString(suffix: true, CultureInfo.InvariantCulture);
+        }
+
+        public string ToString(bool suffix = true, CultureInfo? culture = null)
+        {
+            if (suffix)
+            {
+                return $"{Format(culture)} {Suffix}";
+            }
+
+            return Format(culture);
+        }
+
+        private string GetSuffix()
+        {
+            return (Bytes, Unit) switch
+            {
+                (_, FileSizeUnit.KiloByte) => "KB",
+                (_, FileSizeUnit.MegaByte) => "MB",
+                (_, FileSizeUnit.GigaByte) => "GB",
+                (_, FileSizeUnit.TeraByte) => "TB",
+                (_, FileSizeUnit.PetaByte) => "PB",
+                (_, FileSizeUnit.ExaByte) => "EB",
+                (_, FileSizeUnit.ZettaByte) => "ZB",
+                (_, FileSizeUnit.YottaByte) => "YB",
+                (1, _) => "byte",
+                (_, _) => "bytes",
+            };
+        }
+
+        private static FileSizeUnit Detect(double bytes)
+        {
+            foreach (var unit in (FileSizeUnit[])Enum.GetValues(typeof(FileSizeUnit)))
+            {
+                if (bytes < (GetBase(unit) * 1024))
+                {
+                    return unit;
+                }
+            }
+
+            return FileSizeUnit.Bytes;
+        }
+
+        private static double GetBase(FileSizeUnit unit)
+        {
+            return Math.Pow(1024, (int)unit);
+        }
+    }
+}

src/Spectre.Console/Internal/FileSizeUnit.cs

@@ -0,0 +1,17 @@
+using System;
+
+namespace Spectre.Console.Internal
+{
+    internal enum FileSizeUnit
+    {
+        Bytes = 0,
+        KiloByte = 1,
+        MegaByte = 2,
+        GigaByte = 3,
+        TeraByte = 4,
+        PetaByte = 5,
+        ExaByte = 6,
+        ZettaByte = 7,
+        YottaByte = 8,
+    }
+}