Import functionality for wino accounts, calendar sync UI, bunch of shell improvements

Wino.Core/Misc/ColorHelpers.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Drawing;
+using System.Globalization;
 using System.Linq;
 using Wino.Core.Domain.Misc;
 
@@ -12,9 +13,21 @@ public static class ColorHelpers
 
     public static string GenerateFlatColorHex() => GetDistinctFlatColorHex(Array.Empty<string>());
 
-    public static string GetDistinctFlatColorHex(IEnumerable<string> usedColors)
+    public static string GetDistinctFlatColorHex(IEnumerable<string> usedColors, string preferredColor = null)
     {
         var palette = CalendarColorPalette.GetColors();
+        var normalizedUsedColors = usedColors?
+            .Select(NormalizeHexColor)
+            .Where(color => !string.IsNullOrWhiteSpace(color))
+            .ToHashSet(StringComparer.OrdinalIgnoreCase) ?? new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+
+        if (TryNormalizeHexColor(preferredColor, out var normalizedPreferred) &&
+            palette.Contains(normalizedPreferred, StringComparer.OrdinalIgnoreCase) &&
+            !normalizedUsedColors.Contains(normalizedPreferred))
+        {
+            return normalizedPreferred;
+        }
+
         var distinctColor = CalendarColorPalette.GetDistinctColor(usedColors);
         if (palette.Contains(distinctColor))
         {
@@ -26,6 +39,18 @@ public static class ColorHelpers
         return candidate;
     }
 
+    public static string GetReadableTextColorHex(string backgroundColor)
+    {
+        if (!TryNormalizeHexColor(backgroundColor, out var normalizedColor))
+        {
+            return "#FFFFFF";
+        }
+
+        var color = ColorTranslator.FromHtml(normalizedColor);
+        var luminance = ((0.299 * color.R) + (0.587 * color.G) + (0.114 * color.B)) / 255d;
+        return luminance > 0.6 ? "#111111" : "#FFFFFF";
+    }
+
     public static string ToHexString(this Color c) => $"#{c.R:X2}{c.G:X2}{c.B:X2}";
 
     public static string ToRgbString(this Color c) => $"RGB({c.R}, {c.G}, {c.B})";
@@ -41,4 +66,35 @@ public static class ColorHelpers
 
         return adjusted.ToHexString();
     }
+
+    private static bool TryNormalizeHexColor(string value, out string normalized)
+    {
+        normalized = string.Empty;
+        if (string.IsNullOrWhiteSpace(value))
+        {
+            return false;
+        }
+
+        var color = value.Trim();
+        if (color.StartsWith('#'))
+        {
+            color = color[1..];
+        }
+
+        if (color.Length != 6)
+        {
+            return false;
+        }
+
+        if (!int.TryParse(color, NumberStyles.HexNumber, CultureInfo.InvariantCulture, out _))
+        {
+            return false;
+        }
+
+        normalized = $"#{color.ToUpperInvariant()}";
+        return true;
+    }
+
+    private static string NormalizeHexColor(string value)
+        => TryNormalizeHexColor(value, out var normalized) ? normalized : string.Empty;
 }