Change password generator to use ColoredPassword (#686)

* Change password generator to use ColoredPassword

* Change ColoredPassword from FormattedString to HTML string for improved performance

* PasswordFormatter fixes

* Correct || to && condition

* Apply password colouring to history pages

src/App/Utilities/ColoredPasswordConverter.cs

@@ -0,0 +1,28 @@
+using System;
+using Xamarin.Forms;
+
+namespace Bit.App.Utilities
+{
+    public class ColoredPasswordConverter : IValueConverter
+    {
+        public object Convert(object value, Type targetType, object parameter,
+            System.Globalization.CultureInfo culture)
+        {
+            if(targetType != typeof(string))
+            {
+                throw new InvalidOperationException("The target must be a string.");
+            }
+            if(value == null)
+            {
+                return string.Empty;
+            }
+            return PasswordFormatter.FormatPassword((string)value);
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter,
+            System.Globalization.CultureInfo culture)
+        {
+            throw new NotSupportedException();
+        }
+    }
+}

src/App/Utilities/PasswordFormatter.cs

@@ -21,17 +21,19 @@ namespace Bit.App.Utilities
             Special
         }
 
-        public static FormattedString FormatPassword(string password)
+        public static string FormatPassword(string password)
         {
             if(password == null)
             {
-                return new FormattedString();
+                return string.Empty;
             }
 
-            var result = new FormattedString();
-            // Start off with an empty span to prevent possible NPEs. Due to the way the state machine
-            // works, this will actually always be replaced by a new span anyway.
-            var currentSpan = new Span();
+            // First two digits of returned hex code contains the alpha,
+            // which is not supported in HTML color, so we need to cut those out.
+            var numberColor = $"<span style=\"color:#{((Color)Application.Current.Resources["PasswordNumberColor"]).ToHex().Substring(2)}\">";
+            var specialColor = $"<span style=\"color:#{((Color)Application.Current.Resources["PasswordSpecialColor"]).ToHex().Substring(2)}\">";
+            var result = string.Empty;
+
             // Start with an otherwise uncovered case so we will definitely enter the "something changed"
             // state.
             var currentType = CharType.None;
@@ -56,24 +58,36 @@ namespace Bit.App.Utilities
                 // If the char type changed, build a new span to append the text to.
                 if(charType != currentType)
                 {
-                    currentSpan = new Span();
-                    result.Spans.Add(currentSpan);
+                    // Close off previous span.
+                    if (currentType != CharType.None && currentType != CharType.Normal)
+                    {
+                        result += "</span>";
+                    }
+                    
                     currentType = charType;
 
                     // Switch the color if it is not a normal text. Otherwise leave the
                     // default value.
                     switch(currentType)
                     {
+                        // Apply color style to span.
                         case CharType.Number:
-                            currentSpan.TextColor = (Color)Application.Current.Resources["PasswordNumberColor"];
+                            result += numberColor;
                             break;
                         case CharType.Special:
-                            currentSpan.TextColor = (Color)Application.Current.Resources["PasswordSpecialColor"];
+                            result += specialColor;
                             break;
                     }
                 }
-                currentSpan.Text += c;
+                result += c;
             }
+
+            // Close off last span.
+            if (currentType != CharType.None && currentType != CharType.Normal)
+            {
+                result += "</span>";
+            }
+
             return result;
         }
     }