Colorized passwords (#424)

* Added utility to format passwords using spans

* Use the password formatter to render the cipher password

* Colorize the password in the password generator

src/App/Utilities/PasswordFormatter.cs

@@ -0,0 +1,82 @@
+using System;
+using Xamarin.Forms;
+
+namespace Bit.App.Utilities
+{
+    /**
+     * Helper class to format a password with numeric encoding to separate
+     * normal text from numbers and special characters.
+     */
+    class PasswordFormatter
+    {
+        /**
+         * This enum is used for the statemachine when building the colorized
+         * password string.
+         */
+        private enum CharType
+        {
+            None,
+            Normal,
+            Number,
+            Special
+        }
+
+        public static FormattedString FormatPassword(String password)
+        {
+            var result = new FormattedString();
+
+            // Start off with an empty span to prevent possible NPEs. Due to the way the statemachine
+            // works, this will actually always be replaced by a new span anyway.
+            var currentSpan = new Span();
+            // Start with an otherwise uncovered case so we will definitely enter the "something changed"
+            // state.
+            var currentType = CharType.None;
+
+            foreach (var c in password)
+            {
+                // First, identify what the current char is.
+                CharType charType;
+                if (char.IsLetter(c))
+                {
+                    charType = CharType.Normal;
+                }
+                else if (char.IsDigit(c))
+                {
+                    charType = CharType.Number;
+                }
+                else
+                {
+                    charType = CharType.Special;
+                }
+
+                // If the char type changed, build a new span to append the text to.
+                if (charType != currentType)
+                {
+                    currentSpan = new Span();
+                    result.Spans.Add(currentSpan);
+                    currentType = charType;
+
+                    // Switch the color if it is not a normal text. Otherwise leave the
+                    // default value.
+                    switch (currentType)
+                    {
+                        case CharType.Number:
+                        {
+                            currentSpan.TextColor = Color.DodgerBlue;
+                            break;
+                        }
+                        case CharType.Special:
+                        {
+                            currentSpan.TextColor = Color.Firebrick;
+                            break;
+                        }
+                    }
+                }
+
+                currentSpan.Text += c;
+            }
+
+            return result;
+        }
+    }
+}