Add new Encoder to the Dependency Injection extension method

Author: colinangusmackay

src/Example/appsettings.json

@@ -8,6 +8,18 @@
     },
     "Stravaig": {
         "ShortCode": {
+            "Pattern":[{
+                    "Type": "EncodeIntoCharacterSpace",
+                    "CharacterSpace": "0123456789QWERTYUIOPLKJHGFDSAZXCVBNM",
+                    "Length": 4
+                },{
+                "Type": "Fixed",
+                "FixedString": "-"
+            },{
+                "Type": "EncodeIntoCharacterSpace",
+                "CharacterSpace": "0123456789QWERTYUIOPLKJHGFDSAZXCVBNM",
+                "Length": 4
+            }],
             "CharacterSpace": "0123456789QWERTYUIOPLKJHGFDSAZXCVBNM",
             "FixedLength": 7,
             "Generator": {

src/Stravaig.ShortCode.DependencyInjection/PatternOptionsExtensions.cs

@@ -0,0 +1,12 @@
+namespace Stravaig.ShortCode.DependencyInjection
+{
+    internal static class PatternOptionsExtensions
+    {
+        public static PatternPart ToPatternPart(this ShortCodeOptions.PatternOptions options)
+        {
+            if (options.Type == PatternType.Fixed)
+                return new PatternPart(options.FixedString);
+            return new PatternPart(options.CharacterSpace, options.Length);
+        }
+    }
+}

src/Stravaig.ShortCode.DependencyInjection/ServiceProviderExtensions.cs

@@ -1,4 +1,6 @@
 using System;
+using System.Collections.Generic;
+using System.Linq;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Options;
@@ -39,7 +41,10 @@ private static void AddCommonParts<TGenerator>(this IServiceCollection services)
             services.AddSingleton<IEncoder>(p =>
             {
                 var options = p.GetRequiredService<IOptions<ShortCodeOptions>>();
-                return new Encoder(options.Value.CharacterSpace);
+                if (options.Value.Pattern.Length == 0)
+                    return new Encoder(options.Value.CharacterSpace);
+                return new PatternedEncoder(options.Value.Pattern
+                    .Select(pat => pat.ToPatternPart()));
             });
             services.AddSingleton<IShortCodeGenerator, TGenerator>();
             services.AddSingleton<IShortCodeFactory, ShortCodeFactory>();

src/Stravaig.ShortCode/PatternedEncoder.cs

@@ -61,6 +61,14 @@ public ulong RangeRequired(int numChars)
         public int MaxLength()
         {
             throw new NotImplementedException();
+            int result = 0;
+            ulong remainingRange = ulong.MaxValue; 
+            foreach (var part in _parts)
+            {
+                result += (int)(Math.Log(remainingRange) / Math.Log(part.Length));
+            }
+
+            return result;
         }
 
         public string NamedCharacterSpace =>

src/Stravaig.ShortCode/ShortCodeFactory.cs

@@ -40,7 +40,7 @@ public ShortCodeFactory(IShortCodeGenerator generator, IEncoder encoder, IOption
 
         private void WarnOnInconsistentOptions()
         {
-            if (_options.FixedLength.HasValue && _options.FixedLength.Value > _encoder.MaxLength())
+            if (_options.Pattern.Length == 0 && _options.FixedLength.HasValue && _options.FixedLength.Value > _encoder.MaxLength())
                 _logger.LogWarning("The Short Code generator will always produce codes with padding because the Fixed Length ({fixedLength}) option is greater than maximum length the encoder can generate ({encoderMaxLength}).",
                     _options.FixedLength.Value,
                     _encoder.MaxLength());

src/Stravaig.ShortCode/ShortCodeOptions.cs

@@ -5,6 +5,25 @@ namespace Stravaig.ShortCode
 {
     public class ShortCodeOptions
     {
+        public class PatternOptions
+        {
+            private string _characterSpace;
+            public PatternType Type { get; set; }
+
+            public string CharacterSpace
+            {
+                get => _characterSpace;
+                set
+                {
+                    ValidateCharacterSpace(value);
+                    _characterSpace = value;
+                }
+            }
+            
+            public int Length { get; set; }
+            
+            public string FixedString { get; set; }
+        }
         private const int AbsoluteMinLength = 1;
         private const int AbsoluteMaxLength = 64;
         private const int CharacterSpaceMinLength = 2;
@@ -18,18 +37,23 @@ public string CharacterSpace
             get => _characterSpace;
             set
             {
-                if (string.IsNullOrWhiteSpace(value))
-                    throw new ArgumentException(
-                        "The value cannot be, null, Empty or contain whitespace.",
-                        nameof(CharacterSpace));
-                if (value.Length < CharacterSpaceMinLength)
-                    throw new ArgumentException(
-                        $"The value must contain at least {CharacterSpaceMinLength} characters.",
-                        nameof(CharacterSpace));
+                ValidateCharacterSpace(value);
                 _characterSpace = value;
             }
         }
 
+        private static void ValidateCharacterSpace(string value)
+        {
+            if (string.IsNullOrWhiteSpace(value))
+                throw new ArgumentException(
+                    "The value cannot be, null, Empty or contain whitespace.",
+                    nameof(CharacterSpace));
+            if (value.Length < CharacterSpaceMinLength)
+                throw new ArgumentException(
+                    $"The value must contain at least {CharacterSpaceMinLength} characters.",
+                    nameof(CharacterSpace));
+        }
+
         public int MaxLength
         {
             get => _maxLength;
@@ -57,5 +81,7 @@ public int? FixedLength
         }
 
         public Dictionary<string, object> Generator { get; set; } = new Dictionary<string, object>();
+
+        public PatternOptions[] Pattern { get; set; } = Array.Empty<PatternOptions>();
     }
 }