Improve the emoji extension (code review remarks)

src/Markdig/Extensions/Emoji/EmojiExtension.cs

@@ -12,21 +12,19 @@ namespace Markdig.Extensions.Emoji
     /// <seealso cref="Markdig.IMarkdownExtension" />
     public class EmojiExtension : IMarkdownExtension
     {
-        public EmojiExtension(bool enableSmiley = true, EmojiMapping customEmojiMapping = null)
-        {
-            EnableSmiley = enableSmiley;
-            CustomEmojiMapping = customEmojiMapping;
+        public EmojiExtension(EmojiMapping emojiMapping)
+        {
+            EmojiMapping = emojiMapping;
         }
-
-        public bool EnableSmiley { get; set; }
-        public EmojiMapping CustomEmojiMapping { get; }
+
+        public EmojiMapping EmojiMapping { get; }
 
         public void Setup(MarkdownPipelineBuilder pipeline)
         {
             if (!pipeline.InlineParsers.Contains<EmojiParser>())
             {
                 // Insert the parser before any other parsers
-                pipeline.InlineParsers.Insert(0, new EmojiParser(EnableSmiley, CustomEmojiMapping));
+                pipeline.InlineParsers.Insert(0, new EmojiParser(EmojiMapping));
             }
         }
 

src/Markdig/Extensions/Emoji/EmojiMapping.cs

@@ -16,12 +16,18 @@ public class EmojiMapping
         /// <summary>
         /// The default emojis and smileys mapping.
         /// </summary>
-        public static readonly EmojiMapping DefaultEmojiMapping = new EmojiMapping();
+        public static readonly EmojiMapping DefaultEmojiAndSmileyMapping = new EmojiMapping();
+
+        /// <summary>
+        /// The default emojis mapping, without smileys.
+        /// </summary>
+        public static readonly EmojiMapping DefaultEmojiOnlyMapping = new EmojiMapping(enableSmiley: false);
 
-        internal CompactPrefixTree<string> EmojiPrefixTree { get; }
-        internal CompactPrefixTree<string> EmojiSmileyPrefixTree { get; }
-        internal char[] EmojiOpeningCharacters { get; }
-        internal char[] EmojiSmileyOpeningCharacters { get; }
+        private static readonly Dictionary<string, string> _emptyDictionary = new Dictionary<string, string>();
+
+        internal CompactPrefixTree<string> PrefixTree { get; }
+
+        internal char[] OpeningCharacters { get; }
 
         #region Emojis and Smileys
 
@@ -1729,21 +1735,29 @@ public static IDictionary<string, string> GetDefaultSmileyToEmoji()
 
         #endregion
 
-        public EmojiMapping(IDictionary<string, string> emojiToUnicode = null, IDictionary<string, string> smileyToEmoji = null)
+        /// <summary>
+        /// Constructs a mapping for the default emojis and smileys.
+        /// </summary>
+        public EmojiMapping(bool enableSmiley = true)
+            : this(GetDefaultEmojiToUnicode(), enableSmiley ? GetDefaultSmileyToEmoji() : _emptyDictionary) { }
+
+        /// <summary>
+        /// Constructs a mapping from a dictionary of emojis to unicode, and a dictionary of smileys to emojis.
+        /// </summary>
+        public EmojiMapping(IDictionary<string, string> emojiToUnicode, IDictionary<string, string> smileyToEmoji)
         {
             if (emojiToUnicode == null)
-                emojiToUnicode = GetDefaultEmojiToUnicode();
-
-            if (smileyToEmoji == null)
-                smileyToEmoji = GetDefaultSmileyToEmoji();
-
-            // Build Emoji and Smiley CompactPrefixTree
+                throw new ArgumentNullException(nameof(emojiToUnicode));
 
-            EmojiPrefixTree = new CompactPrefixTree<string>(emojiToUnicode.Count, emojiToUnicode.Count, emojiToUnicode.Count);
+            if (smileyToEmoji == null)
+                throw new ArgumentNullException(nameof(smileyToEmoji));
 
-            int jointCount = emojiToUnicode.Count + smileyToEmoji.Count;
-            // Count * 2 seems to be a good fit for the data set
-            EmojiSmileyPrefixTree = new CompactPrefixTree<string>(jointCount, jointCount * 2, jointCount * 2);
+            // Build Emoji and Smiley CompactPrefixTree
+
+            int jointCount = emojiToUnicode.Count + smileyToEmoji.Count;
+
+            // Count * 2 seems to be a good fit for the data set
+            PrefixTree = new CompactPrefixTree<string>(jointCount, jointCount * 2, jointCount * 2);
 
             // This is not the best data set for the prefix tree as it will have to check the first character linearly
             // A work-around would require a bunch of substrings / removing the leading ':' from emojis, neither one is pretty
@@ -1753,32 +1767,28 @@ public EmojiMapping(IDictionary<string, string> emojiToUnicode = null, IDictiona
 
             foreach (var emoji in emojiToUnicode)
             {
-                EmojiPrefixTree.Add(emoji);
-                EmojiSmileyPrefixTree.Add(emoji);
-
                 if (string.IsNullOrEmpty(emoji.Key))
                     throw new ArgumentException("The dictionaries cannot contain null or empty keys", nameof(emojiToUnicode));
 
                 firstChars.Add(emoji.Key[0]);
-            }
-
-            EmojiOpeningCharacters = new List<char>(firstChars).ToArray();
+                PrefixTree.Add(emoji);
+            }
 
             foreach (var smiley in smileyToEmoji)
-            {
+            {
+                if (string.IsNullOrEmpty(smiley.Key))
+                    throw new ArgumentException("The dictionaries cannot contain null or empty keys", nameof(smileyToEmoji));
+
                 if (!emojiToUnicode.TryGetValue(smiley.Value, out string unicode))
                     throw new ArgumentException(string.Format("Invalid smiley target: {0} is not present in the emoji dictionary", smiley.Value));
 
-                if (string.IsNullOrEmpty(smiley.Key))
-                    throw new ArgumentException("The dictionaries cannot contain null or empty keys", nameof(smileyToEmoji));
-
                 firstChars.Add(smiley.Key[0]);
 
-                if (!EmojiSmileyPrefixTree.TryAdd(smiley.Key, unicode))
+                if (!PrefixTree.TryAdd(smiley.Key, unicode))
                     throw new ArgumentException(string.Format("Smiley {0} is already present in the Emoji dictionary", smiley.Key));
             }
 
-            EmojiSmileyOpeningCharacters = new List<char>(firstChars).ToArray();
+            OpeningCharacters = new List<char>(firstChars).ToArray();
         }
     }
 }

src/Markdig/Extensions/Emoji/EmojiParser.cs

@@ -14,28 +14,15 @@ namespace Markdig.Extensions.Emoji
     /// <seealso cref="InlineParser" />
     public class EmojiParser : InlineParser
     {
-        private readonly EmojiMapping _emojiMapping;
-        private CompactPrefixTree<string> _emojiPrefixTree;
+        private readonly EmojiMapping _emojiMapping;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="EmojiParser"/> class.
         /// </summary>
-        public EmojiParser(bool enableSmiley = true, EmojiMapping emojiMapping = null)
-        {
-            EnableSmiley = enableSmiley;
-            _emojiMapping = emojiMapping ?? EmojiMapping.DefaultEmojiMapping;
-            OpeningCharacters = null;
-        }
-
-        /// <summary>
-        /// Gets or sets a boolean indicating whether to process smiley.
-        /// </summary>
-        public bool EnableSmiley { get; set; }
-
-        public override void Initialize()
-        {
-            OpeningCharacters = EnableSmiley ? _emojiMapping.EmojiSmileyOpeningCharacters : _emojiMapping.EmojiOpeningCharacters;
-            _emojiPrefixTree = EnableSmiley ? _emojiMapping.EmojiSmileyPrefixTree : _emojiMapping.EmojiPrefixTree;
+        public EmojiParser(EmojiMapping emojiMapping)
+        {
+            _emojiMapping = emojiMapping;
+            OpeningCharacters = _emojiMapping.OpeningCharacters;
         }
 
         public override bool Match(InlineProcessor processor, ref StringSlice slice)
@@ -47,7 +34,7 @@ public override bool Match(InlineProcessor processor, ref StringSlice slice)
             }
 
             // Try to match an emoji
-            if (!_emojiPrefixTree.TryMatchLongest(slice.Text, slice.Start, slice.Length, out KeyValuePair<string, string> match))
+            if (!_emojiMapping.PrefixTree.TryMatchLongest(slice.Text, slice.Start, slice.Length, out KeyValuePair<string, string> match))
             {
                 return false;
             }

src/Markdig/MarkdownExtensions.cs

@@ -92,8 +92,8 @@ public static MarkdownPipelineBuilder UseAdvancedExtensions(this MarkdownPipelin
                 .UseDiagrams()
                 .UseAutoLinks()
                 .UseGenericAttributes(); // Must be last as it is one parser that is modifying other parsers
-        }
-        
+        }
+
         /// <summary>
         /// Uses this extension to enable autolinks from text `http://`, `https://`, `ftp://`, `mailto:`, `www.xxx.yyy`
         /// </summary>
@@ -425,17 +425,31 @@ public static MarkdownPipelineBuilder UseGenericAttributes(this MarkdownPipeline
         /// </summary>
         /// <param name="pipeline">The pipeline.</param>
         /// <param name="enableSmiley">Enable smiley in addition to Emoji, <c>true</c> by default.</param>
-        /// <param name="customEmojiMapping">Enable optional customization of the emojis and smileys mapping.</param>
         /// <returns>The modified pipeline</returns>
-        public static MarkdownPipelineBuilder UseEmojiAndSmiley(this MarkdownPipelineBuilder pipeline, bool enableSmiley = true, EmojiMapping customEmojiMapping = null)
+        public static MarkdownPipelineBuilder UseEmojiAndSmiley(this MarkdownPipelineBuilder pipeline, bool enableSmiley = true)
         {
             if (!pipeline.Extensions.Contains<EmojiExtension>())
             {
-                pipeline.Extensions.Add(new EmojiExtension(enableSmiley, customEmojiMapping));
+                var emojiMapping = enableSmiley ? EmojiMapping.DefaultEmojiAndSmileyMapping : EmojiMapping.DefaultEmojiOnlyMapping;
+                pipeline.Extensions.Add(new EmojiExtension(emojiMapping));
             }
             return pipeline;
         }
 
+        /// <summary>
+        /// Uses the emoji and smiley extension.
+        /// </summary>
+        /// <param name="pipeline">The pipeline.</param>
+        /// <param name="customEmojiMapping">Enable customization of the emojis and smileys mapping.</param>
+        /// <returns>The modified pipeline</returns>
+        public static MarkdownPipelineBuilder UseEmojiAndSmiley(this MarkdownPipelineBuilder pipeline, EmojiMapping customEmojiMapping)
+        {
+            if (!pipeline.Extensions.Contains<EmojiExtension>())
+            {
+                pipeline.Extensions.Add(new EmojiExtension(customEmojiMapping));
+            }
+            return pipeline;
+        }
         /// <summary>
         /// Add rel=nofollow to all links rendered to HTML.
         /// </summary>