Initial commit

GameOfLife/IO/RleDecoder.cs

@@ -0,0 +1,82 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text.RegularExpressions;
+using GameOfLife.Entities;
+
+namespace GameOfLife.IO
+{
+    public class RleDecoder
+    {
+        public Pattern Pattern { get; }
+        public PatternMetadata Metadata { get; }
+
+        public RleDecoder(string filename) : this(new FileInfo(filename)) { }
+
+        public RleDecoder(FileSystemInfo fi) : this(GetLines(fi)) { }
+
+        public RleDecoder(IEnumerable<string> encodedRle)
+        {
+            var groups =
+                (from line in encodedRle
+                    let trimmed = line.Trim()
+                    where
+                        !string.IsNullOrEmpty(trimmed)
+                    group line by line.StartsWith("#") into g
+                    select g
+                ).ToArray();
+
+            var comments = groups.First(g => g.Key);
+            var nonComments = groups.First(g => !g.Key).ToArray();
+
+            Metadata = new RlePatternMetaData(nonComments.First(), comments);
+            var rleData = string.Join("", nonComments.Skip(1));
+            Pattern = Pattern.Extract(ExpandRle(rleData).ToArray());
+        }
+
+        /// <summary>
+        /// Returns RLE encoded string into decoded expansion, breaking lines into an enumeration
+        /// </summary>
+        private static IEnumerable<string> ExpandRle(string rleData)
+        {
+            if (!rleData.Contains("!"))
+                throw new ArgumentException("RLE pattern did not contain terminating character '!'");
+
+            var encodedRle
+                = rleData.Substring(0, rleData.IndexOf("!", StringComparison.Ordinal));
+
+            var rleDecodingRegex = new Regex(@"(?<count>\d*)(?<char>[a-z$])");
+
+            var matches = rleDecodingRegex.Matches(encodedRle);
+            var decoded = string.Empty;
+            foreach (Match match in matches)
+            {
+                var countStr = match.Groups["count"].Value;
+                var count = string.IsNullOrEmpty(countStr) ? 1 : int.Parse(countStr);
+                var c = match.Groups["char"].Value.First();
+                for (var i = 0; i < count; i++)
+                {
+                    switch (c)
+                    {
+                        case '$':
+                            yield return decoded;
+                            decoded = string.Empty;
+                            break;
+                        default:
+                            decoded += c;
+                            break;
+                    }
+                }
+            }
+            yield return decoded;
+        }
+
+        private static IEnumerable<string> GetLines(FileSystemInfo fi)
+        {
+            if (!fi.Exists)
+                throw new FileNotFoundException(fi.FullName);
+            return File.ReadAllLines(fi.FullName);
+        }
+    }
+}