1 files changed, 371 insertions, 0 deletions
diff --git a/Emby.Server.Implementations/TextEncoding/NLangDetect/Detector.cs b/Emby.Server.Implementations/TextEncoding/NLangDetect/Detector.cs
new file mode 100644
index 000000000..507dd5e42
--- /dev/null
+++ b/Emby.Server.Implementations/TextEncoding/NLangDetect/Detector.cs
@@ -0,0 +1,371 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Text.RegularExpressions;
+using NLangDetect.Core.Extensions;
+using NLangDetect.Core.Utils;
+
+namespace NLangDetect.Core
+{
+    public class Detector
+    {
+        private const double _AlphaDefault = 0.5;
+        private const double _AlphaWidth = 0.05;
+
+        private const int _IterationLimit = 1000;
+        private const double _ProbThreshold = 0.1;
+        private const double _ConvThreshold = 0.99999;
+        private const int _BaseFreq = 10000;
+
+        private static readonly Regex _UrlRegex = new Regex("https?://[-_.?&~;+=/#0-9A-Za-z]+", RegexOptions.Compiled);
+        private static readonly Regex _MailRegex = new Regex("[-_.0-9A-Za-z]+@[-_0-9A-Za-z]+[-_.0-9A-Za-z]+", RegexOptions.Compiled);
+
+        private readonly Dictionary<string, ProbVector> _wordLangProbMap;
+        private readonly List<string> _langlist;
+
+        private StringBuilder _text;
+        private double[] _langprob;
+
+        private double _alpha = _AlphaDefault;
+        private const int _trialsCount = 7;
+        private int _maxTextLength = 10000;
+        private double[] _priorMap;
+        private int? _seed;
+
+        #region Constructor(s)
+
+        public Detector(DetectorFactory factory)
+        {
+            _wordLangProbMap = factory.WordLangProbMap;
+            _langlist = factory.Langlist;
+            _text = new StringBuilder();
+            _seed = factory.Seed;
+        }
+
+        #endregion
+
+        #region Public methods
+
+        public void SetAlpha(double alpha)
+        {
+            _alpha = alpha;
+        }
+
+        public void SetPriorMap(Dictionary<string, double> priorMap)
+        {
+            _priorMap = new double[_langlist.Count];
+
+            double sump = 0;
+
+            for (int i = 0; i < _priorMap.Length; i++)
+            {
+                string lang = _langlist[i];
+
+                if (priorMap.ContainsKey(lang))
+                {
+                    double p = priorMap[lang];
+
+                    if (p < 0)
+                    {
+                        throw new NLangDetectException("Prior probability must be non-negative.", ErrorCode.InitParamError);
+                    }
+
+                    _priorMap[i] = p;
+                    sump += p;
+                }
+            }
+
+            if (sump <= 0)
+            {
+                throw new NLangDetectException("More one of prior probability must be non-zero.", ErrorCode.InitParamError);
+            }
+
+            for (int i = 0; i < _priorMap.Length; i++)
+            {
+                _priorMap[i] /= sump;
+            }
+        }
+
+        public void SetMaxTextLength(int max_text_length)
+        {
+            _maxTextLength = max_text_length;
+        }
+
+        // TODO IMM HI: TextReader?
+        public void Append(StreamReader streamReader)
+        {
+            var buf = new char[_maxTextLength / 2];
+
+            while (_text.Length < _maxTextLength && !streamReader.EndOfStream)
+            {
+                int length = streamReader.Read(buf, 0, buf.Length);
+
+                Append(new string(buf, 0, length));
+            }
+        }
+
+        public void Append(string text)
+        {
+            text = _UrlRegex.Replace(text, " ");
+            text = _MailRegex.Replace(text, " ");
+
+            char pre = '\0';
+
+            for (int i = 0; i < text.Length && i < _maxTextLength; i++)
+            {
+                char c = NGram.Normalize(text[i]);
+
+                if (c != ' ' || pre != ' ')
+                {
+                    _text.Append(c);
+                }
+
+                pre = c;
+            }
+        }
+
+        private void CleanText()
+        {
+            int latinCount = 0, nonLatinCount = 0;
+
+            for (int i = 0; i < _text.Length; i++)
+            {
+                char c = _text[i];
+
+                if (c <= 'z' && c >= 'A')
+                {
+                    latinCount++;
+                }
+                else if (c >= '\u0300' && c.GetUnicodeBlock() != UnicodeBlock.LatinExtendedAdditional)
+                {
+                    nonLatinCount++;
+                }
+            }
+
+            if (latinCount * 2 < nonLatinCount)
+            {
+                var textWithoutLatin = new StringBuilder();
+
+                for (int i = 0; i < _text.Length; i++)
+                {
+                    char c = _text[i];
+
+                    if (c > 'z' || c < 'A')
+                    {
+                        textWithoutLatin.Append(c);
+                    }
+                }
+
+                _text = textWithoutLatin;
+            }
+        }
+
+        public string Detect()
+        {
+            List<Language> probabilities = GetProbabilities();
+
+            return
+              probabilities.Count > 0
+                ? probabilities[0].Name
+                : null;
+        }
+
+        public List<Language> GetProbabilities()
+        {
+            if (_langprob == null)
+            {
+                DetectBlock();
+            }
+
+            List<Language> list = SortProbability(_langprob);
+
+            return list;
+        }
+
+        #endregion
+
+        #region Private helper methods
+
+        private static double NormalizeProb(double[] probs)
+        {
+            double maxp = 0, sump = 0;
+
+            sump += probs.Sum();
+
+            for (int i = 0; i < probs.Length; i++)
+            {
+                double p = probs[i] / sump;
+
+                if (maxp < p)
+                {
+                    maxp = p;
+                }
+
+                probs[i] = p;
+            }
+
+            return maxp;
+        }
+
+        private static string UnicodeEncode(string word)
+        {
+            var resultSb = new StringBuilder();
+
+            foreach (char ch in word)
+            {
+                if (ch >= '\u0080')
+                {
+                    string st = string.Format("{0:x}", 0x10000 + ch);
+
+                    while (st.Length < 4)
+                    {
+                        st = "0" + st;
+                    }
+
+                    resultSb
+                      .Append("\\u")
+                      .Append(st.SubSequence(1, 5));
+                }
+                else
+                {
+                    resultSb.Append(ch);
+                }
+            }
+
+            return resultSb.ToString();
+        }
+
+        private void DetectBlock()
+        {
+            CleanText();
+
+            List<string> ngrams = ExtractNGrams();
+
+            if (ngrams.Count == 0)
+            {
+                throw new NLangDetectException("no features in text", ErrorCode.CantDetectError);
+            }
+
+            _langprob = new double[_langlist.Count];
+
+            Random rand = (_seed.HasValue ? new Random(_seed.Value) : new Random());
+
+            for (int t = 0; t < _trialsCount; t++)
+            {
+                double[] prob = InitProbability();
+
+                // TODO IMM HI: verify it works
+                double alpha = _alpha + rand.NextGaussian() * _AlphaWidth;
+
+                for (int i = 0; ; i++)
+                {
+                    int r = rand.Next(ngrams.Count);
+
+                    UpdateLangProb(prob, ngrams[r], alpha);
+
+                    if (i % 5 == 0)
+                    {
+                        if (NormalizeProb(prob) > _ConvThreshold || i >= _IterationLimit)
+                        {
+                            break;
+                        }
+                    }
+                }
+
+                for (int j = 0; j < _langprob.Length; j++)
+                {
+                    _langprob[j] += prob[j] / _trialsCount;
+                }
+            }
+        }
+
+        private double[] InitProbability()
+        {
+            var prob = new double[_langlist.Count];
+
+            if (_priorMap != null)
+            {
+                for (int i = 0; i < prob.Length; i++)
+                {
+                    prob[i] = _priorMap[i];
+                }
+            }
+            else
+            {
+                for (int i = 0; i < prob.Length; i++)
+                {
+                    prob[i] = 1.0 / _langlist.Count;
+                }
+            }
+            return prob;
+        }
+
+        private List<string> ExtractNGrams()
+        {
+            var list = new List<string>();
+            NGram ngram = new NGram();
+
+            for (int i = 0; i < _text.Length; i++)
+            {
+                ngram.AddChar(_text[i]);
+
+                for (int n = 1; n <= NGram.GramsCount; n++)
+                {
+                    string w = ngram.Get(n);
+
+                    if (w != null && _wordLangProbMap.ContainsKey(w))
+                    {
+                        list.Add(w);
+                    }
+                }
+            }
+
+            return list;
+        }
+
+        private void UpdateLangProb(double[] prob, string word, double alpha)
+        {
+            if (word == null || !_wordLangProbMap.ContainsKey(word))
+            {
+                return;
+            }
+
+            ProbVector langProbMap = _wordLangProbMap[word];
+            double weight = alpha / _BaseFreq;
+
+            for (int i = 0; i < prob.Length; i++)
+            {
+                prob[i] *= weight + langProbMap[i];
+            }
+        }
+
+        private List<Language> SortProbability(double[] prob)
+        {
+            var list = new List<Language>();
+
+            for (int j = 0; j < prob.Length; j++)
+            {
+                double p = prob[j];
+
+                if (p > _ProbThreshold)
+                {
+                    for (int i = 0; i <= list.Count; i++)
+                    {
+                        if (i == list.Count || list[i].Probability < p)
+                        {
+                            list.Insert(i, new Language(_langlist[j], p));
+
+                            break;
+                        }
+                    }
+                }
+            }
+
+            return list;
+        }
+
+        #endregion
+    }
+}