// Copyright (c) Dr. Dirk Lellinger. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Threading;
using HtmlToFlowDocument.Dom;
using SlobViewer.Common;
using SlobViewer.Slob;

namespace SlobViewer.Gui
{
  /// <summary>
  /// ViewModel for the <see cref="DictionaryControl"/>.
  /// </summary>
  /// <seealso cref="System.ComponentModel.INotifyPropertyChanged" />
  public class DictionaryController : System.ComponentModel.INotifyPropertyChanged
  {
    private Settings _settings = new Settings();
    private HtmlToFlowDocument.Converter _converter = new HtmlToFlowDocument.Converter();

    /// <summary>
    /// The currently loaded dictionaries.
    /// </summary>
    private List<IWordDictionary> _dictionaries = new List<IWordDictionary>();
    private SortKey[] _sortKeys;
    private CompareInfo _compareInfo;
    private Collections.Text.LongestCommonSubstringsOfStringAndStringArray _bestMatches = new Collections.Text.LongestCommonSubstringsOfStringAndStringArray().Preallocate(255, 255);
    private CancellationTokenSource _bestMatchesCancellationTokenSource = new CancellationTokenSource();
    private static readonly char[] _wordTrimChars = new char[] { ' ', '\t', '\r', '\n', ',', '.', '!', '?', ';', ':', '-', '+', '\"', '\'', '(', ')', '[', ']', '{', '}', '<', '>', '|', '=' };


    #region Bindable Properties

    /// <summary>
    /// Occurs when a property value changes.
    /// </summary>
    public event PropertyChangedEventHandler PropertyChanged;

    private string[] _keys;
    private ObservableCollection<string> _keysColl;

    /// <summary>
    /// Gets or sets the keys. This list contains the collected keys of all dictionaries currently loaded. Used for data binding to the key list.
    /// </summary>
    /// <value>
    /// The keys.
    /// </value>
    public ObservableCollection<string> KeyList
    {
      get
      {
        return _keysColl;
      }
      set
      {
        if (!object.ReferenceEquals(_keys, value))
        {
          _keysColl = value;
          PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(KeyList)));
        }
      }
    }

    internal void Action_ShowSecondaryWord(string text)
    {
      if (!string.IsNullOrEmpty(text))
      {
        ShowContentForUntrimmedKey(text);
      }
    }

    private string _selectedKeyInKeyList;

    /// <summary>
    /// Gets or sets the selected search text (used for binding to the search text TextBox).
    /// </summary>
    /// <value>
    /// The selected search text.
    /// </value>
    public string SelectedKeyInKeyList
    {
      get
      {
        return _selectedKeyInKeyList;
      }
      set
      {
        if (!(_selectedKeyInKeyList == value))
        {
          _selectedKeyInKeyList = value;
          PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SelectedKeyInKeyList)));
        }
      }
    }

    private List<string> _bestMatchesList;

    /// <summary>
    /// Gets or sets the list of best matches (key words that are most similar to the original key). Used for data binding to the best matches list.
    /// </summary>
    /// <value>
    /// The best matches list.
    /// </value>
    public List<string> BestMatchesList
    {
      get { return _bestMatchesList; }
      set
      {
        if (!object.ReferenceEquals(_bestMatchesList, value))
        {
          _bestMatchesList = value;
          PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(BestMatchesList)));
        }
      }
    }

    private FlowDocument _flowDocument;

    /// <summary>
    /// Gets or sets the flow document (used for data binding to the FlowDocumentViewer).
    /// </summary>
    /// <value>
    /// The flow document.
    /// </value>
    public FlowDocument FlowDocument
    {
      get
      {
        return _flowDocument;
      }
      set
      {
        if (!object.ReferenceEquals(_flowDocument, value))
        {
          _flowDocument = value;
          PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(FlowDocument)));
        }
      }
    }

    private string _searchText;

    /// <summary>
    /// Gets or sets the selected search text (used for binding to the search text TextBox).
    /// </summary>
    /// <value>
    /// The selected search text.
    /// </value>
    public string SearchText
    {
      get
      {
        return _searchText;
      }
      set
      {
        if (!(_searchText == value))
        {
          _searchText = value;
          PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SearchText)));
          ShowContentForKey(_searchText);
          UpdateBestMatches(_searchText);
        }
      }
    }

    private bool _isInDarkMode;

    public bool IsInDarkMode
    {
      get
      {
        return _isInDarkMode;
      }
      set
      {
        if (!(_isInDarkMode == value))
        {
          _isInDarkMode = value;
          PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(IsInDarkMode)));
        }
      }
    }

    #endregion

    /// <summary>
    /// Gets the currently loaded dictionaries.
    /// </summary>
    /// <value>
    /// The currently loaded dictionaries.
    /// </value>
    public IList<IWordDictionary> Dictionaries { get { return _dictionaries; } }


    public void LoadDictionariesUsingSettings(Settings settings)
    {
      if (settings.DictionaryFileNames.Count >= 1)
      {
        for (int i = settings.DictionaryFileNames.Count - 1; i >= 0; --i)
          LoadDictionary(settings.DictionaryFileNames[i], i == 0);
      }
    }



    /// <summary>
    /// Loads a Slob dictionary.
    /// </summary>
    /// <param name="fileName">Name of the dictionary file. The dictionary must be in SLOB format.</param>
    /// <param name="collectKeys">If set to <c>true</c>, the keys of all dictionaries will be collected. When loading multiple dictionaries subsequently, you should set this parameter to true only for the last dictionary loaded.</param>
    public void LoadDictionary(string fileName, bool collectKeys = true)
    {
      var extension = System.IO.Path.GetExtension(fileName).ToLowerInvariant();

      IWordDictionary dictionary = null;

      switch (extension)
      {
        case ".ifo":
          {
            var starDict = new StarDict.StarDictionaryInMemory();
            starDict.Open(fileName);
            dictionary = starDict;
          }
          break;
        case ".slob":
          {
            var slobReader = new SlobReaderWriter(fileName);
            dictionary = slobReader.Read();
            dictionary.FileName = fileName;
          }
          break;
      }


      if (null != dictionary)
      {
        _dictionaries.Add(dictionary);

        if (collectKeys)
        {
          CollectAndSortKeys();
        }
      }
    }

    /// <summary>
    /// Collects the keys of all loaded dictionaries and sorts them alphabetically. The list of keys is then published in <see cref="KeyList"/>.
    /// </summary>
    public void CollectAndSortKeys()
    {
      var hashSet = new HashSet<string>();

      foreach (var dict in _dictionaries)
      {
        hashSet.UnionWith(dict.GetKeys());
      }

      _keys = hashSet.ToArray();

      _compareInfo = new CultureInfo("en-US", false).CompareInfo;

      _sortKeys = _keys.Select(x => _compareInfo.GetSortKey(x)).ToArray();
      Array.Sort(_sortKeys, _keys, new UnicodeStringSorter());

      KeyList = new ObservableCollection<string>(_keys);
    }

    /// <summary>
    /// Given the search key <paramref name="searchText"/>, the function looks out for other keys that have the most number of chars in common with the orignal key.
    /// The first 100 best matches are then put into the list <see cref="BestMatchesList"/>.
    /// </summary>
    /// <param name="searchText">The search text.</param>
    public void UpdateBestMatches(string searchText)
    {
      _bestMatchesCancellationTokenSource.Cancel();
      _bestMatchesCancellationTokenSource.Dispose();

      _bestMatchesCancellationTokenSource = new CancellationTokenSource();

      var token = _bestMatchesCancellationTokenSource.Token;

      System.Threading.Tasks.Task.Run(
          () =>
          {
            _bestMatches.Evaluate(searchText, _keys, token);

            if (!token.IsCancellationRequested)
            {
              BestMatchesList = new List<string>(_bestMatches.BestMatches.Select(x => x.Phrase).Take(Math.Min(100, _keys.Length)));
            }
          }, token
          );
    }

    public int SearchListLock { get; private set; } = 0;

    /// <summary>
    /// Given the key <paramref name="untrimmedSearchText"/>, this function first of all trims the key a the start and end from unwanted characters. Then it enumerates through all currently loaded dictionaries, 
    /// collects the content found for this key, and finally shows the collected content in a FlowDocument.
    /// </summary>
    /// <param name="untrimmedSearchText">The untrimmed key.</param>
    public void ShowContentForUntrimmedKey(string untrimmedSearchText)
    {
      SearchText = TrimKeyString(untrimmedSearchText);
    }

    private string TrimKeyString(string untrimmedSearchText)
    {
      var idxStart = 0;
      var idxEnd = untrimmedSearchText.Length - 1;

      for (; idxEnd >= 0; --idxEnd)
        if (char.IsLetterOrDigit(untrimmedSearchText[idxEnd]))
          break;

      for (; idxStart <= idxEnd; ++idxStart)
        if (char.IsLetterOrDigit(untrimmedSearchText[idxStart]))
          break;

      return idxStart <= idxEnd ? untrimmedSearchText.Substring(idxStart, idxEnd - idxStart + 1) : string.Empty;

    }

    /// <summary>
    /// Given the key <paramref name="originalSearchText"/>, this function enumerates through all currently loaded dictionaries, 
    /// collects the content found for this key, and finally shows the collected content in a FlowDocument.
    /// </summary>
    /// <param name="originalSearchText">The original search text.</param>
    public void ShowContentForKey(string originalSearchText)
    {
      if (string.IsNullOrEmpty(originalSearchText))
        return;

      (IWordDictionary Dictionary, string Content, string ContentId, string SearchText)? firstResult = null;

      var listDirect = new List<(IWordDictionary Dictionary, string Content, string ContentId, string SearchText)>();
      var listVerb = new List<(IWordDictionary Dictionary, string Content, string ContentId, string SearchText)>();

      var originalSearchTexts = char.IsUpper(originalSearchText[0]) ? new[] { originalSearchText, originalSearchText.ToLowerInvariant() } : new[] { originalSearchText };

      foreach (var originalSearchTextVariant in originalSearchTexts)
      {
        foreach (var dictionary in _dictionaries)
        {
          var searchText1 = originalSearchTextVariant;
          var (result1, result1Id, found1) = GetResult(ref searchText1, dictionary);

          if (null == firstResult)
            firstResult = (dictionary, result1, result1Id, searchText1);

          if (found1)
            listDirect.Add((dictionary, result1, result1Id, searchText1));

          var searchText2 = "to " + originalSearchText;
          var (result2, result2Id, found2) = GetResult(ref searchText2, dictionary);

          if (found2)
            listVerb.Add((dictionary, result2, result2Id, searchText2));
        }

        if (listDirect.Count != 0 || listVerb.Count != 0)
          break;

      }

      string searchText = listDirect.Count > 0 ? listDirect[0].SearchText : listVerb.Count > 0 ? listVerb[0].SearchText : firstResult?.SearchText;

      try
      {
        ++SearchListLock;
        SelectedKeyInKeyList = searchText;
      }
      finally
      {
        --SearchListLock;
      }


      if (listDirect.Count > 0 && listVerb.Count > 0)
        ShowContent(listDirect.Concat(listVerb).ToArray());
      else if (listDirect.Count > 0)
        ShowContent(listDirect.ToArray());
      else if (listVerb.Count > 0)
        ShowContent(listVerb.ToArray());
      else if (firstResult.HasValue)
        ShowContent(firstResult.Value);
    }


    /// <summary>
    /// Converts plain text to a <see cref="Section"/>.
    /// </summary>
    /// <param name="key">The key. It is neccessary here because text files do not neccessarily contain the key, so that the key is used as title here.</param>
    /// <param name="content">The content in plain text format.</param>
    /// <returns>A <see cref="Section"/> that represents the plain text content.</returns>
    public Section ConvertTextContentToSection(string key, string content)
    {
      var doc = new Section();

      var para = new Paragraph();
      var run = new Run(key);
      run.FontSize = 22;

      para.AppendChild(run);
      doc.AppendChild(para);

      para = new Paragraph();
      run = new Run(content);

      para.AppendChild(run);
      doc.AppendChild(para);

      return doc;
    }

    /// <summary>
    /// Converts TEI XML content to a <see cref="Section"/>.
    /// </summary>
    /// <param name="content">The content to convert. It must be in TEI XML format (see README.md of <see href="https://github.com/freedict/fd-dictionaries"/>).</param>
    /// <returns>A <see cref="Section"/> that represents the TEI XML content.</returns>
    public Section ConvertTeiContentToSection(string content)
    {
      var doc = new Section();


      using (var tr = System.Xml.XmlReader.Create(new StringReader(content)))
      {
        tr.MoveToContent();
        tr.ReadToDescendant("orth");
        var orth = tr.ReadElementContentAsString();

        if (null != orth)
        {
          var para = new Paragraph();
          para.AppendChild(new Run(orth) { FontSize = 23 });
          doc.AppendChild(para);
        }

        if (tr.Name == "pron")
        {
          var pron = tr.ReadElementContentAsString();
          var para = new Paragraph();
          para.AppendChild(new Run(pron) { FontSize = 18 });
          doc.AppendChild(para);
        }

        tr.ReadToFollowing("sense");
        tr.ReadStartElement("sense");

        var sensePara = new Paragraph();
        doc.AppendChild(sensePara);

        while (tr.Name == "cit")
        {
          string quote = null;

          tr.ReadStartElement("cit");
          if (tr.Name == "quote")
          {
            quote = tr.ReadElementContentAsString();
          }

          if (null != quote)
          {
            if (sensePara.Childs.Count != 0)
            {
              sensePara.AppendChild(new Run("; ") { FontSize = 15 });
            }
            sensePara.AppendChild(new Run(quote) { FontSize = 15 });
          }

          tr.ReadToFollowing("cit");
        }

      }


      return doc;
    }

    /// <summary>
    /// Converts HTML content returned by a dictionary to a <see cref="Section"/>.
    /// </summary>
    /// <param name="dictionary">The dictionary. It is neccessary to retrieve CSS files referenced by the HTML content.</param>
    /// <param name="htmlContent">The HTML to convert.</param>
    /// <returns>A <see cref="Section"/> that represents the HTML content.</returns>
    public Section ConvertHtmlContentToSection(IWordDictionary dictionary, string htmlContent)
    {
      Func<string, string, string> cssStyleSheetProvider = (cssFileName, refFileName) =>
      {
        if (dictionary.TryGetValue(cssFileName, out var entry))
        {
          return entry.Content;
        }
        else
        {
          return null;
        }
      };

      try
      {
        var section = (Section)_converter.Convert(htmlContent, false, cssStyleSheetProvider, null);
        return section;
      }
      catch (Exception ex)
      {

      }


      return null;

    }

    /// <summary>
    /// Converts HTML content returned by a dictionary to a <see cref="Section"/>.
    /// </summary>
    /// <param name="dictionary">The dictionary. It is neccessary to retrieve CSS files referenced by the HTML content.</param>
    /// <param name="htmlContent">The HTML to convert.</param>
    /// <returns>A <see cref="Section"/> that represents the HTML content.</returns>
    public Section ConvertXHtmlContentToSection(IWordDictionary dictionary, string htmlContent)
    {
      Func<string, string, string> cssStyleSheetProvider = (cssFileName, refFileName) =>
      {
        if (dictionary.TryGetValue(cssFileName, out var entry))
        {
          return entry.Content;
        }
        else
        {
          return DefaultStyleSheet;
        }
      };

      try
      {
        var section = (Section)_converter.ConvertXHtml(htmlContent, false, cssStyleSheetProvider, null);
        return section;
      }
      catch (Exception ex)
      {

      }


      return null;

    }

    const string DefaultStyleSheet =
    """
    body {
      font-family: Arial, sans-serif;
      font-size: 14px;
      line-height: 1.5;
    }
    
    h1 {
      font-size: 24px;
      margin-bottom: 2px;
    }
    
    h2 {
      font-size: 20px;
      margin-top: 10px;
      margin-bottom: 10px;
    }
    
    h3 {
      font-size: 17px;
      margin-bottom: 7px;
    }
    
    p {
      font-size: 14px;
    }
    """;


    /// <summary>
    /// Tries to find the key <paramref name="searchText"/> in the dictionary.
    /// </summary>
    /// <param name="searchText">The text to search. If this original text was not found, on return, the parameter contains the key for which the content is returned.</param>
    /// <param name="dictionary">The dictionary.</param>
    /// <returns>A tuple consisting of the content, the content identifer, and a boolean. The boolean is true if the original search text was found in the dictionary.
    /// If the original search text was not found, the boolean is false, and <paramref name="searchText"/>contains the search text that was found.</returns>
    private (string Content, string ContentId, bool foundOriginal) GetResult(ref string searchText, IWordDictionary dictionary)
    {
      var searchKey = _compareInfo.GetSortKey(searchText);
      var index = Array.BinarySearch(_sortKeys, searchKey, new UnicodeStringSorter());


      (string Content, string ContentId) result = (null, null);
      bool found = false;

      if (index >= 0)
      {
        result = dictionary[searchText];
        found = true;
      }
      else
      {
        index = ~index;

        if (index < _keys.Length)
        {
          searchText = _keys[index];
          result = dictionary[searchText];
        }
      }

      return (result.Content, result.ContentId, found);
    }

    public FlowDocument ShowContent(params (IWordDictionary Dictionary, string ContentText, string ContentID, string SearchKey)[] contents)
    {
      var doc = new FlowDocument();

      foreach (var (Dictionary, ContentText, ContentID, SearchKey) in contents)
      {
        if (string.IsNullOrEmpty(ContentID) || string.IsNullOrEmpty(ContentText) || string.IsNullOrEmpty(SearchKey))
          continue;

        if (ContentID.StartsWith("text/html"))
        {
          var section = ConvertHtmlContentToSection(Dictionary, ContentText);
          if (null != section)
            doc.AppendChild(section);

        }
        if (ContentID.StartsWith("text/xhtml"))
        {
          var section = ConvertXHtmlContentToSection(Dictionary, ContentText);
          if (null != section)
            doc.AppendChild(section);

        }
        else if (ContentID.StartsWith("text/plain"))
        {
          var section = ConvertTextContentToSection(SearchKey, ContentText);
          if (null != section)
            doc.AppendChild(section);

        }
        else if (ContentID.StartsWith("application/tei+xml"))
        {
          var section = ConvertTeiContentToSection(ContentText);
          doc.AppendChild(section);
        }
      }

      FlowDocument = doc;
      return doc;
    }




  }
}