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// 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.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
namespace SlobViewer.Collections.Text
{
/// <summary>
/// Determination of those strings from a string array, which have the longest common substrings with a provided string.
/// </summary>
public class LongestCommonSubstringsOfStringAndStringArray
{
private LongestCommonSubstringOfTwoStrings _twoStringsEvaluator = new LongestCommonSubstringOfTwoStrings();
private int[] _counts = new int[0];
private string[] _yTemp = new string[0];
/// <summary>
/// Evaluates the strings from array <paramref name="Y"/>, which have the longest common
/// substrings with string <paramref name="X"/>. Those strings can then be found in <see cref="BestMatches"/>.
/// </summary>
/// <param name="X">The first string.</param>
/// <param name="Y">The array of strings.</param>
/// <param name="cancellationToken">Cancellation token.</param>
public void Evaluate(string X, string[] Y, CancellationToken cancellationToken)
{
if (Y.Length != _yTemp.Length)
{
_yTemp = new string[Y.Length];
_counts = new int[Y.Length];
}
if (cancellationToken.IsCancellationRequested)
{
return;
}
Array.Copy(Y, _yTemp, Y.Length);
for (int i = 0; i < Y.Length; ++i)
{
_counts[i] = _twoStringsEvaluator.LongestCommonSubstring(X, Y[i]);
if (cancellationToken.IsCancellationRequested)
{
return;
}
}
Array.Sort(_counts, _yTemp);
}
/// <summary>
/// Preallocates storage space to help avoid repeated allocations.
/// </summary>
/// <param name="maxLengthOfFirstString">The maximum length of the first string.</param>
/// <param name="maxLengthOfArrayStrings">The maximum length of the strings in the string array.</param>
/// <returns></returns>
public LongestCommonSubstringsOfStringAndStringArray Preallocate(int maxLengthOfFirstString, int maxLengthOfArrayStrings)
{
_twoStringsEvaluator.Preallocate(maxLengthOfFirstString, maxLengthOfArrayStrings);
return this;
}
/// <summary>
/// Gets the best matches.
/// </summary>
/// <value>
/// The best matches. Returns tuples, containing the string, and the length of the longest common substring of this match with the search string.
/// </value>
public IEnumerable<(string Phrase, int CommonCharCount)> BestMatches
{
get
{
for (int i = _yTemp.Length - 1; i >= 0; --i)
{
yield return (_yTemp[i], _counts[i]);
}
}
}
}
}
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