public void OverloadsTest()
{
var ac = new AhoCorasick(new List <string> {
"a"
});
CollectionAssert.AreEqual(new WordMatchList {
{ 0, "a" }
}, ac.Search("a").ToList());
Assert.AreEqual(0, ac.Search("b").Count());
ac = new AhoCorasick(CharComparer.OrdinalIgnoreCase, new List <string> {
"a", "ab", "bab", "bC", "bca", "c", "caa"
});
var m = ac.Search("abCcab").ToList();
var expected = new WordMatchList {
{ 0, "a" }, { 0, "ab" }, { 1, "bC" }, { 2, "c" }, { 3, "c" }, { 4, "a" }, { 4, "ab" }
};
CollectionAssert.AreEqual(expected, m);
ac = new AhoCorasick();
ac.Add("a");
ac.BuildFail();
CollectionAssert.AreEqual(new WordMatchList {
{ 0, "a" }
}, ac.Search("a").ToList());
Assert.AreEqual(0, ac.Search("b").Count());
ac = new AhoCorasick(CharComparer.Create(CultureInfo.InvariantCulture, true), "a", "ab", "bab", "bc", "bca", "c", "caa");
m = ac.Search("abccab").ToList();
expected = new WordMatchList {
{ 0, "a" }, { 0, "ab" }, { 1, "bc" }, { 2, "c" }, { 3, "c" }, { 4, "a" }, { 4, "ab" }
};
CollectionAssert.AreEqual(expected, m);
}
public static AhoCorasick ComputeRules(
List <string> rules,
Dictionary <string, List <Expression> > groupByLonguestCommonExpression)
{
int nextId = 0;
for (int i = 0; i < rules.Count; i++)
{
var pattern = rules[i];
pattern = RemoveAccents(pattern);
pattern = pattern.ToLower();
// We will take the longuest fixed expression.
var longuestCommonExpression = pattern
.Split(new char[] { '*' }, StringSplitOptions.RemoveEmptyEntries)
.OrderByDescending(m => m.Length)
.First();
var matches = regexKeepWordOnly.Matches(longuestCommonExpression);
var words = matches.Select(m => m.Value);
longuestCommonExpression = string.Join(' ', words);
// Exact expression is faster.
var exactExpression = !pattern.Contains("*");
if (exactExpression)
{
// Exact word or group of words. (add extra space to prevent matching)
longuestCommonExpression = " " + longuestCommonExpression + " ";
}
else
{
// We are using only a part of the expression.
// We will not append extra space.
}
// Prepare the future Regex.
var matches2 = regexKeepWordOnlyAndSpecialCharacters.Matches(pattern);
var words2 = matches2.Select(m => m.Value.Replace("*", "[\\p{L}]+"));
pattern = string.Join(' ', words2);
if (!groupByLonguestCommonExpression.ContainsKey(longuestCommonExpression))
{
groupByLonguestCommonExpression[longuestCommonExpression] =
new List <Expression>();
}
var expr = new Expression
{
Id = nextId++,
Expr = rules[i],
IsExactExpression = exactExpression
};
if (!exactExpression)
{
// The pattern will be use if it is not an exact expression
// to resolve the wildcard.
expr.Pattern = pattern;
}
groupByLonguestCommonExpression[longuestCommonExpression].Add(expr);
}
var keywords = groupByLonguestCommonExpression.Select(m => m.Key).ToList();
// We are using the Aho–Corasick algorithm.
// (https://en.wikipedia.org/wiki/Aho%E2%80%93Corasick_algorithm)
// Unfortunately, it doesn't support wildcard.
// But, we will use the longuest fixed expression.
// So, we reduce the complexities and the number of regex check.
// The algorithm will tell us which Regex to evaluate.
// But, if it is an exact expression, no need to do extra processing.
AhoCorasick treeAhoCorasick = new AhoCorasick();
treeAhoCorasick.Add(keywords);
treeAhoCorasick.BuildFail();
return(treeAhoCorasick);
}
