WildcardKeyword.cs

using System.Collections.Generic;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
 
namespace Waher.Persistence.FullTextSearch.Keywords
{
    public class WildcardKeyword : RegexKeyword
    {
        public WildcardKeyword(string Keyword)
            : this(Keyword + "*", "*")
        {
        }
 
        public WildcardKeyword(string Keyword, string Wildcard)
            : base(Database.WildcardToRegex(Keyword, Wildcard))
        {
            this.Keyword = Keyword;
            this.Wildcard = Wildcard;
        }
 
        public string Keyword { get; }
 
        public string Wildcard { get; }
 
        public override int OrderComplexity => this.Keyword.Length;
 
        public override bool Equals(object obj)
        {
            return obj is WildcardKeyword k && this.Keyword == k.Keyword && this.Wildcard == k.Wildcard;
        }
 
        public override string ToString()
        {
            return this.Keyword;
        }
 
        public override async Task<IEnumerable<KeyValuePair<string, TokenReferences>>> GetTokenReferences(SearchProcess Process)
        {
            int i = this.Keyword.IndexOf(this.Wildcard);
            if (i <= 0)
                return await base.GetTokenReferences(Process);
 
            string Preamble = this.Keyword.Substring(0, i);
            char[] Characters = Preamble.ToCharArray();
            Characters[i - 1]++;
            string ToExclusive = new string(Characters);
 
            LinkedList<KeyValuePair<string, TokenReferences>> Result = new LinkedList<KeyValuePair<string, TokenReferences>>();
            KeyValuePair<string, object>[] Records = await Process.Index.GetEntriesAsync(Preamble, ToExclusive);
 
            foreach (KeyValuePair<string, object> Rec in Records)
            {
                Match M = this.Parsed.Match(Rec.Key);
                if (M.Success && M.Index == 0 && M.Length == Rec.Key.Length && Rec.Value is TokenReferences References)
                    Result.AddLast(new KeyValuePair<string, TokenReferences>(Rec.Key, References));
            }
 
            return Result;
        }
    }
}