Possibility.cs

using System.Collections;
using System.Collections.Generic;
using System.Text;
using Waher.Content.Semantic;
using Waher.Content.Semantic.Model.Literals;
 
namespace Waher.Script.Persistence.SPARQL
{
    public class Possibility : ISparqlResultRecord, ISparqlResultItem
    {
        public Possibility(string VariableName, ISemanticElement Value)
            : this(VariableName, Value, null)
        {
        }
 
        public Possibility(string VariableName, ISemanticElement Value, Possibility NextVariable)
        {
            this.Name = VariableName;
            this.Value = Value ?? new NullValue();
            this.NextVariable = NextVariable;
        }
 
        public string Name { get; }
 
        public ISemanticElement Value { get; set; }
 
        public Possibility NextVariable { get; private set; }
 
        public ISemanticElement this[string VariableName]
        {
            get => this.GetValue(VariableName);
            set => this.SetValue(VariableName, value);
        }
 
        public ISemanticElement GetValue(string VariableName)
        {
            if (this.Name == VariableName)
                return this.Value;
 
            Possibility Loop = this.NextVariable;
            while (!(Loop is null))
            {
                if (Loop.Name == VariableName)
                    return Loop.Value;
 
                Loop = Loop.NextVariable;
            }
 
            return null;
        }
 
        public void SetValue(string VariableName, ISemanticElement Value)
        {
            if (this.Name == VariableName)
                this.Value = Value;
            else
            {
                Possibility Loop = this;
 
                while (!(Loop.NextVariable is null) && Loop.NextVariable.Name != VariableName)
                    Loop = Loop.NextVariable;
 
                if (Loop.NextVariable is null)
                    Loop.NextVariable = new Possibility(VariableName, Value);
                else
                    Loop.NextVariable.Value = Value;
            }
        }
 
        public override string ToString()
        {
            return GetSortedDescription(this);
        }
 
        public static string GetSortedDescription(Possibility P)
        {
            SortedDictionary<string, ISemanticElement> Sorted = new SortedDictionary<string, ISemanticElement>();
 
            while (!(P is null))
            {
                Sorted[P.Name] = P.Value;
                P = P.NextVariable;
            }
 
            StringBuilder sb = new StringBuilder();
            bool First = true;
 
            foreach (KeyValuePair<string, ISemanticElement> P2 in Sorted)
            {
                if (First)
                    First = false;
                else
                    sb.Append(", ");
 
                sb.Append(P2.Key);
                sb.Append(':');
                sb.Append(P2.Value.ToString());
            }
 
            return sb.ToString();
        }
 
        public IEnumerator<ISparqlResultItem> GetEnumerator()
        {
            return new PossibilityEnumerator(this);
        }
 
        IEnumerator IEnumerable.GetEnumerator()
        {
            return new PossibilityEnumerator(this);
        }
 
        private class PossibilityEnumerator : IEnumerator<ISparqlResultItem>
        {
            private readonly Possibility first;
            private Possibility current;
 
            public PossibilityEnumerator(Possibility First)
            {
                this.first = First;
                this.current = null;
            }
 
            public ISparqlResultItem Current => this.current;
            object IEnumerator.Current => this.current;
 
            public void Dispose() { }
 
            public bool MoveNext()
            {
                if (this.current is null)
                    this.current = this.first;
                else
                    this.current = this.current.NextVariable;
 
                return !(this.current is null);
            }
 
            public void Reset()
            {
                this.current = null;
            }
        }
    }
}