SemanticQueryTriple.cs

using System.Text;
using Waher.Content.Semantic;
using Waher.Content.Semantic.Model;
using Waher.Script.Model;
 
namespace Waher.Script.Persistence.SPARQL
{
    public enum QueryTripleType
    {
        Constant = 0,
 
        SubjectVariable = 1,
 
        PredicateVariable = 2,
 
        SubjectPredicateVariables = 3,
 
        ObjectVariable = 4,
 
        SubjectObjectVariable = 5,
 
        PredicateObjectVariable = 6,
 
        SubjectPredicateObjectVariable = 7
    }
 
    public class SemanticQueryTriple : ISemanticTriple
    {
        public SemanticQueryTriple(ISemanticTriple Triple)
            : this(Triple.Subject, Triple.Predicate, Triple.Object)
        {
        }
 
        public SemanticQueryTriple(ISemanticElement Subject, ISemanticElement Predicate,
            ISemanticElement Object)
        {
            this.Subject = Subject;
            this.Predicate = Predicate;
            this.Object = Object;
 
            int i = 0;
 
            if (Subject is SemanticScriptElement ScriptElement &&
                ScriptElement.Node is VariableReference VarRef)
            {
                this.SubjectIsVariable = true;
                this.SubjectVariable = VarRef.VariableName;
                i = 1;
            }
            else if (Subject is BlankNode Node)  // §4.1.4: Blank nodes in graph patterns act as variables
            {
                this.SubjectIsVariable = true;
                this.SubjectVariable = Node.ToString();
                i = 1;
            }
            else
            {
                this.SubjectIsVariable = false;
                this.SubjectVariable = null;
            }
 
            if (Predicate is SemanticScriptElement ScriptElement2 &&
                ScriptElement2.Node is VariableReference VarRef2)
            {
                this.PredicateIsVariable = true;
                this.PredicateVariable = VarRef2.VariableName;
                i += 2;
            }
            else if (Predicate is BlankNode Node)  // §4.1.4: Blank nodes in graph patterns act as variables
            {
                this.PredicateIsVariable = true;
                this.PredicateVariable = Node.ToString();
                i += 2;
            }
            else
            {
                this.PredicateIsVariable = false;
                this.PredicateVariable = null;
            }
 
            if (Object is SemanticScriptElement ScriptElement3 &&
                ScriptElement3.Node is VariableReference VarRef3)
            {
                this.ObjectIsVariable = true;
                this.ObjectVariable = VarRef3.VariableName;
                i += 4;
            }
            else if (Object is BlankNode Node)  // §4.1.4: Blank nodes in graph patterns act as variables
            {
                this.ObjectIsVariable = true;
                this.ObjectVariable = Node.ToString();
                i += 4;
            }
            else
            {
                this.ObjectIsVariable = false;
                this.ObjectVariable = null;
            }
 
            this.Type = (QueryTripleType)i;
        }
 
        public ISemanticElement Subject { get; }
 
        public ISemanticElement Predicate { get; }
 
        public ISemanticElement Object { get; }
 
        public bool SubjectIsVariable { get; }
 
        public bool PredicateIsVariable { get; }
 
        public bool ObjectIsVariable { get; }
 
        public string SubjectVariable { get; }
 
        public string PredicateVariable { get; }
 
        public string ObjectVariable { get; }
 
        public QueryTripleType Type { get; }
 
        public ISemanticElement this[int Index]
        {
            get
            {
                switch (Index)
                {
                    case 0: return this.Subject;
                    case 1: return this.Predicate;
                    case 2: return this.Object;
                    default: return null;
                }
            }
        }
 
        public string VariableName(int Index)
        {
            switch (Index)
            {
                case 0: return this.SubjectVariable;
                case 1: return this.PredicateVariable;
                case 2: return this.ObjectVariable;
                default: return null;
            }
        }
 
        public override string ToString()
        {
            StringBuilder sb = new StringBuilder();
 
            if (this.SubjectIsVariable)
            {
                sb.Append('?');
                sb.Append(this.SubjectVariable);
            }
            else
                sb.Append(this.Subject.ToString());
 
            sb.Append('\t');
 
            if (this.PredicateIsVariable)
            {
                sb.Append('?');
                sb.Append(this.PredicateVariable);
            }
            else
                sb.Append(this.Predicate.ToString());
 
            sb.Append('\t');
 
            if (this.ObjectIsVariable)
            {
                sb.Append('?');
                sb.Append(this.ObjectVariable);
            }
            else
                sb.Append(this.Object.ToString());
 
            return base.ToString();
        }
    }
}