DeleteDataCommand.cs

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using VDS.RDF.Query.Patterns;

namespace VDS.RDF.Update.Commands
{
    /// <summary>
    /// Represents a SPARQL Update DELETE DATA command.
    /// </summary>
    public class DeleteDataCommand : SparqlUpdateCommand
    {
        private GraphPattern _pattern;

        /// <summary>
        /// Creates a new DELETE DATA command.
        /// </summary>
        /// <param name="pattern">Pattern composed of concrete Triples to delete.</param>
        public DeleteDataCommand(GraphPattern pattern)
            : base(SparqlUpdateCommandType.DeleteData) 
        {
            if (!IsValidDataPattern(pattern, true)) throw new SparqlUpdateException("Cannot create a DELETE DATA command where any of the Triple Patterns are not concrete triples (Variables/Blank Nodes are not permitted) or a GRAPH clause has nested Graph Patterns");
            _pattern = pattern;
        }

        /// <summary>
        /// Determines whether a Graph Pattern is valid for use in an DELETE DATA command.
        /// </summary>
        /// <param name="p">Graph Pattern.</param>
        /// <param name="top">Is this the top level pattern?.</param>
        /// <returns></returns>
        public static bool IsValidDataPattern(GraphPattern p, bool top)
        {
            if (p.IsGraph)
            {
                // If a GRAPH clause then all triple patterns must be constructable and have no Child Graph Patterns
                return !p.HasChildGraphPatterns && p.TriplePatterns.All(tp => tp is IConstructTriplePattern && ((IConstructTriplePattern)tp).HasNoVariables);
            }
            else if (p.IsExists || p.IsMinus || p.IsNotExists || p.IsOptional || p.IsService || p.IsSubQuery || p.IsUnion)
            {
                // EXISTS/MINUS/NOT EXISTS/OPTIONAL/SERVICE/Sub queries/UNIONs are not permitted
                return false;
            }
            else
            {
                // For other patterns all Triple patterns must be constructable with no explicit variables
                // If top level then any Child Graph Patterns must be valid
                // Otherwise must have no Child Graph Patterns
                return p.TriplePatterns.All(tp => tp is IConstructTriplePattern && ((IConstructTriplePattern)tp).HasNoVariables) && ((top && p.ChildGraphPatterns.All(gp => IsValidDataPattern(gp, false))) || !p.HasChildGraphPatterns);
            }
        }

        /// <summary>
        /// Gets the Data Pattern containing Triples to delete.
        /// </summary>
        public GraphPattern DataPattern
        {
            get
            {
                return _pattern;
            }
        }

        /// <summary>
        /// Gets whether the Command affects a single Graph.
        /// </summary>
        public override bool AffectsSingleGraph
        {
            get
            {
                if (!_pattern.HasChildGraphPatterns)
                {
                    return true;
                }
                else
                {
                    var affectedUris = new List<string>();
                    if (_pattern.IsGraph)
                    {
                        affectedUris.Add(_pattern.GraphSpecifier.Value);
                    }
                    else
                    {
                        affectedUris.Add(null);
                    }
                    affectedUris.AddRange(from p in _pattern.ChildGraphPatterns
                                          where p.IsGraph
                                          select p.GraphSpecifier.Value);

                    return affectedUris.Distinct().Count() <= 1;
                }
            }
        }

        /// <summary>
        /// Gets whether the Command affects a given Graph.
        /// </summary>
        /// <param name="graphUri">Graph URI.</param>
        /// <returns></returns>
        [Obsolete("Replaced by AffectsGraph(IRefNode)")]
        public override bool AffectsGraph(Uri graphUri)
        {
            var affectedUris = new List<string>();
            if (_pattern.IsGraph)
            {
                affectedUris.Add(_pattern.GraphSpecifier.Value);
            }
            else
            {
                affectedUris.Add(string.Empty);
            }
            if (_pattern.HasChildGraphPatterns)
            {
                affectedUris.AddRange(from p in _pattern.ChildGraphPatterns
                                      where p.IsGraph
                                      select p.GraphSpecifier.Value);
            }
            if (affectedUris.Any(u => u != null)) affectedUris.Add(string.Empty);

            return affectedUris.Contains(graphUri.ToSafeString());
        }

        /// <summary>
        /// Gets whether the Command affects a given Graph.
        /// </summary>
        /// <param name="graphName">Graph name.</param>
        /// <returns></returns>
        public override bool AffectsGraph(IRefNode graphName)
        {
            var affectedUris = new List<string>();
            if (_pattern.IsGraph)
            {
                affectedUris.Add(_pattern.GraphSpecifier.Value);
            }
            else
            {
                affectedUris.Add(string.Empty);
            }

            if (_pattern.HasChildGraphPatterns)
            {
                affectedUris.AddRange(from p in _pattern.ChildGraphPatterns
                    where p.IsGraph
                    select p.GraphSpecifier.Value);
            }

            if (affectedUris.Any(u => u != null)) affectedUris.Add(string.Empty);

            return affectedUris.Contains(graphName.ToSafeString());
        }


        /// <summary>
        /// Processes the Command using the given Update Processor.
        /// </summary>
        /// <param name="processor">SPARQL Update Processor.</param>
        public override void Process(ISparqlUpdateProcessor processor)
        {
            processor.ProcessDeleteDataCommand(this);
        }

        /// <summary>
        /// Gets the String representation of the Command.
        /// </summary>
        /// <returns></returns>
        public override string ToString()
        {
            var output = new StringBuilder();
            output.AppendLine("DELETE DATA");
            if (_pattern.IsGraph) output.AppendLine("{");
            output.AppendLine(_pattern.ToString());
            if (_pattern.IsGraph) output.AppendLine("}");
            return output.ToString();
        }
    }
}