DeleteCommand.cs

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

namespace VDS.RDF.Update.Commands
{
    /// <summary>
    /// Represents the SPARQL Update DELETE command.
    /// </summary>
    public class DeleteCommand : BaseModificationCommand
    {
        /// <summary>
        /// Creates a new DELETE command.
        /// </summary>
        /// <param name="deletions">Pattern to construct Triples to delete.</param>
        /// <param name="where">Pattern to select data which is then used in evaluating the deletions pattern.</param>
        /// <param name="graphUri">URI of the affected Graph.</param>
        [Obsolete("Replaced by DeleteCommand(GraphPatten, GraphPatter, IRefNode")]
        public DeleteCommand(GraphPattern deletions, GraphPattern where, Uri graphUri)
            : base(SparqlUpdateCommandType.Delete)
        {
            if (!IsValidDeletePattern(deletions, true)) throw new SparqlUpdateException("Cannot create a DELETE command where any of the Triple Patterns are not constructable triple patterns (Blank Node Variables are not permitted) or a GRAPH clause has nested Graph Patterns");

            DeletePattern = deletions;
            WherePattern = where;
            WithGraphName = graphUri == null ? null : new UriNode(graphUri);
        }

        /// <summary>
        /// Creates a new DELETE command.
        /// </summary>
        /// <param name="deletions">Pattern to construct Triples to delete.</param>
        /// <param name="where">Pattern to select data which is then used in evaluating the deletions pattern.</param>
        /// <param name="graphName">Name of the affected Graph.</param>
        public DeleteCommand(GraphPattern deletions, GraphPattern where, IRefNode graphName)
            : base(SparqlUpdateCommandType.Delete)
        {
            if (!IsValidDeletePattern(deletions, true)) throw new SparqlUpdateException("Cannot create a DELETE command where any of the Triple Patterns are not constructable triple patterns (Blank Node Variables are not permitted) or a GRAPH clause has nested Graph Patterns");

            DeletePattern = deletions;
            WherePattern = where;
            WithGraphName = graphName;
        }
        /// <summary>
        /// Creates a new DELETE command which operates on the Default Graph.
        /// </summary>
        /// <param name="deletions">Pattern to construct Triples to delete.</param>
        /// <param name="where">Pattern to select data which is then used in evaluating the deletions pattern.</param>
        public DeleteCommand(GraphPattern deletions, GraphPattern where)
            : base(SparqlUpdateCommandType.Delete)
        {
            if (!IsValidDeletePattern(deletions, true)) throw new SparqlUpdateException("Cannot create a DELETE command where any of the Triple Patterns are not constructable triple patterns (Blank Node Variables are not permitted) or a GRAPH clause has nested Graph Patterns");

            DeletePattern = deletions;
            WherePattern = where;
        }

        /// <summary>
        /// Creates a new DELETE command. 
        /// </summary>
        /// <param name="where">Pattern to construct Triples to delete.</param>
        /// <param name="graphUri">URI of the affected Graph.</param>
        [Obsolete("Replaced by DeleteCommand(GraphPattern, IRefNode)")]
        public DeleteCommand(GraphPattern where, Uri graphUri)
            : this(where, where, graphUri) { }

        /// <summary>
        /// Creates a new DELETE command. 
        /// </summary>
        /// <param name="where">Pattern to construct Triples to delete.</param>
        /// <param name="graphName">Name of the affected Graph.</param>
        public DeleteCommand(GraphPattern where, IRefNode graphName)
            : this(where, where, graphName)
        {
        }

        /// <summary>
        /// Createa a new DELETE command which operates on the Default Graph.
        /// </summary>
        /// <param name="where">Pattern to construct Triples to delete.</param>
        public DeleteCommand(GraphPattern where)
            : this(where, where, (IRefNode)null) { }

        /// <summary>
        /// Gets whether the Command affects a single Graph.
        /// </summary>
        public override bool AffectsSingleGraph
        {
            get
            {
                var affectedUris = new List<string>();
                if (TargetGraph != null)
                {
                    affectedUris.Add(TargetGraph.ToString());
                }
                if (DeletePattern.IsGraph) affectedUris.Add(DeletePattern.GraphSpecifier.Value);
                if (DeletePattern.HasChildGraphPatterns)
                {
                    affectedUris.AddRange(from p in DeletePattern.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 (TargetUri != null)
            {
                affectedUris.Add(TargetUri.AbsoluteUri);
            }
            else
            {
                affectedUris.Add(string.Empty);
            }
            if (DeletePattern.IsGraph) affectedUris.Add(DeletePattern.GraphSpecifier.Value);
            if (DeletePattern.HasChildGraphPatterns)
            {
                affectedUris.AddRange(from p in DeletePattern.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 will potentially affect the given Graph.
        /// </summary>
        /// <param name="graphName">Graph name.</param>
        /// <returns></returns>
        public override bool AffectsGraph(IRefNode graphName)
        {
            var affectedUris = new List<string> {TargetGraph.ToSafeString()};

            if (DeletePattern.IsGraph)
            {
                affectedUris.Add(DeletePattern.GraphSpecifier.Value);
            }
            if (DeletePattern.HasChildGraphPatterns)
            {
                affectedUris.AddRange(from p in DeletePattern.ChildGraphPatterns
                    where p.IsGraph
                    select p.GraphSpecifier.Value);
            }
            if (affectedUris.Any(u => u != null)) affectedUris.Add(string.Empty);

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

        /// <summary>
        /// Gets the URI of the Graph the deletions are made from.
        /// </summary>
        [Obsolete("Replaced by TargetGraph")]
        public Uri TargetUri
        {
            get
            {
                return (WithGraphName as UriNode)?.Uri;
            }
        }

        /// <summary>
        /// Gets the name of the graph the deletions are made from.
        /// </summary>
        public IRefNode TargetGraph => WithGraphName;
       
        /// <summary>
        /// Gets the pattern used for Deletions.
        /// </summary>
        public GraphPattern DeletePattern { get; }

        /// <summary>
        /// Gets the pattern used for the WHERE clause.
        /// </summary>
        public GraphPattern WherePattern { get; }

        /// <summary>
        /// Optimises the Commands WHERE pattern.
        /// </summary>
        public override void Optimise(IQueryOptimiser optimiser)
        {
            WherePattern.Optimise(optimiser);
        }


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

        /// <summary>
        /// Gets the String representation of the Command.
        /// </summary>
        /// <returns></returns>
        public override string ToString()
        {
            var output = new StringBuilder();
            var formatter = new SparqlFormatter();
            if (WithGraphName != null)
            {
                output.Append("WITH ");
                output.AppendLine(formatter.Format(WithGraphName));
            }
            output.AppendLine("DELETE");
            if (!ReferenceEquals(DeletePattern, WherePattern)) output.AppendLine(DeletePattern.ToString());
            if (_usingUris != null)
            {
                foreach (Uri u in _usingUris)
                {
                    output.AppendLine("USING <" + u.AbsoluteUri.Replace(">", "\\>") + ">");
                }
            }
            if (_usingNamedUris != null)
            {
                foreach (Uri u in _usingNamedUris)
                {
                    output.AppendLine("USING NAMED <" + u.AbsoluteUri.Replace(">", "\\>") + ">");
                }
            }
            output.AppendLine("WHERE");
            output.AppendLine(WherePattern.ToString());
            return output.ToString();
        }
    }
}