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GraphVizWriter.cs
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GraphVizWriter.cs
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/*
// <copyright>
// dotNetRDF is free and open source software licensed under the MIT License
// -------------------------------------------------------------------------
//
// Copyright (c) 2009-2024 dotNetRDF Project (http://dotnetrdf.org/)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is furnished
// to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
// </copyright>
*/
using System;
using System.IO;
using System.Text;
using VDS.RDF.Writing.Contexts;
namespace VDS.RDF.Writing
{
/// <summary>
/// A Writer which generates GraphViz DOT Format files from an RDF Graph.
/// </summary>
public class GraphVizWriter : BaseRdfWriter, IPrettyPrintingWriter, ICollapseLiteralsWriter
{
/// <summary>
/// Gets/Sets Pretty Print Mode for the Writer.
/// </summary>
public bool PrettyPrintMode { get; set; } = true;
/// <summary>
/// Gets/Sets whether to collapse distinct literal nodes.
/// </summary>
public bool CollapseLiterals { get; set; } = true;
/// <summary>
/// Saves a Graph into GraphViz DOT Format.
/// </summary>
/// <param name="g">Graph to save.</param>
/// <param name="filename">File to save to.</param>
public override void Save(IGraph g, string filename)
{
// Open the Stream for the File
using var output = new StreamWriter(File.OpenWrite(filename), Encoding.UTF8);
// Call the other version of Save to do the actual work
Save(g, output);
}
/// <summary>
/// Saves a Graph into GraphViz DOT Format.
/// </summary>
/// <param name="g">Graph to save.</param>
/// <param name="output">Stream to save to.</param>
protected override void SaveInternal(IGraph g, TextWriter output)
{
var context = new BaseWriterContext(g, output) { PrettyPrint = PrettyPrintMode };
WriteGraph(context, CollapseLiterals);
}
private static void WriteGraph(BaseWriterContext context, bool collapseLiterals)
{
context.Output.Write(Dot.Digraph);
if (context.Graph.BaseUri != null)
{
var graphId = ReduceToQName(context.Graph.BaseUri, context);
Prettify(Dot.Space, context);
WriteQuoted(graphId, context);
}
Prettify(Dot.Space, context);
context.Output.Write(Dot.OpenCurly);
Prettify(Dot.NewLine, context);
foreach (Triple t in context.Graph.Triples)
{
WriteTriple(t, context, collapseLiterals);
}
context.Output.Write(Dot.CloseCurly);
}
private static void WriteTriple(Triple triple, BaseWriterContext context, bool collapseLiterals)
{
if (triple.Predicate is IUriNode predicateNode)
{
// Output Node lines for Literal Node so we show them as Boxes
// This is in keeping with Standard Graph representation of RDF
// Literals are shown in Boxes, Uri Nodes in ellipses (GraphViz's default shape)
var subjectId = ProcessNode(triple, TripleSegment.Subject, context, collapseLiterals);
var objectId = ProcessNode(triple, TripleSegment.Object, context, collapseLiterals);
// Output the actual lines that state the relationship between the Nodes
// We use the Predicate as the Label on the relationship
var predicateLabel = ReduceToQName(predicateNode.Uri, context);
Prettify(Dot.Tab, context);
WriteQuoted(subjectId, context);
Prettify(Dot.Space, context);
context.Output.Write(Dot.Arrow);
Prettify(Dot.Space, context);
WriteQuoted(objectId, context);
Prettify(Dot.Space, context);
context.Output.Write(Dot.OpenSquare);
context.Output.Write(Dot.Label);
Prettify(Dot.Space, context);
context.Output.Write(Dot.Equal);
Prettify(Dot.Space, context);
WriteQuoted(predicateLabel, context);
context.Output.Write(Dot.CloseSquare);
context.Output.Write(Dot.Semicolon);
Prettify(Dot.NewLine, context);
}
}
private static string ProcessNode(Triple t, TripleSegment segment, BaseWriterContext context, bool collapseLiterals)
{
INode node = GetNode(t, segment);
switch (node)
{
case ILiteralNode literalNode:
return WriteLiteralNode(literalNode, t, context, collapseLiterals);
case IUriNode uriNode:
return ReduceToQName(uriNode.Uri, context);
case IBlankNode blankNode:
return blankNode.ToString();
default:
throw new RdfOutputException("Only Uri nodes, literal nodes and blank nodes can be converted to GraphViz DOT Format.");
}
}
private static string WriteLiteralNode(ILiteralNode literalNode, Triple t, BaseWriterContext context, bool collapseLiterals)
{
// Example output:
// "h" [label = "v", shape = box];
// where h is the hash of the triple containing the literal node
// and v is value of literal node
// Literal nodes are identified either by their value or by their containing triple.
// When identified by value, there will be a single node representing all literals with the same value.
// When identified by triple, there will be a separate node representing each triple that has an object with that value.
var idObject = collapseLiterals ? literalNode : t as object;
var nodeId = idObject.GetHashCode().ToString();
Prettify(Dot.Tab, context);
WriteQuoted(nodeId, context);
Prettify(Dot.Space, context);
context.Output.Write(Dot.OpenSquare);
context.Output.Write(Dot.Label);
Prettify(Dot.Space, context);
context.Output.Write(Dot.Equal);
Prettify(Dot.Space, context);
WriteLiteralNodeLabel(literalNode, context);
context.Output.Write(Dot.Comma);
Prettify(Dot.Space, context);
context.Output.Write(Dot.Shape);
Prettify(Dot.Space, context);
context.Output.Write(Dot.Equal);
Prettify(Dot.Space, context);
context.Output.Write(Dot.Box);
context.Output.Write(Dot.CloseSquare);
context.Output.Write(Dot.NewLine);
return nodeId;
}
private static void WriteQuoted(string value, IWriterContext context)
{
context.Output.Write(Dot.Quote);
context.Output.Write(value);
context.Output.Write(Dot.Quote);
}
private static void WriteLiteralNodeLabel(ILiteralNode literalNode, BaseWriterContext context)
{
var nodeValue = Escape(literalNode.Value);
context.Output.Write(Dot.Quote);
context.Output.Write(nodeValue);
if (!string.IsNullOrEmpty(literalNode.Language))
{
context.Output.Write("@");
context.Output.Write(literalNode.Language);
}
if (literalNode.DataType != null)
{
var datatype = ReduceToQName(literalNode.DataType, context);
context.Output.Write("^^");
context.Output.Write(datatype);
}
context.Output.Write(Dot.Quote);
}
private static string ReduceToQName(Uri uri, BaseWriterContext context)
{
if (!context.QNameMapper.ReduceToQName(uri.ToString(), out var result))
{
result = uri.ToString();
}
return result;
}
private static void Prettify(string value, BaseWriterContext context)
{
if (context.PrettyPrint)
{
context.Output.Write(value);
}
}
private static string Escape(string value)
{
value = value.Replace("\"", "\\\"");
value = value.Replace("\n", "\\n");
return value;
}
private static INode GetNode(Triple t, TripleSegment segment)
{
switch (segment)
{
case TripleSegment.Subject:
return t.Subject;
case TripleSegment.Object:
return t.Object;
default:
return null;
}
}
/// <summary>
/// Event that is raised if there is a potential problem with the RDF being output
/// </summary>
/// <remarks>This class does not raise this event.</remarks>
#pragma warning disable CS0067
public override event RdfWriterWarning Warning;
#pragma warning restore CS0067
/// <summary>
/// Gets the String representation of the writer which is a description of the syntax it produces.
/// </summary>
/// <returns></returns>
public override string ToString()
{
return "GraphViz DOT";
}
private static class Dot
{
internal const string Digraph = "digraph";
internal const string Label = "label";
internal const string Shape = "shape";
internal const string Box = "box";
internal const string Quote = "\"";
internal const string Arrow = "->";
internal const string Equal = "=";
internal const string OpenSquare = "[";
internal const string CloseSquare = "]";
internal const string OpenCurly = "{";
internal const string CloseCurly = "}";
internal const string Semicolon = ";";
internal const string Space = " ";
internal const string Tab = " ";
internal const string Comma = ",";
internal const string NewLine = "\n";
}
}
}