/**
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements. See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership. The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
    *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.rdf.experimental;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.nio.charset.StandardCharsets;
  import java.nio.file.Path;
  import java.util.Optional;
  import java.util.concurrent.Future;
  import java.util.function.Consumer;
  
  import org.apache.commons.rdf.api.BlankNode;
  import org.apache.commons.rdf.api.Dataset;
  import org.apache.commons.rdf.api.Graph;
  import org.apache.commons.rdf.api.IRI;
  import org.apache.commons.rdf.api.Quad;
  import org.apache.commons.rdf.api.RDFSyntax;
  import org.apache.commons.rdf.api.RDFTerm;
  import org.apache.commons.rdf.api.RDF;
  import org.apache.commons.rdf.api.Triple;
  
  /**
   * Parse an RDF source into a target (e.g. a Graph/Dataset).
   * <h2>Experimental</h2> This interface (and its implementations) should be
   * considered <strong>at risk</strong>; they might change or be removed in the
   * next minor update of Commons RDF. It may move to the the
   * {@link org.apache.commons.rdf.api} package when it has stabilized.
   * <h2>Description</h2>
   * <p>
   * This interface follows the
   * <a href="https://en.wikipedia.org/wiki/Builder_pattern">Builder pattern</a>,
   * allowing to set parser settings like {@link #contentType(RDFSyntax)} and
   * {@link #base(IRI)}. A caller MUST call one of the <code>source</code> methods
   * (e.g. {@link #source(IRI)}, {@link #source(Path)},
   * {@link #source(InputStream)}), and MUST call one of the <code>target</code>
   * methods (e.g. {@link #target(Consumer)}, {@link #target(Dataset)},
   * {@link #target(Graph)}) before calling {@link #parse()} on the returned
   * RDFParser - however methods can be called in any order.
   * <p>
   * The call to {@link #parse()} returns a {@link Future}, allowing asynchronous
   * parse operations. Callers are recommended to check {@link Future#get()} to
   * ensure parsing completed successfully, or catch exceptions thrown during
   * parsing.
   * <p>
   * Setting a method that has already been set will override any existing value
   * in the returned builder - regardless of the parameter type (e.g.
   * {@link #source(IRI)} will override a previous {@link #source(Path)}. Settings
   * can be unset by passing <code>null</code> - note that this may require
   * casting, e.g. <code>contentType( (RDFSyntax) null )</code> to undo a previous
   * call to {@link #contentType(RDFSyntax)}.
   * <p>
   * It is undefined if a RDFParser is mutable or thread-safe, so callers should
   * always use the returned modified RDFParser from the builder methods. The
   * builder may return itself after modification, or a cloned builder with the
   * modified settings applied. Implementations are however encouraged to be
   * immutable, thread-safe and document this. As an example starting point, see
   * <code>org.apache.commons.rdf.simple.AbstractRDFParser</code>.
   * <p>
   * Example usage:
   * </p>
   * 
   * <pre>
   * Graph g1 = rDFTermFactory.createGraph();
   * new ExampleRDFParserBuilder().source(Paths.get("/tmp/graph.ttl")).contentType(RDFSyntax.TURTLE).target(g1).parse()
   *         .get(30, TimeUnit.Seconds);
   * </pre>
   *
   */
  public interface RDFParser {
  
      /**
       * The result of {@link RDFParser#parse()} indicating parsing completed.
       * <p>
       * This is a marker interface that may be subclassed to include parser
       * details, e.g. warning messages or triple counts.
       */
      public interface ParseResult {
      }
  
      /**
       * Specify which {@link RDF} to use for generating {@link RDFTerm}s.
       * <p>
       * This option may be used together with {@link #target(Graph)} to override
      * the implementation's default factory and graph.
      * <p>
      * <strong>Warning:</strong> Using the same {@link RDF} for multiple
      * {@link #parse()} calls may accidentally merge {@link BlankNode}s having
      * the same label, as the parser may use the
      * {@link RDF#createBlankNode(String)} method from the parsed blank node
      * labels.
      * 
      * @see #target(Graph)
      * @param rdfTermFactory
      *            {@link RDF} to use for generating RDFTerms.
      * @return An {@link RDFParser} that will use the specified rdfTermFactory
      */
     RDFParser rdfTermFactory(RDF rdfTermFactory);
 
     /**
      * Specify the content type of the RDF syntax to parse.
      * <p>
      * This option can be used to select the RDFSyntax of the source, overriding
      * any <code>Content-Type</code> headers or equivalent.
      * <p>
      * The character set of the RDFSyntax is assumed to be
      * {@link StandardCharsets#UTF_8} unless overridden within the document
      * (e.g. {@code <?xml version="1.0" encoding="iso-8859-1"?>} in
      * {@link RDFSyntax#RDFXML}).
      * <p>
      * This method will override any contentType set with
      * {@link #contentType(String)}.
      * 
      * @see #contentType(String)
      * @param rdfSyntax
      *            An {@link RDFSyntax} to parse the source according to, e.g.
      *            {@link RDFSyntax#TURTLE}.
      * @throws IllegalArgumentException
      *             If this RDFParser does not support the specified RDFSyntax.
      * @return An {@link RDFParser} that will use the specified content type.
      */
     RDFParser contentType(RDFSyntax rdfSyntax) throws IllegalArgumentException;
 
     /**
      * Specify the content type of the RDF syntax to parse.
      * <p>
      * This option can be used to select the RDFSyntax of the source, overriding
      * any <code>Content-Type</code> headers or equivalent.
      * <p>
      * The content type MAY include a <code>charset</code> parameter if the RDF
      * media types permit it; the default charset is
      * {@link StandardCharsets#UTF_8} unless overridden within the document.
      * <p>
      * This method will override any contentType set with
      * {@link #contentType(RDFSyntax)}.
      * 
      * @see #contentType(RDFSyntax)
      * @param contentType
      *            A content-type string, e.g. <code>application/ld+json</code>
      *            or <code>text/turtle;charset="UTF-8"</code> as specified by
      *            <a href="https://tools.ietf.org/html/rfc7231#section-3.1.1.1">
      *            RFC7231</a>.
      * @return An {@link RDFParser} that will use the specified content type.
      * @throws IllegalArgumentException
      *             If the contentType has an invalid syntax, or this RDFParser
      *             does not support the specified contentType.
      */
     RDFParser contentType(String contentType) throws IllegalArgumentException;
 
     /**
      * Specify a {@link Graph} to add parsed triples to.
      * <p>
      * If the source supports datasets (e.g. the {@link #contentType(RDFSyntax)}
      * set has {@link RDFSyntax#supportsDataset} is true)), then only quads in
      * the <em>default graph</em> will be added to the Graph as {@link Triple}s.
      * <p>
      * It is undefined if any triples are added to the specified {@link Graph}
      * if {@link #parse()} throws any exceptions. (However implementations are
      * free to prevent this using transaction mechanisms or similar). If
      * {@link Future#get()} does not indicate an exception, the parser
      * implementation SHOULD have inserted all parsed triples to the specified
      * graph.
      * <p>
      * Calling this method will override any earlier targets set with
      * {@link #target(Graph)}, {@link #target(Consumer)} or
      * {@link #target(Dataset)}.
      * <p>
      * The default implementation of this method calls {@link #target(Consumer)}
      * with a {@link Consumer} that does {@link Graph#add(Triple)} with
      * {@link Quad#asTriple()} if the quad is in the default graph.
      * 
      * @param graph
      *            The {@link Graph} to add triples to.
      * @return An {@link RDFParser} that will insert triples into the specified
      *         graph.
      */
     default RDFParser target(final Graph graph) {
         return target(q -> {
             if (!q.getGraphName().isPresent()) {
                 graph.add(q.asTriple());
             }
         });
     }
 
     /**
      * Specify a {@link Dataset} to add parsed quads to.
      * <p>
      * It is undefined if any quads are added to the specified {@link Dataset}
      * if {@link #parse()} throws any exceptions. (However implementations are
      * free to prevent this using transaction mechanisms or similar). On the
      * other hand, if {@link #parse()} does not indicate an exception, the
      * implementation SHOULD have inserted all parsed quads to the specified
      * dataset.
      * <p>
      * Calling this method will override any earlier targets set with
      * {@link #target(Graph)}, {@link #target(Consumer)} or
      * {@link #target(Dataset)}.
      * <p>
      * The default implementation of this method calls {@link #target(Consumer)}
      * with a {@link Consumer} that does {@link Dataset#add(Quad)}.
      * 
      * @param dataset
      *            The {@link Dataset} to add quads to.
      * @return An {@link RDFParser} that will insert triples into the specified
      *         dataset.
      */
     default RDFParser target(final Dataset dataset) {
         return target(dataset::add);
     }
 
     /**
      * Specify a consumer for parsed quads.
      * <p>
      * The quads will include triples in all named graphs of the parsed source,
      * including any triples in the default graph. When parsing a source format
      * which do not support datasets, all quads delivered to the consumer will
      * be in the default graph (e.g. their {@link Quad#getGraphName()} will be
      * as {@link Optional#empty()}), while for a source
      * <p>
      * It is undefined if any quads are consumed if {@link #parse()} throws any
      * exceptions. On the other hand, if {@link #parse()} does not indicate an
      * exception, the implementation SHOULD have produced all parsed quads to
      * the specified consumer.
      * <p>
      * Calling this method will override any earlier targets set with
      * {@link #target(Graph)}, {@link #target(Consumer)} or
      * {@link #target(Dataset)}.
      * <p>
      * The consumer is not assumed to be thread safe - only one
      * {@link Consumer#accept(Object)} is delivered at a time for a given
      * {@link RDFParser#parse()} call.
      * <p>
      * This method is typically called with a functional consumer, for example:
      * 
      * <pre>
      * {@code
      * List<Quad> quads = new ArrayList<Quad>;
      * parserBuilder.target(quads::add).parse();
      * }
      * </pre>
      * 
      * @param consumer
      *            A {@link Consumer} of {@link Quad}s
      * @return An {@link RDFParser} that will call the consumer for into the
      *         specified dataset.
      */
     RDFParser target(Consumer<Quad> consumer);
 
     /**
      * Specify a base IRI to use for parsing any relative IRI references.
      * <p>
      * Setting this option will override any protocol-specific base IRI (e.g.
      * <code>Content-Location</code> header) or the {@link #source(IRI)} IRI,
      * but does not override any base IRIs set within the source document (e.g.
      * <code>@base</code> in Turtle documents).
      * <p>
      * If the source is in a syntax that does not support relative IRI
      * references (e.g. {@link RDFSyntax#NTRIPLES}), setting the
      * <code>base</code> has no effect.
      * <p>
      * This method will override any base IRI set with {@link #base(String)}.
      *
      * @see #base(String)
      * @param base
      *            An absolute IRI to use as a base.
      * @return An {@link RDFParser} that will use the specified base IRI.
      */
     RDFParser base(IRI base);
 
     /**
      * Specify a base IRI to use for parsing any relative IRI references.
      * <p>
      * Setting this option will override any protocol-specific base IRI (e.g.
      * <code>Content-Location</code> header) or the {@link #source(IRI)} IRI,
      * but does not override any base IRIs set within the source document (e.g.
      * <code>@base</code> in Turtle documents).
      * <p>
      * If the source is in a syntax that does not support relative IRI
      * references (e.g. {@link RDFSyntax#NTRIPLES}), setting the
      * <code>base</code> has no effect.
      * <p>
      * This method will override any base IRI set with {@link #base(IRI)}.
      *
      * @see #base(IRI)
      * @param base
      *            An absolute IRI to use as a base.
      * @return An {@link RDFParser} that will use the specified base IRI.
      * @throws IllegalArgumentException
      *             If the base is not a valid absolute IRI string
      */
     RDFParser base(String base) throws IllegalArgumentException;
 
     /**
      * Specify a source {@link InputStream} to parse.
      * <p>
      * The source set will not be read before the call to {@link #parse()}.
      * <p>
      * The InputStream will not be closed after parsing. The InputStream does
      * not need to support {@link InputStream#markSupported()}.
      * <p>
      * The parser might not consume the complete stream (e.g. an RDF/XML parser
      * may not read beyond the closing tag of
      * <code>&lt;/rdf:Description&gt;</code>).
      * <p>
      * The {@link #contentType(RDFSyntax)} or {@link #contentType(String)}
      * SHOULD be set before calling {@link #parse()}.
      * <p>
      * The character set is assumed to be {@link StandardCharsets#UTF_8} unless
      * the {@link #contentType(String)} specifies otherwise or the document
      * declares its own charset (e.g. RDF/XML with a
      * <code>&lt;?xml encoding="iso-8859-1"&gt;</code> header).
      * <p>
      * The {@link #base(IRI)} or {@link #base(String)} MUST be set before
      * calling {@link #parse()}, unless the RDF syntax does not permit relative
      * IRIs (e.g. {@link RDFSyntax#NTRIPLES}).
      * <p>
      * This method will override any source set with {@link #source(IRI)},
      * {@link #source(Path)} or {@link #source(String)}.
      * 
      * @param inputStream
      *            An InputStream to consume
      * @return An {@link RDFParser} that will use the specified source.
      */
     RDFParser source(InputStream inputStream);
 
     /**
      * Specify a source file {@link Path} to parse.
      * <p>
      * The source set will not be read before the call to {@link #parse()}.
      * <p>
      * The {@link #contentType(RDFSyntax)} or {@link #contentType(String)}
      * SHOULD be set before calling {@link #parse()}.
      * <p>
      * The character set is assumed to be {@link StandardCharsets#UTF_8} unless
      * the {@link #contentType(String)} specifies otherwise or the document
      * declares its own charset (e.g. RDF/XML with a
      * <code>&lt;?xml encoding="iso-8859-1"&gt;</code> header).
      * <p>
      * The {@link #base(IRI)} or {@link #base(String)} MAY be set before calling
      * {@link #parse()}, otherwise {@link Path#toUri()} will be used as the base
      * IRI.
      * <p>
      * This method will override any source set with {@link #source(IRI)},
      * {@link #source(InputStream)} or {@link #source(String)}.
      * 
      * @param file
      *            A Path for a file to parse
      * @return An {@link RDFParser} that will use the specified source.
      */
     RDFParser source(Path file);
 
     /**
      * Specify an absolute source {@link IRI} to retrieve and parse.
      * <p>
      * The source set will not be read before the call to {@link #parse()}.
      * <p>
      * If this builder does not support the given IRI protocol (e.g.
      * <code>urn:uuid:ce667463-c5ab-4c23-9b64-701d055c4890</code>), this method
      * should succeed, while the {@link #parse()} should throw an
      * {@link IOException}.
      * <p>
      * The {@link #contentType(RDFSyntax)} or {@link #contentType(String)} MAY
      * be set before calling {@link #parse()}, in which case that type MAY be
      * used for content negotiation (e.g. <code>Accept</code> header in HTTP),
      * and SHOULD be used for selecting the RDFSyntax.
      * <p>
      * The character set is assumed to be {@link StandardCharsets#UTF_8} unless
      * the protocol's equivalent of <code>Content-Type</code> specifies
      * otherwise or the document declares its own charset (e.g. RDF/XML with a
      * <code>&lt;?xml encoding="iso-8859-1"&gt;</code> header).
      * <p>
      * The {@link #base(IRI)} or {@link #base(String)} MAY be set before calling
      * {@link #parse()}, otherwise the source IRI will be used as the base IRI.
      * <p>
      * This method will override any source set with {@link #source(Path)},
      * {@link #source(InputStream)} or {@link #source(String)}.
      * 
      * @param iri
      *            An IRI to retrieve and parse
      * @return An {@link RDFParser} that will use the specified source.
      */
     RDFParser source(IRI iri);
 
     /**
      * Specify an absolute source IRI to retrieve and parse.
      * <p>
      * The source set will not be read before the call to {@link #parse()}.
      * <p>
      * If this builder does not support the given IRI (e.g.
      * <code>urn:uuid:ce667463-c5ab-4c23-9b64-701d055c4890</code>), this method
      * should succeed, while the {@link #parse()} should throw an
      * {@link IOException}.
      * <p>
      * The {@link #contentType(RDFSyntax)} or {@link #contentType(String)} MAY
      * be set before calling {@link #parse()}, in which case that type MAY be
      * used for content negotiation (e.g. <code>Accept</code> header in HTTP),
      * and SHOULD be used for selecting the RDFSyntax.
      * <p>
      * The character set is assumed to be {@link StandardCharsets#UTF_8} unless
      * the protocol's equivalent of <code>Content-Type</code> specifies
      * otherwise or the document declares its own charset (e.g. RDF/XML with a
      * <code>&lt;?xml encoding="iso-8859-1"&gt;</code> header).
      * <p>
      * The {@link #base(IRI)} or {@link #base(String)} MAY be set before calling
      * {@link #parse()}, otherwise the source IRI will be used as the base IRI.
      * <p>
      * This method will override any source set with {@link #source(Path)},
      * {@link #source(InputStream)} or {@link #source(IRI)}.
      * 
      * @param iri
      *            An IRI to retrieve and parse
      * @return An {@link RDFParser} that will use the specified source.
      * @throws IllegalArgumentException
      *             If the base is not a valid absolute IRI string
      * 
      */
     RDFParser source(String iri) throws IllegalArgumentException;
 
     /**
      * Parse the specified source.
      * <p>
      * A source method (e.g. {@link #source(InputStream)}, {@link #source(IRI)},
      * {@link #source(Path)}, {@link #source(String)} or an equivalent subclass
      * method) MUST have been called before calling this method, otherwise an
      * {@link IllegalStateException} will be thrown.
      * <p>
      * A target method (e.g. {@link #target(Consumer)},
      * {@link #target(Dataset)}, {@link #target(Graph)} or an equivalent
      * subclass method) MUST have been called before calling parse(), otherwise
      * an {@link IllegalStateException} will be thrown.
      * <p>
      * It is undefined if this method is thread-safe, however the
      * {@link RDFParser} may be reused (e.g. setting a different source) as soon
      * as the {@link Future} has been returned from this method.
      * <p>
      * The RDFParser SHOULD perform the parsing as an asynchronous operation,
      * and return the {@link Future} as soon as preliminary checks (such as
      * validity of the {@link #source(IRI)} and {@link #contentType(RDFSyntax)}
      * settings) have finished. The future SHOULD not mark
      * {@link Future#isDone()} before parsing is complete. A synchronous
      * implementation MAY be blocking on the <code>parse()</code> call and
      * return a Future that is already {@link Future#isDone()}.
      * <p>
      * The returned {@link Future} contains a {@link ParseResult}.
      * Implementations may subclass this interface to provide any parser
      * details, e.g. list of warnings. <code>null</code> is a possible return
      * value if no details are available, but parsing succeeded.
      * <p>
      * If an exception occurs during parsing, (e.g. {@link IOException} or
      * <code>org.apache.commons.rdf.simple.experimental.RDFParseException</code>),
      * it should be indicated as the
      * {@link java.util.concurrent.ExecutionException#getCause()} in the
      * {@link java.util.concurrent.ExecutionException} thrown on
      * {@link Future#get()}.
      * 
      * @return A Future that will return the populated {@link Graph} when the
      *         parsing has finished.
      * @throws IOException
      *             If an error occurred while starting to read the source (e.g.
      *             file not found, unsupported IRI protocol). Note that IO
      *             errors during parsing would instead be the
      *             {@link java.util.concurrent.ExecutionException#getCause()} of
      *             the {@link java.util.concurrent.ExecutionException} thrown on
      *             {@link Future#get()}.
      * @throws IllegalStateException
      *             If the builder is in an invalid state, e.g. a
      *             <code>source</code> has not been set.
      */
     Future<? extends ParseResult> parse() throws IOException, IllegalStateException;
 }