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A shape-based JSON modelling framework.
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/*
 * Copyright © 2013-2022 Metreeca srl
 *
 * Licensed 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 com.metreeca.json;

import com.metreeca.json.queries.*;

import org.eclipse.rdf4j.model.IRI;

import java.util.*;
import java.util.function.Function;

import static java.lang.String.format;
import static java.util.Collections.unmodifiableList;


/**
 * Shape-driven linked data query.
 */
public abstract class Query {

	private final Shape shape;

	private final List path;
	private final List orders;

	private final int offset;
	private final int limit;


	protected Query(final Shape shape,
			final List path, final List orders,
			final int offset, final int limit
	) {

		if ( shape == null ) {
			throw new NullPointerException("null shape");
		}

		if ( path == null || path.stream().anyMatch(Objects::isNull) ) {
			throw new NullPointerException("null path or path IRI");
		}

		if ( orders == null ) {
			throw new NullPointerException("null orders");
		}

		if ( offset < 0 ) {
			throw new IllegalArgumentException("illegal offset <"+offset+">");
		}

		if ( limit < 0 ) {
			throw new IllegalArgumentException("illegal limit <"+limit+">");
		}

		this.shape=shape;

		this.path=new ArrayList<>(path);
		this.orders=new ArrayList<>(orders);

		this.offset=offset;
		this.limit=limit;
	}


	public Shape shape() {
		return shape;
	}


	public List path() {
		return unmodifiableList(path);
	}

	public List orders() {
		return unmodifiableList(orders);
	}


	public int offset() {
		return offset;
	}

	public int limit() {
		return limit;
	}


	////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

	public abstract  V map(final Probe probe);

	public final  V map(final Function mapper) {

		if ( mapper == null ) {
			throw new NullPointerException("null mapper");
		}

		return mapper.apply(this);
	}


	////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

	@Override public boolean equals(final Object object) {
		return this == object || getClass().equals(object.getClass())
				&& shape.equals(((Query)object).shape)
				&& path.equals(((Query)object).path)
				&& orders.equals(((Query)object).orders)
				&& offset == ((Query)object).offset
				&& limit == ((Query)object).limit;
	}

	@Override public int hashCode() {
		return shape.hashCode()
				^path.hashCode()
				^orders.hashCode()
				^Integer.hashCode(offset)
				^Integer.hashCode(limit);
	}

	@Override public String toString() {
		return format(
				"%s {\n\tshape: %s\n\tpath: %s\n\torder: %s\n\toffset: %d\n\tlimit: %d\n}",
				getClass().getSimpleName().toLowerCase(Locale.ROOT),
				Values.indent(shape.toString()),
				path, orders, offset, limit
		);
	}


	////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

	/**
	 * Query probe.
	 *
	 * Generates a result by probing queries.
	 *
	 * @param  the type of the generated result value
	 */
	public abstract static class Probe implements Function {

		@Override public final V apply(final Query query) {
			return query == null ? null : query.map(this);
		}


		//// Queries ///////////////////////////////////////////////////////////////////////////////////////////////////

		public V probe(final Items items) { return probe((Query)items); }

		public V probe(final Terms terms) { return probe((Query)terms); }

		public V probe(final Stats stats) { return probe((Query)stats); }


		//// Fallback //////////////////////////////////////////////////////////////////////////////////////////////////

		/**
		 * Probes a generic query.
		 *
		 * @param query the generic query to be probed
		 *
		 * @return the result generated by probing {@code query}; by default {@code null}
		 */
		public V probe(final Query query) { return null; }

	}

}