/*
 * 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.jena.arq.querybuilder.handlers;

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.apache.jena.arq.querybuilder.AbstractQueryBuilder;
import org.apache.jena.arq.querybuilder.Converters;
import org.apache.jena.arq.querybuilder.clauses.SelectClause;
import org.apache.jena.arq.querybuilder.rewriters.BuildElementVisitor;
import org.apache.jena.arq.querybuilder.rewriters.ElementRewriter;
import org.apache.jena.graph.Node;
import org.apache.jena.graph.NodeFactory;
import org.apache.jena.graph.Triple;
import org.apache.jena.query.Query;
import org.apache.jena.shared.PrefixMapping;
import org.apache.jena.sparql.core.TriplePath;
import org.apache.jena.sparql.core.Var;
import org.apache.jena.sparql.expr.Expr;
import org.apache.jena.sparql.lang.sparql_11.ParseException;
import org.apache.jena.sparql.syntax.Element;
import org.apache.jena.sparql.syntax.ElementBind;
import org.apache.jena.sparql.syntax.ElementFilter;
import org.apache.jena.sparql.syntax.ElementGroup;
import org.apache.jena.sparql.syntax.ElementMinus;
import org.apache.jena.sparql.syntax.ElementNamedGraph;
import org.apache.jena.sparql.syntax.ElementOptional;
import org.apache.jena.sparql.syntax.ElementPathBlock;
import org.apache.jena.sparql.syntax.ElementSubQuery;
import org.apache.jena.sparql.syntax.ElementTriplesBlock;
import org.apache.jena.sparql.syntax.ElementUnion;
import org.apache.jena.sparql.util.ExprUtils;
import org.apache.jena.vocabulary.RDF;

/**
 * The where handler. Generally handles GroupGraphPattern.
 *
 * @see <a href=
 * "http://www.w3.org/TR/2013/REC-sparql11-query-20130321/#rGroupGraphPattern">
 * SPARQL 11 Query Language - Group Graph Pattern</a>
 *
 */
public class WhereHandler implements Handler {

    // the query to modify
    private final Query query;

    private final ValuesHandler valuesHandler;

    /**
     * Constructor.
     *
     * @param query The query to manipulate.
     */
    public WhereHandler(Query query) {
        this.query = query;
        this.valuesHandler = new ValuesHandler();
    }

    /**
     * Creates a where handler with a new query.
     */
    public WhereHandler() {
        this(new Query());
    }

    /**
     * Get the query pattern from this where handler.
     * 
     * @return the query pattern
     */
    public Element getQueryPattern() {
        return query.getQueryPattern();
    }

    /**
     * @return The query this where handler is using.
     */
    public Query getQuery() {
        return query;
    }

    /**
     * Add all where attributes from the Where Handler argument.
     *
     * @param whereHandler The Where Handler to copy from.
     */
    public void addAll(WhereHandler whereHandler) {
        Element e = whereHandler.query.getQueryPattern();
        if (e != null) {
            // clone the Element
            ElementRewriter rewriter = new ElementRewriter(Collections.emptyMap());
            e.visit(rewriter);
            Element clone = rewriter.getResult();
            Element mine = query.getQueryPattern();
            if (mine == null) {
                query.setQueryPattern(clone);
            } else {
                ElementGroup eg = null;
                if (mine instanceof ElementGroup) {
                    eg = (ElementGroup) mine;
                } else {
                    eg = new ElementGroup();
                    eg.addElement(mine);
                }
                if (clone instanceof ElementGroup) {
                    for (Element ele : ((ElementGroup) clone).getElements()) {
                        eg.addElement(ele);
                    }
                } else {
                    eg.addElement(clone);
                }
                query.setQueryPattern(eg);
            }
        }
        valuesHandler.addAll(whereHandler.valuesHandler);
    }

    /**
     * Get the base element from the where clause. If the clause does not contain an
     * element return the element group, otherwise return the enclosed element.
     *
     * @return the base element.
     */
    public Element getElement() {
        Element result = query.getQueryPattern();
        if (result == null) {
            result = getClause();
        }
        return result;
    }

    /**
     * Get the element group for the clause. if The element group is not set, create
     * and set it.
     *
     * Public for ExprFactory use.
     *
     * @return The element group.
     */
    public ElementGroup getClause() {
        Element e = query.getQueryPattern();
        if (e == null) {
            e = new ElementGroup();
            query.setQueryPattern(e);
        }
        if (e instanceof ElementGroup) {
            return (ElementGroup) e;
        }

        ElementGroup eg = new ElementGroup();
        eg.addElement(e);
        query.setQueryPattern(eg);
        return eg;
    }

    /**
     * Test that a triple is valid. Throws an IllegalArgumentException if the triple
     * is not valid.
     *
     * @param t The trip to test.
     */
    private static void testTriple(TriplePath t) {
        // verify Triple is valid
        boolean validSubject = t.getSubject().isURI() || t.getSubject().isBlank() || t.getSubject().isVariable()
                || t.getSubject().equals(Node.ANY);
        boolean validPredicate;

        if (t.isTriple()) {
            validPredicate = t.getPredicate().isURI() || t.getPredicate().isVariable()
                    || t.getPredicate().equals(Node.ANY);
        } else {
            validPredicate = t.getPath() != null;
        }

        boolean validObject = t.getObject().isURI() || t.getObject().isLiteral() || t.getObject().isBlank()
                || t.getObject().isVariable() || t.getObject().equals(Node.ANY);

        if (!validSubject || !validPredicate || !validObject) {
            StringBuilder sb = new StringBuilder();
            if (!validSubject) {
                sb.append(String.format("Subject (%s) must be a URI, blank, variable, or a wildcard. %n",
                        t.getSubject()));
            }
            if (!validPredicate) {
                sb.append(String.format("Predicate (%s) must be a Path, URI , variable, or a wildcard. %n",
                        t.getPredicate()));
            }
            if (!validObject) {
                sb.append(String.format("Object (%s) must be a URI, literal, blank, , variable, or a wildcard. %n",
                        t.getObject()));
            }
            if (!validSubject || !validPredicate) {
                sb.append(String.format("Is a prefix missing?  Prefix must be defined before use. %n"));
            }
            throw new IllegalArgumentException(sb.toString());
        }
    }

    /**
     * Add the triple path to the where clause
     *
     * @param t The triple path to add.
     * @throws IllegalArgumentException If the triple path is not a valid triple
     * path for a where clause.
     */
    public void addWhere(TriplePath t) throws IllegalArgumentException {
        testTriple(t);
        ElementGroup eg = getClause();
        List<Element> lst = eg.getElements();
        if (lst.isEmpty()) {
            ElementPathBlock epb = new ElementPathBlock();
            epb.addTriple(t);
            eg.addElement(epb);
        } else {
            Element e = lst.get(lst.size() - 1);
            if (e instanceof ElementTriplesBlock && t.isTriple()) {
                ElementTriplesBlock etb = (ElementTriplesBlock) e;
                etb.addTriple(t.asTriple());
            } else if (e instanceof ElementPathBlock) {
                ElementPathBlock epb = (ElementPathBlock) e;
                epb.addTriple(t);
            } else {
                ElementPathBlock etb = new ElementPathBlock();
                etb.addTriple(t);
                eg.addElement(etb);
            }

        }
    }

    /**
     * Add the triple path to the where clause
     *
     * @param values The values to add to this where clause.
     * @throws IllegalArgumentException If the triple path is not a valid triple
     * path for a where clause.
     */
    public void addWhere(ValuesHandler values) throws IllegalArgumentException {
        valuesHandler.addAll(values);
    }

    /**
     * Add an optional triple to the where clause
     *
     * @param t The triple path to add.
     * @throws IllegalArgumentException If the triple is not a valid triple for a
     * where clause.
     */
    public void addOptional(TriplePath t) throws IllegalArgumentException {
        testTriple(t);
        ElementPathBlock epb = new ElementPathBlock();
        epb.addTriple(t);
        ElementOptional opt = new ElementOptional(epb);
        getClause().addElement(opt);
    }

    /**
     * Add the contents of a where handler as an optional statement.
     * 
     * @param whereHandler The where handler to use as the optional statement.
     */
    public void addOptional(WhereHandler whereHandler) {
        getClause().addElement(new ElementOptional(whereHandler.getClause()));
    }

    /**
     * Add an expression string as a filter.
     *
     * @param expression The expression string to add.
     * @throws ParseException If the expression can not be parsed.
     */
    public void addFilter(String expression) throws ParseException {
        getClause().addElement(new ElementFilter(ExprUtils.parse(query, expression, true)));
    }

    /**
     * add an expression as a filter.
     *
     * @param expr The expression to add.
     */
    public void addFilter(Expr expr) {
        getClause().addElement(new ElementFilter(expr));
    }

    /**
     * Add a subquery to the where clause.
     *
     * @param subQuery The sub query to add.
     */
    public void addSubQuery(AbstractQueryBuilder<?> subQuery) {
        getClause().addElement(makeSubQuery(subQuery));
    }

    /**
     * Convert a subquery into a subquery element.
     *
     * @param subQuery The sub query to convert
     * @return THe converted element.
     */
    public ElementSubQuery makeSubQuery(AbstractQueryBuilder<?> subQuery) {
        Query q = new Query();
        q.setQuerySelectType();
        PrologHandler ph = new PrologHandler(query);
        ph.addPrefixes(subQuery.getPrologHandler().getPrefixes());
        HandlerBlock handlerBlock = new HandlerBlock(q);
        handlerBlock.addAll(subQuery.getHandlerBlock());
        // remove the prefix mappings from the sub query.
        handlerBlock.getPrologHandler().clearPrefixes();

        // make sure we have a query pattern before we start building.
        if (q.getQueryPattern() == null) {
            q.setQueryPattern(new ElementGroup());
        }
        handlerBlock.build();
        return new ElementSubQuery(q);
    }

    /**
     * Add a union to the where clause.
     *
     * @param subQuery The subquery to add as the union.
     */
    public void addUnion(AbstractQueryBuilder<?> subQuery) {
        ElementUnion union = null;
        ElementGroup clause = getClause();
        // if the last element is a union make sure we add to it.
        if (!clause.isEmpty()) {
            Element lastElement = clause.getElements().get(clause.getElements().size() - 1);
            if (lastElement instanceof ElementUnion) {
                union = (ElementUnion) lastElement;
            } else {
                // clauses is not empty and is not a union so it is the left
                // side of the union.
                union = new ElementUnion();
                union.addElement(clause);
                query.setQueryPattern(union);
            }
        } else {
            // add the union as the first element in the clause.
            union = new ElementUnion();
            clause.addElement(union);
        }
        // if there are projected vars then do a full blown subquery
        // otherwise just add the clause.
        if (subQuery instanceof SelectClause && ((SelectClause<?>) subQuery).getVars().size() > 0) {
            union.addElement(makeSubQuery(subQuery));
        } else {
            PrologHandler ph = new PrologHandler(query);
            ph.addPrefixes(subQuery.getPrologHandler().getPrefixes());
            union.addElement(subQuery.getWhereHandler().getClause());
        }

    }

    /**
     * Add a graph to the where clause.
     *
     * @param graph The name of the graph.
     * @param subQuery The where handler that defines the graph.
     */
    public void addGraph(Node graph, WhereHandler subQuery) {
        getClause().addElement(new ElementNamedGraph(graph, subQuery.getElement()));
    }

    /**
     * Add a graph to the where clause.
     *
     * Short hand for graph { s, p, o }
     *
     * @param graph The name of the graph.
     * @param subQuery A triple path to add to the graph.
     */
    public void addGraph(Node graph, TriplePath subQuery) {
        ElementPathBlock epb = new ElementPathBlock();
        epb.addTriple(subQuery);
        getClause().addElement(new ElementNamedGraph(graph, epb));
    }

    /**
     * Add a binding to the where clause.
     *
     * @param expr The expression to bind.
     * @param var The variable to bind it to.
     */
    public void addBind(Expr expr, Var var) {
        getClause().addElement(new ElementBind(var, expr));
    }

    /**
     * Add a binding to the where clause.
     *
     * @param expression The expression to bind.
     * @param var The variable to bind it to.
     * @throws ParseException
     */
    public void addBind(String expression, Var var) throws ParseException {
        getClause().addElement(new ElementBind(var, ExprUtils.parse(query, expression, true)));
    }

    @Override
    public void setVars(Map<Var, Node> values) {
        if (values.isEmpty()) {
            return;
        }

        Element e = query.getQueryPattern();
        if (e != null) {
            ElementRewriter r = new ElementRewriter(values);
            e.visit(r);
            query.setQueryPattern(r.getResult());
        }
        valuesHandler.setVars(values);
    }

    @Override
    public void build() {
        /*
         * cleanup union-of-one and other similar issues.
         */
        BuildElementVisitor visitor = new BuildElementVisitor();
        getElement().visit(visitor);
        if (!valuesHandler.isEmpty()) {
            if (visitor.getResult() instanceof ElementGroup) {
                ((ElementGroup) visitor.getResult()).addElement(valuesHandler.asElement());
                ;
            } else {
                ElementGroup eg = new ElementGroup();
                eg.addElement(visitor.getResult());
                eg.addElement(valuesHandler.asElement());
                visitor.setResult(eg);
            }
        }
        query.setQueryPattern(visitor.getResult());
    }

    /**
     * Create a list node from a list of objects as per RDF Collections.
     *
     * http://www.w3.org/TR/2013/REC-sparql11-query-20130321/#collections
     *
     * @param objs the list of objects for the list.
     * @return the first blank node in the list.
     */
    public Node list(Object... objs) {
        Node retval = NodeFactory.createBlankNode();
        Node lastObject = retval;
        for (int i = 0; i < objs.length; i++) {
            Node n = Converters.makeNode(objs[i], query.getPrefixMapping());
            addWhere(new TriplePath(new Triple(lastObject, RDF.first.asNode(), n)));
            if (i + 1 < objs.length) {
                Node nextObject = NodeFactory.createBlankNode();
                addWhere(new TriplePath(new Triple(lastObject, RDF.rest.asNode(), nextObject)));
                lastObject = nextObject;
            } else {
                addWhere(new TriplePath(new Triple(lastObject, RDF.rest.asNode(), RDF.nil.asNode())));
            }

        }

        return retval;
    }

    /**
     * Add a minus operation to the where clause. The prolog will be updated with
     * the prefixes from the abstract query builder.
     *
     * @param qb the abstract builder that defines the data to subtract.
     */
    public void addMinus(AbstractQueryBuilder<?> qb) {
        PrologHandler ph = new PrologHandler(query);
        ph.addPrefixes(qb.getPrologHandler().getPrefixes());
        ElementGroup clause = getClause();
        ElementMinus minus = new ElementMinus(qb.getWhereHandler().getClause());
        clause.addElement(minus);
    }

    public void addValueVar(PrefixMapping prefixMapping, Object var) {
        if (var == null) {
            throw new IllegalArgumentException("var must not be null.");
        }
        if (var instanceof Collection<?>) {
            Collection<?> column = (Collection<?>) var;
            if (column.size() == 0) {
                throw new IllegalArgumentException("column must have at least one entry.");
            }
            Iterator<?> iter = column.iterator();
            Var v = Converters.makeVar(iter.next());
            valuesHandler.addValueVar(v, Converters.makeValueNodes(iter, prefixMapping));
        } else {
            valuesHandler.addValueVar(Converters.makeVar(var), null);
        }
    }

    public void addValueVar(PrefixMapping prefixMapping, Object var, Object... objects) {

        Collection<Node> values = null;
        if (objects != null) {
            values = Converters.makeValueNodes(Arrays.asList(objects).iterator(), prefixMapping);
        }

        valuesHandler.addValueVar(Converters.makeVar(var), values);
    }

    public <K extends Collection<?>> void addValueVars(PrefixMapping prefixMapping, Map<?, K> dataTable) {
        ValuesHandler hdlr = new ValuesHandler();
        for (Map.Entry<?, K> entry : dataTable.entrySet()) {
            Collection<Node> values = null;
            if (entry.getValue() != null) {
                values = Converters.makeValueNodes(entry.getValue().iterator(), prefixMapping);
            }
            hdlr.addValueVar(Converters.makeVar(entry.getKey()), values);
        }
        valuesHandler.addAll(hdlr);
    }

    public void addValueRow(PrefixMapping prefixMapping, Object... values) {
        valuesHandler.addValueRow(Converters.makeValueNodes(Arrays.asList(values).iterator(), prefixMapping));
    }

    public void addValueRow(PrefixMapping prefixMapping, Collection<?> values) {
        valuesHandler.addValueRow(Converters.makeValueNodes(values.iterator(), prefixMapping));
    }

    public List<Var> getValuesVars() {
        return valuesHandler.getValuesVars();
    }

    public Map<Var, List<Node>> getValuesMap() {
        return valuesHandler.getValuesMap();
    }

    public void clearValues() {
        valuesHandler.clear();
    }
}
