/*
 * 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.sparql.algebra ;

import static org.apache.jena.sparql.core.Vars.addVar ;

import java.util.* ;

import org.apache.jena.atlas.lib.SetUtils ;
import org.apache.jena.atlas.lib.tuple.Tuple ;
import org.apache.jena.atlas.lib.tuple.TupleFactory ;
import org.apache.jena.graph.Node ;
import org.apache.jena.graph.Triple ;
import org.apache.jena.sparql.algebra.OpWalker.OpWalkerVisitor;
//import org.apache.jena.sparql.algebra.walker.WalkerVisitor ;
import org.apache.jena.sparql.algebra.op.* ;
//import org.apache.jena.sparql.algebra.walker.WalkerVisitorVisible;
import org.apache.jena.sparql.core.BasicPattern ;
import org.apache.jena.sparql.core.Var ;
import org.apache.jena.sparql.expr.ExprVars ;
import org.apache.jena.sparql.pfunction.PropFuncArg ;
import org.apache.jena.sparql.util.VarUtils ;

/** Get vars for a pattern */

public class OpVars
{
    // Choose the default collector - LinkedHashSet is predictable and
    // keeps the "found" order
    private static Set<Var> collector() {
        return new LinkedHashSet<>() ;
    }

    public static Set<Var> visibleVars(Op op) {
        Set<Var> acc = collector() ;
        visibleVars(op, acc) ;
        return acc ;
    }

    public static void visibleVars(Op op, Set<Var> acc) {
        OpVarsPattern visitor = new OpVarsPattern(acc, true) ;
        // Does not work yet for new walker.
        OpWalker.walk(new OpWalkerVisitorVisible(visitor, acc), op) ;
    }
    
    /** The set of variables that will be in every solution of this Op */
    public static Set<Var> fixedVars(Op op) {
        Set<Var> acc = collector() ;
        fixedVars(op, acc) ;
        return acc ;
    }

    public static void fixedVars(Op op, Set<Var> acc) {
        OpVarsPattern visitor = new OpVarsPattern(acc, true) ;
        OpWalker.walk(new OpWalkerVisitorFixed(visitor, acc), op) ;
    }
    
    public static Tuple<Set<Var>> mentionedVarsByPosition(Op op) {
        Set<Var> graphAcc = collector() ;
        Set<Var> subjAcc = collector() ;
        Set<Var> predAcc = collector() ;
        Set<Var> objAcc = collector() ;
        Set<Var> unknownAcc = collector() ;
        OpVarsPatternWithPositions visitor = new OpVarsPatternWithPositions(graphAcc, subjAcc, predAcc, objAcc, unknownAcc, false);
        OpWalker.walk(op, visitor);
        return TupleFactory.tuple(graphAcc, subjAcc, predAcc, objAcc, unknownAcc);
    }
    
    public static Tuple<Set<Var>> mentionedVarsByPosition(Op... ops) {
        Set<Var> graphAcc = collector() ;
        Set<Var> subjAcc = collector() ;
        Set<Var> predAcc = collector() ;
        Set<Var> objAcc = collector() ;
        Set<Var> unknownAcc = collector() ;
        OpVarsPatternWithPositions visitor = new OpVarsPatternWithPositions(graphAcc, subjAcc, predAcc, objAcc, unknownAcc, false);
        for (Op op : ops)
            OpWalker.walk(op, visitor);
        return TupleFactory.tuple(graphAcc, subjAcc, predAcc, objAcc, unknownAcc);
    }

    // All mentioned variables regardless of scope/visibility.
    public static Collection<Var> mentionedVars(Op op) {
        Set<Var> acc = collector() ;
        mentionedVars(op, acc) ;
        return acc ;
    }

    // All mentioned variables regardless of scope/visibility.
    public static void mentionedVars(Op op, Set<Var> acc) {
        OpVarsMentioned visitor = new OpVarsMentioned(acc) ;
        OpWalker.walk(op, visitor) ;
    }

    /** Do project and don't walk into it. MINUS vars aren't visible either */
    private static class OpWalkerVisitorVisible extends OpWalkerVisitor 
    {
        private final Collection<Var> acc ;

        public OpWalkerVisitorVisible(OpVarsPattern visitor, Collection<Var> acc) {
            super(visitor) ;
            this.acc = acc ;
        }

        @Override
        public void visit(OpProject op) {
            before(op) ;
            // Skip Project subop.
            acc.addAll(op.getVars()) ;
            after(op) ;
        }

        @Override
        public void visit(OpMinus op) {
            before(op) ;
            if (op.getLeft() != null)
                op.getLeft().visit(this) ;
            // Skip right.
            // if ( op.getRight() != null ) op.getRight().visit(this) ;
            if (visitor != null)
                op.visit(visitor) ;
            after(op) ;
        }
    }

    // Only consider variables that are visible and definitely defined.
    // OPTIONAL (2 forms) and UNION are the interesting cases.
    private static class OpWalkerVisitorFixed extends OpWalkerVisitor
    {
        private final Collection<Var> acc ;

        public OpWalkerVisitorFixed(OpVarsPattern visitor, Collection<Var> acc) {
            //super(visitor, null, null, null) ;
            super(visitor);
            this.acc = acc ;
        }
        
        @Override
        public void visit(OpLeftJoin x) {
            x.getLeft().visit(this);
        }

        @Override
        public void visit(OpConditional x) {
            x.getLeft().visit(this);
        }

        @Override
        public void visit(OpUnion x) {
            Set<Var> left = fixedVars(x.getLeft()) ;
            Set<Var> right = fixedVars(x.getRight()) ;
            Set<Var> r = SetUtils.intersection(left,  right) ;
            acc.addAll(r) ;
        }
        
        @Override
        public void visit(OpProject op) {
            before(op) ;
            // Skip Project subop.
            acc.addAll(op.getVars()) ;
            after(op) ;
        }

        @Override
        public void visit(OpMinus op) {
            before(op) ;
            if (op.getLeft() != null)
                op.getLeft().visit(this) ;
            // Skip right.
            // if ( op.getRight() != null ) op.getRight().visit(this) ;
//            if (opVisitor != null)
//                op.visit(opVisitor) ;
            if (visitor != null)
                op.visit(visitor) ;
            after(op) ;
        }
    }

    /** Collect variables.
     * What to collect from is controlled by the walker e.g. 
     * OpWalkerVisitorFixed, OpWalkerVisitorVisible
     * and for OpVarsMentioned, the full geenral walker.
     */
    private static class OpVarsPattern extends OpVisitorBase
    {
        // The possibly-set-vars
        protected Set<Var> acc ;
        final boolean      visibleOnly ;

        OpVarsPattern(Set<Var> acc, boolean visibleOnly) {
            this.acc = acc ;
            this.visibleOnly = visibleOnly ;
        }

        @Override
        public void visit(OpBGP opBGP) {
            VarUtils.addVars(acc, opBGP.getPattern()) ;
        }

        @Override
        public void visit(OpPath opPath) {
            addVar(acc, opPath.getTriplePath().getSubject()) ;
            addVar(acc, opPath.getTriplePath().getObject()) ;
        }

        @Override
        public void visit(OpQuadPattern quadPattern) {
            addVar(acc, quadPattern.getGraphNode()) ;
            VarUtils.addVars(acc, quadPattern.getBasicPattern()) ;
        }
        
        @Override
        public void visit(OpQuadBlock quadBlock) {
            VarUtils.addVars(acc, quadBlock.getPattern()) ;
        }

        @Override
        public void visit(OpTriple opTriple) {
            VarUtils.addVarsFromTriple(acc, opTriple.getTriple());
        }

        @Override
        public void visit(OpQuad opQuad) {
            VarUtils.addVarsFromQuad(acc, opQuad.getQuad());
        }

        @Override
        public void visit(OpGraph opGraph) {
            addVar(acc, opGraph.getNode()) ;
        }

        @Override
        public void visit(OpDatasetNames dsNames) {
            addVar(acc, dsNames.getGraphNode()) ;
        }

        @Override
        public void visit(OpTable opTable) {
            // Only the variables with values in the tables (When building,
            // undefs didn't get into bindings so no variable mentioned)
            Table t = opTable.getTable() ;
            acc.addAll(t.getVars()) ;
        }

        @Override
        public void visit(OpProject opProject) {
            // The walker (WalkerVisitorVisible) handles this
            // for visible variables, not mentioned variable collecting.
            // The visibleOnly/clear is simply to be as general as possible.
            // visible: OpWalkerVisitorFixed, OpWalkerVisitorVisible,   
            // all (visibleOnly==false) for OpVarsMentioned
            if (visibleOnly)
                acc.clear() ;
            acc.addAll(opProject.getVars()) ;
        }

        @Override
        public void visit(OpAssign opAssign) {
            acc.addAll(opAssign.getVarExprList().getVars()) ;
        }

        @Override
        public void visit(OpExtend opExtend) {
            acc.addAll(opExtend.getVarExprList().getVars()) ;
        }

        @Override
        public void visit(OpPropFunc opPropFunc) {
            PropFuncArg.addVars(acc, opPropFunc.getSubjectArgs()) ;
            PropFuncArg.addVars(acc, opPropFunc.getObjectArgs()) ;
        }

        @Override
        public void visit(OpProcedure opProc) {
            ExprVars.varsMentioned(acc, opProc.getArgs()) ;
        }
        
        @Override
        public void visit(OpExt opExt) {
            // OpWalkerVisitor is taking care of calling opExt.effectiveOp().visit(this)
        }
    }
    
    private static class OpVarsPatternWithPositions extends OpVisitorBase
    {
        // The possibly-set-vars
        protected Set<Var> graphAcc, subjAcc, predAcc, objAcc, unknownAcc ;
        final boolean      visibleOnly ;

        OpVarsPatternWithPositions(Set<Var> graphAcc, Set<Var> subjAcc, Set<Var> predAcc, Set<Var> objAcc, Set<Var> unknownAcc, boolean visibleOnly) {
            this.graphAcc = graphAcc;
            this.subjAcc = subjAcc;
            this.predAcc = predAcc;
            this.objAcc = objAcc;
            this.unknownAcc = unknownAcc;
            this.visibleOnly = visibleOnly ;
        }

        @Override
        public void visit(OpBGP opBGP) {
            vars(opBGP.getPattern()) ;
        }

        @Override
        public void visit(OpPath opPath) {
            addVar(subjAcc, opPath.getTriplePath().getSubject()) ;
            addVar(objAcc, opPath.getTriplePath().getObject()) ;
        }

        @Override
        public void visit(OpQuadPattern quadPattern) {
            addVar(graphAcc, quadPattern.getGraphNode()) ;
            vars(quadPattern.getBasicPattern()) ;
        }

        @Override
        public void visit(OpGraph opGraph) {
            addVar(graphAcc, opGraph.getNode()) ;
        }

        @Override
        public void visit(OpDatasetNames dsNames) {
            addVar(graphAcc, dsNames.getGraphNode()) ;
        }

        @Override
        public void visit(OpTable opTable) {
            // Only the variables with values in the tables
            // (When building, undefs didn't get into bindings so no variable
            // mentioned)
            Table t = opTable.getTable() ;
            // Treat as unknown position
            unknownAcc.addAll(t.getVars()) ;
        }

        @Override
        public void visit(OpProject opProject) {
            // The walker (WalkerVisitorVisible) handles this
            // for visible variables, not mentioned variable collecting.
            // The visibleOnly/clear is simply to be as general as possible.
            List<Var> vs = opProject.getVars();
            if (visibleOnly) {
                clear(graphAcc, vs);
                clear(subjAcc, vs);
                clear(predAcc, vs);
                clear(objAcc, vs);
                
            }
            for (Var v : vs) {
                if (!graphAcc.contains(v) && !subjAcc.contains(v) && !predAcc.contains(v) && !objAcc.contains(v)) {
                    addVar(unknownAcc, v);
                }
            }
        }

        @Override
        public void visit(OpAssign opAssign) {
            // Unknown position
            unknownAcc.addAll(opAssign.getVarExprList().getVars()) ;
        }

        @Override
        public void visit(OpExtend opExtend) {
            // Unknown position
            unknownAcc.addAll(opExtend.getVarExprList().getVars()) ;
        }

        @Override
        public void visit(OpPropFunc opPropFunc) {
            addvars(subjAcc, opPropFunc.getSubjectArgs()) ;
            addvars(objAcc, opPropFunc.getObjectArgs()) ;
        }

        private void addvars(Set<Var> acc, PropFuncArg pfArg) {
            if (pfArg.isNode()) {
                addVar(acc, pfArg.getArg()) ;
                return ;
            }
            for (Node n : pfArg.getArgList())
                addVar(acc, n) ;
        }

        @Override
        public void visit(OpProcedure opProc) {
            unknownAcc.addAll(OpVars.mentionedVars(opProc));
        }
        
        private void vars(BasicPattern bp) {
            for (Triple t : bp.getList())
            {
                addVar(subjAcc, t.getSubject());
                addVar(predAcc, t.getPredicate());
                addVar(objAcc, t.getObject());
            }
        }
        
        private void clear(Set<Var> acc, List<Var> visible) {
            List<Var> toRemove = new ArrayList<>();
            for (Var found : acc)
            {
                if (!visible.contains(found)) {
                    toRemove.add(found);
                }
            }
            for (Var v : toRemove) {
                acc.remove(v);
            }
        }

    }

    private static class OpVarsMentioned extends OpVarsPattern
    {
        OpVarsMentioned(Set<Var> acc) {
            super(acc, false) ;
        }

        @Override
        public void visit(OpFilter opFilter) {
            ExprVars.varsMentioned(acc, opFilter.getExprs()) ;
        }

        @Override
        public void visit(OpOrder opOrder) {
            ExprVars.varsMentioned(acc, opOrder.getConditions()) ;
        }
    }
}