/*
 * 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.sse.lang;

import java.util.ArrayDeque ;
import java.util.Deque ;

import org.apache.jena.atlas.logging.Log ;
import org.apache.jena.datatypes.RDFDatatype ;
import org.apache.jena.datatypes.TypeMapper ;
import org.apache.jena.graph.Node ;
import org.apache.jena.graph.NodeFactory ;
import org.apache.jena.riot.lang.LabelToNode;
import org.apache.jena.riot.system.RiotLib;
import org.apache.jena.sparql.ARQConstants ;
import org.apache.jena.sparql.core.Var ;
import org.apache.jena.sparql.core.VarAlloc ;
import org.apache.jena.sparql.sse.Item ;
import org.apache.jena.sparql.sse.ItemList ;
import org.apache.jena.sparql.sse.ItemLocation ;
import org.apache.jena.sparql.sse.SSEParseException ;

public class ParseHandlerPlain implements ParseHandler 
{
    private ListStack      listStack   = new ListStack() ;
    private Item           currentItem = null ;
    private int            depth       = 0 ;
    private LabelToNode    bNodeLabels = LabelToNode.createScopeGlobal();
    
    // Allocation of fresh variables.
    private VarAlloc       varAlloc        = new VarAlloc(ARQConstants.allocSSEUnamedVars) ;
    private VarAlloc       varAllocND      = new VarAlloc(ARQConstants.allocSSEAnonVars) ;
    private VarAlloc       varAllocIntern  = new VarAlloc(ARQConstants.allocSSENamedVars) ;
    
    @Override
    public Item getItem()
    {
        return currentItem ; 
    }
    
    @Override
    public void parseStart()
    { depth = 0 ; }
    
    @Override
    public void parseFinish()
    {
        if ( depth != 0 )
            Log.warn(this, "Stack error: depth ="+depth+" at end of parse run") ;
        depth = -1 ;
    }
    
    @Override
    public void listStart(int line, int column)
    {
        ItemList list = new ItemList(line, column) ;
        pushList(list) ;
        setCurrentItem(Item.createList(list)) ;
    }

    @Override
    public void listFinish(int line, int column)
    {
        ItemList list = popList() ;
        Item item = Item.createList(list) ;
        listAdd(item) ;
    }

    protected void setCurrentItem(Item item)
    {
        currentItem = item ;
    }
    
    protected void listAdd(Item item)
    {
        if ( listStack.isEmpty() )
        {
            // Top level is outside a list.
            setCurrentItem(item) ;
            return ;
        }
        
        if ( item != null )
        {
            ItemList list = currentList() ;
            list.add(item) ;
        }
        setCurrentItem(item) ;
    }
    
    @Override
    public void emitSymbol(int line, int column, String symbol)
    {
        listAdd(Item.createSymbol(symbol, line, column)) ;
    }

    @Override
    public void emitVar(int line, int column, String varName)
    {
        Var var = null ;
        switch ( varName )
        {
            case "":
// "?"
                var = varAlloc.allocVar();
                break;
            case ARQConstants.allocVarAnonMarker:
// "??" -- Allocate a non-distinguished variable
                var = varAllocND.allocVar();
                break;
            case ARQConstants.allocVarMarker:
// "?." -- Allocate a named variable
                var = varAllocIntern.allocVar();
                break;
            default:
                var = Var.alloc( varName );
                break;
        }
        Item item = Item.createNode(var, line, column) ;
        listAdd(item) ;
    }
    
    @Override
    public void emitLiteral(int line, int column, String lexicalForm, String langTag, String datatypeIRI, String datatypePN)
    {
        Node n = null ;
        
        if ( datatypeIRI != null || datatypePN != null )
        {
            if ( datatypePN != null )
                datatypeIRI = resolvePrefixedName(datatypePN, line, column) ;
            
            RDFDatatype dType = TypeMapper.getInstance().getSafeTypeByName(datatypeIRI) ;
            n = NodeFactory.createLiteral(lexicalForm, dType) ;
        }
        else
            n = NodeFactory.createLiteral(lexicalForm, langTag) ;
        Item item = Item.createNode(n, line, column) ;
        listAdd(item) ;
    }

    @Override
    final
    public void emitBNode(int line, int column, String label)
    {
        Node n = null ;
        if ( label.equals("") )
            // Fresh anonymous bNode
            n = NodeFactory.createBlankNode() ; 
        else
            n = bNodeLabels.get(null, label) ;
        Item item = Item.createNode(n, line, column) ;
        listAdd(item) ;
    }

    @Override
    public void emitIRI(int line, int column, String iriStr)
    {
        Node n = RiotLib.createIRIorBNode(iriStr) ;
        Item item = Item.createNode(n, line, column) ;
        listAdd(item) ;
    }

    @Override
    public void emitPName(int line, int column, String pname)
    {
        String iriStr = resolvePrefixedName(pname, line, column) ;
        emitIRI(line, column, iriStr) ;
    }

    protected ItemList currentList()        { return listStack.getCurrent() ; }
    protected ItemList popList()            { depth-- ; setCurrentItem(null) ; return listStack.pop() ; }
    protected void pushList(ItemList list)  { listStack.push(list) ; depth++ ; }
    
    protected String resolvePrefixedName(String pname, int line, int column)
    {
        // Not resolving.  Make a strange URI.
        return "pname:"+pname ;
    }
    
    protected static class ListStack
    {
        private Deque<ItemList> stack    = new ArrayDeque<>() ;
        
        boolean isEmpty() { return stack.size() == 0 ; }
        
        ItemList getCurrent()
        {
            if ( stack.size() == 0 )
                return null ;
            return stack.peek() ;
        }
    
        void push(ItemList list) { stack.push(list) ; }
        ItemList pop() { return stack.pop() ; }
    }

    
    protected static void throwException(String msg, int line, int column)
    {
        throw new SSEParseException("[" + line + ", " + column + "] " + msg, line, column) ;
    }
    
    protected static void throwException(String msg, ItemLocation loc)
    {
        throwException(msg, loc.getLine(), loc.getColumn()) ;
    }

}
