/*
 * JBoss, Home of Professional Open Source.
 * See the COPYRIGHT.txt file distributed with this work for information
 * regarding copyright ownership.  Some portions may be licensed
 * to Red Hat, Inc. under one or more contributor license agreements.
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA.
 */

package org.teiid.query.processor.relational;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

import javax.script.CompiledScript;
import javax.script.ScriptContext;
import javax.script.ScriptException;
import javax.script.SimpleScriptContext;

import org.teiid.api.exception.query.ExpressionEvaluationException;
import org.teiid.common.buffer.BlockedException;
import org.teiid.common.buffer.BufferManager;
import org.teiid.common.buffer.TupleBatch;
import org.teiid.core.TeiidComponentException;
import org.teiid.core.TeiidProcessingException;
import org.teiid.query.QueryPlugin;
import org.teiid.query.eval.Evaluator;
import org.teiid.query.function.FunctionDescriptor;
import org.teiid.query.processor.ProcessorDataManager;
import org.teiid.query.sql.LanguageObject;
import org.teiid.query.sql.lang.ObjectTable;
import org.teiid.query.sql.lang.ObjectTable.ObjectColumn;
import org.teiid.query.util.CommandContext;

/**
 * Handles object table processing.
 */
public class ObjectTableNode extends SubqueryAwareRelationalNode {

	private static final String TEIID_ROW_NUMBER = "teiid_row_number"; //$NON-NLS-1$
	private static final String TEIID_ROW = "teiid_row"; //$NON-NLS-1$
	private static final String TEIID_CONTEXT = "teiid_context"; //$NON-NLS-1$
	
	private ObjectTable table;
	private List<ObjectColumn> projectedColumns;
	
	//processing state
	private int rowCount = 0;
	private Object item;
	private Iterator<?> result;
	private SimpleScriptContext scriptContext;
	
	public ObjectTableNode(int nodeID) {
		super(nodeID);
	}
	
	@Override
	public void initialize(CommandContext context, BufferManager bufferManager,
			ProcessorDataManager dataMgr) {
		super.initialize(context, bufferManager, dataMgr);
		this.scriptContext = new SimpleScriptContext();
	}
	
	@Override
	public void open() throws TeiidComponentException, TeiidProcessingException {
		super.open();
		if (table.getScriptEngine() == null) {
			table.setScriptEngine(getContext().getMetadata().getScriptEngine(table.getScriptingLanguage()));
		}
		this.scriptContext.setAttribute(TEIID_CONTEXT, this.getContext(), ScriptContext.ENGINE_SCOPE);
	}
	
	@Override
	public synchronized void closeDirect() {
		if (this.scriptContext != null) {
			try {
				this.scriptContext.getErrorWriter().flush();
			} catch (IOException e) {
			}
			try {
				this.scriptContext.getWriter().flush();
			} catch (IOException e) {
			}
		}
		super.closeDirect();
		reset();
	}
	
	@Override
	public void reset() {
		super.reset();
		item = null;
		result = null;
		rowCount = 0;
		if (this.scriptContext != null) {
			this.scriptContext.getBindings(ScriptContext.ENGINE_SCOPE).clear();
		}
	}
	
	public void setTable(ObjectTable table) {
		this.table = table;
	}
	
	public void setProjectedColumns(List<ObjectColumn> projectedColumns) {
		this.projectedColumns = projectedColumns;
	}
	
	@Override
	public ObjectTableNode clone() {
		ObjectTableNode clone = new ObjectTableNode(getID());
		this.copyTo(clone);
		clone.setTable(table);
		clone.setProjectedColumns(projectedColumns);
		return clone;
	}

	@Override
	protected synchronized TupleBatch nextBatchDirect() throws BlockedException,
			TeiidComponentException, TeiidProcessingException {
		
		evaluate();
		
		while (!isBatchFull() && result.hasNext()) {
			if (item == null) {
				item = result.next();
				if (item == null) {
					continue;
				}
				rowCount++;
			}
			addBatchRow(processRow());
		}
		if (!result.hasNext()) {
			terminateBatches();
		}
		return pullBatch();
	}

	private void evaluate() throws TeiidComponentException,
			ExpressionEvaluationException, BlockedException,
			TeiidProcessingException {
		if (result != null) {
			return;
		}
		setReferenceValues(this.table);
		Evaluator eval = getEvaluator(Collections.emptyMap());
		Object context = eval.evaluateParameters(this.table.getPassing(), null, scriptContext.getBindings(ScriptContext.ENGINE_SCOPE));
		assert context == null;

		Object value = evalScript(this.table.getCompiledScript(), this.table.getRowScript());
		if (value instanceof Iterable<?>) {
			result = ((Iterable<?>)value).iterator();
		} else if (value instanceof Iterator<?>) {
			result = (Iterator<?>)value;
		} else {
			result = Arrays.asList(value).iterator();
		}
	}

	private Object evalScript(CompiledScript compiledScript, String script) throws TeiidProcessingException {
		try {
			if (compiledScript != null) {
				return compiledScript.eval(this.scriptContext);
			}
			return this.table.getScriptEngine().eval(script, this.scriptContext);
		} catch (ScriptException e) {
			throw new TeiidProcessingException(QueryPlugin.Event.TEIID31110, e, QueryPlugin.Util.gs(QueryPlugin.Event.TEIID31110, script, e.getMessage()));
		}
	}

	private List<?> processRow() throws ExpressionEvaluationException,
			TeiidComponentException, TeiidProcessingException {
		List<Object> tuple = new ArrayList<Object>(projectedColumns.size());
		this.scriptContext.setAttribute(TEIID_ROW, this.item, ScriptContext.ENGINE_SCOPE);
		this.scriptContext.setAttribute(TEIID_ROW_NUMBER, this.rowCount, ScriptContext.ENGINE_SCOPE);
		for (ObjectColumn proColumn : projectedColumns) {
			Object value = evalScript(proColumn.getCompiledScript(), proColumn.getPath());
			if (value == null) {
				if (proColumn.getDefaultExpression() != null) {
					tuple.add(getEvaluator(Collections.emptyMap()).evaluate(proColumn.getDefaultExpression(), null));
				} else {
					tuple.add(null);
				}
				continue;
			}
			value = FunctionDescriptor.importValue(value, proColumn.getSymbol().getType());
			tuple.add(value);
		}
		item = null;
		return tuple;
	}

	@Override
	protected Collection<? extends LanguageObject> getObjects() {
		return this.table.getPassing();
	}

}