/*******************************************************************************
 * 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.sling.scripting.sightly.impl.engine;

import java.io.Reader;
import java.io.StringReader;

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

import org.apache.sling.scripting.api.AbstractSlingScriptEngine;
import org.apache.sling.scripting.sightly.impl.engine.precompiled.PrecompiledUnitManager;
import org.apache.sling.scripting.sightly.impl.engine.compiled.SlingHTLMasterCompiler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * The HTL Script engine
 */
public class SightlyScriptEngine extends AbstractSlingScriptEngine implements Compilable {

    private static final Logger LOGGER = LoggerFactory.getLogger(SightlyScriptEngine.class);

    private SlingHTLMasterCompiler slingHTLMasterCompiler;
    private PrecompiledUnitManager precompiledUnitManager;
    private ExtensionRegistryService extensionRegistryService;

    SightlyScriptEngine(SightlyScriptEngineFactory factory, ExtensionRegistryService extensionRegistryService,
                        SlingHTLMasterCompiler slingHTLMasterCompiler, PrecompiledUnitManager precompiledUnitManager) {
        super(factory);
        this.extensionRegistryService = extensionRegistryService;
        this.slingHTLMasterCompiler = slingHTLMasterCompiler;
        this.precompiledUnitManager = precompiledUnitManager;
    }

    @Override
    public CompiledScript compile(String script) throws ScriptException {
        return compile(new StringReader(script));
    }

    @Override
    public CompiledScript compile(final Reader script) throws ScriptException {
        if (slingHTLMasterCompiler != null) {
            return slingHTLMasterCompiler.compileHTLScript(this, script, null);
        }
        throw new ScriptException("Missing compilation support.");
    }

    @Override
    public Object eval(Reader reader, ScriptContext scriptContext) throws ScriptException {
        checkArguments(reader, scriptContext);
        try {
            SightlyCompiledScript compiledScript = null;
            if (precompiledUnitManager != null) {
                compiledScript = precompiledUnitManager.getSightlyCompiledScript(this, scriptContext);
            } else if (slingHTLMasterCompiler != null) {
                compiledScript = slingHTLMasterCompiler.compileHTLScript(this, reader, scriptContext);
            }
            if (compiledScript != null) {
                return compiledScript.eval(scriptContext);
            }
        } catch (Exception e) {
            throw new ScriptException(e);
        }
        LOGGER.warn("Did not find a compilable or executable unit.");
        return null;
    }

    public ExtensionRegistryService getExtensionRegistryService() {
        return extensionRegistryService;
    }

    private void checkArguments(Reader reader, ScriptContext scriptContext) {
        if (reader == null) {
            throw new NullPointerException("Reader cannot be null");
        }
        if (scriptContext == null) {
            throw new NullPointerException("ScriptContext cannot be null");
        }
    }


}