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/*
 * =============================================================================
 *
 *   Copyright (c) 2011-2018, The THYMELEAF team (http://www.thymeleaf.org)
 *
 *   Licensed 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.thymeleaf.context;

import java.util.Locale;
import java.util.Map;
import java.util.Set;

import org.thymeleaf.IEngineConfiguration;
import org.thymeleaf.exceptions.TemplateProcessingException;
import org.thymeleaf.expression.ExpressionObjects;
import org.thymeleaf.expression.IExpressionObjects;
import org.thymeleaf.linkbuilder.ILinkBuilder;
import org.thymeleaf.messageresolver.IMessageResolver;
import org.thymeleaf.model.IModelFactory;
import org.thymeleaf.templatemode.TemplateMode;
import org.thymeleaf.util.Validate;

/**
 * 
 *   Utility abstract class partially implementing {@link IEngineContext}.
 * 
 * 
 *   This class is meant to be used as a base for implementations of {@link IEngineContext}. Note however that creating
 *   an implementation of {@link IEngineContext} can be very complex and normally unneeded. The default
 *   implementations should suffice for most scenarios.
 * 
 * 
 *   Note this abstract implementation does not implement basic variable-management methods such as those coming from
 *   the {@link IContext} interface because that is considered the responsibility of the implementing subclasses.
 * 
 *
 * @author Daniel Fernández
 * @since 3.0.0
 * 
 */
public abstract class AbstractEngineContext implements IEngineContext {

    // NOTE we are not extending AbstractContext or AbstractExpressionContext on purpose, as the variable-oriented
    // methods are going to be handled by the subclasses, not any superclasses.

    private final IEngineConfiguration configuration;
    private final Map templateResolutionAttributes;
    private final Locale locale;

    private IExpressionObjects expressionObjects = null;
    private IdentifierSequences identifierSequences = null;



    protected AbstractEngineContext(
            final IEngineConfiguration configuration,
            final Map templateResolutionAttributes,
            final Locale locale) {

        super();

        Validate.notNull(configuration, "Configuration cannot be null");
        // templateResolutionAttributes CAN be null
        Validate.notNull(locale, "Locale cannot be null");

        this.configuration = configuration;
        this.locale = locale;
        this.templateResolutionAttributes = templateResolutionAttributes;
        // Most templates will not need this, so we will initialize it lazily
        this.identifierSequences = null;

    }


    public final IEngineConfiguration getConfiguration() {
        return this.configuration;
    }


    public final Map getTemplateResolutionAttributes() {
        return this.templateResolutionAttributes;
    }


    public final Locale getLocale() {
        return this.locale;
    }


    public final IExpressionObjects getExpressionObjects() {
        // We delay creation of expression objects in case they are not needed at all
        if (this.expressionObjects == null) {
            this.expressionObjects = new ExpressionObjects(this, this.configuration.getExpressionObjectFactory());
        }
        return this.expressionObjects;
    }


    public final TemplateMode getTemplateMode() {
        return getTemplateData().getTemplateMode();
    }


    public final IModelFactory getModelFactory() {
        return this.configuration.getModelFactory(getTemplateMode());
    }


    public final String getMessage(
            final Class origin, final String key, final Object[] messageParameters, final boolean useAbsentMessageRepresentation) {

        // origin CAN be null
        Validate.notNull(key, "Message key cannot be null");
        // messageParameter CAN be null

        final Set messageResolvers = this.configuration.getMessageResolvers();

        // Try to resolve the message
        for (final IMessageResolver messageResolver : messageResolvers) {
            final String resolvedMessage =
                    messageResolver.resolveMessage(this, origin, key, messageParameters);
            if (resolvedMessage != null) {
                return resolvedMessage;
            }
        }

        // Message unresolved: try to create an "absent message representation" (if specified to do so)
        if (useAbsentMessageRepresentation) {

            for (final IMessageResolver messageResolver : messageResolvers) {
                final String absentMessageRepresentation =
                        messageResolver.createAbsentMessageRepresentation(this, origin, key, messageParameters);
                if (absentMessageRepresentation != null) {
                    return absentMessageRepresentation;
                }
            }

        }

        return null;

    }


    public final String buildLink(final String base, final Map parameters) {

        // base CAN be null
        // parameters CAN be null

        final Set linkBuilders = this.configuration.getLinkBuilders();

        // Try to resolve the message
        for (final ILinkBuilder linkBuilder : linkBuilders) {
            final String link = linkBuilder.buildLink(this, base, parameters);
            if (link != null) {
                return link;
            }
        }

        // Message unresolved: this should never happen, so we should fail

        throw new TemplateProcessingException(
                "No configured link builder instance was able to build link with base \"" + base + "\" and " +
                "parameters " + parameters);

    }


    public final IdentifierSequences getIdentifierSequences() {
        // No problem in lazily initializing this here, as context objects should not be used by
        // multiple threads.
        if (this.identifierSequences == null) {
            this.identifierSequences = new IdentifierSequences();
        }
        return this.identifierSequences;
    }



}