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/*
 * Copyright (c) 2008-2025 The Aspectran Project
 *
 * 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 com.aspectran.thymeleaf;

import com.aspectran.core.activity.Activity;
import com.aspectran.core.component.template.engine.TemplateEngine;
import com.aspectran.core.component.template.engine.TemplateEngineProcessException;
import com.aspectran.thymeleaf.context.ActivityExpressionContext;
import com.aspectran.thymeleaf.context.ActivityExpressionContextFactory;
import com.aspectran.utils.Assert;
import org.thymeleaf.IEngineConfiguration;
import org.thymeleaf.ITemplateEngine;
import org.thymeleaf.TemplateSpec;
import org.thymeleaf.exceptions.TemplateProcessingException;
import org.thymeleaf.standard.expression.FragmentExpression;
import org.thymeleaf.standard.expression.IStandardExpressionParser;
import org.thymeleaf.standard.expression.StandardExpressions;

import java.io.IOException;
import java.io.Writer;
import java.util.Locale;
import java.util.Map;
import java.util.Set;

/**
 * The Class ThymeleafTemplateEngine.
 *
 * Created: 2024. 11. 18.
 *
 * @since 8.2.0
 */
public class ThymeleafTemplateEngine implements TemplateEngine {

    private final ITemplateEngine templateEngine;

    public ThymeleafTemplateEngine(AspectranTemplateEngine templateEngine) {
        Assert.notNull(templateEngine, "templateEngine must not be null");
        this.templateEngine = templateEngine;
    }

    public ITemplateEngine getTemplateEngine() {
        return templateEngine;
    }

    @Override
    public void process(String templateName, Activity activity) throws TemplateEngineProcessException {
        try {
            process(templateEngine, templateName, activity);
            activity.getResponseAdapter().getWriter().flush();
        } catch (Exception e) {
            throw new TemplateEngineProcessException(e);
        }
    }

    @Override
    public void process(String templateSource, String contentType, Activity activity)
            throws TemplateEngineProcessException {
        try {
            if (contentType == null) {
                contentType = activity.getResponseAdapter().getContentType();
            }
            Locale locale = activity.getRequestAdapter().getLocale();
            Writer writer = activity.getResponseAdapter().getWriter();

            IEngineConfiguration configuration = templateEngine.getConfiguration();
            ActivityExpressionContext context = ActivityExpressionContextFactory.create(activity, configuration, locale);
            TemplateSpec templateSpec = new TemplateSpec(templateSource, contentType);
            templateEngine.process(templateSpec, context, writer);

            writer.flush();
        } catch (Exception e) {
            throw new TemplateEngineProcessException(e);
        }
    }

    public static void process(ITemplateEngine templateEngine, String templateName, Activity activity)
            throws IOException {
        Assert.notNull(templateEngine, "templateEngine must not be null");
        Assert.notNull(templateName, "templateName must not be null");
        Assert.notNull(activity, "activity must not be null");

        String contentType = activity.getResponseAdapter().getContentType();
        Locale locale = activity.getRequestAdapter().getLocale();
        Writer writer = activity.getResponseAdapter().getWriter();

        IEngineConfiguration configuration = templateEngine.getConfiguration();
        ActivityExpressionContext context = ActivityExpressionContextFactory.create(activity, configuration, locale);

        TemplateSpec templateSpec;
        if (templateName.contains("::")) {
            // Template name contains a fragment name, so we should parse it as such
            IStandardExpressionParser parser = StandardExpressions.getExpressionParser(configuration);
            FragmentExpression fragmentExpression;
            try {
                // By parsing it as a standard expression, we might profit from the expression cache
                fragmentExpression = (FragmentExpression)parser.parseExpression(context, "~{" + templateName + "}");
            } catch (TemplateProcessingException e) {
                throw new IllegalArgumentException("Invalid template name specification: '" + templateName + "'");
            }

            FragmentExpression.ExecutedFragmentExpression fragment =
                FragmentExpression.createExecutedFragmentExpression(context, fragmentExpression);

            String templateNameToUse = FragmentExpression.resolveTemplateName(fragment);
            Set markupSelectors = FragmentExpression.resolveFragments(fragment);

            Map nameFragmentParameters = fragment.getFragmentParameters();
            if (nameFragmentParameters != null && fragment.hasSyntheticParameters()) {
                // We cannot allow synthetic parameters because there is no way to specify them at the template
                // engine execution!
                throw new IllegalArgumentException(
                        "Parameters in a view specification must be named (non-synthetic): '" + templateName + "'");
            }

            templateSpec = new TemplateSpec(templateNameToUse, markupSelectors, contentType, nameFragmentParameters);
        } else {
            // No fragment specified at the template name
            templateSpec = new TemplateSpec(templateName, contentType);
        }

        templateEngine.process(templateSpec, context, writer);
    }

}