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package org.apereo.cas.services.web;

import lombok.Getter;
import lombok.RequiredArgsConstructor;
import lombok.Setter;
import lombok.extern.slf4j.Slf4j;
import lombok.val;
import org.springframework.core.Ordered;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import org.springframework.web.servlet.ThemeResolver;
import org.springframework.web.servlet.View;
import org.springframework.web.servlet.ViewResolver;

import java.util.Locale;
import java.util.Map;
import java.util.Optional;
import java.util.concurrent.ConcurrentHashMap;

/**
 * {@link ThemeBasedViewResolver} is a View Resolver that takes the active theme into account to selectively choose
 * which set of UI views will be used to generate the standard views.
 *
 * @author Daniel Frett
 * @since 5.2.0
 */
@Slf4j
@Setter
@Getter
@RequiredArgsConstructor
public class ThemeBasedViewResolver implements ViewResolver, Ordered {

    private final ThemeResolver themeResolver;

    private final ThemeViewResolverFactory viewResolverFactory;

    private final Map resolvers = new ConcurrentHashMap<>();

    private int order = LOWEST_PRECEDENCE;

    @Override
    public View resolveViewName(final String viewName, final Locale locale) {
        try {
            val theme = Optional.of(RequestContextHolder.currentRequestAttributes())
                .filter(ServletRequestAttributes.class::isInstance)
                .map(ServletRequestAttributes.class::cast)
                .map(ServletRequestAttributes::getRequest)
                .map(themeResolver::resolveThemeName);
            val delegate = theme.map(this::getViewResolver);
            if (delegate.isPresent()) {
                return delegate.get().resolveViewName(viewName, locale);
            }
        } catch (final Exception e) {
            LOGGER.debug("error resolving view [{}] for theme", viewName, e);
        }
        return null;
    }

    /**
     * Get (or create) the view resolver for the theme.
     *
     * @param theme the theme
     * @return the view resolver
     */
    protected ViewResolver getViewResolver(final String theme) {
        if (resolvers.containsKey(theme)) {
            return resolvers.get(theme);
        }
        val resolver = viewResolverFactory.create(theme);
        resolvers.put(theme, resolver);
        return resolver;
    }
}