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/**
 * Copyright (C) the original author or authors.
 *
 * 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 ninja.utils;

import static ninja.utils.NinjaConstant.HTTP_CACHE_CONTROL;
import static ninja.utils.NinjaConstant.HTTP_CACHE_CONTROL_DEFAULT;
import static ninja.utils.NinjaConstant.HTTP_USE_ETAG;
import static ninja.utils.NinjaConstant.HTTP_USE_ETAG_DEFAULT;

import java.util.Date;
import java.util.Optional;

import ninja.Context;
import ninja.Result;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.inject.Inject;

public class HttpCacheToolkitImpl implements HttpCacheToolkit {
    
    private static final Logger logger = LoggerFactory.getLogger(HttpCacheToolkitImpl.class);
    
    private final NinjaProperties ninjaProperties;
    
    @Inject
    public HttpCacheToolkitImpl(NinjaProperties ninjaProperties) {
        this.ninjaProperties = ninjaProperties;
        
    }

    public boolean isModified(Optional etag, Optional lastModified, Context context) {

        final String browserEtag = context.getHeader(HttpHeaderConstants.IF_NONE_MATCH);

        if (browserEtag != null && etag.isPresent()) {
            if (browserEtag.equals(etag.get())) {
                return false;
            } else {
                return true;
            }
        }

        final String ifModifiedSince = context.getHeader(HttpHeaderConstants.IF_MODIFIED_SINCE);

        if (ifModifiedSince != null && lastModified.isPresent()) {

            if (!ifModifiedSince.isEmpty()) {
                try {
                    Date browserDate = DateUtil
                            .parseHttpDateFormat(ifModifiedSince);
                    if (browserDate.getTime() >= lastModified.get()) {
                        return false;
                    }
                } catch (IllegalArgumentException ex) {
                    logger.warn("Can't parse HTTP date", ex);
                }
                return true;
            }
        }
        return true;
    }

    public void addEtag(Context context, Result result, Long lastModified) {

        if (!ninjaProperties.isProd()) {
            result.addHeader(HttpHeaderConstants.CACHE_CONTROL, "no-cache");
        } else {
            String maxAge = ninjaProperties.getWithDefault(HTTP_CACHE_CONTROL,
                    HTTP_CACHE_CONTROL_DEFAULT);

            if (maxAge.equals("0")) {
                result.addHeader(HttpHeaderConstants.CACHE_CONTROL, "no-cache");
            } else {
                result.addHeader(HttpHeaderConstants.CACHE_CONTROL, "max-age=" + maxAge);
            }
        }
        
        // Use etag on demand:
        String etag = null; 
        boolean useEtag = ninjaProperties.getBooleanWithDefault(HTTP_USE_ETAG,
                HTTP_USE_ETAG_DEFAULT);
        
        if (useEtag) {
            // ETag right now is only lastModified long.
            // maybe we change that in the future.
            etag = "\""
                    + lastModified.toString() + "\"";
            result.addHeader(HttpHeaderConstants.ETAG, etag);
            
        }


        if (!isModified(Optional.ofNullable(etag), Optional.ofNullable(lastModified), context)) {

            if (context.getMethod().toLowerCase().equals("get")) {
                result.status(Result.SC_304_NOT_MODIFIED);
            }
            
        } else {
            result.addHeader(HttpHeaderConstants.LAST_MODIFIED,
                    DateUtil.formatForHttpHeader(lastModified));

        }       
        


    }

}