package io.dropwizard.jetty;

import com.fasterxml.jackson.annotation.JsonProperty;
import com.google.common.base.Joiner;
import io.dropwizard.util.Duration;
import io.dropwizard.validation.MinDuration;
import org.eclipse.jetty.servlet.ServletContextHandler;
import org.eclipse.jetty.servlets.PushCacheFilter;

import javax.annotation.Nullable;
import javax.servlet.DispatcherType;
import javax.validation.constraints.Min;
import java.util.EnumSet;
import java.util.List;
import java.util.concurrent.TimeUnit;

A factory for building HTTP/2 PushCacheFilter, 

Configuration Parameters:

    

        
Name
        
Default
        
Description
    
    

        
enabled
        
false
        

            If true, the filter will organize resources as primary resources (those referenced by the
            Referer header) and secondary resources (those that have the Referer header).
            Secondary resources that have been requested within a time window from the request of the
            primary resource will be associated with the it. The next time a client will
            request the primary resource, the server will send to the client the secondary resources
            along with the primary in a single response.
        
    
    

        
associatePeriod
        
4 seconds
        

            The time window within which a request for a secondary resource will be associated to a
            primary resource.
        
    
    

        
maxAssociations
        
16
        

            The maximum number of secondary resources that may be associated to a primary resource.
        
    
    

        
refererHosts
        
All hosts
        

            The list of referrer hosts for which the server push technology is supported.
        
    
    

        
refererPorts
        
All ports
        

            The list of referrer ports for which the server push technology is supported.
        
    

/**
 * A factory for building HTTP/2 {@link PushCacheFilter},
 * <p/>
 * <b>Configuration Parameters:</b>
 * <table>
 *     <tr>
 *         <td>Name</td>
 *         <td>Default</td>
 *         <td>Description</td>
 *     </tr>
 *     <tr>
 *         <td>{@code enabled}</td>
 *         <td>false</td>
 *         <td>
 *             If true, the filter will organize resources as primary resources (those referenced by the
 *             <i>Referer</i> header) and secondary resources (those that have the <i>Referer</i> header).
 *             Secondary resources that have been requested within a time window from the request of the
 *             primary resource will be associated with the it. The next time a client will
 *             request the primary resource, the server will send to the client the secondary resources
 *             along with the primary in a single response.
 *         </td>
 *     </tr>
 *     <tr>
 *         <td>{@code associatePeriod}</td>
 *         <td>4 seconds</td>
 *         <td>
 *             The time window within which a request for a secondary resource will be associated to a
 *             primary resource.
 *         </td>
 *     </tr>
 *     <tr>
 *         <td>{@code maxAssociations}</td>
 *         <td>16</td>
 *         <td>
 *             The maximum number of secondary resources that may be associated to a primary resource.
 *         </td>
 *     </tr>
 *     <tr>
 *         <td>{@code refererHosts}</td>
 *         <td>All hosts</td>
 *         <td>
 *             The list of referrer hosts for which the server push technology is supported.
 *         </td>
 *     </tr>
 *     <tr>
 *         <td>{@code refererPorts}</td>
 *         <td>All ports</td>
 *         <td>
 *             The list of referrer ports for which the server push technology is supported.
 *         </td>
 *     </tr>
 * </table>
 */
public class ServerPushFilterFactory {

    private static final Joiner COMMA_JOINER = Joiner.on(",");

    private boolean enabled = false;

    @MinDuration(value = 1, unit = TimeUnit.MILLISECONDS)
    private Duration associatePeriod = Duration.seconds(4);

    @Min(1)
    private int maxAssociations = 16;

    @Nullable
    private List<String> refererHosts;

    @Nullable
    private List<Integer> refererPorts;

    @JsonProperty
    public boolean isEnabled() {
        return enabled;
    }

    @JsonProperty
    public void setEnabled(boolean enabled) {
        this.enabled = enabled;
    }

    @JsonProperty
    public Duration getAssociatePeriod() {
        return associatePeriod;
    }

    @JsonProperty
    public void setAssociatePeriod(Duration associatePeriod) {
        this.associatePeriod = associatePeriod;
    }

    @JsonProperty
    public int getMaxAssociations() {
        return maxAssociations;
    }

    @JsonProperty
    public void setMaxAssociations(int maxAssociations) {
        this.maxAssociations = maxAssociations;
    }

    @Nullable
    @JsonProperty
    public List<String> getRefererHosts() {
        return refererHosts;
    }

    @JsonProperty
    public void setRefererHosts(@Nullable List<String> refererHosts) {
        this.refererHosts = refererHosts;
    }

    @Nullable
    @JsonProperty
    public List<Integer> getRefererPorts() {
        return refererPorts;
    }

    @JsonProperty
    public void setRefererPorts(@Nullable List<Integer> refererPorts) {
        this.refererPorts = refererPorts;
    }

    public void addFilter(ServletContextHandler handler) {
        if (!enabled) {
            return;
        }

        handler.setInitParameter("associatePeriod", String.valueOf(associatePeriod.toMilliseconds()));
        handler.setInitParameter("maxAssociations", String.valueOf(maxAssociations));
        if (refererHosts != null) {
            handler.setInitParameter("hosts", COMMA_JOINER.join(refererHosts));
        }
        if (refererPorts != null) {
            handler.setInitParameter("ports", COMMA_JOINER.join(refererPorts));
        }
        handler.addFilter(PushCacheFilter.class, "/*", EnumSet.of(DispatcherType.REQUEST));
    }
}