Utility Handlers

public class GzipHandler extends Handler.Wrapper implements GzipFactory {
    // Constructors
    public GzipHandler();
    
    // Compression configuration
    public int getMinGzipSize();
    public void setMinGzipSize(int minGzipSize);
    public int getCompressionLevel();
    public void setCompressionLevel(int compressionLevel);
    
    // Content type filtering
    public Set<String> getIncludedMimeTypes();
    public void setIncludedMimeTypes(String... types);
    public Set<String> getExcludedMimeTypes();  
    public void setExcludedMimeTypes(String... types);
    public Set<String> getIncludedMethods();
    public void setIncludedMethods(String... methods);
    public Set<String> getExcludedMethods();
    public void setExcludedMethods(String... methods);
    
    // Path filtering
    public PathMappings<Boolean> getIncludedPaths();
    public void addIncludedPaths(String... pathspecs);
    public PathMappings<Boolean> getExcludedPaths();
    public void addExcludedPaths(String... pathspecs);
    
    // User agent filtering
    public Set<String> getIncludedAgentPatterns();
    public void setIncludedAgentPatterns(String... patterns);
    public Set<String> getExcludedAgentPatterns();
    public void setExcludedAgentPatterns(String... patterns);
    
    // Deflater configuration
    public boolean isCheckGzExists();
    public void setCheckGzExists(boolean checkGzExists);
    public boolean isSyncFlush();
    public void setSyncFlush(boolean syncFlush);
    public int getInflateBufferSize();
    public void setInflateBufferSize(int size);
}

public class GzipConfiguration {
    
    public void setupGzipHandler(Server server) {
        // Create GZIP handler
        GzipHandler gzipHandler = new GzipHandler();
        
        // Configure minimum size for compression (1KB)
        gzipHandler.setMinGzipSize(1024);
        
        // Set compression level (6 = default, good balance of speed/compression)
        gzipHandler.setCompressionLevel(6);
        
        // Include text-based content types
        gzipHandler.setIncludedMimeTypes(
            "text/html",
            "text/plain", 
            "text/xml",
            "text/css",
            "application/javascript",
            "application/json",
            "application/xml"
        );
        
        // Exclude already compressed content
        gzipHandler.setExcludedMimeTypes(
            "image/jpeg",
            "image/png", 
            "image/gif",
            "application/zip",
            "application/gzip"
        );
        
        // Only compress GET and POST requests
        gzipHandler.setIncludedMethods("GET", "POST");
        
        // Exclude paths that shouldn't be compressed
        gzipHandler.addExcludedPaths("/api/binary/*", "/downloads/*");
        
        // Set application handler as child
        gzipHandler.setHandler(new ApplicationHandler());
        
        server.setHandler(gzipHandler);
    }
}

public class CrossOriginHandler extends Handler.Wrapper {
    // Origin configuration
    public Set<String> getAllowedOriginPatterns();
    public void setAllowedOriginPatterns(Set<String> allowedOriginPatterns);
    public void addAllowedOrigin(String origin);
    
    // Method configuration
    public Set<String> getAllowedMethods();
    public void setAllowedMethods(Set<String> allowedMethods);
    public void addAllowedMethod(String method);
    
    // Header configuration
    public Set<String> getAllowedHeaders();
    public void setAllowedHeaders(Set<String> allowedHeaders);
    public void addAllowedHeader(String header);
    public Set<String> getExposedHeaders();
    public void setExposedHeaders(Set<String> exposedHeaders);
    public void addExposedHeader(String header);
    
    // Preflight configuration
    public boolean isAllowCredentials();
    public void setAllowCredentials(boolean allowCredentials);
    public int getPreflightMaxAge();
    public void setPreflightMaxAge(int preflightMaxAge);
    
    // Chain configuration
    public boolean isChainPreflight();
    public void setChainPreflight(boolean chainPreflight);
}

public class CORSConfiguration {
    
    public void setupCORSHandler(Server server) {
        CrossOriginHandler corsHandler = new CrossOriginHandler();
        
        // Allow specific origins
        corsHandler.setAllowedOriginPatterns(Set.of(
            "https://example.com",
            "https://*.example.com",
            "http://localhost:*"
        ));
        
        // Allow specific HTTP methods
        corsHandler.setAllowedMethods(Set.of(
            "GET", "POST", "PUT", "DELETE", "OPTIONS", "HEAD"
        ));
        
        // Allow specific headers
        corsHandler.setAllowedHeaders(Set.of(
            "Content-Type",
            "Authorization", 
            "X-Requested-With",
            "Accept",
            "Origin"
        ));
        
        // Expose custom headers to client
        corsHandler.setExposedHeaders(Set.of(
            "X-Total-Count",
            "X-Page-Count"
        ));
        
        // Allow credentials (cookies, authorization headers)
        corsHandler.setAllowCredentials(true);
        
        // Cache preflight requests for 1 hour
        corsHandler.setPreflightMaxAge(3600);
        
        corsHandler.setHandler(new ApiHandler());
        server.setHandler(corsHandler);
    }
    
    public void setupDevelopmentCORS(Server server) {
        // Permissive CORS for development
        CrossOriginHandler corsHandler = new CrossOriginHandler();
        
        corsHandler.setAllowedOriginPatterns(Set.of("*"));
        corsHandler.setAllowedMethods(Set.of("*"));
        corsHandler.setAllowedHeaders(Set.of("*"));
        corsHandler.setAllowCredentials(false); // Can't use * origins with credentials
        
        corsHandler.setHandler(new DevelopmentHandler());
        server.setHandler(corsHandler);
    }
}

public class StatisticsHandler extends EventsHandler {
    // Request statistics
    public int getRequests();
    public int getRequestsActive();
    public int getRequestsActiveMax();
    
    // Timing statistics
    public long getStatsOnMs();
    public long getRequestTimeTotal();
    public long getRequestTimeMax();
    public long getRequestTimeMean();
    public long getRequestTimeStdDev();
    
    // Response statistics by status
    public int getResponses1xx();
    public int getResponses2xx(); 
    public int getResponses3xx();
    public int getResponses4xx();
    public int getResponses5xx();
    
    // Byte statistics
    public long getBytesReceived();
    public long getBytesSent();
    
    // Error statistics
    public int getErrors();
    public int getTimeouts();
    
    // Async statistics
    public int getAsyncRequests();
    public int getAsyncRequestsWaiting();
    public int getAsyncRequestsWaitingMax();
    
    // Connection statistics
    public int getConnections();
    public int getConnectionsOpen();
    public int getConnectionsOpenMax();
    public Duration getConnectionsOpenMax();
    
    // Statistics control
    public void statsReset();
    public String toStatsHTML();
}

public class StatisticsConfiguration {
    
    public void setupStatisticsHandler(Server server) {
        StatisticsHandler statsHandler = new StatisticsHandler();
        
        // Set up statistics collection
        statsHandler.setHandler(new ApplicationHandler());
        
        // Add statistics reporting endpoint
        Handler.Sequence rootHandler = new Handler.Sequence();
        rootHandler.addHandler(new StatsReportingHandler(statsHandler));
        rootHandler.addHandler(statsHandler);
        
        server.setHandler(rootHandler);
        
        // Start periodic statistics logging
        ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
        scheduler.scheduleAtFixedRate(() -> {
            logStatistics(statsHandler);
        }, 60, 60, TimeUnit.SECONDS);
    }
    
    private void logStatistics(StatisticsHandler stats) {
        System.out.println("=== Server Statistics ===");
        System.out.println("Active Requests: " + stats.getRequestsActive());
        System.out.println("Total Requests: " + stats.getRequests());
        System.out.println("2xx Responses: " + stats.getResponses2xx());
        System.out.println("4xx Responses: " + stats.getResponses4xx());
        System.out.println("5xx Responses: " + stats.getResponses5xx());
        System.out.println("Bytes Sent: " + stats.getBytesSent());
        System.out.println("Mean Response Time: " + stats.getRequestTimeMean() + "ms");
        System.out.println("Errors: " + stats.getErrors());
    }
}

// Handler to expose statistics via HTTP
public class StatsReportingHandler extends Handler.Abstract {
    private final StatisticsHandler statisticsHandler;
    
    public StatsReportingHandler(StatisticsHandler statisticsHandler) {
        this.statisticsHandler = statisticsHandler;
    }
    
    @Override
    public boolean handle(Request request, Response response, Callback callback) 
            throws Exception {
        
        if ("/stats".equals(request.getHttpURI().getPath())) {
            response.setStatus(200);
            response.getHeaders().put("Content-Type", "application/json");
            
            String statsJson = createStatsJson(statisticsHandler);
            response.write(true, ByteBuffer.wrap(statsJson.getBytes()), callback);
            return true;
        }
        
        return false; // Not handled
    }
    
    private String createStatsJson(StatisticsHandler stats) {
        Map<String, Object> statsMap = new HashMap<>();
        statsMap.put("requests", stats.getRequests());
        statsMap.put("requestsActive", stats.getRequestsActive());
        statsMap.put("responses2xx", stats.getResponses2xx());
        statsMap.put("responses4xx", stats.getResponses4xx());
        statsMap.put("responses5xx", stats.getResponses5xx());
        statsMap.put("bytesSent", stats.getBytesSent());
        statsMap.put("bytesReceived", stats.getBytesReceived());
        statsMap.put("meanResponseTime", stats.getRequestTimeMean());
        statsMap.put("maxResponseTime", stats.getRequestTimeMax());
        statsMap.put("errors", stats.getErrors());
        statsMap.put("uptime", stats.getStatsOnMs());
        
        // Convert to JSON (simplified)
        return toJson(statsMap);
    }
}

public class QoSHandler extends ConditionalHandler.Abstract {
    // Request limiting
    public int getMaxRequests();
    public void setMaxRequests(int maxRequests);
    
    // Suspend configuration
    public long getMaxSuspend();
    public void setMaxSuspend(long maxSuspend);
    
    // Current state
    public int getRequests();
    public int getSuspended();
    
    // Priority configuration
    public int getPriority(Request request);
    public void setPriority(Request request, int priority);
}

public class ThreadLimitHandler extends ConditionalHandler.Abstract {
    // Thread limiting
    public int getThreadLimit();
    public void setThreadLimit(int threadLimit);
    
    // Current state
    public int getThreads();
    public boolean isForwardedIdleTimeout();
    public void setForwardedIdleTimeout(boolean forwardedIdleTimeout);
}

public class QoSConfiguration {
    
    public void setupQoSHandlers(Server server) {
        // Thread limiting handler
        ThreadLimitHandler threadLimit = new ThreadLimitHandler();
        threadLimit.setThreadLimit(50); // Max 50 concurrent processing threads
        
        // Request limiting handler
        QoSHandler qosHandler = new QoSHandler() {
            @Override
            protected boolean shouldHandle(Request request) {
                // Apply QoS only to API requests
                return request.getHttpURI().getPath().startsWith("/api/");
            }
        };
        qosHandler.setMaxRequests(100);    // Max 100 concurrent API requests
        qosHandler.setMaxSuspend(30000);   // Wait up to 30 seconds
        
        // Chain handlers
        threadLimit.setHandler(qosHandler);
        qosHandler.setHandler(new ApplicationHandler());
        
        server.setHandler(threadLimit);
    }
    
    public void setupPriorityQoS(Server server) {
        QoSHandler priorityQoS = new QoSHandler() {
            @Override
            public int getPriority(Request request) {
                // Prioritize authenticated users
                if (request.getHeaders().get("Authorization") != null) {
                    return 0; // High priority
                }
                
                // Lower priority for anonymous users
                return 1;
            }
        };
        
        priorityQoS.setMaxRequests(50);
        priorityQoS.setHandler(new ApplicationHandler());
        server.setHandler(priorityQoS);
    }
}

public class ErrorHandler implements Request.Handler {
    // Error page generation
    public void handle(Request request, Response response, Callback callback) throws Exception;
    public String getErrorPage(Request request, int code, String message);
    public void writeErrorPage(Request request, Response response, Callback callback, 
                             int code, String message, boolean showStacks);
    
    // Configuration
    public boolean isShowStacks();
    public void setShowStacks(boolean showStacks);
    public boolean isShowMessageInTitle();
    public void setShowMessageInTitle(boolean showMessageInTitle);
    
    // Caching
    public String getCacheControl();
    public void setCacheControl(String cacheControl);
}

public class CustomErrorHandler extends ErrorHandler {
    
    @Override
    public void writeErrorPage(Request request, Response response, Callback callback,
                             int code, String message, boolean showStacks) {
        
        response.getHeaders().put("Content-Type", "text/html; charset=utf-8");
        
        String errorPage = generateCustomErrorPage(code, message, request);
        response.write(true, ByteBuffer.wrap(errorPage.getBytes()), callback);
    }
    
    private String generateCustomErrorPage(int code, String message, Request request) {
        StringBuilder html = new StringBuilder();
        html.append("<!DOCTYPE html>\n");
        html.append("<html>\n<head>\n");
        html.append("<title>Error ").append(code).append("</title>\n");
        html.append("<style>\n");
        html.append("body { font-family: Arial, sans-serif; margin: 40px; }\n");
        html.append(".error-container { max-width: 600px; margin: 0 auto; }\n");
        html.append(".error-code { font-size: 72px; color: #dc3545; margin: 0; }\n");
        html.append(".error-message { font-size: 24px; color: #6c757d; margin: 10px 0; }\n");
        html.append("</style>\n");
        html.append("</head>\n<body>\n");
        html.append("<div class='error-container'>\n");
        html.append("<h1 class='error-code'>").append(code).append("</h1>\n");
        html.append("<p class='error-message'>").append(escapeHtml(message)).append("</p>\n");
        
        if (code == 404) {
            html.append("<p>The requested resource was not found on this server.</p>\n");
        } else if (code >= 500) {
            html.append("<p>An internal server error occurred. Please try again later.</p>\n");
        }
        
        html.append("<hr>\n");
        html.append("<p><small>Request ID: ").append(request.getId()).append("</small></p>\n");
        html.append("</div>\n</body>\n</html>");
        
        return html.toString();
    }
    
    private String escapeHtml(String text) {
        return text.replace("&", "&amp;")
                  .replace("<", "&lt;")
                  .replace(">", "&gt;")
                  .replace("\"", "&quot;")
                  .replace("'", "&#39;");
    }
}

public class SizeLimitHandler extends Handler.Wrapper {
    // Request size limiting
    public long getRequestLimit();
    public void setRequestLimit(long requestLimit);
    
    // Response size limiting
    public long getResponseLimit();
    public void setResponseLimit(long responseLimit);
    
    // Limit exceeded behavior
    public String getLimitExceededMessage();
    public void setLimitExceededMessage(String limitExceededMessage);
}

public class SizeLimitConfiguration {
    
    public void setupSizeLimits(Server server) {
        SizeLimitHandler sizeLimitHandler = new SizeLimitHandler();
        
        // Limit request size to 10MB
        sizeLimitHandler.setRequestLimit(10 * 1024 * 1024);
        
        // Limit response size to 50MB
        sizeLimitHandler.setResponseLimit(50 * 1024 * 1024);
        
        // Custom error message
        sizeLimitHandler.setLimitExceededMessage("Content size limit exceeded");
        
        sizeLimitHandler.setHandler(new ApplicationHandler());
        server.setHandler(sizeLimitHandler);
    }
}

public class IdleTimeoutHandler extends Handler.Wrapper {
    // Timeout configuration
    public long getIdleTimeout();
    public void setIdleTimeout(long idleTimeout);
    
    // Apply timeout conditions
    public boolean apply(String pathInContext, Request request, Response response);
}

public class DelayedHandler extends Handler.Wrapper {
    // Delay configuration
    public long getDelayMs();
    public void setDelayMs(long delayMs);
}

public class UtilityHandlerChain {
    
    public Handler createUtilityChain() {
        // Statistics collection (outermost)
        StatisticsHandler statsHandler = new StatisticsHandler();
        
        // GZIP compression
        GzipHandler gzipHandler = new GzipHandler();
        gzipHandler.setMinGzipSize(1024);
        gzipHandler.setIncludedMimeTypes("text/html", "text/css", "application/javascript", "application/json");
        
        // CORS support
        CrossOriginHandler corsHandler = new CrossOriginHandler();
        corsHandler.setAllowedOriginPatterns(Set.of("https://*.example.com"));
        corsHandler.setAllowedMethods(Set.of("GET", "POST", "PUT", "DELETE"));
        
        // Size limiting
        SizeLimitHandler sizeLimitHandler = new SizeLimitHandler();
        sizeLimitHandler.setRequestLimit(10 * 1024 * 1024); // 10MB
        
        // QoS limiting
        QoSHandler qosHandler = new QoSHandler();
        qosHandler.setMaxRequests(200);
        
        // Application handler
        Handler applicationHandler = new ApplicationHandler();
        
        // Chain them together
        statsHandler.setHandler(gzipHandler);
        gzipHandler.setHandler(corsHandler);
        corsHandler.setHandler(sizeLimitHandler);
        sizeLimitHandler.setHandler(qosHandler);
        qosHandler.setHandler(applicationHandler);
        
        return statsHandler;
    }
}