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A middleware Lambda function that handles all the cross-cutting concerns for the downstream Lambda function.
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package com.networknt.aws.lambda.app;

import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.RequestHandler;
import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyRequestEvent;
import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyResponseEvent;
import com.networknt.aws.lambda.handler.Handler;
import com.networknt.aws.lambda.LightLambdaExchange;
import com.networknt.aws.lambda.handler.chain.Chain;
import com.networknt.config.Config;
import com.networknt.utility.ModuleRegistry;
import com.networknt.utility.PathTemplateMatcher;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.HashMap;
import java.util.Map;


/**
 * This is the entry point for the middleware Lambda function that is responsible for cross-cutting concerns for the business Lambda
 * function which is called from the is Lambda function once all cross-cutting concerns are addressed. The middleware Lambda function
 * receives the APIGatewayProxyRequestEvent from the API Gateway and returns the APIGatewayProxyResponseEvent to the API Gateway.
 *
 * @author Steve Hu
 */
public class LambdaApp implements RequestHandler {

    private static final Logger LOG = LoggerFactory.getLogger(LambdaApp.class);
    public static final LambdaAppConfig CONFIG = (LambdaAppConfig) Config.getInstance().getJsonObjectConfig(LambdaAppConfig.CONFIG_NAME, LambdaAppConfig.class);
    static final Map> methodToMatcherMap = new HashMap<>();

    public LambdaApp() {
        if (LOG.isInfoEnabled()) LOG.info("LambdaApp is constructed");
        Handler.init();
        ModuleRegistry.registerModule(
                LambdaAppConfig.CONFIG_NAME,
                LambdaApp.class.getName(),
                Config.getNoneDecryptedInstance().getJsonMapConfigNoCache(LambdaAppConfig.CONFIG_NAME),
                null
        );
    }

    @Override
    public APIGatewayProxyResponseEvent handleRequest(final APIGatewayProxyRequestEvent apiGatewayProxyRequestEvent, final Context context) {
        LOG.debug("Lambda CCC --start with request: {}", apiGatewayProxyRequestEvent);
        var requestPath = apiGatewayProxyRequestEvent.getPath();
        var requestMethod = apiGatewayProxyRequestEvent.getHttpMethod();
        LOG.debug("Request path: {} -- Request method: {}", requestPath, requestMethod);
        Chain chain = Handler.getChain(apiGatewayProxyRequestEvent);
        if(chain == null) chain = Handler.getDefaultChain();
        final var exchange = new LightLambdaExchange(context, chain);
        exchange.setInitialRequest(apiGatewayProxyRequestEvent);
        exchange.executeChain();
        APIGatewayProxyResponseEvent response = exchange.getFinalizedResponse(false);
        LOG.debug("Lambda CCC --end with response: {}", response);
        return response;
    }
}