diff --git a/handler.js b/handler.js
index 2e720b7..9ba75c5 100644
--- a/handler.js
+++ b/handler.js
@@ -1,25 +1,156 @@
 // Define the handler function
-export const handler = async (event, res) => {
+export const handler = async (request, res) => {
     try {
-        // Prepare the response JSON
-        const responseJson = {
-            message: "Hello World"
-        };
+        console.log("Request strated")
+        const { request } = req.body;
+        const modified = preRequestHandlerWrapper(request);
+        res.status(200).json(modified);
+    } catch (err) {
 
-        // Print the JSON response to stdout
-        console.log(JSON.stringify(responseJson));
-
-        // Set the response headers
-        res.setHeader('Content-Type', 'application/json');
-
-        // Send the response JSON
-        res.end(JSON.stringify(responseJson));
-    } catch (error) {
-        // Handle errors
-        console.error(error);
-        // Send an error response if needed
-        res.statusCode = 500;
-        res.setHeader('Content-Type', 'text/plain');
-        res.end('Internal Server Error');
+        if (err?.message.includes('Body content-type is not valid JSON')) {
+            res.status(err.statusCode).json({
+                error: err.name,
+                message: err.message,
+                ...(err.details && { details: err.details })
+            });
+        } else {
+            res.status(500).json({
+                error: err.name || 'InternalServerError',
+                message: err.message || 'Something went wrong',
+            });
+        }
     }
 };
+
+let currentContext = null;
+let currentRequest = null;
+
+function createContext() {
+    return {
+        addedQueryParams: {},
+        removedQueryParams: [],
+        addedHeaders: {},
+        removedHeaders: [],
+        method: null,
+        body: null
+    };
+}
+
+export function preRequestHandlerWrapper(request) {
+    currentContext = createContext();
+    currentRequest = request;
+    preRequestHandler();
+    const ctx = currentContext;
+    currentContext = null;
+    currentRequest = null;
+    return ctx;
+}
+
+export function preRequestHandler() {
+    const headerValue = getHeader('x-api-key');
+    setHeader('x-api-key-1', headerValue);
+    setQueryParam('accessKey', getQueryParam('queryParam2'));
+    removeQueryParam('queryParam2');
+
+    const body = getJsonBody();
+    if (body) {
+        body.modifiedAt = Date.now();
+        body.transformedText = "Pre Request Transformed Text";
+        setJsonBody(body);
+    }
+}
+
+// ========== Utility functions using currentRequest ==========
+
+export function setHeader(key, value) {
+    if (!currentRequest?.headers) currentRequest.headers = {};
+    currentRequest.headers[key.toLowerCase()] = value;
+    currentContext?.addedHeaders && (currentContext.addedHeaders[key.toLowerCase()] = value);
+}
+
+export function removeHeader(key) {
+    if (currentRequest?.headers?.[key.toLowerCase()] !== undefined) {
+        delete currentRequest.headers[key.toLowerCase()];
+        currentContext?.removedHeaders?.push(key.toLowerCase());
+    }
+}
+
+export function setQueryParam(key, value) {
+    const url = new URL(currentRequest.url);
+    url.searchParams.set(key, value);
+    currentRequest.url = url.toString();
+    currentContext?.addedQueryParams && (currentContext.addedQueryParams[key] = value);
+}
+
+export function removeQueryParam(key) {
+    const url = new URL(currentRequest.url);
+    url.searchParams.delete(key);
+    currentRequest.url = url.toString();
+    currentContext?.removedQueryParams?.push(key);
+}
+
+export function setMethod(method) {
+    if (typeof method === 'string') {
+        currentRequest.method = method.toUpperCase();
+        currentContext && (currentContext.method = currentRequest.method);
+    }
+}
+
+export function getJsonBody() {
+    if (!currentRequest?.body) return null;
+
+    const contentType = currentRequest.contentType || currentRequest.headers?.['content-type'] || '';
+
+    if (!contentType.includes('application/json')) {
+        throw new InvalidJsonContentTypeError();
+    }
+
+    try {
+        return typeof currentRequest.body === 'string'
+            ? JSON.parse(currentRequest.body)
+            : currentRequest.body;
+    } catch (err) {
+        throw new InvalidJsonContentTypeError('Failed to parse JSON body', 415, { originalError: err });
+    }
+}
+
+export function setJsonBody(json) {
+    const contentType = currentRequest.contentType || currentRequest.headers?.['content-type'] || '';
+
+    if (!contentType.includes('application/json')) {
+        throw new InvalidJsonContentTypeError();
+    }
+
+    try {
+        currentRequest.body = JSON.stringify(json);
+        currentContext && (currentContext.body = json);
+    } catch (err) {
+        throw new InvalidJsonContentTypeError('Failed to stringify JSON body', 415, { originalError: err });
+    }
+}
+
+export function getQueryParam(key) {
+    try {
+        const url = new URL(currentRequest.url);
+        return url.searchParams.get(key);
+    } catch {
+        return null;
+    }
+}
+
+export function getHeader(key) {
+    if (!currentRequest?.headers) return null;
+    return currentRequest.headers[key.toLowerCase()] || null;
+}
+
+// === Custom Exception Class ===
+class InvalidJsonContentTypeError extends Error {
+    constructor(message = 'Body content-type is not valid JSON', statusCode = 415, details = {}) {
+        super(message);
+        this.name = 'InvalidJsonContentTypeError';
+        this.statusCode = statusCode;
+        this.details = details;
+    }
+}
+
+