create the CoordinatorWebServer

src/main/java/com/distributed/search/web/CoordinatorWebServer.java

+package com.distributed.search.web;
+
+import com.distributed.search.grpc.SearchClient;
+import com.distributed.search.logic.FileManager;
+import com.distributed.search.model.SearchResponse;
+import com.google.gson.Gson;
+import com.sun.net.httpserver.HttpExchange;
+import com.sun.net.httpserver.HttpServer;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.net.InetSocketAddress;
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.Executors;
+
+/**
+ * Internal HTTP Server running on the Leader node.
+ * It receives search queries from the Frontend and returns results in JSON format.
+ */
+public class CoordinatorWebServer {
+    private static final String SEARCH_ENDPOINT = "/search";
+    private final int port;
+    private final SearchClient searchClient;
+    private final String storageDir;
+    private HttpServer server;
+    private final Gson gson = new Gson();
+
+    public CoordinatorWebServer(int port, SearchClient searchClient, String storageDir) {
+        this.port = port;
+        this.searchClient = searchClient;
+        this.storageDir = storageDir;
+    }
+
+    public void startServer() {
+        try {
+            this.server = HttpServer.create(new InetSocketAddress(port), 0);
+            server.createContext(SEARCH_ENDPOINT, this::handleSearchRequest);
+            server.setExecutor(Executors.newFixedThreadPool(8));
+            server.start();
+            System.out.println("Leader Internal Web Server started on port: " + port);
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+    public void stopServer() {
+        if (server != null) server.stop(0);
+    }
+
+    /**
+     * Handles search requests from the Frontend.
+     * Expects query param: /search?query=word1+word2
+     */
+    private void handleSearchRequest(HttpExchange exchange) throws IOException {
+        if (!exchange.getRequestMethod().equalsIgnoreCase("get")) {
+            exchange.close();
+            return;
+        }
+
+        // Extract query from URI
+        String query = exchange.getRequestURI().getQuery().split("=")[1];
+        List<String> terms = Arrays.asList(query.toLowerCase().split("\\+"));
+
+        System.out.println("Internal API received query: " + terms);
+
+        // Execute distributed search
+        List<String> allFiles = FileManager.getSortedDocumentNames(storageDir);
+        List<SearchResponse.DocumentResult> results = searchClient.performSearch(terms, allFiles);
+
+        // Convert results to JSON using GSON
+        String jsonResponse = gson.toJson(results);
+
+        sendResponse(jsonResponse.getBytes(), exchange);
+    }
+
+    private void sendResponse(byte[] responseBytes, HttpExchange exchange) throws IOException {
+        exchange.getResponseHeaders().add("Content-Type", "application/json");
+        exchange.sendResponseHeaders(200, responseBytes.length);
+        OutputStream outputStream = exchange.getResponseBody();
+        outputStream.write(responseBytes);
+        outputStream.flush();
+        outputStream.close();
+    }
+}
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