protohackersc/server05.c

//
// Created by Ajurna on 30/07/2025.
//

#include "server05.h"
#include <pthread.h>
#include <winsock2.h>
#include <stdio.h>
#include "data.h"
#include <ctype.h>
#include <stdint.h>
#include <windows.h>
#define PCRE2_CODE_UNIT_WIDTH 8
#include <pcre2.h>


const char *newline = "\n";
const char *bogus_address = "7YWHMfk9JZe0LM0g1ZauHuiSxhI";

int main() {
    SOCKET server = get_listen_socket();
    SOCKADDR_IN clientAddr;
    SOCKET client;
    int clientAddrSize = sizeof(clientAddr);
    int connection_number = 1;

    char *message = "Please pay the ticket price of 15 Boguscoins to one of these addresses: 7ABnYzozPt2cyDHQqDq2ExIMz53xXVcErn 7z6kM0VlNJpZiqTEHmRjxW9FbVCkv2flb 7qReHdk11Ai67nRvvfTQXFjPZH3X";
    char *new_message = replace_bogus_coin(message);
    // replace_bogus_coin(message);
    printf("%s\n", new_message);
    // exit(0);
    printf("Listening for incoming connections...\n");
    while((client = accept(server, (SOCKADDR *)&clientAddr, &clientAddrSize)) != INVALID_SOCKET)
    {
        handle_args_t *args = malloc(sizeof(handle_args_t));
        args->client = client;
        args->server = get_chat_socket();
        args->connection = connection_number++;
        pthread_t thread;
        pthread_create(&thread, nullptr, handle_server, args);
        pthread_create(&thread, nullptr, handle_client, args);
    }
    return 0;
}

void *handle_server(void *args) {
    handle_args_t *handleArgs = args;
    char buffer[1024] = {};
    int bytesReceived;
    printf("{%d} Server connected\n", handleArgs->connection);
    char_array_t *data = char_array_create(1024);
    while ((bytesReceived = recv(handleArgs->server, buffer, sizeof(buffer), 0)) > 0) {
        printf("server sent {%d}: |%d| \n", handleArgs->connection, bytesReceived);
        char_array_append(data, buffer, bytesReceived);
        char *request;
        while ((request = char_array_get_until_char(data, '\n')) != NULL) {
            printf("{%d} server Said: %s\n", handleArgs->connection, request);
            request = replace_bogus_coin(request);
            send(handleArgs->client, request, strlen(request), 0);
            send(handleArgs->client, newline, strlen(newline), 0);
            free(request);
        }
        memset(buffer, 0, sizeof(buffer));
    }
    // closesocket(handleArgs->server);
    return nullptr;
}

char *replace_bogus_coin(char *message) {
    pcre2_code *re;
    PCRE2_SPTR pattern = (PCRE2_SPTR)"\\b7\\w{25,34}\\b";
    PCRE2_SPTR subject = (PCRE2_SPTR)message;
    size_t subject_length = strlen((char *)subject);
    int errornumber;
    PCRE2_SIZE erroroffset;
    PCRE2_SIZE *ovector;
    int rc;
    size_t offset = 0;  // Keep track of where we are in the string

    // Compile the pattern
    re = pcre2_compile(
        pattern,
        PCRE2_ZERO_TERMINATED,
        0,
        &errornumber,
        &erroroffset,
        NULL);

    if (re == NULL) {
        PCRE2_UCHAR buff[256];
        pcre2_get_error_message(errornumber, buff, sizeof(buff));
        printf("PCRE2 compilation failed at offset %d: %s\n", (int)erroroffset, buff);
        return message;
    }

    // Create match data block
    pcre2_match_data *match_data = pcre2_match_data_create_from_pattern(re, NULL);
    char *result = strdup(message);  // Create a copy of the original message
    
    // Loop until no more matches are found
    while (offset < subject_length) {
        rc = pcre2_match(
            re,
            subject,
            subject_length,
            offset,     // Start from last match position
            0,
            match_data,
            NULL);

        if (rc < 0) {
            break;  // No more matches
        }

        ovector = pcre2_get_ovector_pointer(match_data);
        PCRE2_SIZE start = ovector[0];
        PCRE2_SIZE end = ovector[1];
        
        // Replace the matched text with bogus_address
        char *temp = calloc(strlen(result) + strlen(bogus_address) + 1, sizeof(char));
        strncpy(temp, result, start);
        strcat(temp, bogus_address);
        strcat(temp, result + end);
        
        free(result);
        result = temp;
        
        // Update the subject and length for next iteration
        subject = (PCRE2_SPTR)result;
        subject_length = strlen(result);
        offset = start + strlen(bogus_address);
    }

    // Clean up
    pcre2_match_data_free(match_data);
    pcre2_code_free(re);

    return result;
}

void *handle_client(void *args) {
    handle_args_t *handleArgs = args;
    char buffer[1024] = {};
    int bytesReceived;
    printf("{%d} Client connected\n", handleArgs->connection);
    char_array_t *data = char_array_create(1024);
    while ((bytesReceived = recv(handleArgs->client, buffer, sizeof(buffer), 0)) > 0) {
        printf("server sent {%d}: |%d| \n", handleArgs->connection, bytesReceived);
        char_array_append(data, buffer, bytesReceived);
        char *request;

        while ((request = char_array_get_until_char(data, '\n')) != NULL) {
            printf("{%d} client Said: %s\n", handleArgs->connection, request);
            request = replace_bogus_coin(request);
            send(handleArgs->server, request, strlen(request), 0);
            send(handleArgs->server, newline, strlen(newline), 0);
            free(request);
        }
        memset(buffer, 0, sizeof(buffer));
    }
    // closesocket(handleArgs->client);
    return nullptr;
}



SOCKET get_chat_socket() {
    WSADATA WSAData;

    SOCKADDR_IN serverAddr;
    struct hostent * host = gethostbyname("chat.protohackers.com");
    WSAStartup(MAKEWORD(2,0), &WSAData);
    SOCKET server = socket(AF_INET, SOCK_STREAM, 0 );
    serverAddr.sin_addr.s_addr = AF_INET;
    serverAddr.sin_family = AF_INET;
    memcpy(&serverAddr.sin_addr.s_addr, host->h_addr_list[0], host->h_length);

    serverAddr.sin_port = htons(16963);

    connect(server, (SOCKADDR *) & serverAddr, sizeof (serverAddr));
    return server;
}