#include <stdio.h>
#include <netdb.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#define SA struct sockaddr

struct packet {
    char oper[5];
    int int1;
    int int2;
};

struct resultpacket {
    int success;
    int result;
};

//addition procedure
int addition(int num1, int num2) {
    return num1 + num2;
}

//subtraction procedure
int subtract(int num1, int num2) {
    return num1 - num2;
}

//multiplication procedure
int multiply(int num1, int num2) {
    return num1 * num2;
}

//division procedure
int divide(int num1, int num2) {
    if (num2 == 0)
    {
        return -1;
    }
    return num1 / num2;
}

// Function for send/receive between client and server.
void talk(int sockfd)
{
    // infinite loop for send/receive
    for (;;) {
        int result, success;

        //create packet for receiving from client
        struct packet pkt;
        recv(sockfd, &pkt, sizeof(pkt), 0);
        printf("Packet from client: %s %d %d\n", pkt.oper, pkt.int1, pkt.int2);

        struct resultpacket respkt;

        //check operator from packet
        if (strcmp(pkt.oper,"add") == 0) {
            result = addition(pkt.int1, pkt.int2);
            success = 1;
        } else if (strcmp(pkt.oper,"sub") == 0) {
            result = subtract(pkt.int1, pkt.int2);
            success = 1;
        } else if (strcmp(pkt.oper,"mul") == 0) {
            result = multiply(pkt.int1, pkt.int2);
            success = 1;
        } else if (strcmp(pkt.oper,"div") == 0) {
            result = divide(pkt.int1, pkt.int2);
            if (result == -1) {
                success = 0;
            } else {
                success = 1;
            }
        }
        respkt.success = success;
        respkt.result = result;

        //sending the result packet to client
        printf("Sending to client - success: %d / result: %d\n",respkt.success, respkt.result);
        send(sockfd, &respkt, sizeof(respkt), 0);
    }
}

// Server setup function
int main()
{
    int sockfd, connfd, len;
    struct sockaddr_in servaddr, cli;

    // socket create and verification
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd == -1) {
        printf("socket creation failed...\n");
        exit(0);
    }
    else
        printf("Socket successfully created..\n");
    bzero(&servaddr, sizeof(servaddr));

    // assign IP, PORT
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons( 8888 );

    // Binding newly created socket to given IP and verification
    if ((bind(sockfd, (SA*)&servaddr, sizeof(servaddr))) != 0) {
        printf("socket bind failed...\n");
        exit(0);
    }
    else
        printf("Socket successfully binded..\n");

    // Now server is ready to listen and verification
    if ((listen(sockfd, 5)) != 0) {
        printf("Listen failed...\n");
        exit(0);
    }
    else
        printf("Server listening..\n");
    len = sizeof(cli);

    // Accept the data packet from client and verification
    connfd = accept(sockfd, (SA*)&cli, &len);
    if (connfd < 0) {
        printf("server acccept failed...\n");
        exit(0);
    }
    else
        printf("server acccept the client...\n");

    // Function for send/receive between client and server
    talk(connfd);

    // After chatting close the socket
    close(sockfd);
}