#include <arpa/inet.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <unistd.h>
#include <stdbool.h>

struct Transfer {
    char request;
    char filename[64];
    int fileSize;
};

struct TransferResponse {
    char response;
    int fileSize;
};

int main(int argc, char** argv){

    char ip[16];
    int port;

    scanf("%s %d", ip, &port); // reading the IP and PORT

    struct sockaddr_in serverAdress;
    memset(&serverAdress, 0, sizeof(serverAdress));

    serverAdress.sin_family = AF_INET; // IPv4
    serverAdress.sin_port = htons(port); // convert port to network byte order
    serverAdress.sin_addr.s_addr = inet_addr(ip);

    /// Creating a TCP socket
    int sock = socket(AF_INET, SOCK_STREAM, 0);
    int connectionResult = connect(sock, (struct sockaddr*)&serverAdress, sizeof(serverAdress));

    if(connectionResult < 0) {printf("Connection failed :<");}

    while(true)
    {
        char b1; scanf("%c", &b1);
        char operation;
        scanf("%c", &operation);

        if(operation == 'D')
        {
            char buff;
            scanf("%c", &buff); // reading the space

            char filename[64];
            scanf("%s", filename);

            struct Transfer t;
            memset(&t, 0, sizeof(t));
            t.request = operation;
            strcpy(t.filename, filename);
            t.fileSize = 0;

            // Sending a transfer request to the server
            send(sock, &t, sizeof(t), 0);

            struct TransferResponse r;
            recv(sock, &r, sizeof(r), 0);

            if(r.response == 'N')
            {
                printf("File %s does not exist on server.\n", filename);
                continue;
            }

            // receiving the file content
            char buffer[1024];
            int bytesR = 0;
            if(!(r.fileSize <= 0 || r.fileSize > 1024))
            {
                bytesR = recv(sock, buffer, r.fileSize, 0);
            }

            FILE *dwn = fopen(filename, "w");
            fwrite(buffer, sizeof(char), bytesR, dwn);
            fclose(dwn);
            buffer[bytesR] = '\0';
            printf("File %s downloaded.\n", filename);
            printf("%s\n", buffer);
        }
        if(operation == 'U')
        {
            char buff;
            scanf("%c", &buff); // skip space

            char filename[64];
            scanf("%s", filename);

            // Open file to read content
            FILE* file = fopen(filename, "r");
            if (!file)
            {
                printf("File %s not found.\n", filename);
                continue;
            }

            // Determine file size
            fseek(file, 0, SEEK_END);
            int fileSize = ftell(file);
            rewind(file); // reset pointer to beginning

            // Read file content into buffer
            char buffer[1024];
            fread(buffer, sizeof(char), fileSize, file);
            fclose(file);

            // Prepare Transfer struct
            struct Transfer t = {0};
            t.request = 'U';
            strcpy(t.filename, filename);
            t.fileSize = fileSize;

            // Send Transfer struct
            send(sock, &t, sizeof(t), 0);

            // Receive server response
            struct TransferResponse r;
            recv(sock, &r, sizeof(r), 0);

            if (r.response == 'N') {
                printf("File %s already exists on server.\n", filename);
                continue;
            }

            // Send file content
            send(sock, buffer, fileSize, 0);
            printf("File %s uploaded.\n", filename);

        }
        if(operation == 'C')
        {
            struct Transfer t;
            memset(&t, 0, sizeof(t));
            t.request = operation;
            strcpy(t.filename, "");
            t.fileSize = 0;
            send(sock, &t, sizeof(t), 0);
            close(sock);

            break;
        }
    }

    return 0;
}