//
// Name: Taylor Carr
// Date: December 3, 2017
// CS4310: Project #2
//

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



#define MAXBUF 1024

int main(int argc, const char * argv[]) {
    
    // Initialize log.txt file
    FILE *log,
    *reader;
    log = fopen("log.txt", "w+");
    
    struct sockaddr_in my_addr;
    socklen_t arrdLen = sizeof(my_addr);
    short port = 0;
    
    
    int SIZE = 10; // Max number of agents
    char *agents[SIZE], // List of current connections
    *times[SIZE]; // List of connection times
    
    printf("Enter the port: ");
    scanf("%hu", &port); // store port from user
    
    // Set values for struct
    memset(&my_addr, '\0', arrdLen); // set everything to 0
    my_addr.sin_family = AF_INET;
    my_addr.sin_port = htons(port);
    my_addr.sin_addr.s_addr = INADDR_ANY;
    memset(my_addr.sin_zero, '\0', sizeof(my_addr.sin_zero));
    
    int sd;
    // Create a new socket
    if ((sd = socket (AF_INET, SOCK_STREAM, 0)) < 0) {
        fprintf (stderr, "ERROR: socket() failed\n");
        exit (-1);
    }
    printf("\nSocket created\n");
    
    // Bind socket
    if (bind (sd, (struct sockaddr *)&my_addr, arrdLen) < 0){
        fprintf (stderr, "ERROR: bind() failed\n");
        exit (-1);
    }
    printf("\nBind successful\n");
    
    // Get listening IP and print it
    char szHostName[255];
    gethostname(szHostName, 255);
    struct hostent *host_entry;
    host_entry= gethostbyname(szHostName);
    char * szLocalIP;
    szLocalIP = inet_ntoa (*(struct in_addr *)*host_entry->h_addr_list);
    printf("\nServer IP: %s\n", szLocalIP);
    
    // Listen for connection
    printf("\nListening for client\n");
    if ((listen(sd, 1)) < 0){
        fprintf (stderr, "ERROR: listen() failed\n");
        exit (-1);
    }
    
    // Variable Declarations
    char buffer[MAXBUF];
    int bytes_read = 0;
    int total_bytes_read = 0;
    int found = 0, // Bool flag
    i;
    struct tm  ts;
    struct timeval connected[SIZE],
    current,
    difference;
    time_t TIME;
    
    // Initialize array to NULL
    for(i = 0; i < SIZE; i++) {
        agents[i] =  NULL;
    }
    
    // Infinite Loop
    while (true) {
        // Client variables
        struct sockaddr_in client;
        int clientSocket;
        socklen_t clientLength = sizeof(client);
        memset(&client, 0, clientLength);
        
        // Accept connection
        clientSocket = accept(sd, (struct sockaddr *)&client, &clientLength);
        
        // Read command from client
        memset(buffer,0,MAXBUF);
        bytes_read = read(clientSocket, buffer, MAXBUF);
        if (bytes_read < 0)
            break;
        fprintf(stdout,"\nRead %d bytes: [%s]\r\n", bytes_read,buffer);
        
        // Store client's IP in string
        char *connectedIP = strdup(inet_ntoa(client.sin_addr));
        
        // Option 1:
        if ((strcmp(buffer, "#JOIN")) == 0) { // Join list of connected agents
            found = 0;
            
            // Get current time for log
            TIME = time(NULL);
            ts = *localtime(&TIME);
            
            // Print message to log
            char buf[80];
            strftime(buf, sizeof(buf), "%a %Y-%m-%d %H:%M:%S %Z", &ts);
            fprintf(log, "%s: Received a \"#JOIN\" action from agent \"%s\"", buf, connectedIP);
            fprintf(log, "\n\n");
            fflush(log);
            
            // Handle #JOIN request appropriately
            for (i = 0; i < SIZE; i++) {
                if (agents[i] == NULL) {
                    
                }
                else if (strcmp(agents[i], connectedIP) == 0){ // Agent found in list
                    found = 1;
                    
                    // Write to agent
                    char response[] = "#ALREADY MEMBER";
                    write (clientSocket, response, strlen(response));
                    
                    // Get time for log
                    TIME = time(NULL);
                    ts = *localtime(&TIME);
                    
                    // Write to log
                    char buf[80];
                    strftime(buf, sizeof(buf), "%a %Y-%m-%d %H:%M:%S %Z", &ts);
                    fprintf(log, "%s: Responded to agent \"%s\" with \"#ALREADY MEMBER\"", buf, connectedIP);
                    fprintf(log, "\n\n");
                    fflush(log);
                    i = SIZE;
                }
            }
            if (found == 0) { // Save IP to list/queue
                for(i = 0; i < SIZE; i++) {
                    if (agents[i] == NULL) {
                        
                        // Save IP to array
                        agents[i] = connectedIP;
                        
                        // Save time to arrays
                        gettimeofday(&connected[i], NULL);
                        TIME = time(NULL);
                        times[i] = TIME;
                        ts = *localtime(&TIME);
                        
                        // Write to log
                        char buf[80];
                        strftime(buf, sizeof(buf), "%a %Y-%m-%d %H:%M:%S %Z", &ts);
                        fprintf(log, "%s: Responded to agent \"%s\" with \"#OK\"", buf, connectedIP);
                        fprintf(log, "\n\n");
                        fflush(log);
                        
                        // Write to agent
                        char response[] = "#OK";
                        write (clientSocket, response, strlen(response));
                        i = SIZE;
                    }
                }
            }
        }
        
        // Option 2: Leave list of connected agents
        else if ((strcmp(buffer, "#LEAVE")) == 0) {
            found = 0;
            
            // Get time for log
            TIME = time(NULL);
            ts = *localtime(&TIME);
            
            // Write to log
            char buf[80];
            strftime(buf, sizeof(buf), "%a %Y-%m-%d %H:%M:%S %Z", &ts);
            fprintf(log, "%s: Received a \"#LEAVE\" action from agent \"%s\"", buf, connectedIP);
            fprintf(log, "\n\n");
            fflush(log);
            
            // Handle #LEAVE request apprpriately
            for (i = 0; i < SIZE; i++) {
                if (agents[i] == NULL){
                    
                }
                else if (!strcmp(agents[i], connectedIP)) { // Agent found in list
                    found = 1;
                    
                    // Erase agent from arrays
                    agents[i] = NULL; // Replace IP with NULL
                    times[i] = NULL;
                    
                    // Write to agent
                    char response[] = "#OK";
                    write (clientSocket, response, strlen(response));
                    
                    // Get time for log
                    TIME = time(NULL);
                    ts = *localtime(&TIME);
                    
                    // Write to log
                    char buf[80];
                    strftime(buf, sizeof(buf), "%a %Y-%m-%d %H:%M:%S %Z", &ts);
                    fprintf(log, "%s: Responded to agent \"%s\" with \"#OK\"", buf, connectedIP);
                    fprintf(log, "\n\n");
                    fflush(log);
                }
            }
            if (found == 0) { // Agent not found in list
                
                // Write to agent
                char response[] = "#NOT MEMBER";
                write (clientSocket, response, strlen(response));
                
                // Write to log
                char buf[80];
                strftime(buf, sizeof(buf), "%a %Y-%m-%d %H:%M:%S %Z", &ts);
                fprintf(log, "%s: Responded to agent \"%s\" with \"#NOT MEMBER\"", buf, connectedIP);
                fprintf(log, "\n\n");
                fflush(log);
            }
        }
        
        // Option 3: Share list of connected agents
        else if ((strcmp(buffer, "#LIST")) == 0) {
            int index = -1;
            found = 0;
            
            // Get time for log
            TIME = time(NULL);
            ts = *localtime(&TIME);
            
            // Write to log
            char buf[80];
            strftime(buf, sizeof(buf), "%a %Y-%m-%d %H:%M:%S %Z", &ts);
            fprintf(log, "%s: Received a \"#LIST\" action from agent \"%s\"", buf, connectedIP);
            fprintf(log, "\n\n");
            fflush(log);
            
            // See if requesting agent is currently in the list
            for(i = 0; i < SIZE; i++) {
                if (agents[i] == NULL){
                    
                }
                else if(strcmp(agents[i], connectedIP) == 0) {
                    found = 1;
                    index = i;
                    i = SIZE; // Exit for loop
                }
            }
            if (found == 1){ // Agent found in list
                for(i = 0; i < SIZE; i++) {
                    if(agents[i] != NULL) { // ensure slot in list is taken by an agent
                        
                        // Get the number of seconds that agent has been connected
                        gettimeofday(&current, NULL);
                        timersub(&current, &connected[i], &difference);
                        
                        // Write to agent
                        char response[100];
                        sprintf(response, "<%s, %ld.%06ld>", agents[i], (long int)difference.tv_sec, (long int)difference.tv_usec);
                        write(clientSocket, response, strlen(response));
                    }
                }
                // Get time for log
                TIME = time(NULL);
                ts = *localtime(&TIME);
                
                // Write to log
                char buf[80];
                strftime(buf, sizeof(buf), "%a %Y-%m-%d %H:%M:%S %Z", &ts);
                fprintf(log, "%s: Responded to agent \"%s\" with current list", buf, connectedIP);
                fprintf(log, "\n\n");
                fflush(log);
            }
            else {
                // Get time for log
                TIME = time(NULL);
                ts = *localtime(&TIME);
                
                // Write to log
                char buf[80];
                strftime(buf, sizeof(buf), "%a %Y-%m-%d %H:%M:%S %Z", &ts);
                fprintf(log, "%s: No response supplied to agent \"%s\"", buf, connectedIP);
                fprintf(log, "\n\n");
                fflush(log);
            }
            
        }
        
        // Option 4: Send log.txt to agent
        else if ((strcmp(buffer, "#LOG")) == 0) {
            found = 0;
            int index = -1;
            
            // Get time for log
            TIME = time(NULL);
            ts = *localtime(&TIME);
            
            // Write to log
            char buf[80];
            strftime(buf, sizeof(buf), "%a %Y-%m-%d %H:%M:%S %Z", &ts);
            fprintf(log, "%s: Received a \"#LOG\" action from agent \"%s\"", buf, connectedIP);
            fprintf(log, "\n\n");
            fflush(log);
            
            // See if requesting agent is currently in the list
            for(i = 0; i < SIZE; i++) {
                if (agents[i] == NULL){
                    
                }
                else if(strcmp(agents[i], connectedIP) == 0) { // Agent found in list
                    found = 1;
                    index = i;
                    i = SIZE; // Exit for loop
                }
            }
            
            if (found == 0) { // Agent not in list, ignore request
                
                // Get time for log
                TIME = time(NULL);
                ts = *localtime(&TIME);
                
                // Write to log
                char buf[80];
                strftime(buf, sizeof(buf), "%a %Y-%m-%d %H:%M:%S %Z", &ts);
                fprintf(log, "%s: No response supplied to agent \"%s\"", buf, connectedIP);
                fprintf(log, "\n\n");
                fflush(log);
            }
            else {
                
                // Read from log and write to agent
                memset(buffer,0,MAXBUF);
                reader = fopen("log.txt", "r");
                if (reader == NULL) perror ("Error opening file");
                else
                {
                    while ( ! feof (reader) )
                    {
                        if ( fgets (buffer , MAXBUF , reader) == NULL ) break;
                        write(clientSocket, buffer, strlen(buffer));
                    }
                    fclose (reader);
                }
                
                // Get time for log
                TIME = time(NULL);
                ts = *localtime(&TIME);
                
                // Write to log
                char buf[80];
                strftime(buf, sizeof(buf), "%a %Y-%m-%d %H:%M:%S %Z", &ts);
                fprintf(log, "%s: Responded to agent \"%s\" with current log", buf, connectedIP);
                fprintf(log, "\n\n");
                fflush(log);
            }
        }
        
        // Option 5: Invalid request from agent
        else {
            printf("ERROR: Invalid command from agent\n");
            
            // Write to agent
            char response[] = "#INVALID";
            write (clientSocket, response, strlen(response));
            
            // Get time for log
            TIME = time(NULL);
            ts = *localtime(&TIME);
            
            // Write to log
            char buf[80];
            strftime(buf, sizeof(buf), "%a %Y-%m-%d %H:%M:%S %Z", &ts);
            fprintf(log, "%s: Received an \"#INVALID\" action from agent \"%s\"", buf, connectedIP);
            fprintf(log, "\n\n");
            fflush(log);
        }
        
        // Close socket, flush log, close log
        close(clientSocket);
        memset(&client, 0, sizeof(client));
        fflush(log);
    }
    
    return 0;
}