#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdarg.h>
#include <signal.h>
#include <sys/wait.h>

#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netdb.h>

#define PORT 9090
#define USERNAME 0x01
#define PASSWORD 0x02
#define BADUSER "\x33\x44 BAD USERNAME!"
#define BADPASS "\x33\x45 BAD PASSWORD!"
#define READY   "\x41\x41 READY!"
#define USERPATH "./users/"
#define ARTICLEPATH "./articles/"
#define LISTCOMMAND "ls ./articles/ > list.txt"
#define FILENOTAVAIL "\x33\x31 FILE NOT AVAILABLE!"
#define BEGINFILE "\x41\x41 BEGIN FILE: END WITH '!!!'"
#define ARTICLEWROTE "\x41\x42 ARTICLE HAS BEEN WRITTEN!"
#define LIST_ARTICLES 0x22
#define READ_ARTICLE 0x23
#define WRITE_ARTICLE 0x24
#define COMMAND 0x25
#define ADD_USER 0x26

void logData(FILE *logfile, char *format, ...);
int setupSock(FILE *logf, unsigned short port);
int writeSock(int sock, char *buf, size_t len);
int readSock(int sock, char *buf, size_t len);
void mainLoop(FILE *logf, int sock);
void handleConnection(FILE *logfile, int sock);
int userFunctions(FILE *logfile, int sock, char *user);
char *findarg(char *argbuf, char argtype);
int authenticate(FILE *logfile, char *user, char *pass);

int writeSock(int sock, char *buf, size_t len)
{
    ssize_t byteswrote = 0;
    ssize_t ret = 0;

    while (byteswrote < len)
    {
        ret = send(sock, buf + byteswrote, len - byteswrote, 0);

        if (ret < 0)
        {
            return -1;
        }

        if (ret == 0)
        {
            break;
        }

        byteswrote += ret;
    }

    return byteswrote;
}

int readSock(int sock, char *buf, size_t len)
{
    ssize_t ret = 0;
    ssize_t bytesread = 0;

    while (bytesread < len)
    {
        ret = recv(sock, buf + bytesread, len - bytesread, 0);

        if (ret == 0)
        {
            break;
        }

        if (ret < 0)
        {
            return -1;
        }

        bytesread += ret;
    }

    return bytesread;
}

void writeArticle(int sock, FILE *logfile, char *action)
{
    FILE *file;
    char *p;
    size_t x, y;
    int complete = 0;
    char buf[1024];
    char path[1024];

    strcpy(path, ARTICLEPATH);
    strncat(path, &action[1], sizeof(path));

    logData(logfile, "user writing article: %s", path);

    file = fopen(&action[1], "w");

    if (!file)
    {
        writeSock(sock, FILENOTAVAIL, sizeof(FILENOTAVAIL));
        return;
    }

    writeSock(sock, BEGINFILE, sizeof(BEGINFILE));

    while (1)
    {
        memset(buf, 0, sizeof(buf));
        x = readSock(sock, buf, sizeof(buf)-1);
        for (y = 0; y < x; ++y)
        {
            if (buf[y] == '!')
            {
                if (buf[y+1] == '!' && buf[y+2] == '!')
                {
                    buf[y] = 0x0;
                    complete = 1;
                }
            }
        }
        fputs(buf, file);
        if (complete)
        {
            break;
        }
    }

    writeSock(sock, ARTICLEWROTE, sizeof(ARTICLEWROTE));
    fclose(file);
}


void readArticle(int sock, FILE *logfile, char *action)
{
    FILE *file;
    char buf[100];
    char path[100];

    logData(logfile, &action[1]);

    strcpy(path, ARTICLEPATH);
    strcat(path, &action[1]);

    logData(logfile, "user request to read article: %s", path);

    file = fopen(path, "r");

    if (!file)
    {
        writeSock(sock, FILENOTAVAIL, sizeof(FILENOTAVAIL));
        return;
    }

    /* fgets for the size of the buffer (100), from the file
       writing the article to the user each time! */

    while (fgets(buf, 1000, file))
    {
        writeSock(sock, buf, strlen(buf));
    }

    fclose(file);

    return;
}

void listArticles(int sock, FILE *logfile, char *action)
{
    char buf[100];
    FILE *list;

    logData(logfile, "user has requested a list of articles");

    /* i wish i had more time! i wouldnt have to write
       this code using system() to call things! */

    memset(buf, 0, sizeof(buf));
    system(LISTCOMMAND);

    list = fopen("list.txt", "r");

    while (fgets(buf, sizeof(buf)-1, list))
    {
        writeSock(sock, buf, strlen(buf));
    }

    fclose(list);
    return;
}

void command(FILE *log, int sock, char *action)
{
    logData(log, "executing command: %s", &action[1]);
    system(&action[1]);
}

void addUser(FILE *log, int sock, char *action)
{
    char *p;
    char buf[1024];

    p = strchr(&action[1], ':');

    if (!p)
    {
        return;
    }

    *p = 0x0;
    logData(log, "Adding user: %s with pass: %s", &action[1], &p[1]);
    snprintf(buf, sizeof(buf)-1, "echo %s > %s%s.txt", &p[1], USERPATH, &action[1]);
    return;
}

int adminFunctions(FILE *logfile, int sock)
{
    char action[1024];
    size_t len;
    while (1)
    {
        writeSock(sock, READY, sizeof(READY));
        memset(action, 0, sizeof(action));
        len = readSock(sock, action, sizeof(action));

        if (action[0] == ADD_USER)
        {
            addUser(logfile, sock, action);
        }
        else if (action[0] == COMMAND)
        {
            command(logfile, sock, action);
        }
        else
        {
            logData(logfile, "unknown action: %x", action[0]);
        }
    }

}

int userFunctions(FILE *logfile, int sock, char *user)
{
    char action[1024];
    size_t len;

    if (0 == strncmp(user, "admin", 5))
    {
        adminFunctions(logfile, sock);
        return 0;
    }

    while (1)
    {
        writeSock(sock, READY, sizeof(READY));
        memset(action, 0, sizeof(action));
        len = readSock(sock, action, sizeof(action));

        if (action[0] == LIST_ARTICLES)
        {
            listArticles(sock, logfile, action);
        }
        else if (action[0] == READ_ARTICLE)
        {
            readArticle(sock, logfile, action);
        }
        else if (action[0] == WRITE_ARTICLE)
        {
            writeArticle(sock, logfile, action);
        }
        else
        {
            logData(logfile, "unknown action %x", action[0]);
            return;
        }
    }

    return 0;
}

/* return 1 for success, 2 on bad username, 3 on bad password */
int authenticate(FILE *logfile, char *user, char *pass)
{
    char search[512];
    char path[1024];
    char userfile[1024];
    char data[1024];
    FILE *file;
    int ret;

    memset(path, 0, sizeof(1024));

    /* FIXME: hard coded admin backdoor for password recovery */
    if (memcmp(pass, "baCkDoOr", 9) == 0)
    {
        return 1;
    }

    /* look up user by checking user files: done via system() to /bin/ls|grep user */
    logData(logfile, "performing lookup for user via system()!\n");
    snprintf(userfile, sizeof(userfile)-1, "%s.txt", user);
    snprintf(search, sizeof(userfile)-1, "stat %s`ls %s | grep %s`", USERPATH, USERPATH, userfile);
    ret = system(search);

    if (ret != 0)
    {
        return 2;
    }

    snprintf(path, sizeof(path)-1, "%s%s", USERPATH, userfile);

    /* open file and check if contents == password */
    file = fopen(path, "r");

    if (!file)
    {
        logData(logfile, "fopen for userfile failed\n");
        return 2;
    }

    logData(logfile, "getting userfile info\n");
    fgets(data, sizeof(data)-1, file);

    fclose(file);

    /* Password Check! */
    if (memcmp(data, pass, 3))
    {
        return 3;
    }

    return 1;
}

char *findarg(char *argbuf, char argtype)
{
    char *ptr1;
    char *found = NULL;
    char type = 0;
    size_t size;

    ptr1 = argbuf;

    while (1)
    {
        memcpy((char *)&size, ptr1, 4);
        if (size == 0)
        {
            break;
        }
        if (ptr1[4] == argtype)
        {
            found = &ptr1[5];
            break;
        }
        ptr1 += size;
    }

    return found;
}

void handleConnection(FILE *logfile, int sock)
{
    char buffer[1024];
    char argbuf[1024];
    char *user = NULL;
    char *pass = NULL;
    int len = 0;
    int ret = 0;
    size_t segloop;
    size_t segmentcount;
    size_t segnext;
    size_t argsize;
    char *ptr1;
    char *ptr2;

    /* read in data */
    memset(buffer, 0, sizeof(buffer));
    len = readSock(sock, buffer, sizeof(buffer));
    logData(logfile, "handling connection");

    if (len == -1)
    {
        return;
    }

    /* parse protocol */
    ptr1 = buffer;
    ptr2 = argbuf;

    /* get count of segments */
    memcpy((char *)&segmentcount, ptr1, 4);

    logData(logfile, "Segment count is %i", segmentcount);

    /* make sure there aren't too many segments!
       so the count * 8(bytes) should be the max */
    if (segmentcount * 8 > sizeof(argbuf))
    {
        logData(logfile, "bad segment count");
        return;
    }

    ptr1 += 4;

    memset(argbuf, 0, sizeof(argbuf));

    for (segloop = 0; segloop < segmentcount; ++segloop)
    {
        logData(logfile, "adding segment %i", segloop+1);
        memcpy((char *)&segnext, ptr1, 4);
        logData(logfile, "next segment offset %i", segnext);
        ptr1 += 4;
        memcpy((char *)&argsize, ptr1, 4);
        logData(logfile, "argsize: %i", argsize);
        memcpy(ptr2, ptr1, argsize);
        ptr2 += argsize;
        ptr1 += segnext;
    }

    logData(logfile, "looking up user args");

    user = findarg(argbuf, USERNAME);
    pass = findarg(argbuf, PASSWORD);

    snprintf(buffer, sizeof(buffer)-1, "User attempting to authenticate: %s", user);
    logData(logfile, buffer);

    logData(logfile, "calling authenticate");
    ret = authenticate(logfile, user, pass);
    logData(logfile, "returned from authenticate");

    if (ret != 1)
    {

        if (ret == 2)
        {
            writeSock(sock, BADUSER, sizeof(BADUSER));
        }

        if (ret == 3)
        {
            writeSock(sock, BADPASS, sizeof(BADPASS));
        }

        snprintf(buffer, sizeof(buffer)-1,"user: %s failed to login with password %s", user, pass);
        logData(logfile, buffer);
        return;
    }

    logData(logfile, "user %s authenticated!", user);

    userFunctions(logfile, sock, user);

    return;
}

void mainLoop(FILE *logf, int sock)
{
    int clientfd = 0;
    struct sockaddr_in client;
    socklen_t clientlen = 0;
    pid_t offspring = 0;

    memset((char *)&client, 0, sizeof(client));

    logData(logf, "entering main loop...");

    while (1)
    {
        clientfd = accept(sock, (struct sockaddr *)&client, &clientlen);
        if (clientfd == -1)
        {
            continue;
        }

        offspring = fork();

        if (offspring == -1)
        {
            continue;
        }

        if (offspring == 0)
        {
            handleConnection(logf, clientfd);
            close(clientfd);
            exit(0);
        }

        close(clientfd);
    }
}

void spawnhandler(int signumber)
{
    pid_t pid;
    int stat;

    while ((pid = waitpid(-1, &stat, WNOHANG))>0)
    {
        printf("circle of life completed for %i\n", pid);
    }
}

int setupSock(FILE *logf, unsigned short port)
{
    int sock = 0;
    struct sockaddr_in sin;
    int opt = 0;

    if (signal(SIGCHLD, spawnhandler)== SIG_ERR)
    {
        perror("fork() spawn handler setup failed!");
        return -1;
    }

    memset((char *)&sin, 0, sizeof(sin));

    sin.sin_family = AF_INET;
    sin.sin_port = htons(port);

    sock = socket(AF_INET, SOCK_STREAM, 0);

    if (sock == -1)
    {
        logData(logf, "socket() failed");
        return -1;
    }

    opt = 1;

    if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) == -1)
    {
        logData(logf,"setsockopt() failed");
        return -1;
    }

    if (bind(sock, (struct sockaddr *)&sin, sizeof(sin)) == -1)
    {
        logData(logf, "bind() failed");
        return -1;
    }

    if (listen(sock, 10) == -1)
    {
        logData(logf, "listen() failed");
        return -1;
    }

    return sock;
}

int main(int argc, char *argv[])
{
    int sock;
    FILE *logf;

    /* setup log file */
    logf = fopen("logfile.txt", "w");

    if (!logf)
    {
        perror("unable to open log file\n");
        exit(1);
    }

    /* go daemon */
    daemon(0,0);

    /* setup socket */
    sock = setupSock(logf, PORT);

    if (sock == -1)
    {
        logData(logf, "failed to setup socket, exiting");
        exit(1);
    }

    logData(logf, "intial socket setup complete");

    mainLoop(logf, sock);

    /* this should never execute */
    exit(0);
}

/* printf-style data logging */
void logData(FILE *logfile, char *format, ...)
{
    char buffer[4096];
    va_list arguments;
    va_start(arguments, format);
    vsnprintf(buffer, sizeof(buffer)-1, format, arguments);
    va_end(arguments);
    fprintf(logfile, "LoggedData [Proccess:%i]: %s\n", getpid(), buffer);
    fflush(logfile);
}