#include "cube.h"
#include <signal.h>
#include <enet/time.h>

#define INPUT_LIMIT 4096
#define OUTPUT_LIMIT (64*1024)
#define CLIENT_TIME (3*60*1000)
#define AUTH_TIME (60*1000)
#define AUTH_LIMIT 100
#define AUTH_THROTTLE 1000
#define CLIENT_LIMIT 8192
#define DUP_LIMIT 16
#define PING_TIME 3000
#define PING_RETRY 5
#define KEEPALIVE_TIME (65*60*1000)
#define SERVER_LIMIT (10*1024)

FILE *logfile = NULL;

// for AUTH:
struct userinfo
{
    char *name;
    void *pubkey;
};
hashtable<char *, userinfo> users;

void adduser(char *name, char *pubkey)
{
    name = newstring(name);
    userinfo &u = users[name];
    u.name = name;
    u.pubkey = parsepubkey(pubkey);
}
COMMAND(adduser, "ss");

void clearusers()
{
    enumerate(users, userinfo, u, { delete[] u.name; freepubkey(u.pubkey); });
    users.clear();
}
COMMAND(clearusers, "");
// :for AUTH

struct baninfo
{
    enet_uint32 ip, mask;
};
vector<baninfo> bans, servbans, gbans;

void clearbans()
{
    bans.shrink(0);
    servbans.shrink(0);
    gbans.shrink(0);
}
COMMAND(clearbans, "");

void addban(vector<baninfo> &bans, const char *name)
{
    union { uchar b[sizeof(enet_uint32)]; enet_uint32 i; } ip, mask;
    ip.i = 0;
    mask.i = 0;
    loopi(4)
    {
        char *end = NULL;
        int n = strtol(name, &end, 10);
        if(!end) break;
        if(end > name) { ip.b[i] = n; mask.b[i] = 0xFF; }
        name = end;
        while(*name && *name++ != '.');
    }
    baninfo &ban = bans.add();
    ban.ip = ip.i;
    ban.mask = mask.i;
}
COMMANDF(ban, "s", (char *name) { addban(bans, name); });
COMMANDF(servban, "s", (char *name) { addban(servbans, name); });
COMMANDF(gban, "s", (char *name) { addban(gbans, name); });

char *printban(const baninfo &ban, char *buf)
{
    union { uchar b[sizeof(enet_uint32)]; enet_uint32 i; } ip, mask;
    ip.i = ban.ip;
    mask.i = ban.mask;
    int lastdigit = -1;
    loopi(4) if(mask.b[i])
    {
        if(lastdigit >= 0) *buf++ = '.';
        loopj(i - lastdigit - 1) { *buf++ = '*'; *buf++ = '.'; }
        buf += sprintf(buf, "%d", ip.b[i]);
        lastdigit = i;
    }
    return buf;
}

bool checkban(vector<baninfo> &bans, enet_uint32 host)
{
    loopv(bans) if((host & bans[i].mask) == bans[i].ip) return true;
    return false;
}

// for AUTH:
struct authreq
{
    enet_uint32 reqtime;
    uint id;
    void *answer;
};
// :for AUTH

struct gameserver
{
    ENetAddress address;
    string ip;
    int port, numpings;
    enet_uint32 lastping, lastpong;
};
vector<gameserver *> gameservers;

struct messagebuf
{
    vector<messagebuf *> &owner;
    vector<char> buf;
    int refs;

    messagebuf(vector<messagebuf *> &owner) : owner(owner), refs(0) {}

    const char *getbuf() { return buf.getbuf(); }
    int length() { return buf.length(); }
    void purge();

    bool equals(const messagebuf &m) const
    {
        return buf.length() == m.buf.length() && !memcmp(buf.getbuf(), m.buf.getbuf(), buf.length());
    }

    bool endswith(const messagebuf &m) const
    {
        return buf.length() >= m.buf.length() && !memcmp(&buf[buf.length() - m.buf.length()], m.buf.getbuf(), m.buf.length());
    }

    void concat(const messagebuf &m)
    {
        if(buf.length() && buf.last() == '\0') buf.pop();
        buf.put(m.buf.getbuf(), m.buf.length());
    }
};
vector<messagebuf *> gameserverlists, gbanlists;
bool updateserverlist = true;

struct client
{
    ENetAddress address;
    ENetSocket socket;
    char input[INPUT_LIMIT];
    messagebuf *message;
    vector<char> output;
    int inputpos, outputpos;
    enet_uint32 connecttime, lastinput;
    int servport;
    enet_uint32 lastauth; // for AUTH
    vector<authreq> authreqs; // for AUTH
    bool shouldpurge;
    bool registeredserver;

    client() : message(NULL), inputpos(0), outputpos(0), servport(-1), lastauth(0), shouldpurge(false), registeredserver(false) {}
};
vector<client *> clients;

ENetSocket serversocket = ENET_SOCKET_NULL;

time_t starttime;
enet_uint32 servtime = 0;

void fatal(const char *fmt, ...)
{
    va_list args;
    va_start(args, fmt);
    vfprintf(logfile, fmt, args);
    fputc('\n', logfile);
    va_end(args);
    exit(EXIT_FAILURE);
}

void conoutfv(const char *fmt, va_list args)
{
    vfprintf(logfile, fmt, args);
    fputc('\n', logfile);
}

void conoutf(const char *fmt, ...)
{
    va_list args;
    va_start(args, fmt);
    conoutfv(fmt, args);
    va_end(args);
}

void purgeclient(int n)
{
    client &c = *clients[n];
    if(c.message) c.message->purge();
    enet_socket_destroy(c.socket);
    delete clients[n];
    clients.remove(n);
}

void output(client &c, const char *msg, int len = 0)
{
    if(!len) len = strlen(msg);
    c.output.put(msg, len);
}

void outputf(client &c, const char *fmt, ...)
{
    string msg;
    va_list args;
    va_start(args, fmt);
    vformatstring(msg, fmt, args);
    va_end(args);

    output(c, msg);
}

ENetSocket pingsocket = ENET_SOCKET_NULL;

bool setuppingsocket()
{
    if(pingsocket != ENET_SOCKET_NULL) return true;
    pingsocket = enet_socket_create(ENET_SOCKET_TYPE_DATAGRAM);
    if(pingsocket == ENET_SOCKET_NULL) return false;
    enet_socket_set_option(pingsocket, ENET_SOCKOPT_NONBLOCK, 1);
    return true;
}

void setupserver(int port, const char *ip = NULL)
{
    ENetAddress address;
    address.host = ENET_HOST_ANY;
    address.port = port;

    if(ip)
    {
        if(enet_address_set_host(&address, ip)<0)
            fatal("failed to resolve server address: %s", ip);
    }
    serversocket = enet_socket_create(ENET_SOCKET_TYPE_STREAM);
    if(serversocket==ENET_SOCKET_NULL ||
       enet_socket_set_option(serversocket, ENET_SOCKOPT_REUSEADDR, 1) < 0 ||
       enet_socket_bind(serversocket, &address) < 0 ||
       enet_socket_listen(serversocket, -1) < 0)
        fatal("failed to create server socket");
    if(enet_socket_set_option(serversocket, ENET_SOCKOPT_NONBLOCK, 1)<0)
        fatal("failed to make server socket non-blocking");
    if(!setuppingsocket())
        fatal("failed to create ping socket");

    enet_time_set(0);

    starttime = time(NULL);
    char *ct = ctime(&starttime);
    if(strchr(ct, '\n')) *strchr(ct, '\n') = '\0';
    conoutf("*** Starting master server on %s %d at %s ***", ip ? ip : "localhost", port, ct);
}

void genserverlist()
{
    if(!updateserverlist) return;
    while(gameserverlists.length() && gameserverlists.last()->refs<=0)
        delete gameserverlists.pop();
    messagebuf *l = new messagebuf(gameserverlists);
    loopv(gameservers)
    {
        gameserver &s = *gameservers[i];
        if(!s.lastpong) continue;
        defformatstring(cmd)("addserver %s %d\n", s.ip, s.port);
        l->buf.put(cmd, strlen(cmd));
    }
    l->buf.add('\0');
    gameserverlists.add(l);
    updateserverlist = false;
}

void gengbanlist()
{
    messagebuf *l = new messagebuf(gbanlists);
    const char *header = "cleargbans\n";
    l->buf.put(header, strlen(header));
    string cmd = "addgban ";
    int cmdlen = strlen(cmd);
    loopv(gbans)
    {
        baninfo &b = gbans[i];
        l->buf.put(cmd, printban(b, &cmd[cmdlen]) - cmd);
        l->buf.add('\n');
    }
    if(gbanlists.length() && gbanlists.last()->equals(*l))
    {
        delete l;
        return;
    }
    while(gbanlists.length() && gbanlists.last()->refs<=0)
        delete gbanlists.pop();
    loopv(gbanlists)
    {
        messagebuf *m = gbanlists[i];
        if(m->refs > 0 && !m->endswith(*l)) m->concat(*l);
    }
    gbanlists.add(l);
    loopv(clients)
    {
        client &c = *clients[i];
        if(c.servport >= 0 && !c.message)
        {
            c.message = l;
            c.message->refs++;
        }
    }
}

void addgameserver(client &c)
{
    if(gameservers.length() >= SERVER_LIMIT) return;
    loopv(gameservers)
    {
        gameserver &s = *gameservers[i];
        if(s.address.host == c.address.host && s.port == c.servport)
        {
            s.lastping = 0;
            s.numpings = 0;
            return;
        }
    }
    string hostname;
    if(enet_address_get_host_ip(&c.address, hostname, sizeof(hostname)) < 0)
    {
        outputf(c, "failreg failed resolving ip\n");
        return;
    }
    gameserver &s = *gameservers.add(new gameserver);
    s.address.host = c.address.host;
    s.address.port = c.servport+1;
    copystring(s.ip, hostname);
    s.port = c.servport;
    s.numpings = 0;
    s.lastping = s.lastpong = 0;
}

client *findclient(gameserver &s)
{
    loopv(clients)
    {
        client &c = *clients[i];
        if(s.address.host == c.address.host && s.port == c.servport)
            return &c;
    }
    return NULL;
}

void servermessage(gameserver &s, const char *msg)
{
    client *c = findclient(s);
    if(c) outputf(*c, msg);
}

void checkserverpongs()
{
    ENetBuffer buf;
    ENetAddress addr;
    static uchar pong[MAXTRANS];
    for(;;)
    {
        buf.data = pong;
        buf.dataLength = sizeof(pong);
        int len = enet_socket_receive(pingsocket, &addr, &buf, 1);
        if(len <= 0) break;
        loopv(gameservers)
        {
            gameserver &s = *gameservers[i];
            if(s.address.host == addr.host && s.address.port == addr.port)
            {
                if(s.lastping && (!s.lastpong || ENET_TIME_GREATER(s.lastping, s.lastpong)))
                {
                    client *c = findclient(s);
                    if(c)
                    {
                        c->registeredserver = true;
                        outputf(*c, "succreg\n");
                        if(!c->message && gbanlists.length())
                        {
                            c->message = gbanlists.last();
                            c->message->refs++;
                        }
                    }
                }
                if(!s.lastpong) updateserverlist = true;
                s.lastpong = servtime ? servtime : 1;
                break;
            }
        }
    }
}

void bangameservers()
{
    loopvrev(gameservers) if(checkban(servbans, gameservers[i]->address.host))
    {
        delete gameservers.remove(i);
        updateserverlist = true;
    }
}

void checkgameservers()
{
    ENetBuffer buf;
    loopv(gameservers)
    {
        gameserver &s = *gameservers[i];
        if(s.lastping && s.lastpong && ENET_TIME_LESS_EQUAL(s.lastping, s.lastpong))
        {
            if(ENET_TIME_DIFFERENCE(servtime, s.lastpong) > KEEPALIVE_TIME)
            {
                delete gameservers.remove(i--);
                updateserverlist = true;
            }
        }
        else if(!s.lastping || ENET_TIME_DIFFERENCE(servtime, s.lastping) > PING_TIME)
        {
            if(s.numpings >= PING_RETRY)
            {
                servermessage(s, "failreg failed pinging server\n");
                delete gameservers.remove(i--);
                updateserverlist = true;
            }
            else
            {
                static const uchar ping[] = { 1 };
                buf.data = (void *)ping;
                buf.dataLength = sizeof(ping);
                s.numpings++;
                s.lastping = servtime ? servtime : 1;
                enet_socket_send(pingsocket, &s.address, &buf, 1);
            }
        }
    }
}

void messagebuf::purge()
{
    refs = max(refs - 1, 0);
    if(refs<=0 && owner.last()!=this)
    {
        owner.removeobj(this);
        delete this;
    }
}

// for AUTH:
void purgeauths(client &c)
{
    int expired = 0;
    loopv(c.authreqs)
    {
        if(ENET_TIME_DIFFERENCE(servtime, c.authreqs[i].reqtime) >= AUTH_TIME)
        {
            outputf(c, "failauth %u\n", c.authreqs[i].id);
            freechallenge(c.authreqs[i].answer);
            expired = i + 1;
        }
        else break;
    }
    if(expired > 0) c.authreqs.remove(0, expired);
}

void reqauth(client &c, uint id, char *name)
{
    if(ENET_TIME_DIFFERENCE(servtime, c.lastauth) < AUTH_THROTTLE)
        return;

    c.lastauth = servtime;

    purgeauths(c);

    time_t t = time(NULL);
    char *ct = ctime(&t);
    if(ct)
    {
        char *newline = strchr(ct, '\n');
        if(newline) *newline = '\0';
    }
    string ip;
    if(enet_address_get_host_ip(&c.address, ip, sizeof(ip)) < 0) copystring(ip, "-");
    conoutf("%s: attempting \"%s\" as %u from %s", ct ? ct : "-", name, id, ip);

    userinfo *u = users.access(name);
    if(!u)
    {
        outputf(c, "failauth %u\n", id);
        return;
    }

    if(c.authreqs.length() >= AUTH_LIMIT)
    {
        outputf(c, "failauth %u\n", c.authreqs[0].id);
        freechallenge(c.authreqs[0].answer);
        c.authreqs.remove(0);
    }

    authreq &a = c.authreqs.add();
    a.reqtime = servtime;
    a.id = id;
    uint seed[3] = { starttime, servtime, randomMT() };
    static vector<char> buf;
    buf.setsize(0);
    a.answer = genchallenge(u->pubkey, seed, sizeof(seed), buf);

    outputf(c, "chalauth %u %s\n", id, buf.getbuf());
}

void confauth(client &c, uint id, const char *val)
{
    purgeauths(c);

    loopv(c.authreqs) if(c.authreqs[i].id == id)
    {
        string ip;
        if(enet_address_get_host_ip(&c.address, ip, sizeof(ip)) < 0) copystring(ip, "-");
        if(checkchallenge(val, c.authreqs[i].answer))
        {
            outputf(c, "succauth %u\n", id);
            conoutf("succeeded %u from %s", id, ip);
        }
        else
        {
            outputf(c, "failauth %u\n", id);
            conoutf("failed %u from %s", id, ip);
        }
        freechallenge(c.authreqs[i].answer);
        c.authreqs.remove(i--);
        return;
    }
    outputf(c, "failauth %u\n", id);
}
// :for AUTH

bool checkclientinput(client &c)
{
    if(c.inputpos<0) return true;
    char *end = (char *)memchr(c.input, '\n', c.inputpos);
    while(end)
    {
        *end++ = '\0';
        c.lastinput = servtime;

        uint id; // for AUTH
        string user, val; // for AUTH

        int port;
        if(!strncmp(c.input, "list", 4) && (!c.input[4] || isspace(c.input[4])))
        {
            genserverlist();
            if(gameserverlists.empty() || c.message) return false;
            c.message = gameserverlists.last();
            c.message->refs++;
            c.output.setsize(0);
            c.outputpos = 0;
            c.shouldpurge = true;
            return true;
        }
        else if(sscanf(c.input, "regserv %d", &port) == 1)
        {
            if(checkban(servbans, c.address.host)) return false;
            if(port < 0 || port + 1 < 0 || (c.servport >= 0 && port != c.servport)) outputf(c, "failreg invalid port\n");
            else
            {
                c.servport = port;
                addgameserver(c);
            }
        }
        // for AUTH:
        else if(sscanf(c.input, "reqauth %u %100s", &id, user) == 2)
        {
            reqauth(c, id, user);
        }
        else if(sscanf(c.input, "confauth %u %100s", &id, val) == 2)
        {
            confauth(c, id, val);
        }
        // :for AUTH
        c.inputpos = &c.input[c.inputpos] - end;
        memmove(c.input, end, c.inputpos);

        end = (char *)memchr(c.input, '\n', c.inputpos);
    }
    return c.inputpos<(int)sizeof(c.input);
}

ENetSocketSet readset, writeset;

void checkclients()
{
    ENetSocketSet readset, writeset;
    ENetSocket maxsock = max(serversocket, pingsocket);
    ENET_SOCKETSET_EMPTY(readset);
    ENET_SOCKETSET_EMPTY(writeset);
    ENET_SOCKETSET_ADD(readset, serversocket);
    ENET_SOCKETSET_ADD(readset, pingsocket);
    loopv(clients)
    {
        client &c = *clients[i];
        if(c.message || c.output.length()) ENET_SOCKETSET_ADD(writeset, c.socket);
        else ENET_SOCKETSET_ADD(readset, c.socket);
        maxsock = max(maxsock, c.socket);
    }
    if(enet_socketset_select(maxsock, &readset, &writeset, 1000)<=0) return;

    if(ENET_SOCKETSET_CHECK(readset, pingsocket)) checkserverpongs();
    if(ENET_SOCKETSET_CHECK(readset, serversocket))
    {
        ENetAddress address;
        ENetSocket clientsocket = enet_socket_accept(serversocket, &address);
        if(clients.length()>=CLIENT_LIMIT || checkban(bans, address.host)) enet_socket_destroy(clientsocket);
        else if(clientsocket!=ENET_SOCKET_NULL)
        {
            int dups = 0, oldest = -1;
            loopv(clients) if(clients[i]->address.host == address.host)
            {
                dups++;
                if(oldest<0 || clients[i]->connecttime < clients[oldest]->connecttime) oldest = i;
            }
            if(dups >= DUP_LIMIT) purgeclient(oldest);

            client *c = new client;
            c->address = address;
            c->socket = clientsocket;
            c->connecttime = servtime;
            c->lastinput = servtime;
            clients.add(c);
        }
    }

    loopv(clients)
    {
        client &c = *clients[i];
        if((c.message || c.output.length()) && ENET_SOCKETSET_CHECK(writeset, c.socket))
        {
            const char *data = c.output.length() ? c.output.getbuf() : c.message->getbuf();
            int len = c.output.length() ? c.output.length() : c.message->length();
            ENetBuffer buf;
            buf.data = (void *)&data[c.outputpos];
            buf.dataLength = len-c.outputpos;
            int res = enet_socket_send(c.socket, NULL, &buf, 1);
            if(res>=0)
            {
                c.outputpos += res;
                if(c.outputpos>=len)
                {
                    if(c.output.length()) c.output.setsize(0);
                    else
                    {
                        c.message->purge();
                        c.message = NULL;
                    }
                    c.outputpos = 0;
                    if(!c.message && c.output.empty() && c.shouldpurge)
                    {
                        purgeclient(i--);
                        continue;
                    }
                }
            }
            else { purgeclient(i--); continue; }
        }
        if(ENET_SOCKETSET_CHECK(readset, c.socket))
        {
            ENetBuffer buf;
            buf.data = &c.input[c.inputpos];
            buf.dataLength = sizeof(c.input) - c.inputpos;
            int res = enet_socket_receive(c.socket, NULL, &buf, 1);
            if(res>0)
            {
                c.inputpos += res;
                c.input[min(c.inputpos, (int)sizeof(c.input)-1)] = '\0';
                if(!checkclientinput(c)) { purgeclient(i--); continue; }
            }
            else { purgeclient(i--); continue; }
        }
        if(c.output.length() > OUTPUT_LIMIT) { purgeclient(i--); continue; }
        if(ENET_TIME_DIFFERENCE(servtime, c.lastinput) >= (c.registeredserver ? KEEPALIVE_TIME : CLIENT_TIME)) { purgeclient(i--); continue; }
    }
}

void banclients()
{
    loopvrev(clients) if(checkban(bans, clients[i]->address.host)) purgeclient(i);
}

volatile bool reloadcfg = true;

void reloadsignal(int signum)
{
    reloadcfg = true;
}

int main(int argc, char **argv)
{
    if(enet_initialize()<0) fatal("Unable to initialise network module");
    atexit(enet_deinitialize);

    const char *dir = "", *ip = AC_MASTER_URI;
    int port = AC_MASTER_PORT;
    if(argc>=2) dir = argv[1];
    if(argc>=3 && argv[2][0]) port = atoi(argv[2]);
    if(argc>=4) ip = argv[3][0] ? argv[3] : NULL;
    defformatstring(logname)("%smaster.log", dir);
    defformatstring(cfgname)("%smaster.cfg", dir);
    path(logname);
    path(cfgname);
    logfile = fopen(logname, "a");
    if(!logfile) logfile = stdout;
    setvbuf(logfile, NULL, _IOLBF, 0);
#ifndef WIN32
    signal(SIGUSR1, reloadsignal);
#endif
    setupserver(port, ip);
    for(;;)
    {
        if(reloadcfg)
        {
            conoutf("reloading master.cfg");
            execfile(cfgname);
            bangameservers();
            banclients();
            gengbanlist();
            reloadcfg = false;
        }

        servtime = enet_time_get();
        checkclients();
        checkgameservers();
    }

    return EXIT_SUCCESS;
}

