path: root/usr/ircd.c

#include "sock.h"
/* ircd [PORT] - an IRC server running on the Game Boy. Default port 6667.
 *
 *   /# ircd &
 *   host$ irssi -c 10.0.0.2          (or any client)
 *   ... and gbos's own irc(1) can join the same channel from another GB.
 *
 * Implements the subset a real client needs to get in and talk: NICK, USER,
 * PING/PONG, JOIN, PART, PRIVMSG/NOTICE (to a channel or a nick), NAMES,
 * QUIT, plus the 001/004/375/372/376 numerics clients wait for on registration
 * and 353/366 on join. One channel per client keeps the bookkeeping to a
 * fixed-size table - this is a 1997 handheld with 8 KiB of task RAM.
 *
 * MAXCL is bounded by the kernel socket table (MAX_SOCKS), which the listener
 * and every client each take one of; the rest are left for other programs.
 *
 * Statics are fine here because main() copies the command line off $A000
 * before touching any of them - sock.h's _nr already lives there.
 */

#define PORT_DEF 6667
#define MAXCL    3   /* MAX_SOCKS(6) - listener - 2 spare */
#define INBUF    128 /* longest line we will reassemble */
#define NICKSZ   10
#define CHANSZ   12
#define OBUFSZ   200 /* one segment */
#define RBUFSZ   200

static unsigned char lsock;
static unsigned char csock[MAXCL];
static unsigned char cused[MAXCL];
static unsigned char creg[MAXCL];  /* sent the welcome burst      */
static unsigned char cgotu[MAXCL]; /* seen USER                   */
static char cnick[MAXCL][NICKSZ];
static char cchan[MAXCL][CHANSZ];
static char cin[MAXCL][INBUF];
static unsigned char cinlen[MAXCL];
static unsigned char rbuf[RBUFSZ];
static char msg[OBUFSZ];
static unsigned char mlen;
static char line[INBUF]; /* the line being dispatched */

/* ---- tiny string helpers -------------------------------------------------- */
static unsigned char up(char c) { return (unsigned char)((c >= 'a' && c <= 'z') ? c - 32 : c); }
/* case-insensitive compare of a command word */
static unsigned char cmdis(const char *w, const char *name) {
    while (*name) {
        if (up(*w) != (unsigned char)*name) return 0;
        w++;
        name++;
    }
    return (unsigned char)(*w == 0);
}
/* IRC names - nicknames AND channels - are case-insensitive, so "Alice" and
   "alice" are one person, "#GB" and "#gb" one channel. (RFC 1459 also folds
   []\\~ onto {}|^; plain ASCII is close enough for a Game Boy.) */
static unsigned char irceq(const char *a, const char *b) {
    while (*a && up(*a) == up(*b)) {
        a++;
        b++;
    }
    return (unsigned char)(*a == 0 && *b == 0);
}
static void scpy(char *d, const char *s, unsigned char max) {
    unsigned char i = 0;
    while (s[i] && i < max - 1) {
        d[i] = s[i];
        i++;
    }
    d[i] = 0;
}

/* ---- outgoing message builder --------------------------------------------- */
static void m(const char *s) {
    while (*s && mlen < OBUFSZ - 2) msg[mlen++] = *s++;
}
static void mstart(void) { mlen = 0; }
static void mend(void) {
    msg[mlen++] = '\r';
    msg[mlen++] = '\n';
}
static void msend(unsigned char ci) {
    if (cused[ci]) net_send(csock[ci], msg, mlen);
}
/* ":nick!u@gbos " - the prefix a client needs to attribute an event */
static void mprefix(unsigned char ci) {
    mstart();
    m(":");
    m(cnick[ci]);
    m("!u@gbos ");
}
/* ":gbos NNN nick " - a numeric reply */
static void mnumeric(unsigned char ci, const char *num) {
    mstart();
    m(":gbos ");
    m(num);
    m(" ");
    m(cnick[ci][0] ? cnick[ci] : "*");
    m(" ");
}
/* everyone in ci's channel (except `except`, use 0xFF for nobody) */
static void bcast(const char *chan, unsigned char except) {
    unsigned char i;
    if (!chan[0]) return;
    for (i = 0; i < MAXCL; i++)
        if (cused[i] && creg[i] && i != except && irceq(cchan[i], chan)) msend(i);
}

/* is `n` already in use by some OTHER client? */
static unsigned char nick_taken(const char *n, unsigned char except) {
    unsigned char i;
    for (i = 0; i < MAXCL; i++)
        if (cused[i] && i != except && cnick[i][0] && irceq(cnick[i], n)) return 1;
    return 0;
}

static void logline(const char *a, const char *b) {
    puts(a);
    if (b) puts(b);
    nl();
}

/* ---- client lifecycle ------------------------------------------------------ */
static void drop(unsigned char ci, const char *why) {
    if (!cused[ci]) return;
    if (creg[ci] && cchan[ci][0]) { /* tell the channel it lost them */
        mprefix(ci);
        m("QUIT :");
        m(why);
        mend();
        bcast(cchan[ci], ci);
    }
    logline("- ", cnick[ci][0] ? cnick[ci] : "(unregistered)");
    net_close(csock[ci]);
    cused[ci] = 0;
    creg[ci] = 0;
    cgotu[ci] = 0;
    cinlen[ci] = 0;
    cnick[ci][0] = 0;
    cchan[ci][0] = 0;
}

static void welcome(unsigned char ci) {
    creg[ci] = 1;
    mnumeric(ci, "001");
    m(":Welcome to gbos IRC, ");
    m(cnick[ci]);
    mend();
    msend(ci);
    mnumeric(ci, "004");
    m("gbos gbos-1.0 o o");
    mend();
    msend(ci);
    mnumeric(ci, "375");
    m(":- gbos Message of the Day -");
    mend();
    msend(ci);
    mnumeric(ci, "372");
    m(":- an IRC server on a Game Boy Color");
    mend();
    msend(ci);
    mnumeric(ci, "376");
    m(":End of /MOTD command.");
    mend();
    msend(ci);
    logline("+ ", cnick[ci]);
}

/* 353 (names) + 366 (end of names) for ci's channel */
static void names(unsigned char ci) {
    unsigned char i;
    mnumeric(ci, "353");
    m("= ");
    m(cchan[ci]);
    m(" :");
    for (i = 0; i < MAXCL; i++)
        if (cused[i] && creg[i] && irceq(cchan[i], cchan[ci])) {
            m(cnick[i]);
            m(" ");
        }
    mend();
    msend(ci);
    mnumeric(ci, "366");
    m(cchan[ci]);
    m(" :End of /NAMES list");
    mend();
    msend(ci);
}

/* ---- command dispatch ------------------------------------------------------ */
/* line[] holds one command, already stripped of CR/LF. Splits in place. */
static void dispatch(unsigned char ci) {
    char *cmd, *a1, *a2, *p;
    unsigned char i;

    p = line;
    if (*p == ':') { /* ignore any client-sent prefix */
        while (*p && *p != ' ') p++;
        while (*p == ' ') p++;
    }
    cmd = p;
    while (*p && *p != ' ') p++;
    if (*p) {
        *p++ = 0;
        while (*p == ' ') p++;
    }
    a1 = p; /* first argument (may be empty) */
    while (*p && *p != ' ') p++;
    if (*p) {
        *p++ = 0;
        while (*p == ' ') p++;
    }
    a2 = p; /* trailing text (may start ':') */
    if (*a2 == ':') a2++;

    if (cmdis(cmd, "NICK")) {
        if (!a1[0]) return;
        if (nick_taken(a1, ci)) { /* 433: keep the nick they have */
            mnumeric(ci, "433");
            m(a1);
            m(" :Nickname is already in use");
            mend();
            msend(ci);
            return;
        }
        if (irceq(cnick[ci], a1)) { /* same nick, only case: just take it */
            scpy(cnick[ci], a1, NICKSZ);
            return;
        }
        if (creg[ci]) { /* a rename: everyone must be told */
            mprefix(ci);
            m("NICK :");
            m(a1);
            mend();
            msend(ci);
            bcast(cchan[ci], ci);
            logline(cnick[ci], " renamed");
        }
        scpy(cnick[ci], a1, NICKSZ);
        if (cgotu[ci] && !creg[ci]) welcome(ci);
        return;
    }
    if (cmdis(cmd, "USER")) {
        cgotu[ci] = 1;
        if (cnick[ci][0] && !creg[ci]) welcome(ci);
        return;
    }
    if (cmdis(cmd, "PING")) {
        mstart();
        m(":gbos PONG gbos :");
        m(a1[0] ? a1 : "gbos");
        mend();
        msend(ci);
        return;
    }
    if (cmdis(cmd, "QUIT")) {
        drop(ci, a2[0] ? a2 : "Client quit");
        return;
    }
    if (!creg[ci]) return; /* everything below needs a nick */

    if (cmdis(cmd, "JOIN")) {
        if (!a1[0]) return;
        if (cchan[ci][0]) { /* one channel at a time */
            mprefix(ci);
            m("PART ");
            m(cchan[ci]);
            mend();
            bcast(cchan[ci], 0xFF);
        }
        scpy(cchan[ci], a1, CHANSZ);
        mprefix(ci);
        m("JOIN ");
        m(cchan[ci]);
        mend();
        msend(ci); /* the joiner sees it too */
        bcast(cchan[ci], ci);
        names(ci);
        logline(cnick[ci], " joined");
        return;
    }
    if (cmdis(cmd, "PART")) {
        if (!cchan[ci][0]) return;
        mprefix(ci);
        m("PART ");
        m(cchan[ci]);
        mend();
        msend(ci);
        bcast(cchan[ci], ci);
        cchan[ci][0] = 0;
        return;
    }
    if (cmdis(cmd, "NAMES")) {
        if (cchan[ci][0]) names(ci);
        return;
    }
    if (cmdis(cmd, "PRIVMSG") || cmdis(cmd, "NOTICE")) {
        if (!a1[0]) return;
        mprefix(ci);
        m(cmdis(cmd, "NOTICE") ? "NOTICE " : "PRIVMSG ");
        m(a1);
        m(" :");
        m(a2);
        mend();
        if (a1[0] == '#') {
            bcast(a1, ci); /* to a channel, not back to us */
            puts("<");
            puts(cnick[ci]);
            puts("> ");
            puts(a2);
            nl();
        } else {
            for (i = 0; i < MAXCL; i++) /* to one nick */
                if (cused[i] && creg[i] && irceq(cnick[i], a1)) msend(i);
        }
        return;
    }
    mnumeric(ci, "421");
    m(cmd);
    m(" :Unknown command");
    mend();
    msend(ci);
}

/* feed received bytes into ci's line buffer, dispatching each complete line */
static void feed(unsigned char ci, unsigned char n) {
    unsigned char i;
    char c;
    for (i = 0; i < n; i++) {
        c = (char)rbuf[i];
        if (c == '\n' || c == '\r') {
            if (cinlen[ci]) {
                scpy(line, cin[ci], INBUF);
                cinlen[ci] = 0;
                cin[ci][0] = 0;
                dispatch(ci);
                if (!cused[ci]) return; /* QUIT closed us mid-buffer */
            }
            continue;
        }
        if (cinlen[ci] < INBUF - 1) {
            cin[ci][cinlen[ci]++] = c;
            cin[ci][cinlen[ci]] = 0;
        }
    }
}

static unsigned int atou16(const char *s) {
    unsigned int n = 0;
    while (*s >= '0' && *s <= '9') {
        n = n * 10 + (unsigned char)(*s - '0');
        s++;
    }
    return n;
}

void main(void) {
    char args[16];
    unsigned int port;
    unsigned char i, s, n, idle;

    { /* copy argv before any static (incl. _nr) lands on $A000 */
        char *a = getargs();
        for (i = 0; a[i] && i < 15; i++) args[i] = a[i];
        args[i] = 0;
    }
    for (i = 0; i < MAXCL; i++) { /* gbos does not zero statics */
        cused[i] = 0;
        creg[i] = 0;
        cgotu[i] = 0;
        cinlen[i] = 0;
        cnick[i][0] = 0;
        cchan[i][0] = 0;
        cin[i][0] = 0;
    }
    mlen = 0;
    port = (args[0] >= '0' && args[0] <= '9') ? atou16(args) : PORT_DEF;

    lsock = net_socket(SOCK_TCP);
    if (lsock == 0xFF) {
        puts("ircd: no socket");
        nl();
        sexit(1);
    }
    if (net_listen(lsock, port) == 0xFF) {
        puts("ircd: listen failed (port in use?)");
        nl();
        net_close(lsock);
        sexit(1);
    }
    puts("ircd: listening on port ");
    putu(port);
    puts(" (max ");
    putu(MAXCL);
    puts(" clients)");
    nl();

    idle = 0;
    for (;;) {
        s = net_accept(lsock); /* one RX pump per call */
        if (s != 0xFE) {
            for (i = 0; i < MAXCL && cused[i]; i++);
            if (i == MAXCL) {
                net_close(s); /* full: let them try later */
                logline("! refused (full)", 0);
            } else {
                csock[i] = s;
                cused[i] = 1;
                creg[i] = 0;
                cgotu[i] = 0;
                cinlen[i] = 0;
                cnick[i][0] = 0;
                cchan[i][0] = 0;
                cin[i][0] = 0;
                logline("* client connected", 0);
            }
            idle = 0;
        }
        for (i = 0; i < MAXCL; i++) {
            if (!cused[i]) continue;
            n = net_recv_nb(csock[i], rbuf, RBUFSZ);
            if (n == 0) {
                drop(i, "Connection closed");
                continue;
            }
            if (n == 0xFE || n == 0xFF) continue;
            feed(i, n);
            idle = 0;
        }
        if (++idle >= 4) {
            msleep(20);
            idle = 4;
        }
    }
}