irc_parser.c

#include "irc_parser.h"

static void span_set(Span *s, const char *p, size_t n) {
    s->ptr = p;
    s->len = n;
}

static int span_eq(const Span *s, const char *str){
    size_t i = 0;
    while (str[i]) {
        if (i >= s->len || s->ptr[i] != str[i])
            return 0;
        i++;
    }
    return i == s->len;
}

static int is_numeric(const Span *s){
    if (s->len != 3)
        return 0;

    for (int i = 0; i < 3; i++)
        if (s->ptr[i] < '0' || s->ptr[i] > '9')
            return 0;

    return 1;
}

static IRCCommand get_command(const Span *cmd){
    if (span_eq(cmd, "PING"))    return PING;
    if (span_eq(cmd, "PRIVMSG")) return PRIVMSG;
    if (span_eq(cmd, "JOIN"))    return JOIN;
    if (span_eq(cmd, "PART"))    return PART;
    if (span_eq(cmd, "NICK"))    return NICK;
    if (span_eq(cmd, "QUIT"))    return QUIT;
    if (is_numeric(cmd))         return NUMERIC;
    return OTHER;
}

// https://datatracker.ietf.org/doc/html/rfc2812#section-2.3.1

int irc_parse(const char *buf, size_t len, IRCMessage *msg){
    const char *p = buf;
    const char *end = buf + len;

    msg->prefix.len = 0;
    msg->param_count = 0;

    // message    =  [ ":" prefix SPACE ] command [ params ] crlf

    // prefix     =  servername / ( nickname [ [ "!" user ] "@" host ] )
    if (p < end && *p == ':') {
        const char *start = ++p;

        while (p < end && *p != ' ') p++;
        if (p == end) return 0;

        span_set(&msg->prefix, start, p - start);
        p++;
    }

    // command    =  1*letter / 3digit
    {
        const char *start = p;

        while (p < end && *p != ' ') p++;

        span_set(&msg->command_text, start, p - start);
        msg->command = get_command(&msg->command_text);
    }

    // params     =  *14( SPACE middle ) [ SPACE ":" trailing ]
    //            =/  14( SPACE middle ) [ SPACE [ ":" ] trailing ]
    while (p < end && msg->param_count < IRC_MAX_PARAMS) {
        if (p < end && *p == ' ') p++;
        else break;
        // while (p < end && *p == ' ') p++;
        // if (p == end) break;

        if (p < end && *p == ':') {
            p++;
            span_set(&msg->params[msg->param_count++], p, end - p);
            break;
        }

        const char *start = p;
        while (p < end && *p != ' ') p++;

        span_set(&msg->params[msg->param_count++], start, p - start);
    }

    return 1;
}