/*
 * Debug functions.
 *
 * Copyright (C) 2013  Simon Ruderich
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef DEBUG_H
#define DEBUG_H 1

static void debug_write(int fd, int first_call, char const *format, va_list ap) {
    char buffer[1024];

    int written = vsnprintf(buffer, sizeof(buffer), format, ap);
    /* Overflow. */
    if ((size_t)written >= sizeof(buffer)) {
        written = sizeof(buffer) - 1;
    }

    /* Make sure these functions are loaded. */
    DLSYM_FUNCTION(real_write, "write");
    DLSYM_FUNCTION(real_close, "close");

    if (first_call) {
        char nl = '\n';
        real_write(fd, &nl, 1);
    }
    real_write(fd, buffer, (size_t)written);
    real_close(fd);
}

static void debug(char const *format, ...) {
    va_list ap;

    int saved_errno = errno;

    /* If the file doesn't exist, do nothing. Prevents writing log files in
     * unexpected places. The user must create the file manually. */
    int fd = open(DEBUG_FILE, O_WRONLY | O_APPEND);
    if (fd == -1) {
        errno = saved_errno;
        return;
    }

    static int call_count = 0;
    call_count++;

    va_start(ap, format);
    debug_write(fd, call_count == 1, format, ap);
    va_end(ap);

    errno = saved_errno;
}

static void warning(char const *format, ...) {
    va_list ap;

    int saved_errno = errno;

    char const *home = getenv("HOME");
    if (!home) {
        errno = saved_errno;
        return;
    }

    char path[strlen(home) + 1 + strlen(WARNING_FILE) + 1];
    strcpy(path, home);
    strcat(path, "/");
    strcat(path, WARNING_FILE);

    /* Create the warning file if it doesn't exist yet. */
    int fd = open(path, O_WRONLY | O_APPEND | O_CREAT, S_IRUSR | S_IWUSR);
    if (fd == -1) {
        errno = saved_errno;
        return;
    }

    static int call_count = 0;
    call_count++;

    va_start(ap, format);
    debug_write(fd, call_count == 1, format, ap);
    va_end(ap);

    errno = saved_errno;
}

#endif