/*
 * Message and error reporting (possibly fatal).
 *
 * Usage:
 *
 *     extern int cleanup(void);
 *     extern void log(int, const char *, va_list, int);
 *
 *     message_fatal_cleanup = cleanup;
 *     message_program_name = argv[0];
 *
 *     warn("Something horrible happened at %lu", time);
 *     syswarn("Couldn't unlink temporary file %s", tmpfile);
 *
 *     die("Something fatal happened at %lu", time);
 *     sysdie("open of %s failed", filename);
 *
 *     debug("Some debugging message about %s", string);
 *     notice("Informational notices");
 *
 *     message_handlers_warn(1, log);
 *     warn("This now goes through our log function");
 *
 * These functions implement message reporting through user-configurable
 * handler functions.  debug() only does something if DEBUG is defined, and
 * notice() and warn() just output messages as configured.  die() similarly
 * outputs a message but then exits, normally with a status of 1.
 *
 * The sys* versions do the same, but append a colon, a space, and the results
 * of strerror(errno) to the end of the message.  All functions accept
 * printf-style formatting strings and arguments.
 *
 * If message_fatal_cleanup is non-NULL, it is called before exit by die and
 * sysdie and its return value is used as the argument to exit.  It is a
 * pointer to a function taking no arguments and returning an int, and can be
 * used to call cleanup functions or to exit in some alternate fashion (such
 * as by calling _exit).
 *
 * If message_program_name is non-NULL, the string it points to, followed by a
 * colon and a space, is prepended to all error messages logged through the
 * message_log_stdout and message_log_stderr message handlers (the former is
 * the default for notice, and the latter is the default for warn and die).
 *
 * Honoring error_program_name and printing to stderr is just the default
 * handler; with message_handlers_* the handlers for any message function can
 * be changed.  By default, notice prints to stdout, warn and die print to
 * stderr, and the others don't do anything at all.  These functions take a
 * count of handlers and then that many function pointers, each one to a
 * function that takes a message length (the number of characters snprintf
 * generates given the format and arguments), a format, an argument list as a
 * va_list, and the applicable errno value (if any).
 *
 * The canonical version of this file is maintained in the rra-c-util package,
 * which can be found at <https://www.eyrie.org/~eagle/software/rra-c-util/>.
 *
 * Written by Russ Allbery <eagle@eyrie.org>
 * Copyright 2015-2016, 2020 Russ Allbery <eagle@eyrie.org>
 * Copyright 2008-2010, 2013-2014
 *     The Board of Trustees of the Leland Stanford Junior University
 * Copyright 2004-2006 Internet Systems Consortium, Inc. ("ISC")
 * Copyright 1991, 1994-2003 The Internet Software Consortium and Rich Salz
 *
 * This code is derived from software contributed to the Internet Software
 * Consortium by Rich Salz.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 *
 * SPDX-License-Identifier: ISC
 */

#include <config.h>
#include <portable/system.h>

#include <errno.h>
#ifdef HAVE_SYSLOG_H
#    include <syslog.h>
#endif

#ifdef _WIN32
#    include <windows.h>
#    define LOG_DEBUG   EVENTLOG_SUCCESS
#    define LOG_INFO    EVENTLOG_INFORMATION_TYPE
#    define LOG_NOTICE  EVENTLOG_INFORMATION_TYPE
#    define LOG_WARNING EVENTLOG_WARNING_TYPE
#    define LOG_ERR     EVENTLOG_ERROR_TYPE
#    define LOG_CRIT    EVENTLOG_ERROR_TYPE
#endif

#include <util/macros.h>
#include <util/messages.h>
#include <util/xmalloc.h>

/* The default handler lists. */
static message_handler_func stdout_handlers[2] = {message_log_stdout, NULL};
static message_handler_func stderr_handlers[2] = {message_log_stderr, NULL};

/* The list of logging functions currently in effect. */
static message_handler_func *debug_handlers = NULL;
static message_handler_func *notice_handlers = stdout_handlers;
static message_handler_func *warn_handlers = stderr_handlers;
static message_handler_func *die_handlers = stderr_handlers;

/* If non-NULL, called before exit and its return value passed to exit. */
int (*message_fatal_cleanup)(void) = NULL;

/* If non-NULL, prepended (followed by ": ") to messages. */
const char *message_program_name = NULL;


/*
 * Set the handlers for a particular message function.  Takes a pointer to the
 * handler list, the count of handlers, and the argument list.
 */
static void
message_handlers(message_handler_func **list, unsigned int count, va_list args)
{
    unsigned int i;

    if (*list != stdout_handlers && *list != stderr_handlers)
        free(*list);
    *list = xcalloc(count + 1, sizeof(message_handler_func));
    for (i = 0; i < count; i++)
        (*list)[i] = (message_handler_func) va_arg(args, message_handler_func);
    (*list)[count] = NULL;
}


/*
 * There's no good way of writing these handlers without a bunch of code
 * duplication since we can't assume variadic macros, but I can at least make
 * it easier to write and keep them consistent.
 */
/* clang-format off */
#define HANDLER_FUNCTION(type)                              \
    void                                                    \
    message_handlers_ ## type(unsigned int count, ...)      \
    {                                                       \
        va_list args;                                       \
                                                            \
        va_start(args, count);                              \
        message_handlers(& type ## _handlers, count, args); \
        va_end(args);                                       \
    }
/* clang-format on */
HANDLER_FUNCTION(debug)
HANDLER_FUNCTION(notice)
HANDLER_FUNCTION(warn)
HANDLER_FUNCTION(die)


/*
 * Reset all handlers back to the defaults and free all allocated memory.
 * This is primarily useful for programs that undergo comprehensive memory
 * allocation analysis.
 */
void
message_handlers_reset(void)
{
    free(debug_handlers);
    debug_handlers = NULL;
    if (notice_handlers != stdout_handlers) {
        free(notice_handlers);
        notice_handlers = stdout_handlers;
    }
    if (warn_handlers != stderr_handlers) {
        free(warn_handlers);
        warn_handlers = stderr_handlers;
    }
    if (die_handlers != stderr_handlers) {
        free(die_handlers);
        die_handlers = stderr_handlers;
    }
}


/*
 * Print a message to stdout, supporting message_program_name.
 */
void
message_log_stdout(size_t len UNUSED, const char *fmt, va_list args, int err)
{
    if (message_program_name != NULL)
        fprintf(stdout, "%s: ", message_program_name);
    vfprintf(stdout, fmt, args);
    if (err)
        fprintf(stdout, ": %s", strerror(err));
    fprintf(stdout, "\n");
    fflush(stdout);
}


/*
 * Print a message to stderr, supporting message_program_name.  Also flush
 * stdout so that errors and regular output occur in the right order.
 */
void
message_log_stderr(size_t len UNUSED, const char *fmt, va_list args, int err)
{
    fflush(stdout);
    if (message_program_name != NULL)
        fprintf(stderr, "%s: ", message_program_name);
    vfprintf(stderr, fmt, args);
    if (err)
        fprintf(stderr, ": %s", strerror(err));
    fprintf(stderr, "\n");
}


/*
 * Log a message to syslog.  This is a helper function used to implement all
 * of the syslog message log handlers.  It takes the same arguments as a
 * regular message handler function but with an additional priority argument.
 *
 * This needs further attention on Windows.  For example, it currently doesn't
 * log the errno information.
 */
static void __attribute__((__format__(printf, 3, 0)))
message_log_syslog(int pri, size_t len, const char *fmt, va_list args, int err)
{
    char *buffer;
    int status;

    buffer = malloc(len + 1);
    if (buffer == NULL) {
        fprintf(stderr, "failed to malloc %lu bytes at %s line %d: %s",
                (unsigned long) len + 1, __FILE__, __LINE__, strerror(errno));
        exit(message_fatal_cleanup ? (*message_fatal_cleanup)() : 1);
    }
    status = vsnprintf(buffer, len + 1, fmt, args);
    if (status < 0 || (size_t) status >= len + 1) {
        warn("failed to format output with vsnprintf in syslog handler");
        free(buffer);
        return;
    }
#ifdef _WIN32
    {
        HANDLE eventlog;

        eventlog = RegisterEventSource(NULL, message_program_name);
        if (eventlog != NULL) {
            ReportEvent(eventlog, (WORD) pri, 0, 0, NULL, 1, 0, &buffer, NULL);
            CloseEventLog(eventlog);
        }
    }
#else  /* !_WIN32 */
    if (err == 0)
        syslog(pri, "%s", buffer);
    else
        syslog(pri, "%s: %s", buffer, strerror(err));
#endif /* !_WIN32 */
    free(buffer);
}


/*
 * Do the same sort of wrapper to generate all of the separate syslog logging
 * functions.
 */
/* clang-format off */
#define SYSLOG_FUNCTION(name, type)                                        \
    void                                                                   \
    message_log_syslog_ ## name(size_t l, const char *f, va_list a, int e) \
    {                                                                      \
        message_log_syslog(LOG_ ## type, l, f, a, e);                      \
    }
SYSLOG_FUNCTION(debug,   DEBUG)
SYSLOG_FUNCTION(info,    INFO)
SYSLOG_FUNCTION(notice,  NOTICE)
SYSLOG_FUNCTION(warning, WARNING)
SYSLOG_FUNCTION(err,     ERR)
SYSLOG_FUNCTION(crit,    CRIT)
/* clang-format on */


/*
 * All of the message handlers.  There's a lot of code duplication here too,
 * but each one is still *slightly* different and va_start has to be called
 * multiple times, so it's hard to get rid of the duplication.
 */

void
debug(const char *format, ...)
{
    va_list args;
    message_handler_func *log;
    ssize_t length;

    if (debug_handlers == NULL)
        return;
    va_start(args, format);
    length = vsnprintf(NULL, 0, format, args);
    va_end(args);
    if (length < 0)
        return;
    for (log = debug_handlers; *log != NULL; log++) {
        va_start(args, format);
        (**log)((size_t) length, format, args, 0);
        va_end(args);
    }
}

void
notice(const char *format, ...)
{
    va_list args;
    message_handler_func *log;
    ssize_t length;

    va_start(args, format);
    length = vsnprintf(NULL, 0, format, args);
    va_end(args);
    if (length < 0)
        return;
    for (log = notice_handlers; *log != NULL; log++) {
        va_start(args, format);
        (**log)((size_t) length, format, args, 0);
        va_end(args);
    }
}

void
sysnotice(const char *format, ...)
{
    va_list args;
    message_handler_func *log;
    ssize_t length;
    int error = errno;

    va_start(args, format);
    length = vsnprintf(NULL, 0, format, args);
    va_end(args);
    if (length < 0)
        return;
    for (log = notice_handlers; *log != NULL; log++) {
        va_start(args, format);
        (**log)((size_t) length, format, args, error);
        va_end(args);
    }
}

void
warn(const char *format, ...)
{
    va_list args;
    message_handler_func *log;
    ssize_t length;

    va_start(args, format);
    length = vsnprintf(NULL, 0, format, args);
    va_end(args);
    if (length < 0)
        return;
    for (log = warn_handlers; *log != NULL; log++) {
        va_start(args, format);
        (**log)((size_t) length, format, args, 0);
        va_end(args);
    }
}

void
syswarn(const char *format, ...)
{
    va_list args;
    message_handler_func *log;
    ssize_t length;
    int error = errno;

    va_start(args, format);
    length = vsnprintf(NULL, 0, format, args);
    va_end(args);
    if (length < 0)
        return;
    for (log = warn_handlers; *log != NULL; log++) {
        va_start(args, format);
        (**log)((size_t) length, format, args, error);
        va_end(args);
    }
}

void
die(const char *format, ...)
{
    va_list args;
    message_handler_func *log;
    ssize_t length;

    va_start(args, format);
    length = vsnprintf(NULL, 0, format, args);
    va_end(args);
    if (length >= 0)
        for (log = die_handlers; *log != NULL; log++) {
            va_start(args, format);
            (**log)((size_t) length, format, args, 0);
            va_end(args);
        }
    exit(message_fatal_cleanup ? (*message_fatal_cleanup)() : 1);
}

void
sysdie(const char *format, ...)
{
    va_list args;
    message_handler_func *log;
    ssize_t length;
    int error = errno;

    va_start(args, format);
    length = vsnprintf(NULL, 0, format, args);
    va_end(args);
    if (length >= 0)
        for (log = die_handlers; *log != NULL; log++) {
            va_start(args, format);
            (**log)((size_t) length, format, args, error);
            va_end(args);
        }
    exit(message_fatal_cleanup ? (*message_fatal_cleanup)() : 1);
}