/*
 * Copyright (c) 2011 Vojtech Horky
 * Copyright (c) 2011 Jiri Svoboda
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup libc
 * @{
 */

#include <assert.h>
#include <errno.h>
#include <fibril_synch.h>
#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <async.h>
#include <io/log.h>
#include <ipc/logger.h>
#include <ns.h>

/** Log messages are printed under this name. */
static const char *log_prog_name;

/** IPC session with the logger service. */
static async_sess_t *logger_session;

/** Maximum length of a single log message (in bytes). */
#define MESSAGE_BUFFER_SIZE 4096

FIBRIL_RWLOCK_INITIALIZE(current_observed_level_lock);
log_level_t current_observed_level;

static int logger_register(async_sess_t *session, const char *prog_name)
{
	async_exch_t *exchange = async_exchange_begin(session);
	if (exchange == NULL) {
		return ENOMEM;
	}

	aid_t reg_msg = async_send_0(exchange, LOGGER_REGISTER, NULL);
	int rc = async_data_write_start(exchange, prog_name, str_size(prog_name));
	sysarg_t reg_msg_rc;
	async_wait_for(reg_msg, &reg_msg_rc);

	async_exchange_end(exchange);

	if (rc != EOK) {
		return rc;
	}

	return reg_msg_rc;
}

static int logger_message(async_sess_t *session, log_level_t level, const char *message)
{
	async_exch_t *exchange = async_exchange_begin(session);
	if (exchange == NULL) {
		return ENOMEM;
	}

	aid_t reg_msg = async_send_1(exchange, LOGGER_MESSAGE, level, NULL);
	int rc = async_data_write_start(exchange, message, str_size(message));
	sysarg_t reg_msg_rc;
	async_wait_for(reg_msg, &reg_msg_rc);

	async_exchange_end(exchange);

	/*
	 * Getting ENAK means no-one wants our message. That is not an
	 * error at all.
	 */
	if (rc == ENAK)
		rc = EOK;

	if (rc != EOK) {
		return rc;
	}

	return reg_msg_rc;
}

static void cannot_use_level_changed_monitor(void)
{
	fibril_rwlock_write_lock(&current_observed_level_lock);
	current_observed_level = LVL_LIMIT;
	fibril_rwlock_write_unlock(&current_observed_level_lock);
}

static int observed_level_changed_monitor(void *arg)
{
	async_sess_t *monitor_session = service_connect_blocking(EXCHANGE_SERIALIZE, SERVICE_LOGGER, LOGGER_INTERFACE_SINK, 0);
	if (monitor_session == NULL) {
		cannot_use_level_changed_monitor();
		return ENOMEM;
	}

	int rc = logger_register(monitor_session, log_prog_name);
	if (rc != EOK) {
		cannot_use_level_changed_monitor();
		return rc;
	}

	async_exch_t *exchange = async_exchange_begin(monitor_session);
	if (exchange == NULL) {
		cannot_use_level_changed_monitor();
		return ENOMEM;
	}

	while (true) {
		sysarg_t has_reader;
		sysarg_t msg_rc = async_req_0_1(exchange,
		    LOGGER_BLOCK_UNTIL_READER_CHANGED, &has_reader);
		if (msg_rc != EOK) {
			cannot_use_level_changed_monitor();
			break;
		}

		fibril_rwlock_write_lock(&current_observed_level_lock);
		if ((bool) has_reader) {
			current_observed_level = LVL_LIMIT;
		} else {
			current_observed_level = LVL_NOTE;
		}
		fibril_rwlock_write_unlock(&current_observed_level_lock);
	}

	async_exchange_end(exchange);

	return EOK;
}

static log_level_t get_current_observed_level(void)
{
	fibril_rwlock_read_lock(&current_observed_level_lock);
	log_level_t level = current_observed_level;
	fibril_rwlock_read_unlock(&current_observed_level_lock);
	return level;
}

/** Initialize the logging system.
 *
 * @param prog_name	Program name, will be printed as part of message
 * @param level		Minimum message level to print
 */
int log_init(const char *prog_name, log_level_t level)
{
	assert(level < LVL_LIMIT);

	log_prog_name = str_dup(prog_name);
	if (log_prog_name == NULL)
		return ENOMEM;

	logger_session = service_connect_blocking(EXCHANGE_SERIALIZE, SERVICE_LOGGER, LOGGER_INTERFACE_SINK, 0);
	if (logger_session == NULL) {
		return ENOMEM;
	}

	int rc = logger_register(logger_session, log_prog_name);

	current_observed_level = LVL_NOTE;

	fid_t observed_level_changed_fibril = fibril_create(observed_level_changed_monitor, NULL);
	if (observed_level_changed_fibril == 0) {
		cannot_use_level_changed_monitor();
	} else {
		fibril_add_ready(observed_level_changed_fibril);
	}

	return rc;
}

bool __log_shall_record(log_level_t level)
{
	return get_current_observed_level() >= level;
}

/** Write an entry to the log.
 *
 * @param level		Message verbosity level. Message is only printed
 *			if verbosity is less than or equal to current
 *			reporting level.
 * @param fmt		Format string (no traling newline).
 */
void __log_msg(log_level_t level, const char *fmt, ...)
{
	va_list args;

	va_start(args, fmt);
	__log_msgv(level, fmt, args);
	va_end(args);
}

/** Write an entry to the log (va_list variant).
 *
 * @param level		Message verbosity level. Message is only printed
 *			if verbosity is less than or equal to current
 *			reporting level.
 * @param fmt		Format string (no trailing newline)
 */
void __log_msgv(log_level_t level, const char *fmt, va_list args)
{
	assert(level < LVL_LIMIT);

	if (get_current_observed_level() < level) {
		return;
	}

	char *message_buffer = malloc(MESSAGE_BUFFER_SIZE);
	if (message_buffer == NULL) {
		return;
	}

	vsnprintf(message_buffer, MESSAGE_BUFFER_SIZE, fmt, args);
	logger_message(logger_session, level, message_buffer);
}

/** @}
 */