/*
 * BSD-3-Clause
 *
 * Copyright 2021 Ozan Tezcan
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Neither the name of the copyright holder nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT HOLDER OR CONTRIBUTORS 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.
 */

#ifndef _XOPEN_SOURCE
#define _XOPEN_SOURCE 700
#endif

#include "sc_log.h"

#include <ctype.h>
#include <errno.h>
#include <time.h>

// clang-format off
#ifndef thread_local
    #if __STDC_VERSION__ >= 201112 && !defined __STDC_NO_THREADS__
        #define thread_local _Thread_local
    #elif defined _WIN32 && (defined _MSC_VER || defined __ICL ||              \
                             defined __DMC__ || defined __BORLANDC__)
        #define thread_local __declspec(thread)
    #elif defined __GNUC__ || defined __SUNPRO_C || defined __xlC__
        #define thread_local __thread
    #else
        #error "Cannot define  thread_local"
    #endif
#endif

#if __STDC_VERSION__ >= 201112 && !defined __STDC_NO_ATOMIC__
    #define SC_ATOMIC
    #include <stdatomic.h>

    #define sc_atomic _Atomic
    #define sc_atomic_store(var, val)                                          \
        (atomic_store_explicit(var, val, memory_order_relaxed))
    #define sc_atomic_load(var)                                                \
        (atomic_load_explicit(var, memory_order_relaxed))
#else
    #define sc_atomic
    #define sc_atomic_store(var, val) ((*(var)) = (val))
    #define sc_atomic_load(var)       (*(var))
#endif
// clang-format on

thread_local char sc_name[32] = "Thread";

#if defined(_WIN32) || defined(_WIN64)

#ifdef _MSC_VER
#pragma warning(disable : 4996)
#endif

#define strcasecmp _stricmp
#define localtime_r(a, b) (localtime_s(b, a) == 0 ? b : NULL)
#include <windows.h>

struct sc_log_mutex {
	CRITICAL_SECTION mtx;
};

int sc_log_mutex_init(struct sc_log_mutex *mtx)
{
	InitializeCriticalSection(&mtx->mtx);
	return 0;
}

int sc_log_mutex_term(struct sc_log_mutex *mtx)
{
	DeleteCriticalSection(&mtx->mtx);
	return 0;
}

void sc_log_mutex_lock(struct sc_log_mutex *mtx)
{
	EnterCriticalSection(&mtx->mtx);
}

void sc_log_mutex_unlock(struct sc_log_mutex *mtx)
{
	LeaveCriticalSection(&mtx->mtx);
}

#else

#include <pthread.h>

struct sc_log_mutex {
	pthread_mutex_t mtx;
};

int sc_log_mutex_init(struct sc_log_mutex *mtx)
{
	int rc;

	pthread_mutexattr_t attr;
	pthread_mutex_t mut = PTHREAD_MUTEX_INITIALIZER;

	mtx->mtx = mut;

	rc = pthread_mutexattr_init(&attr);
	if (rc != 0) {
		return rc;
	}

	pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_NORMAL);
	rc = pthread_mutex_init(&mtx->mtx, &attr);
	pthread_mutexattr_destroy(&attr);

	return rc;
}

void sc_log_mutex_term(struct sc_log_mutex *mtx)
{
	pthread_mutex_destroy(&mtx->mtx);
}

void sc_log_mutex_lock(struct sc_log_mutex *mtx)
{
	pthread_mutex_lock(&mtx->mtx);
}

void sc_log_mutex_unlock(struct sc_log_mutex *mtx)
{
	pthread_mutex_unlock(&mtx->mtx);
}

#endif

struct sc_log {
	FILE *fp;
	char current_file[256];
	char prev_file[256];
	size_t file_size;

	struct sc_log_mutex mtx;
	sc_atomic enum sc_log_level level;
	bool init;
	bool to_stdout;

	void *arg;
	int (*cb)(void *, enum sc_log_level, const char *, va_list);
};

struct sc_log sc_log;

int sc_log_init(void)
{
	int rc;

	sc_log = (struct sc_log){0};

	sc_atomic_store(&sc_log.level, SC_LOG_INFO);
	sc_log.to_stdout = true;

	rc = sc_log_mutex_init(&sc_log.mtx);
	if (rc != 0) {
		errno = rc;
	}

	sc_log.init = true;

	return rc;
}

int sc_log_term(void)
{
	int rc = 0;

	if (!sc_log.init) {
		return -1;
	}

	if (sc_log.fp) {
		rc = fclose(sc_log.fp);
		if (rc != 0) {
			rc = -1;
		}
	}

	sc_log_mutex_term(&sc_log.mtx);
	sc_log = (struct sc_log){0};

	return rc;
}

void sc_log_set_thread_name(const char *name)
{
	strncpy(sc_name, name, sizeof(sc_name) - 1);
}

static int sc_strcasecmp(const char *a, const char *b)
{
	int n;

	for (;; a++, b++) {
		if (*a == 0 && *b == 0) {
			return 0;
		}

		if ((n = tolower(*a) - tolower(*b)) != 0) {
			return n;
		}
	}
}

int sc_log_set_level(const char *str)
{
	size_t count = sizeof(sc_log_levels) / sizeof(sc_log_levels[0]);

	for (size_t i = 0; i < count; i++) {
		if (sc_strcasecmp(str, sc_log_levels[i].str) == 0) {
#ifdef SC_ATOMIC
			sc_atomic_store(&sc_log.level, sc_log_levels[i].id);
#else
			sc_log_mutex_lock(&sc_log.mtx);
			sc_log.level = sc_log_levels[i].id;
			sc_log_mutex_unlock(&sc_log.mtx);
#endif
			return 0;
		}
	}

	return -1;
}

void sc_log_set_stdout(bool enable)
{
	sc_log_mutex_lock(&sc_log.mtx);
	sc_log.to_stdout = enable;
	sc_log_mutex_unlock(&sc_log.mtx);
}

int sc_log_set_file(const char *prev, const char *current)
{
	int rc = 0, saved_errno = 0;
	long size;
	FILE *fp = NULL;

	sc_log_mutex_lock(&sc_log.mtx);

	if (sc_log.fp != NULL) {
		fclose(sc_log.fp);
		sc_log.fp = NULL;
	}

	sc_log.prev_file[0] = '\0';
	sc_log.current_file[0] = '\0';

	if (prev == NULL || current == NULL) {
		goto out;
	}

	if (strlen(prev) >= sizeof(sc_log.prev_file) - 1 ||
	    strlen(current) >= sizeof(sc_log.current_file) - 1) {
		goto error;
	}

	memcpy(sc_log.prev_file, prev, strlen(prev) + 1);
	memcpy(sc_log.current_file, current, strlen(current) + 1);

	fp = fopen(sc_log.current_file, "a+");
	if (fp == NULL) {
		goto error;
	}

	if (fprintf(fp, "\n") < 0) {
		goto error;
	}

	size = ftell(fp);
	if (size < 0) {
		goto error;
	}

	sc_log.file_size = (size_t) size;
	sc_log.fp = fp;

	goto out;

error:
	rc = -1;
	saved_errno = errno;

	if (fp != NULL) {
		fclose(fp);
	}
out:
	sc_log_mutex_unlock(&sc_log.mtx);
	errno = saved_errno;

	return rc;
}

void sc_log_set_callback(void *arg, int (*cb)(void *, enum sc_log_level,
					      const char *, va_list))
{
	sc_log_mutex_lock(&sc_log.mtx);
	sc_log.arg = arg;
	sc_log.cb = cb;
	sc_log_mutex_unlock(&sc_log.mtx);
}

static int sc_log_print_header(FILE *fp, enum sc_log_level level)
{
	int rc;
	time_t t;
	struct tm result, *tm;

	t = time(NULL);
	tm = localtime_r(&t, &result);

	if (tm == NULL) {
		return -1;
	}

	rc = fprintf(fp, "[%d-%02d-%02d %02d:%02d:%02d][%-5s][%s] ",
		     tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,
		     tm->tm_hour, tm->tm_min, tm->tm_sec,
		     sc_log_levels[level].str, sc_name);
	if (rc < 0) {
		return -1;
	}

	return 0;
}

static int sc_log_stdout(enum sc_log_level level, const char *fmt, va_list va)
{
	int rc;
	FILE *dest = level == SC_LOG_ERROR ? stderr : stdout;

	rc = sc_log_print_header(dest, level);
	if (rc < 0) {
		return -1;
	}

	rc = vfprintf(dest, fmt, va);
	if (rc < 0) {
		return -1;
	}

	return 0;
}

static int sc_log_file(enum sc_log_level level, const char *fmt, va_list va)
{
	int rc, size;

	rc = sc_log_print_header(sc_log.fp, level);
	if (rc < 0) {
		return -1;
	}

	size = vfprintf(sc_log.fp, fmt, va);
	if (size < 0) {
		return -1;
	}

	sc_log.file_size += size;

	if (sc_log.file_size > (size_t) SC_LOG_FILE_SIZE) {
		fclose(sc_log.fp);
		(void) rename(sc_log.current_file, sc_log.prev_file);

		sc_log.fp = fopen(sc_log.current_file, "w+");
		if (sc_log.fp == NULL) {
			return -1;
		}

		sc_log.file_size = 0;
	}

	return rc;
}

int sc_log_log(enum sc_log_level level, const char *fmt, ...)
{
	int rc = 0;
	va_list va;

	// Use relaxed atomics to avoid locking cost, e.g., DEBUG logs when
	// level=INFO will get away without any synchronization on most
	// platforms.
#ifdef SC_ATOMIC
	enum sc_log_level curr;

	curr = sc_atomic_load(&sc_log.level);
	if (level < curr) {
		return 0;
	}
#endif

	sc_log_mutex_lock(&sc_log.mtx);

#ifndef SC_ATOMIC
	if (level < sc_log.level) {
		sc_log_mutex_unlock(&sc_log.mtx);
		return 0;
	}
#endif

	if (sc_log.to_stdout) {
		va_start(va, fmt);
		rc |= sc_log_stdout(level, fmt, va);
		va_end(va);
	}

	if (sc_log.fp != NULL) {
		va_start(va, fmt);
		rc |= sc_log_file(level, fmt, va);
		va_end(va);
	}

	if (sc_log.cb) {
		va_start(va, fmt);
		rc |= sc_log.cb(sc_log.arg, level, fmt, va);
		va_end(va);
	}

	sc_log_mutex_unlock(&sc_log.mtx);

	return rc;
}