/*
 * lmo - Lua Machine Objects - Base functions
 *
 *   Copyright (C) 2009-2010 Jo-Philipp Wich <jow@openwrt.org>
 *   Copyright (C) 2018 Matthias Schiffer <mschiffer@universe-factory.net>
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

#include "template_lmo.h"

#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <errno.h>
#include <fnmatch.h>
#include <dirent.h>
#include <ctype.h>
#include <limits.h>


struct lmo_entry {
	uint32_t key_id;
	uint32_t val_id;
	uint32_t offset;
	uint32_t length;
} __attribute__((packed));

typedef struct lmo_entry lmo_entry_t;


struct lmo_archive {
	int         fd;
	int	    length;
	uint32_t    size;
	lmo_entry_t *index;
	char        *mmap;
	char        *end;
	struct lmo_archive *next;
};

typedef struct lmo_archive lmo_archive_t;


struct lmo_catalog {
	char lang[6];
	struct lmo_archive *archives;
	struct lmo_catalog *next;
};

typedef struct lmo_catalog lmo_catalog_t;

/*
 * Hash function from http://www.azillionmonkeys.com/qed/hash.html
 * Copyright (C) 2004-2008 by Paul Hsieh
 */
static inline uint16_t get_le16(const uint8_t *d) {
	return (((uint16_t)d[1]) << 8) | d[0];
}

static uint32_t sfh_hash(const void *input, size_t len)
{
	const uint8_t *data = input;
	uint32_t hash = len, tmp;

	/* Main loop */
	for (; len > 3; len -= 4) {
		hash  += get_le16(data);
		tmp    = (get_le16(data+2) << 11) ^ hash;
		hash   = (hash << 16) ^ tmp;
		data  += 4;
		hash  += hash >> 11;
	}

	/* Handle end cases */
	switch (len) {
	case 3: hash += get_le16(data);
		hash ^= hash << 16;
		hash ^= data[2] << 18;
		hash += hash >> 11;
		break;
	case 2: hash += get_le16(data);
		hash ^= hash << 11;
		hash += hash >> 17;
		break;
	case 1: hash += *data;
		hash ^= hash << 10;
		hash += hash >> 1;
	}

	/* Force "avalanching" of final 127 bits */
	hash ^= hash << 3;
	hash += hash >> 5;
	hash ^= hash << 4;
	hash += hash >> 17;
	hash ^= hash << 25;
	hash += hash >> 6;

	return hash;
}

static lmo_archive_t * lmo_open(const char *file)
{
	int in = -1;
	uint32_t idx_offset = 0;
	struct stat s;

	lmo_archive_t *ar = NULL;

	if ((in = open(file, O_RDONLY|O_CLOEXEC)) == -1)
		goto err;

	if (fstat(in, &s) == -1)
		goto err;

	if ((ar = calloc(1, sizeof(*ar))) != NULL) {

		ar->fd     = in;
		ar->size = s.st_size;

		if ((ar->mmap = mmap(NULL, ar->size, PROT_READ, MAP_SHARED, ar->fd, 0)) == MAP_FAILED)
			goto err;

		idx_offset = ntohl(*((const uint32_t *)
		                     (ar->mmap + ar->size - sizeof(uint32_t))));

		if (idx_offset >= ar->size)
			goto err;

		ar->index  = (lmo_entry_t *)(ar->mmap + idx_offset);
		ar->length = (ar->size - idx_offset - sizeof(uint32_t)) / sizeof(lmo_entry_t);
		ar->end    = ar->mmap + ar->size;

		return ar;
	}

err:
	if (in > -1)
		close(in);

	if (ar != NULL)
	{
		if ((ar->mmap != NULL) && (ar->mmap != MAP_FAILED))
			munmap(ar->mmap, ar->size);

		free(ar);
	}

	return NULL;
}


static lmo_catalog_t *_lmo_catalogs;
static lmo_catalog_t *_lmo_active_catalog;

int lmo_load_catalog(const char *lang, const char *dir)
{
	DIR *dh = NULL;
	char pattern[16];
	char path[PATH_MAX];
	struct dirent *de = NULL;

	lmo_archive_t *ar = NULL;
	lmo_catalog_t *cat = NULL;

	if (!lmo_change_catalog(lang))
		return 0;

	if (!dir || !(dh = opendir(dir)))
		goto err;

	if (!(cat = calloc(1, sizeof(*cat))))
		goto err;

	snprintf(cat->lang, sizeof(cat->lang), "%s", lang);
	snprintf(pattern, sizeof(pattern), "*.%s.lmo", lang);

	while ((de = readdir(dh)) != NULL)
	{
		if (!fnmatch(pattern, de->d_name, 0))
		{
			snprintf(path, sizeof(path), "%s/%s", dir, de->d_name);
			ar = lmo_open(path);

			if (ar)
			{
				ar->next = cat->archives;
				cat->archives = ar;
			}
		}
	}

	closedir(dh);

	cat->next = _lmo_catalogs;
	_lmo_catalogs = cat;

	if (!_lmo_active_catalog)
		_lmo_active_catalog = cat;

	return 0;

err:
	if (dh) closedir(dh);
	if (cat) free(cat);

	return -1;
}

int lmo_change_catalog(const char *lang)
{
	lmo_catalog_t *cat;

	for (cat = _lmo_catalogs; cat; cat = cat->next)
	{
		if (!strncmp(cat->lang, lang, sizeof(cat->lang)))
		{
			_lmo_active_catalog = cat;
			return 0;
		}
	}

	return -1;
}

static lmo_entry_t * lmo_find_entry(lmo_archive_t *ar, uint32_t hash)
{
	unsigned int m, l, r;
	uint32_t k;

	l = 0;
	r = ar->length - 1;

	while (1)
	{
		m = l + ((r - l) / 2);

		if (r < l)
			break;

		k = ntohl(ar->index[m].key_id);

		if (k == hash)
			return &ar->index[m];

		if (k > hash)
		{
			if (!m)
				break;

			r = m - 1;
		}
		else
		{
			l = m + 1;
		}
	}

	return NULL;
}

int lmo_translate(const char *key, size_t keylen, char **out, size_t *outlen)
{
	uint32_t hash;
	lmo_entry_t *e;
	lmo_archive_t *ar;

	if (!key || !_lmo_active_catalog)
		return -2;

	hash = sfh_hash(key, keylen);

	for (ar = _lmo_active_catalog->archives; ar; ar = ar->next)
	{
		if ((e = lmo_find_entry(ar, hash)) != NULL)
		{
			*out = ar->mmap + ntohl(e->offset);
			*outlen = ntohl(e->length);
			return 0;
		}
	}

	return -1;
}