#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>

#include "filterdb.h"

#define PAGE_SIZE		4096
#define ALIGN(s,a)		(((s) + a - 1) & ~(a - 1))

const char *sqdb_section_names[SQDB_SECTION_MAX] = {
	[SQDB_SECTION_STRINGS]		= "strings",
	[SQDB_SECTION_CATEGORIES]	= "categories",
	[SQDB_SECTION_INDEX]		= "index",
	[SQDB_SECTION_INDEX_MPH]	= "index_mph",
	[SQDB_SECTION_KEYWORD]		= "keyword",
	[SQDB_SECTION_KEYWORD_MPH]	= "keyword_mph",
};

static int sqdb_allocate(struct sqdb *db, size_t s, int wr)
{
	size_t old_size, new_size;
	void *base;
	int prot = PROT_READ;

	old_size = db->file_length;
	new_size = ALIGN(db->file_length + s, PAGE_SIZE);

	if (new_size == ALIGN(db->file_length, PAGE_SIZE)) {
		db->file_length += s;
		return old_size;
	}

	if (wr && ftruncate(db->fd, new_size) < 0)
		return -1;

	if (db->mmap_base == NULL) {
		if (wr)
			prot |= PROT_WRITE;
		base = mmap(NULL, new_size, prot, MAP_SHARED, db->fd, 0);
	} else {
		base = mremap(db->mmap_base, ALIGN(old_size, PAGE_SIZE),
			      new_size, MREMAP_MAYMOVE);
	}
	if (base == MAP_FAILED)
		return -1;

	db->mmap_base = base;
	db->file_length += ALIGN(s, 16);

	return old_size;
}

int sqdb_open(struct sqdb *db, const char *fn)
{
	struct stat st;

	db->fd = open(fn, O_RDONLY);
	if (db->fd < 0)
		return -1;

	fstat(db->fd, &st);

	db->file_length = 0;
	db->mmap_base = NULL;
	sqdb_allocate(db, st.st_size, 0);

	return 0;
}

int sqdb_create(struct sqdb *db, const char *fn)
{
	struct sqdb_header *hdr;
	int rc;

	db->fd = open(fn, O_CREAT | O_TRUNC | O_RDWR, 0666);
	if (db->fd < 0)
		return -1;

	db->file_length = 0;
	db->mmap_base = NULL;

	rc = sqdb_allocate(db, sizeof(struct sqdb_header), 1);
	if (rc < 0) {
		close(db->fd);
		return rc;
	}

	hdr = db->mmap_base;
	strcpy(hdr->description, "Squark Filtering Database");
	hdr->version = 1;
	hdr->magic = 0xdbdbdbdb;
	hdr->num_sections = SQDB_SECTION_MAX;

	return 0;
}

int sqdb_open(struct sqdb *db, const char *fn);

void sqdb_close(struct sqdb *db)
{
	if (db->mmap_base)
		munmap(db->mmap_base, ALIGN(db->file_length, PAGE_SIZE));
	close(db->fd);
}

void *sqdb_section_create(struct sqdb *db, int id, uint32_t size)
{
	struct sqdb_header *hdr;
	size_t pos;

	hdr = db->mmap_base;
	if (hdr->section[id].offset || hdr->section[id].length)
		return NULL;

	pos = sqdb_allocate(db, size, 1);
	if (pos < 0)
		return NULL;

	/* sqdb_allocate can remap mmap_base */
	hdr = db->mmap_base;
	hdr->section[id].offset = pos;
	hdr->section[id].length = size;

	return db->mmap_base + pos;
}

void *sqdb_section_get(struct sqdb *db, int id, uint32_t *size)
{
	struct sqdb_header *hdr = db->mmap_base;

	if (hdr->section[id].offset == 0)
		return NULL;

	if (size)
		*size = hdr->section[id].length;

	return db->mmap_base + hdr->section[id].offset;
}

blob_t sqdb_get_string_literal(struct sqdb *db, uint32_t encoded_ptr)
{
	uint32_t section_size;
	unsigned char *ptr;
	unsigned int len, off;

	ptr = sqdb_section_get(db, SQDB_SECTION_STRINGS, &section_size);
	if (ptr == NULL)
		return BLOB_NULL;

	off = encoded_ptr >> SQDB_LENGTH_BITS;
	len = encoded_ptr & ((1 << SQDB_LENGTH_BITS) - 1);

	if (off + len >= section_size)
		return BLOB_NULL;
	if (len == 0)
		len = ptr[off++];
	if (off + len >= section_size)
		return BLOB_NULL;

	return BLOB_PTR_LEN(ptr + off, len);
}