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

#include "storage.h"
#include "intf.h"
#include "debug.h"

static int unmap_chunk(struct tsnif_storage_handle *h,
		       struct tsnif_storage_chunk *chunk);

static int write_header(int fd, struct tsnif_storage_opts *opts)
{
	int err;

	struct tsnif_storage_header_mmap header = {
		.common = {
			.magic         = TSNIF_HEADER_MAGIC,
			.version       = TSNIF_STORAGE_VERSION,
			.storage_type  = TSNIF_STORAGE_TYPE_MMAP,
			.term_type     = opts->term_type,
		},
		.size_max = opts->size_max,
	};

	err = write(fd, &header, sizeof(header));
	if (err < 0)
		return err;

	return ftruncate(fd, sysconf(_SC_PAGESIZE));
}

static int map_header(struct tsnif_storage_handle *h)
{
	void *ptr;
	int flags = PROT_READ;

	if (h->opts->flags & TSNIF_STORAGE_OPT_WRITE)
		flags = PROT_WRITE;

	ptr = mmap(NULL, sysconf(_SC_PAGESIZE),
			flags,
			MAP_SHARED, h->fd, 0);
	if (MAP_FAILED == ptr)
		return -1;

	h->header = ptr;
	return 0;
}

static int check_header(struct tsnif_storage_handle *h)
{
	struct tsnif_storage_header_mmap *header = h->header;
	struct tsnif_storage_header *common = &header->common;

	if (common->magic != TSNIF_HEADER_MAGIC) {
		TSNIF_DEBUG(STORAGE, "failed: wrong header magic %x\n", common->magic);
		return -1;
	}

	if (common->version != TSNIF_STORAGE_VERSION) {
		TSNIF_DEBUG(STORAGE, "failed: wrong storage version %x\n", common->version);
		return -1;
	}

	if (common->storage_type != TSNIF_STORAGE_TYPE_MMAP) {
		TSNIF_DEBUG(STORAGE, "failed: wrong storage type %x\n", common->storage_type);
		return -1;
	}

	TSNIF_DEBUG(STORAGE, "got terminal type %d\n", common->term_type);
	return 0;
}

int tsnif_storage_init(struct tsnif_storage_handle *h,
		       struct tsnif_storage_opts *opts, char *name)
{
	int fd, create, err;
	int flags = O_RDONLY;
	int mode = S_IRUSR | S_IWUSR;

	if (!opts)
		return -1;

	memset(h, 0, sizeof(*h));
	h->opts = opts;

	/* mmap page sized chunks as default */
	if (!opts->chunk_size)
		opts->chunk_size = sysconf(_SC_PAGESIZE);

	create = (opts->flags & TSNIF_STORAGE_OPT_WRITE);
	if (create)
		flags |= O_CREAT | O_TRUNC | O_RDWR;

	fd = open(name, flags, mode);
	if (fd < 0) {
		TSNIF_DEBUG(STORAGE, "open failed for '%s': %s\n",
			    name, strerror(errno));
		return -1;
	}

	TSNIF_DEBUG(STORAGE, "opened '%s'\n", name);

	if (create &&
	    (err = write_header(fd, opts))) {
		TSNIF_DEBUG(STORAGE, "write failed for '%s': %s\n",
			    name, strerror(errno));
		close(fd);
		return err;
	}

	h->fd = fd;

	err = map_header(h);
	if (err) {
		close(fd);
		return err;
	}

	TSNIF_DEBUG(STORAGE, "records count %d\n", h->header->cnt);

	if (opts->flags & TSNIF_STORAGE_OPT_READ) {
		struct stat st;

		err = fstat(fd, &st);
		if (err)
			return err;

		h->file_size = st.st_size;

		return check_header(h);
	}

	return 0;
}

int tsnif_storage_close(struct tsnif_storage_handle *h)
{
	if (h->header) {
		TSNIF_DEBUG(STORAGE, "records count %d\n", h->header->cnt);
		munmap(h->header, sysconf(_SC_PAGESIZE));
	}

	unmap_chunk(h, &h->active_chunk);

	close(h->fd);
	return 0;
}

static int get_open_offset(struct tsnif_storage_handle *h)
{
	return h->header->offset_start;
}

static int unmap_chunk(struct tsnif_storage_handle *h,
		       struct tsnif_storage_chunk *chunk)
{
	if (!chunk->header)
		return -1;

	return munmap(chunk->header, h->opts->chunk_size);
}

enum {
	STORAGE_MMAP_FIRST,
	STORAGE_MMAP_NEXT,
	STORAGE_MMAP_PREV,
};

static int file_trunc(struct tsnif_storage_handle *h, off_t new_size)
{
	off_t old_size;

	TSNIF_DEBUG(STORAGE, "new size %d\n", new_size);

	old_size = lseek(h->fd, 0, SEEK_END);
	if (old_size < 0)
		return -1;

	TSNIF_DEBUG(STORAGE, "old size %d\n", old_size);

	if (old_size >= new_size)
		return 0;

	TSNIF_DEBUG(STORAGE, "truncating to %d\n", new_size);

	return ftruncate(h->fd, new_size);
}

static int map_chunk(struct tsnif_storage_handle *h,
		     struct tsnif_storage_chunk *chunk, int what)
{
	void *ptr;
	off_t offset = 0;
	int err, flags = PROT_READ;


	TSNIF_DEBUG(STORAGE, "what %d\n", what);

	if (what == STORAGE_MMAP_FIRST) {
		if (h->opts->flags & TSNIF_STORAGE_OPT_READ)
			offset = get_open_offset(h);
		else {
			offset = sysconf(_SC_PAGESIZE);
			h->header->offset_start = offset;
		}
	}

	if (what == STORAGE_MMAP_NEXT) {

		offset = chunk->offset + h->opts->chunk_size;

		if (h->opts->flags & TSNIF_STORAGE_OPT_READ) {

			TSNIF_DEBUG(STORAGE, "file size       0x%x\n", h->file_size);
			TSNIF_DEBUG(STORAGE, "offset          0x%x\n", offset);

			if (h->file_size == offset)
				offset = sysconf(_SC_PAGESIZE);

			TSNIF_DEBUG(STORAGE, "offset          0x%x\n", offset);
			TSNIF_DEBUG(STORAGE, "start offset    0x%x\n", h->header->offset_start);

			if (h->header->offset_start == offset)
				return TSNIF_STORAGE_READ_EOF;
		} else {
			/* check the max size only in write mode */
			if (offset > h->opts->size_max)
				offset = sysconf(_SC_PAGESIZE);
		}

		TSNIF_DEBUG(STORAGE, "chunk offset 0x%x\n", chunk->offset);
		TSNIF_DEBUG(STORAGE, "chunk size   0x%x\n", chunk->offset);
		TSNIF_DEBUG(STORAGE, "max size     0x%x\n", h->opts->size_max);
	}

	if (what == STORAGE_MMAP_PREV) {

		if (h->header->offset_start == chunk->offset)
			return TSNIF_STORAGE_READ_EOF;

		if (chunk->offset == sysconf(_SC_PAGESIZE))
			offset = h->file_size - h->opts->chunk_size;
		else
			offset = chunk->offset - h->opts->chunk_size;

		TSNIF_DEBUG(STORAGE, "chunk offset 0x%x\n", chunk->offset);
		TSNIF_DEBUG(STORAGE, "chunk size   0x%x\n", chunk->offset);
		TSNIF_DEBUG(STORAGE, "max size     0x%x\n", h->opts->size_max);
	}

	TSNIF_DEBUG(STORAGE, "new offset 0x%x, old offset 0x%x\n",
		    offset, chunk->offset);

	if (chunk->header)
		unmap_chunk(h, chunk);

	if (h->opts->flags & TSNIF_STORAGE_OPT_WRITE) {
		err = file_trunc(h, offset + h->opts->chunk_size);
		if (err)
			return err;

		flags = PROT_WRITE;
	}

	ptr = mmap(NULL, h->opts->chunk_size,
			flags,
			MAP_SHARED, h->fd, offset);
	if (MAP_FAILED == ptr)
		return -1;

	TSNIF_DEBUG(STORAGE, "mmap-ed offset %ld, size %d\n",
		    offset, h->opts->chunk_size);

	chunk->offset = offset;
	chunk->header = ptr;
	chunk->current_data  = chunk->header->rec0;
	chunk->current_index = (void*) (chunk->header) + h->opts->chunk_size
				- sizeof(uint32_t);
	return 0;
}

static int clear_chunk(struct tsnif_storage_handle *h,
		       struct tsnif_storage_chunk *chunk)
{
	struct tsnif_storage_chunk_header *header = chunk->header;

	memset(header, 0x0, sizeof(*header));
	header->free = h->opts->chunk_size -
		    sizeof(struct tsnif_storage_chunk_header);

	chunk->current_data  = header->rec0;
	chunk->current_index = (void*) (header) + h->opts->chunk_size
				- sizeof(uint32_t);

	TSNIF_DEBUG(STORAGE, "chunk header %p\n", chunk->header);
	TSNIF_DEBUG(STORAGE, "chunk data   %p\n", chunk->current_data);
	TSNIF_DEBUG(STORAGE, "chunk index  %p\n", chunk->current_index);
	TSNIF_DEBUG(STORAGE, "chunk size   0x%x\n", h->opts->chunk_size);
	TSNIF_DEBUG(STORAGE, "chunk free   %d\n", header->free);
	return 0;
}

static int map_write_chunk(struct tsnif_storage_handle *h,
			   struct tsnif_storage_chunk *chunk, int what)
{
	return (map_chunk(h, chunk, what) ||
		clear_chunk(h, chunk));
}

static int map_read_chunk(struct tsnif_storage_handle *h,
			  struct tsnif_storage_chunk *chunk, int what)
{
	int err;

	err = map_chunk(h, chunk, what);
	if ((err < 0 ) ||
	    (err == TSNIF_STORAGE_READ_EOF))
		return err;

	chunk->read_index = -1;
	return 0;
}

static int get_chunk_write_rec(struct tsnif_storage_handle *h, int size)
{
	struct tsnif_storage_chunk *chunk = &h->active_chunk;
	struct tsnif_storage_chunk_header *chunk_header = chunk->header;

	TSNIF_DEBUG(STORAGE, "chunk header %p\n", chunk_header);

	/* first time */
	if (!chunk_header)
		return map_write_chunk(h, chunk, STORAGE_MMAP_FIRST);

	/* we fit into current chunk */
#define INDEX_OVERHEAD (4*sizeof(uint32_t))
	if (chunk_header->free > (size +
			   sizeof(struct tsnif_storage_rec_mmap) +
			   INDEX_OVERHEAD))
		return 0;

	/* we dont fit into current chunk,
	 * let's go for another */
	return map_write_chunk(h, chunk, STORAGE_MMAP_NEXT);
}

static int get_chunk_read_rec(struct tsnif_storage_handle *h, int what)
{
	struct tsnif_storage_chunk *chunk = &h->active_chunk;
	struct tsnif_storage_chunk_header *chunk_header = chunk->header;
	int map_what = 0;

	TSNIF_DEBUG(STORAGE, "chunk header %p\n", chunk_header);

	/* first time */
	if (!chunk_header)
		return map_read_chunk(h, chunk, STORAGE_MMAP_FIRST);

	TSNIF_DEBUG(STORAGE, "chunk cnt   0x%x\n", chunk_header->cnt);
	TSNIF_DEBUG(STORAGE, "read index  0x%x\n", chunk->read_index);

	/* we want next record and we have it */
	if (TSNIF_STORAGE_READ_NEXT == what) {
		if ((chunk->read_index + 1) < chunk_header->cnt)
			return 0;
		map_what = STORAGE_MMAP_NEXT;
	}

	/* we want previous record and we have it */
	if (TSNIF_STORAGE_READ_PREV == what) {
		if (chunk->read_index)
			return 0;
		map_what = STORAGE_MMAP_PREV;
	}

	return map_read_chunk(h, chunk, map_what);
}

static int store_rec(struct tsnif_storage_handle *h,
		     struct tsnif_storage_rec *rec)
{
	struct tsnif_storage_rec_mmap *mrec;
	struct tsnif_storage_chunk *chunk = &h->active_chunk;
	struct tsnif_storage_chunk_header *header = chunk->header;

	TSNIF_DEBUG(STORAGE, "chunk data  %p\n", chunk->current_data);
	TSNIF_DEBUG(STORAGE, "chunk index %p\n", chunk->current_index);
	TSNIF_DEBUG(STORAGE, "time %ld\n", rec->time.tv_sec);

	mrec = chunk->current_data;
	mrec->len   = rec->len;
	mrec->flags = rec->flags;
	mrec->time  = rec->time;
	mrec->ws    = rec->ws;
	memcpy(mrec->data, rec->ptr, rec->len);

#define RECLEN (sizeof(struct tsnif_storage_rec_mmap) + rec->len)

	*(chunk->current_index) = (void*) chunk->current_data - (void*) header;
	TSNIF_DEBUG(STORAGE, "rec offset  0x%x\n", *(chunk->current_index));
	TSNIF_DEBUG(STORAGE, "rec size    0x%x\n", rec->len);

	chunk->current_index--;
	chunk->current_data += RECLEN;

	/* update file header */
	h->header->cnt++;

	/* update chunk header */
	header->cnt++;
	header->free -= (sizeof(uint32_t) + RECLEN);

	TSNIF_DEBUG(STORAGE, "chunk data  %p\n", chunk->current_data);
	TSNIF_DEBUG(STORAGE, "chunk index %p\n", chunk->current_index);
	TSNIF_DEBUG(STORAGE, "chunk free  %d\n", header->free);
	TSNIF_DEBUG(STORAGE, "chunk cnt   %d\n", header->cnt);
	return 0;
}

static int read_rec(struct tsnif_storage_handle *h,
		     struct tsnif_storage_rec *rec, int what)
{
	struct tsnif_storage_rec_mmap *mrec;
	struct tsnif_storage_chunk *chunk = &h->active_chunk;
	struct tsnif_storage_chunk_header *header = chunk->header;
	off_t offset;

	TSNIF_DEBUG(STORAGE, "chunk data  %p\n", chunk->current_data);
	TSNIF_DEBUG(STORAGE, "chunk index %p\n", chunk->current_index);
	TSNIF_DEBUG(STORAGE, "read index  0x%x\n", chunk->read_index);

	/* the chunk got loaded just now */
	if (chunk->read_index == -1) {
		if (what == TSNIF_STORAGE_READ_NEXT)
			chunk->read_index = 0;
		else
			chunk->read_index = chunk->header->cnt - 1;
	/* move within the chunk */
	} else {
		if (what == TSNIF_STORAGE_READ_NEXT)
			chunk->read_index++;
		else
			chunk->read_index--;
	}

	offset = *(chunk->current_index - chunk->read_index);
	mrec = (void*) header + offset;

	rec->ptr   = mrec->data;
	rec->len   = mrec->len;
	rec->flags = mrec->flags;
	rec->time  = mrec->time;
	rec->ws    = mrec->ws;
	return 0;
}

int tsnif_storage_write(struct tsnif_storage_handle *h,
			struct tsnif_storage_rec *rec)
{
	int err;

	TSNIF_DEBUG(STORAGE, "entry\n");

	err = get_chunk_write_rec(h, rec->len);
	if (err)
		return err;

	return store_rec(h, rec);
}

int tsnif_storage_read(struct tsnif_storage_handle *h, int what,
			struct tsnif_storage_rec *rec)
{
	int err;

	TSNIF_DEBUG(STORAGE, "entry\n");

	err = get_chunk_read_rec(h, what);
	if (err)
		return err;

	return read_rec(h, rec, what);
}

int tsnif_storage_term_type(struct tsnif_storage_handle *h)
{
	return h->header->common.term_type;
}