#ifndef DISFLUID_DISFLUID_CACHE_ENTRY_INCLUDED
# define DISFLUID_DISFLUID_CACHE_ENTRY_INCLUDED

# include <config.h>
# include "string-desc.h"
# include <stdbool.h>

MAYBE_UNUSED static int
ao_cache_entry_read (int fd, size_t offset,
		     struct timespec *request_date,
		     struct timespec *response_date,
		     bool *invalidated,
		     bool read_key,
		     bool read_response_header,
		     bool read_response_body,
		     string_desc_t * key,
		     string_desc_t * response_header,
		     string_desc_t * response_body);

MAYBE_UNUSED static int
ao_cache_entry_push (int fd, size_t *offset,
		     const struct timespec *request_date,
		     const struct timespec *response_date,
		     bool invalidated,
		     const string_desc_t key,
		     const string_desc_t response_header,
		     const string_desc_t response_body);

# include "disfluid-append-only-file.h"
# include "safe-alloc.h"

/* The cache entry file is organized as follows:

   - on 8 bytes, the request date (timestamp in seconds),
   - on 4 bytes, the request date (number of nanoseconds),
   - on 8 bytes, the response date (timestamp in seconds),
   - on 4 bytes, the response date (number of nanoseconds),
   - on 8 bytes, the size of the key,
   - on 8 bytes, the offset of the key,
   - on 8 bytes, the size of the header,
   - on 8 bytes, the offset of the header,
   - on 8 bytes, the size of the body,
   - on 8 bytes, the offset of the body,
   - 80 if the entry has been artificially invalidated, 00 otherwise.
   - 7 bytes reserved.
 */

struct cache_entry_header
{
  struct timespec request_date;
  struct timespec response_date;
  size_t key_size;
  size_t key_offset;
  size_t header_size;
  size_t header_offset;
  size_t body_size;
  size_t body_offset;
  bool invalidated;
};

static int
ao_cache_entry_timespec_from_bytes (const uint8_t * bytes,
				    struct timespec *date)
{
  date->tv_sec = 0;
  date->tv_nsec = 0;
  for (size_t i = 0; i < 8; i++)
    {
      date->tv_sec *= 256;
      date->tv_sec += bytes[i];
    }
  for (size_t j = 8; j < 12; j++)
    {
      date->tv_nsec *= 256;
      date->tv_nsec += bytes[j];
    }
  if (date->tv_nsec >= 1000000000)
    {
      return -1;
    }
  return 0;
}

static int
ao_cache_entry_timespec_to_bytes (const struct timespec *date,
				  uint8_t * bytes)
{
  if (date->tv_nsec >= 1000000000)
    {
      return -1;
    }
  uint64_t date_sec = date->tv_sec;
  uint32_t date_nsec = date->tv_nsec;
  for (size_t i = 8; i-- > 0;)
    {
      bytes[i] = date_sec % 256;
      date_sec /= 256;
    }
  for (size_t i = 12; i-- > 8;)
    {
      bytes[i] = date_nsec % 256;
      date_nsec /= 256;
    }
  return 0;
}

static int
ao_cache_entry_offset_from_bytes (const uint8_t * bytes, size_t *length,
				  size_t *offset)
{
  *length = 0;
  *offset = 0;
  for (size_t i = 0; i < 8; i++)
    {
      *length *= 256;
      *length += bytes[i];
    }
  for (size_t j = 8; j < 16; j++)
    {
      *offset *= 256;
      *offset += bytes[j];
    }
  return 0;
}

static int
ao_cache_entry_offset_to_bytes (size_t length, size_t offset, uint8_t * bytes)
{
  for (size_t i = 8; i-- > 0;)
    {
      bytes[i] = length % 256;
      length /= 256;
    }
  for (size_t i = 16; i-- > 8;)
    {
      bytes[i] = offset % 256;
      offset /= 256;
    }
  return 0;
}

static int
ao_cache_entry_from_bytes (const uint8_t * bytes,
			   struct cache_entry_header *entry)
{
  if (ao_cache_entry_timespec_from_bytes (bytes, &(entry->request_date)) < 0)
    {
      return -1;
    }
  bytes += 12;
  if (ao_cache_entry_timespec_from_bytes (bytes, &(entry->response_date)) < 0)
    {
      return -1;
    }
  bytes += 12;
  if (ao_cache_entry_offset_from_bytes
      (bytes, &(entry->key_size), &(entry->key_offset)) < 0)
    {
      return -1;
    }
  bytes += 16;
  if (ao_cache_entry_offset_from_bytes
      (bytes, &(entry->header_size), &(entry->header_offset)) < 0)
    {
      return -1;
    }
  bytes += 16;
  if (ao_cache_entry_offset_from_bytes
      (bytes, &(entry->body_size), &(entry->body_offset)) < 0)
    {
      return -1;
    }
  bytes += 16;
  if (*bytes >= 128)
    {
      entry->invalidated = true;
    }
  else
    {
      entry->invalidated = false;
    }
  return 0;
}

static int
ao_cache_entry_to_bytes (const struct cache_entry_header *header,
			 uint8_t * dest)
{
  if (ao_cache_entry_timespec_to_bytes (&(header->request_date), dest) < 0)
    {
      return -1;
    }
  dest += 12;
  if (ao_cache_entry_timespec_to_bytes (&(header->response_date), dest) < 0)
    {
      return -1;
    }
  dest += 12;
  if (ao_cache_entry_offset_to_bytes
      (header->key_size, header->key_offset, dest) < 0)
    {
      return -1;
    }
  dest += 16;
  if (ao_cache_entry_offset_to_bytes
      (header->header_size, header->header_offset, dest) < 0)
    {
      return -1;
    }
  dest += 16;
  if (ao_cache_entry_offset_to_bytes
      (header->body_size, header->body_offset, dest) < 0)
    {
      return -1;
    }
  dest += 16;
  *dest = 0;
  if (header->invalidated)
    {
      *dest = 128;
    }
  dest += 1;
  for (size_t i = 0; i < 7; i++)
    {
      dest[i] = 0;
    }
  return 0;
}

static int
ao_cache_entry_read (int fd, size_t offset,
		     struct timespec *request_date,
		     struct timespec *response_date,
		     bool *invalidated,
		     bool read_key,
		     bool read_response_header,
		     bool read_response_body,
		     string_desc_t * key,
		     string_desc_t * response_header,
		     string_desc_t * response_body)
{
  struct cache_entry_header header;
  uint8_t header_bytes[12 * 2 + 16 * 3 + 1 + 7] = { 0 };
  string_desc_t data = {._nbytes = sizeof (header_bytes),._data = header_bytes
  };
  key->_data = NULL;
  response_header->_data = NULL;
  response_body->_data = NULL;
  *invalidated = false;
  request_date->tv_sec = request_date->tv_nsec = 0;
  response_date->tv_sec = response_date->tv_nsec = 0;
  if (ao_file_read (fd, offset, data) < 0)
    {
      return -1;
    }
  if (ao_cache_entry_from_bytes (header_bytes, &header) < 0)
    {
      return -1;
    }
  request_date->tv_sec = header.request_date.tv_sec;
  request_date->tv_nsec = header.request_date.tv_nsec;
  response_date->tv_sec = header.response_date.tv_sec;
  response_date->tv_nsec = header.response_date.tv_nsec;
  *invalidated = header.invalidated;
  key->_nbytes = header.key_size;
  response_header->_nbytes = header.header_size;
  response_body->_nbytes = header.body_size;
  if (read_key)
    {
      if (ALLOC_N (key->_data, key->_nbytes) < 0)
	{
	  goto on_error;
	}
      if (ao_file_read (fd, header.key_offset, *key) < 0)
	{
	  goto on_error;
	}
    }
  if (read_response_header)
    {
      if (ALLOC_N (response_header->_data, response_header->_nbytes) < 0)
	{
	  goto on_error;
	}
      if (ao_file_read (fd, header.header_offset, *response_header) < 0)
	{
	  goto on_error;
	}
    }
  if (read_response_body)
    {
      if (ALLOC_N (response_body->_data, response_body->_nbytes) < 0)
	{
	  goto on_error;
	}
      if (ao_file_read (fd, header.body_offset, *response_body) < 0)
	{
	  goto on_error;
	}
    }
  return 0;
  /* Unsuccessful exit: */
on_error:
  FREE (key->_data);
  FREE (response_header->_data);
  FREE (response_body->_data);
  return -1;
}

static int
ao_cache_entry_push (int fd, size_t *offset,
		     const struct timespec *request_date,
		     const struct timespec *response_date,
		     bool invalidated,
		     const string_desc_t key,
		     const string_desc_t response_header,
		     const string_desc_t response_body)
{
  struct cache_entry_header header = {
    .request_date = {
		     .tv_sec = request_date->tv_sec,
		     .tv_nsec = request_date->tv_nsec},
    .response_date = {
		      .tv_sec = response_date->tv_sec,
		      .tv_nsec = response_date->tv_nsec},
    .key_size = key._nbytes,
    .header_size = response_header._nbytes,
    .body_size = response_body._nbytes,
    .invalidated = invalidated
  };
  if (ao_file_push_data (fd, key, &(header.key_offset)) < 0)
    {
      return -1;
    }
  if (ao_file_push_data (fd, response_header, &(header.header_offset)) < 0)
    {
      return -1;
    }
  if (ao_file_push_data (fd, response_body, &(header.body_offset)) < 0)
    {
      return -1;
    }
  uint8_t header_bytes[12 * 2 + 16 * 3 + 1 + 7] = { 0 };
  if (ao_cache_entry_to_bytes (&header, header_bytes) < 0)
    {
      return -1;
    }
  string_desc_t header_str = {
    ._nbytes = sizeof (header_bytes),
    ._data = header_bytes
  };
  if (ao_file_push_data (fd, header_str, offset) < 0)
    {
      return -1;
    }
  return 0;
}
#endif /* DISFLUID_DISFLUID_CACHE_ENTRY_INCLUDED */