/* Pinos
 * Copyright (C) 2015 Wim Taymans <wim.taymans@gmail.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

#include <sys/socket.h>
#include <string.h>

#include <gio/gio.h>
#include <gio/gunixfdmessage.h>

#include "client/properties.h"
#include "client/context.h"
#include "client/buffer.h"
#include "client/private.h"

G_STATIC_ASSERT (sizeof (PinosStackBuffer) <= sizeof (PinosBuffer));

void
pinos_buffer_init_take_data (PinosBuffer       *buffer,
                             gpointer           data,
                             gsize              size,
                             GSocketControlMessage *message)
{
  PinosStackBuffer *sb = PSB (buffer);

  sb->magic = PSB_MAGIC;
  sb->data = data;
  sb->size = size;
  sb->allocated_size = size;
  sb->message = message;
}

void
pinos_buffer_clear (PinosBuffer *buffer)
{
  PinosStackBuffer *sb = PSB (buffer);

  g_return_val_if_fail (is_valid_buffer (buffer), -1);

  g_free (sb->data);
  sb->size = 0;
  sb->allocated_size = 0;
  g_clear_object (&sb->message);
}

const PinosBufferHeader *
pinos_buffer_get_header (PinosBuffer *buffer, guint32 *version)
{
  PinosStackBuffer *sb = PSB (buffer);
  PinosStackHeader *hdr;

  g_return_val_if_fail (is_valid_buffer (buffer), NULL);

  hdr = sb->data;

  if (version)
    *version = hdr->version;

  return (const PinosBufferHeader *) &hdr->header;
}

/**
 * pinos_buffer_get_fd:
 * @buffer: a #PinosBuffer
 * @index: an index
 * @error: a #GError or %NULL
 *
 * Get the file descriptor at @index in @buffer.
 *
 * Returns: a file descriptor ar @index in @buffer. The file descriptor is
 * duplicated using dup() and set as close-on-exec before being returned.
 * You must call close() on it when you are done. -1 is returned on error and
 * @error is set.
 */
int
pinos_buffer_get_fd (PinosBuffer *buffer, gint index, GError **error)
{
  PinosStackBuffer *sb = PSB (buffer);
  GUnixFDList *fds;

  g_return_val_if_fail (is_valid_buffer (buffer), -1);
  g_return_val_if_fail (sb->message != NULL, -1);

  if (g_socket_control_message_get_msg_type (sb->message) != SCM_RIGHTS)
    goto not_found;

  fds = g_unix_fd_message_get_fd_list (G_UNIX_FD_MESSAGE (sb->message));
  if (fds == NULL)
    goto not_found;

  if (g_unix_fd_list_get_length (fds) <= index)
    goto not_found;

  return g_unix_fd_list_get (fds, index, error);

  /* ERRORS */
not_found:
  {
    if (error)
      *error = g_error_new (G_IO_ERROR,
                            G_IO_ERROR_NOT_FOUND,
                            "Buffer does not have any fd at index %d", index);
    return -1;
  }
}

/**
 * pinos_buffer_get_socket_control_message:
 * @buffer: a #PinosBuffer
 *
 * Get the #GSocketControlMessage of @buffer
 *
 * Returns: the #GSocketControlMessage it remains valid as long as @buffer
 * is valid
 */
GSocketControlMessage *
pinos_buffer_get_socket_control_message  (PinosBuffer *buffer)
{
  PinosStackBuffer *sb = PSB (buffer);

  g_return_val_if_fail (is_valid_buffer (buffer), NULL);

  return sb->message;
}

/**
 * pinos_buffer_get_size:
 * @buffer: a #PinosBuffer
 *
 * Get the total size needed to store @buffer with pinos_buffer_store().
 *
 * Returns: the serialized size of @buffer.
 */
gsize
pinos_buffer_get_size (PinosBuffer *buffer)
{
  PinosStackBuffer *sb = PSB (buffer);

  g_return_val_if_fail (is_valid_buffer (buffer), 0);

  return sizeof (PinosStackHeader) + sb->size;
}

/**
 * pinos_buffer_store:
 * @buffer: a #PinosBuffer
 * @data: destination
 *
 * Store the contents of @buffer in @data. @data must be large enough, see
 * pinos_buffer_get_size().
 */
void
pinos_buffer_store (PinosBuffer       *buffer,
                    gpointer           data)
{
  PinosStackBuffer *sb = PSB (buffer);

  g_return_val_if_fail (is_valid_buffer (buffer), 0);

  memcpy (data, sb->data, sizeof (PinosStackHeader) + sb->size);
}

/**
 * PinosPacketIter:
 *
 * #PinosPacketIter is an opaque data structure and can only be accessed
 * using the following functions.
 */
struct stack_iter {
  gsize             magic;
  guint32           version;
  PinosStackBuffer *buffer;
  gsize             offset;

  PinosPacketType   type;
  gsize             size;
  gpointer          data;

  guint             item;
};

G_STATIC_ASSERT (sizeof (struct stack_iter) <= sizeof (PinosPacketIter));

#define PPSI(i)             ((struct stack_iter *) (i))
#define PPSI_MAGIC          ((gsize) 6739527471u)
#define is_valid_iter(i)    (i != NULL && \
                             PPSI(i)->magic == PPSI_MAGIC)

/**
 * pinos_packet_iter_init:
 * @iter: a #PinosPacketIter
 * @buffer: a #PinosBuffer
 *
 * Initialize @iter to iterate the packets in @buffer.
 */
void
pinos_packet_iter_init_full (PinosPacketIter *iter,
                             PinosBuffer     *buffer,
                             guint32          version)
{
  struct stack_iter *si = PPSI (iter);

  g_return_if_fail (iter != NULL);
  g_return_if_fail (is_valid_buffer (buffer));

  si->magic = PPSI_MAGIC;
  si->version = version;
  si->buffer = PSB (buffer);
  si->offset = 0;
  si->type = PINOS_PACKET_TYPE_INVALID;
  si->size = sizeof (PinosStackHeader);
  si->data = NULL;
  si->item = 0;
}

static gboolean
read_length (guint8 * data, guint size, gsize * length, gsize * skip)
{
  gsize len, offset;
  guint8 b;

  /* start reading the length, we need this to skip to the data later */
  len = offset = 0;
  do {
    if (offset >= size)
      return FALSE;
    b = data[offset++];
    len = (len << 7) | (b & 0x7f);
  } while (b & 0x80);

  /* check remaining buffer size */
  if (size - offset < len)
    return FALSE;

  *length = len;
  *skip = offset;

  return TRUE;
}


/**
 * pinos_packet_iter_next:
 * @iter: a #PinosPacketIter
 *
 * Move to the next packet in @iter.
 *
 * Returns: %TRUE if more packets are available.
 */
gboolean
pinos_packet_iter_next (PinosPacketIter *iter)
{
  struct stack_iter *si = PPSI (iter);
  gsize len, size, skip;
  guint8 *data;

  g_return_val_if_fail (is_valid_iter (iter), FALSE);

  /* move to next packet */
  si->offset += si->size;

  /* now read packet */
  data = si->buffer->data;
  size = si->buffer->size;
  if (si->offset >= size)
    return FALSE;

  data += si->offset;
  size -= si->offset;

  if (size < 1)
    return FALSE;

  si->type = *data;

  data++;
  size--;

  if (!read_length (data, size, &len, &skip))
    return FALSE;

  si->size = len;
  si->data = data + skip;
  si->offset += 1 + skip;

  return TRUE;
}

PinosPacketType
pinos_packet_iter_get_type (PinosPacketIter *iter)
{
  struct stack_iter *si = PPSI (iter);

  g_return_val_if_fail (is_valid_iter (iter), PINOS_PACKET_TYPE_INVALID);

  return si->type;
}

gpointer
pinos_packet_iter_get_data (PinosPacketIter *iter, gsize *size)
{
  struct stack_iter *si = PPSI (iter);

  g_return_val_if_fail (is_valid_iter (iter), NULL);

  if (size)
    *size = si->size;

  return si->data;
}


/**
 * PinosPacketBuilder:
 * @buffer: owner #PinosBuffer
 */
struct stack_builder {
  gsize             magic;

  PinosStackHeader *sh;
  PinosStackBuffer  buf;

  PinosPacketType   type;
  gsize             offset;

  guint             n_sockets;
};

G_STATIC_ASSERT (sizeof (struct stack_builder) <= sizeof (PinosPacketBuilder));

#define PPSB(b)             ((struct stack_builder *) (b))
#define PPSB_MAGIC          ((gsize) 8103647428u)
#define is_valid_builder(b) (b != NULL && \
                             PPSB(b)->magic == PPSB_MAGIC)


void
pinos_packet_builder_init_full (PinosPacketBuilder       *builder,
                                guint32                   version,
                                const PinosBufferHeader  *header)
{
  struct stack_builder *sb = PPSB (builder);
  PinosStackHeader *sh;

  g_return_if_fail (builder != NULL);

  sb->magic = PPSB_MAGIC;
  sb->buf.allocated_size = sizeof (PinosStackHeader) + 128;
  sb->buf.data = g_malloc (sb->buf.allocated_size);
  sb->buf.size = sizeof (PinosStackHeader);
  sb->buf.message = NULL;

  sh = sb->sh = sb->buf.data;
  sh->version = version;
  sh->header = *header;
  sh->length = 0;

  sb->type = 0;
  sb->offset = 0;
}

void
pinos_packet_builder_end (PinosPacketBuilder *builder,
                          PinosBuffer        *buffer)
{
  struct stack_builder *sb = PPSB (builder);
  PinosStackBuffer *sbuf = PSB (buffer);

  g_return_if_fail (is_valid_builder (builder));
  g_return_if_fail (buffer != NULL);

  sb->sh->length = sb->buf.size - sizeof (PinosStackHeader);

  sbuf->magic = PSB_MAGIC;
  sbuf->data = sb->buf.data;
  sbuf->size = sb->buf.size;
  sbuf->allocated_size = sb->buf.allocated_size;
  sbuf->message = sb->buf.message;

  sb->buf.data = NULL;
  sb->buf.size = 0;
  sb->buf.allocated_size = 0;
  sb->buf.message = NULL;
  sb->buf.magic = 0;
}

static gpointer
builder_ensure_size (struct stack_builder *sb, gsize size)
{
  if (sb->buf.size + size > sb->buf.allocated_size) {
    sb->buf.allocated_size = sb->buf.size + MAX (size, 1024);
    sb->buf.data = g_realloc (sb->buf.data, sb->buf.allocated_size);
  }
  return (guint8 *) sb->buf.data + sb->buf.size;
}

static gpointer
builder_add_packet (struct stack_builder *sb, PinosPacketType type, gsize size)
{
  guint8 *p;
  guint plen;

  plen = 1;
  while (size >> (7 * plen))
    plen++;

  /* 1 for type, plen for size and size for payload */
  p = builder_ensure_size (sb, 1 + plen + size);

  sb->type = type;
  sb->offset = sb->buf.size;
  sb->buf.size += 1 + plen + size;

  *p++ = type;
  /* write length */
  while (plen) {
    plen--;
    *p++ = ((plen > 0) ? 0x80 : 0) | ((size >> (7 * plen)) & 0x7f);
  }
  return p;
}

/* fd-payload packets */
/**
 * pinos_packet_iter_get_fd_payload:
 * @iter: a #PinosPacketIter
 * @payload: a #PinosPacketFDPayload
 *
 * Get the #PinosPacketFDPayload. @iter must be positioned on a packet of
 * type #PINOS_PACKET_TYPE_FD_PAYLOAD
 */
void
pinos_packet_iter_parse_fd_payload (PinosPacketIter *iter,
                                    PinosPacketFDPayload *payload)
{
  struct stack_iter *si = PPSI (iter);

  g_return_if_fail (is_valid_iter (iter));
  g_return_if_fail (si->type == PINOS_PACKET_TYPE_FD_PAYLOAD);

  *payload = *((PinosPacketFDPayload *) si->data);
}

/**
 * pinos_packet_builder_add_fd_payload:
 * @builder: a #PinosPacketBuilder
 * @offset: an offset
 * @size: a size
 * @fd: a file descriptor
 * @error: a #GError or %NULL
 *
 * Add a #PINOS_PACKET_TYPE_FD_PAYLOAD to @builder.
 *
 * Returns: %TRUE on success. When %FALSE is returned, @error contains more
 *          information.
 */
gboolean
pinos_packet_builder_add_fd_payload (PinosPacketBuilder *builder,
                                     gint64 offset, gint64 size, int fd,
                                     GError **error)
{
  struct stack_builder *sb = PPSB (builder);
  PinosPacketFDPayload *p;

  g_return_if_fail (is_valid_builder (builder));
  g_return_if_fail (size > 0);
  g_return_if_fail (offset >= 0);
  g_return_if_fail (fd != -1);

  if (sb->buf.message == NULL) {
    sb->buf.message = g_unix_fd_message_new ();
    sb->n_sockets = 0;
  }
  if (!g_unix_fd_message_append_fd ((GUnixFDMessage*)sb->buf.message, fd, error))
    return FALSE;

  p = builder_add_packet (sb, PINOS_PACKET_TYPE_FD_PAYLOAD, sizeof (PinosPacketFDPayload));
  p->offset = offset;
  p->size = size;
  p->fd_index = sb->n_sockets++;

  return TRUE;
}