//
// PDF stream functions for pdfio.
//
// Copyright © 2021 by Michael R Sweet.
//
// Licensed under Apache License v2.0.  See the file "LICENSE" for more
// information.
//

//
// Include necessary headers...
//

#include "pdfio-private.h"


//
// Local functions...
//

static ssize_t	stream_read(pdfio_stream_t *st, char *buffer, size_t bytes);


//
// 'pdfioStreamClose()' - Close a (data) stream in a PDF file.
//

bool					// O - `true` on success, `false` on failure
pdfioStreamClose(pdfio_stream_t *st)	// I - Stream
{
  // TODO: Implement me
  (void)st;
  return (false);
}


//
// '_pdfioStreamCreate()' - Create a stream for writing.
//
// Note: pdfioObjCreateStream handles writing the object and its dictionary.
//

pdfio_stream_t *			// O - Stream or `NULL` on error
_pdfioStreamCreate(
    pdfio_obj_t    *obj,		// I - Object
    pdfio_filter_t compression)		// I - Compression to apply
{
  // TODO: Implement me
  (void)obj;
  (void)compression;

  return (NULL);
}


//
// 'pdfioStreamConsume()' - Consume bytes from the stream.
//

bool					// O - `true` on success, `false` on EOF
pdfioStreamConsume(pdfio_stream_t *st,	// I - Stream
                   size_t         bytes)// I - Number of bytes to consume
{
  size_t	remaining;		// Remaining bytes in buffer
  ssize_t	rbytes;			// Bytes read


  // Range check input...
  if (!st || st->pdf->mode != _PDFIO_MODE_READ || !bytes)
    return (false);

  // Skip bytes in the stream buffer until we've consumed the requested number
  // or get to the end of the stream...
  while ((remaining = (size_t)(st->bufend - st->bufptr)) < bytes)
  {
    bytes -= remaining;

    if ((rbytes = stream_read(st, st->buffer, sizeof(st->buffer))) > 0)
    {
      st->bufptr = st->buffer;
      st->bufend = st->buffer + rbytes;
    }
    else
    {
      st->bufptr = st->bufend = st->buffer;
      return (false);
    }
  }

  st->bufptr += bytes;

  return (true);
}


//
// '_pdfioStreamDelete()' - Free all memory used by a stream.
//

void
_pdfioStreamDelete(pdfio_stream_t *st)	// I - Stream
{
  if (st->filter == PDFIO_FILTER_FLATE)
  {
    // Free memory used for flate compression/decompression...
    if (st->pdf->mode == _PDFIO_MODE_READ)
      inflateEnd(&st->flate);
    else // mode == _PDFIO_MODE_WRITE
      deflateEnd(&st->flate);
  }

  free(st);
}


//
// 'pdfioStreamGetToken()' - Read a single PDF token from a stream.
//

bool					// O - `true` on success, `false` on EOF
pdfioStreamGetToken(
    pdfio_stream_t *st,			// I - Stream
    char           *buffer,		// I - String buffer
    size_t         bufsize)		// I - Size of string buffer
{
  return (_pdfioTokenRead(st->pdf, buffer, bufsize, (_pdfio_tpeek_cb_t)pdfioStreamPeek, (_pdfio_tconsume_cb_t)pdfioStreamConsume, st));
}


//
// '_pdfioStreamOpen()' - Create a stream for reading.
//
// Note: pdfioObjOpenStream handles loading the object's dictionary and
// getting the start of the stream data.
//

pdfio_stream_t *			// O - Stream or `NULL` on error
_pdfioStreamOpen(pdfio_obj_t *obj,	// I - Object
                 bool        decode)	// I - Decode/decompress the stream?
{
  pdfio_stream_t	*st;		// Stream
  pdfio_dict_t		*dict = pdfioObjGetDict(obj);
					// Object dictionary
  size_t		length;		// Length of stream


  // Allocate a new stream object...
  if ((st = (pdfio_stream_t *)calloc(1, sizeof(pdfio_stream_t))) == NULL)
  {
    _pdfioFileError(obj->pdf, "Unable to allocate memory for a stream.");
    return (NULL);
  }

  st->pdf = obj->pdf;
  st->obj = obj;

  _pdfioFileSeek(st->pdf, obj->stream_offset, SEEK_SET);

  if ((length = (size_t)pdfioDictGetNumber(dict, "Length")) == 0)
  {
    // Length must be an indirect reference...
    pdfio_obj_t	*lenobj;		// Length object

    if ((lenobj = pdfioDictGetObject(dict, "Length")) == NULL)
    {
      _pdfioFileError(obj->pdf, "Unable to get length of stream.");
      free(st);
      return (NULL);
    }

    if (lenobj->value.type == PDFIO_VALTYPE_NONE)
      _pdfioObjLoad(lenobj);

    if (lenobj->value.type != PDFIO_VALTYPE_NUMBER || lenobj->value.value.number <= 0.0f)
    {
      _pdfioFileError(obj->pdf, "Unable to get length of stream.");
      free(st);
      return (NULL);
    }

    length = (size_t)lenobj->value.value.number;
  }

  st->remaining = length;

  if (decode)
  {
    // Try to decode/decompress the contents of this object...
    const char	*filter = pdfioDictGetName(dict, "Filter");
					// Filter value

    if (!filter)
    {
      // No single filter name, do we have a compound filter?
      if (pdfioDictGetArray(dict, "Filter"))
      {
	// TODO: Implement compound filters...
	_pdfioFileError(st->pdf, "Unsupported compound stream filter.");
	free(st);
	return (NULL);
      }

      // No filter, read as-is...
      st->filter = PDFIO_FILTER_NONE;
    }
    else if (!strcmp(filter, "FlateDecode"))
    {
      // Flate compression
#if 0 // TODO: Determine whether we need to implement support for predictors
      int bpc = (int)pdfioDictGetNumber(dict, "BitsPerComponent");
					// Bits per component
      int colors = (int)pdfioDictGetNumber(dict, "Colors");
					// Number of colors
      int columns = (int)pdfioDictGetNumber(dict, "Columns");
					// Number of columns
      int predictor = (int)pdfioDictGetNumber(dict, "Predictor");
					// Predictory value, if any
#endif // 0

      st->filter = PDFIO_FILTER_FLATE;

      st->flate.zalloc    = (alloc_func)0;
      st->flate.zfree     = (free_func)0;
      st->flate.opaque    = (voidpf)0;
      st->flate.next_in   = (Bytef *)st->cbuffer;
      st->flate.next_out  = NULL;
      st->flate.avail_in  = (uInt)_pdfioFileRead(st->pdf, st->cbuffer, sizeof(st->cbuffer));
      st->flate.avail_out = 0;

      if (inflateInit(&(st->flate)) != Z_OK)
      {
	_pdfioFileError(st->pdf, "Unable to start Flate filter.");
	free(st);
	return (NULL);
      }

      st->remaining -= st->flate.avail_in;
    }
    else if (!strcmp(filter, "LZWDecode"))
    {
      // LZW compression
      st->filter = PDFIO_FILTER_LZW;
    }
    else
    {
      // Something else we don't support
      _pdfioFileError(st->pdf, "Unsupported stream filter '/%s'.", filter);
      free(st);
      return (NULL);
    }
  }
  else
  {
    // Just return the stream data as-is...
    st->filter = PDFIO_FILTER_NONE;
  }

  return (st);
}


//
// 'pdfioStreamPeek()' - Peek at data in a stream.
//

ssize_t					// O - Bytes returned or `-1` on error
pdfioStreamPeek(pdfio_stream_t *st,	// I - Stream
                void           *buffer,	// I - Buffer
                size_t         bytes)	// I - Size of buffer
{
  size_t	remaining;		// Remaining bytes in buffer


  // Range check input...
  if (!st || st->pdf->mode != _PDFIO_MODE_READ || !buffer || !bytes)
    return (-1);

  // See if we have enough bytes in the buffer...
  if ((remaining = (size_t)(st->bufend - st->bufptr)) < bytes)
  {
    // No, shift the buffer and read more
    ssize_t	rbytes;			// Bytes read

    if (remaining > 0)
      memmove(st->buffer, st->bufptr, remaining);

    st->bufptr = st->buffer;
    st->bufend = st->buffer + remaining;

    if ((rbytes = stream_read(st, st->bufptr, sizeof(st->buffer) - remaining)) > 0)
    {
      st->bufend += rbytes;
      remaining  += (size_t)rbytes;
    }
  }

  // Copy bytes from the buffer...
  if (bytes > remaining)
    bytes = remaining;

  memcpy(buffer, st->bufptr, bytes);

  // Return the number of bytes that were copied...
  return ((ssize_t)bytes);
}


//
// 'pdfioStreamPrintf()' - Write a formatted string to a stream.
//

bool					// O - `true` on success, `false` on failure
pdfioStreamPrintf(
    pdfio_stream_t *st,			// I - Stream
    const char     *format,		// I - `printf`-style format string
    ...)				// I - Additional arguments as needed
{
  char		buffer[8192];		// String buffer
  va_list	ap;			// Argument pointer


  // Format the string...
  va_start(ap, format);
  vsnprintf(buffer, sizeof(buffer), format, ap);
  va_end(ap);

  // Write the string...
  return (pdfioStreamWrite(st, buffer, strlen(buffer)));
}


//
// 'pdfioStreamPuts()' - Write a literal string to a stream.
//

bool					// O - `true` on success, `false` on failure
pdfioStreamPuts(pdfio_stream_t *st,	// I - Stream
                const char     *s)	// I - Literal string
{
  if (!st || !s)
    return (false);
  else
    return (pdfioStreamWrite(st, s, strlen(s)));
}


//
// 'pdfioStreamRead()' - Read data from a stream.
//

ssize_t					// O - Number of bytes read or `-1` on error
pdfioStreamRead(
    pdfio_stream_t *st,			// I - Stream
    void           *buffer,		// I - Buffer
    size_t         bytes)		// I - Bytes to read
{
  char		*bufptr = (char *)buffer;
					// Pointer into buffer
  size_t	remaining;		// Remaining bytes in buffer
  ssize_t	rbytes;			// Bytes read


  // Range check input...
  if (!st || st->pdf->mode != _PDFIO_MODE_READ || !buffer || !bytes)
    return (-1);

  // Loop until we have the requested bytes or hit the end of the stream...
  while ((remaining = (size_t)(st->bufend - st->bufptr)) < bytes)
  {
    memcpy(bufptr, st->bufptr, remaining);
    bufptr += remaining;
    bytes -= remaining;

    if (bytes >= sizeof(st->buffer))
    {
      // Read large amounts directly to caller's buffer...
      if ((rbytes = stream_read(st, bufptr, bytes)) > 0)
      {
        bufptr += rbytes;
        bytes  = 0;
      }

      st->bufptr = st->bufend = st->buffer;
      break;
    }
    else if ((rbytes = stream_read(st, st->buffer, sizeof(st->buffer))) > 0)
    {
      st->bufptr = st->buffer;
      st->bufend = st->buffer + rbytes;
    }
    else
    {
      st->bufptr = st->bufend = st->buffer;
      break;
    }
  }

  // Copy any remaining bytes from the stream buffer...
  if (bytes > 0)
  {
    memcpy(bufptr, st->bufptr, bytes);
    bufptr     += bytes;
    st->bufptr += bytes;
  }

  // Return the number of bytes that were read...
  return (bufptr - (char *)buffer);
}


//
// 'pdfioStreamWrite()' - Write data to a stream.
//

bool					// O - `true` on success or `false` on failure
pdfioStreamWrite(
    pdfio_stream_t *st,			// I - Stream
    const void     *buffer,		// I - Data to write
    size_t         bytes)		// I - Number of bytes to write
{
  // TODO: Implement me
  (void)st;
  (void)buffer;
  (void)bytes;

  return (false);
}


//
// 'stream_read()' - Read data from a stream, including filters.
//

static ssize_t				// O - Number of bytes read or `-1` on error
stream_read(pdfio_stream_t *st,		// I - Stream
            char           *buffer,	// I - Buffer
            size_t         bytes)	// I - Number of bytes to read
{
  ssize_t	rbytes;			// Bytes read


  if (st->filter == PDFIO_FILTER_NONE)
  {
    // No filtering, but limit reads to the length of the stream...
    if (bytes > st->remaining)
      rbytes = _pdfioFileRead(st->pdf, buffer, st->remaining);
    else
      rbytes = _pdfioFileRead(st->pdf, buffer, bytes);

    if (rbytes > 0)
      st->remaining -= (size_t)rbytes;

    return (rbytes);
  }
  else if (st->filter == PDFIO_FILTER_FLATE)
  {
    // Deflate compression...
    int	status;				// Status of decompression

    if (st->flate.avail_in == 0)
    {
      // Read more from the file...
      if (sizeof(st->cbuffer) > st->remaining)
        rbytes = _pdfioFileRead(st->pdf, st->cbuffer, st->remaining);
      else
        rbytes = _pdfioFileRead(st->pdf, st->cbuffer, sizeof(st->cbuffer));

      if (rbytes <= 0)
        return (-1);			// End of file...

      st->remaining      -= (size_t)rbytes;
      st->flate.next_in  = (Bytef *)st->cbuffer;
      st->flate.avail_in = (uInt)rbytes;
    }

    // Decompress into the buffer...
    st->flate.next_out  = (Bytef *)buffer;
    st->flate.avail_out = (uInt)bytes;

    if ((status = inflate(&(st->flate), Z_NO_FLUSH)) < Z_OK)
    {
      _pdfioFileError(st->pdf, "Unable to decompress stream data: %d", status);
      return (-1);
    }

    return (st->flate.next_out - (Bytef *)buffer);
  }

  // If we get here something bad happened...
  return (-1);
}