#!/usr/bin/env python
# FormatSMV.py
#   Copyright (C) 2011 Diamond Light Source, Graeme Winter
#
#   This code is distributed under the BSD license, a copy of which is
#   included in the root directory of this package.
#
# Implementation of an ImageFormat class to read SMV format image but not -
# in the first instance - actually provide a full image representation. This
# is simply there to set everything up for the ADSC and Rigaku Saturn image
# readers which really will acquire the full image including header information
# and generate the experimental model representations.

from __future__ import division

from dxtbx.format.Format import Format

class FormatSMV(Format):
  '''An image reading class for SMV format images i.e. those from ADSC and
  Rigaku which start with:

  {
  HEADER_BYTES=  512;

  and contain a list of keyword-value pairs thereafter which define the
  header. The keywords etc. for these will depend on the instrument
  manufacturer and will be interpreted by subclasses of this class. Note
  also that every line is finished with a semicolon.'''

  @staticmethod
  def understand(image_file):
    '''Check to see if this looks like an SMV format image, i.e. we can
    make sense of it.'''

    if FormatSMV.open_file(image_file, 'rb').read(15) == \
           '{\nHEADER_BYTES=':
      return True

    return False

  @staticmethod
  def get_smv_header(image_file):
    header_size = int(FormatSMV.open_file(image_file, 'rb').read(45).split(
        '\n')[1].split('=')[1].replace(';', '').strip())
    header_text = FormatSMV.open_file(image_file, 'rb').read(header_size)
    header_dictionary = { }

    # Check that we have the whole header, contained within { }.  Stop
    # extracting data once a record solely composed of a closing curly
    # brace is seen.  If there is no such character in header_text
    # either HEADER_BYTES caused a short read of the header or the
    # header is malformed.
    for record in header_text.split('\n'):
      if record == '}':
        break
      if not '=' in record:
        continue

      key, value = record.replace(';', '').split('=')

      header_dictionary[key.strip()] = value.strip()

    return header_size, header_dictionary

  def __init__(self, image_file):
    '''Initialise the image structure from the given file.'''

    assert(self.understand(image_file))

    Format.__init__(self, image_file)

    return

  def _start(self):
    '''Open the image file, read the image header, copy the key / value
    pairs into an internal dictionary self._header_dictionary along with
    the length of the header in bytes self._header_size.'''

    self._header_size, self._header_dictionary = FormatSMV.get_smv_header(
        self._image_file)

    return