before_after_filesystem_snapshot.py

def snapshot(before_dict, after_dict):
  '''before_after_snapshot is a simple function that returns which files were
    unchanged, modified, added or removed from an input dictionary (before_dict)
    and an output dictionary (after_dict). Both these dictionaries have file
    names as the keys and their hashes as the values.'''

  unchanged_files = []
  modified_files = []
  added_files = []
  removed_files = []
  for key in before_dict:
    if key in after_dict:
      if before_dict[key] == after_dict[key]:
        # Matching the hashes to check if file was unchanged
        unchanged_files.append(key)
      else:
        modified_files.append(key)
    else:
      removed_files.append(key)
  for key in after_dict:
    if key not in before_dict:
      # Looking for new files
      added_files.append(key)

  # Returning the snapshot of the new file system
  return (sorted(unchanged_files), sorted(modified_files), sorted(added_files),
  sorted(removed_files))

def generate_artifact_rules(snapshot):
  '''
  Generate Artifact Rules given which files have been added, which have been
  removed, which have been modified, and which have remained unchanged.
  '''
  expected_materials = []
  expected_products = []

  # TODO: missing rules for MATCH since we don't have the information of the
  # material from the previous step
  for file in snapshot[0]:
    # unchanged files
    expected_materials.append(["ALLOW", file])
  for file in snapshot[1]:
    # modified files
    expected_materials.append(["ALLOW", file])
  for file in snapshot[3]:
    # removed files
    expected_materials.append(["DELETE", file])
  expected_materials.append(["DISALLOW", "*"])

  for file in snapshot[0]:
    # unchanged files
    expected_products.append(["ALLOW", file])
  for file in snapshot[1]:
    # modified files
    expected_products.append(["MODIFY", file])
  for file in snapshot[2]:
    # added files
    expected_products.append(["CREATE", file])
  expected_products.append(["DISALLOW", "*"])

  return {
    'expected_materials': expected_materials,
    'expected_products': expected_products
  }