import marisa_trie
import os


AUFS_METADATA = u'.wh..wh.'

AUFS_WHITEOUT = u'.wh.'
AUFS_WHITEOUT_PREFIX_LENGTH = len(AUFS_WHITEOUT)


def files_and_dirs(root_path, removed_prefix_collector):
  for root, dirs, files in os.walk(unicode(root_path)):

    rel_root = os.path.relpath(root, root_path)
    yield rel_root

    for one_file in files:
      if one_file.startswith(AUFS_METADATA):
        # Skip
        continue

      elif one_file.startswith(AUFS_WHITEOUT):
        filename = one_file[AUFS_WHITEOUT_PREFIX_LENGTH:]
        removed_prefix_collector.add(os.path.join(rel_root, filename))
        continue

      else:
        yield os.path.join(rel_root, one_file)


def compute_removed(base_trie, removed_prefixes):
  for prefix in removed_prefixes:
    for filename in base_trie.keys(prefix):
      yield filename


def compute_added_changed(base_trie, delta_trie):
  added = set()
  changed = set()

  for filename in delta_trie.keys():
    if filename not in base_trie:
      added.add(filename)
    else:
      changed.add(filename)

  return added, changed


def new_fs(base_trie, added, removed):
  for filename in base_trie.keys():
    if filename not in removed:
      yield filename

  for filename in added:
    yield filename