Set from stdin or get OS X finder comment for file

comment

#!/usr/bin/env /usr/bin/python

#https://gist.github.com/vdave/b6289c7edcd831b3ba75c6d11347e4ff
#
# Manages structured content in Finder Comments
#
# The finder comment is treated as a block of text with a section treated
# as a JSON object. The JSON section is delimited in a manner similar to
# ssl certificates with a BEGIN and END line delimiting the JSON object.
#

from applescript import AppleScript
import sys
import os
import argparse
import logging
import json

IMMUTABLE_FIELDS=["ID",]
JSON_START_SIGNATURE = "-----BEGIN JSON-----"
JSON_END_SIGNATURE = "-----END JSON-----"

setComment = AppleScript('''
on run {arg1, arg2}
   tell application "Finder" to set comment of (POSIX file arg1 as alias) to arg2 as Unicode text
   return
end run
''')

getComment = AppleScript('''
on run {arg1}
   tell application "Finder"
      set theComm to comment of (POSIX file arg1 as alias)
   end tell
   return theComm
end run
''')

appendComment = AppleScript('''
on run {arg1, arg2}
   tell application "Finder"
      set Comm to comment of (POSIX file arg1 as alias)
      set newComm to Comm & (arg2 as Unicode text)
      set comment of (POSIX file arg1 as alias) to newComm
    end tell
   return
end run
''')

def getJSONStartEnd(comment):
  start_pos = comment.find(JSON_START_SIGNATURE)
  end_pos = comment.find(JSON_END_SIGNATURE)
  return start_pos, end_pos


def getTextJSON(file_name):
  '''Retrieves the text and JSON object from the comment of the specified file.
  '''
  comment = getComment.run(file_name)
  start_pos, end_pos = getJSONStartEnd(comment)
  if start_pos < 0:
    #No JSON object, return an empty object
    return comment, {}
  json_text = comment[start_pos + len(JSON_START_SIGNATURE) : end_pos]
  text = comment[:start_pos]
  return text, json.loads(json_text)


def mergeTextJSON(comment, json_text):
  start_pos, end_pos = getJSONStartEnd(comment)
  if start_pos >= 0:
    tmp = comment[:start_pos]
    comment = tmp
  #append the JSON entry
  new_comment = comment.rstrip() + "\n" + JSON_START_SIGNATURE + "\n" + json_text
  new_comment += "\n" + JSON_END_SIGNATURE + "\n"
  return new_comment


def setJSON(file_name, data):
  '''Set the JSON object in the comment of the specified file.

  IMPORTANT: this method does no merging with an existing entry. It sets the
  entire JSON entry to that provided.
  '''
  json_text = json.dumps(data)
  comment = getComment.run(file_name)
  new_comment = mergeTextJSON(comment, json_text)
  setComment.run(file_name, new_comment)


def mergeObjects(original_object, new_object, override=False):
  '''Simple top level merge of two dictionaries
  '''
  res = original_object
  for k in new_object.keys():
    if k in IMMUTABLE_FIELDS:
      if original_object.has_key(k):
        logging.warn("Attempt to set immutable field %s", k)
        if not override:
          logging.warning("Immutable field %s not changed.", k)
          break
    res[k] = new_object[k]
  return res


def presentJSON(file_name, indent=2):
  '''Retrieves the JSON object form the file and presents it.
  '''
  text,data = getTextJSON(file_name)
  print json.dumps(data, indent=indent)


def updateJSON(file_name, data, replace=False, override=False):
  '''Updates the JSON entry in the specified file.

  If replace is True, then the entire JSON object is replaced, otherwise a
  merge is performed.
  '''
  if replace:
    setJSON(file_name, data)
    return
  text, existing_data = getTextJSON(file_name)
  new_data = mergeObjects( existing_data, data, override=override)
  setJSON(file_name, new_data)


def updateComment(file_name, comment):
  '''Sets the plain text portion of the comment.
  '''
  text,data = getTextJSON(file_name)
  json_text = json.dumps(data)
  new_comment = mergeTextJSON(comment, json_text)
  setComment.run(file_name, new_comment)


def main(args):
  file_name = fname = os.path.abspath(args.fname)
  if not os.path.exists(fname):
    logging.error("Path %s does not exist.", fname)
    return 1
  #no stdin
  if sys.stdin.isatty():
    logging.info("Reading comment from %s", fname)
    if args.keys:
      text,data = getTextJSON(file_name)
      if args.json:
        print json.dumps(data.keys())
        return 0
      print "\n".join(data.keys())
      return 0
    if args.json:
      presentJSON(file_name)
      return 0
    if args.setvalue is not None:
      kv = args.setvalue.split(':', 1)
      data = {kv[0]:kv[1]}
      updateJSON(file_name, data, replace=args.replace, override=args.override_immutable)
      return 0
    if args.all:
      print getComment.run(file_name)
      return 0
    text,data = getTextJSON(file_name)
    print text
    return 0
  comment = sys.stdin.read()
  #stdin, json flag set
  if args.json:
    data = json.loads(comment)
    updateJSON(file_name, data, replace=args.replace, override=args.override_immutable)
    return 0
  #replace the plain text portion of the comment
  updateComment(file_name, comment)
  return 0


if __name__ == "__main__":
  parser = argparse.ArgumentParser(description='Set by stdin or get finder comment for file.')
  parser.add_argument('-l', '--log_level',
                      action='count',
                      default=0,
                      help='Set logging level, multiples for more detailed.')
  parser.add_argument('-k','--keys',
                      action='store_true',
                      default=False,
                      help='List the keys in the comment YAML section')
  parser.add_argument('-s','--setvalue',
                      default=None,
                      help='Set a value, indicate as key:value or JSON (with -j)')
  parser.add_argument('--all',
                      action='store_true',
                      default=False,
                      help='Dump the entire comment including text and JSON portions.')
  parser.add_argument('-j','--json',
                      action='store_true',
                      default=False,
                      help='Set or dump YAML section as JSON.')
  parser.add_argument('-r', '--replace',
                      action='store_true',
                      help='Replace JSON data rather than merge.')
  parser.add_argument('--override_immutable',
                      action='store_true',
                      default=False,
                      help='Force overwriting of immutable fields.')
  parser.add_argument('fname', default=None,
                      help='The file to update or file to read from.')
  args = parser.parse_args()
  # Setup logging verbosity
  levels = [logging.WARNING, logging.INFO, logging.DEBUG]
  level = levels[min(len(levels) - 1, args.log_level)]
  logging.basicConfig(level=level,
                      format="%(asctime)s %(levelname)s %(message)s")
  # do the work
  sys.exit( main(args) )