scripts/dot-local/bin/j2y

#!/usr/bin/env python3

from yaml import dump

try:
  from yaml import CDumper as Dumper
except ImportError:
  from yaml import Dumper

from collections.abc import Sized
import json, re, sys

def dict_representer(dumper, d):
  node = dumper.represent_dict(d)
  # Don't use YAML flow style for large dicts, because the flow style output
  # only really looks good with a very small number of keys.
  if len(d) > 5 or sum(len(v) for v in d.values() if isinstance(v, Sized)) > 30:
    node.flow_style = False
  return node
Dumper.add_representer(dict, dict_representer)

def cat(files):
  usedStdin = False
  for f in files:
    if f == '-':
      if usedStdin: continue
      usedStdin = True
    with open(f) if f != '-' else sys.stdin as s:
      for line in s: yield line

# http://stackoverflow.com/a/7795029/1208816
braces = '{}[]'
whitespace_esc = ' \t'
braces_esc = '\\' + '\\'.join(braces)
braces_pat = '[' + braces_esc + ']'
no_braces_pat = '[^' + braces_esc + ']*'
until_braces_pat = re.compile(no_braces_pat + braces_pat)
balance_map = dict(zip(braces, [1, -1, 1, -1]))

def streamingfinditer(pat, stream):
  for s in stream:
    while True:
      m = pat.search(s)
      if not m:
        yield (0,s)
        break
      yield (1, m.group())
      s = pat.split(s, 1)[1]

def simpleorcompoundobjects(stream):
  obj = ""
  unbalanced = 0
  for (c, m) in streamingfinditer(until_braces_pat, stream):
    if (c == 0): # remainder of line returned, nothing interesting
      if (unbalanced == 0):
        yield (0, m)
      else:
        obj += m
    if (c == 1): # match returned
      if (unbalanced == 0):
        yield (0, m[:-1])
        obj += m[-1]
      else:
        obj += m
      unbalanced += balance_map[m[-1]]
      if (unbalanced == 0):
        yield (1, obj)
        obj = ""

def streamingiterload(stream):
  for c,o in simpleorcompoundobjects(stream):
    for x in iterload(o):
      yield x

# http://stackoverflow.com/a/6886743/1208816
def iterload(string_or_fp, cls=json.JSONDecoder, **kwargs):
  try:
    string = string_or_fp.read()
  except AttributeError:
    string = str(string_or_fp)

  decoder = cls(**kwargs)
  idx = json.decoder.WHITESPACE.match(string, 0).end()
  while idx < len(string):
    obj, end = decoder.raw_decode(string, idx)
    yield obj
    idx = json.decoder.WHITESPACE.match(string, end).end()

files = sys.argv[1:] or ('-',)
for obj in streamingiterload(cat(files)):
  print(dump(obj, Dumper=Dumper, explicit_start=True), end='', flush=True)