target.py

#!/usr/bin/env python3

import re
import sys
# install this dependency from pip:
from wrapt import ObjectProxy

class FormattableMatch(ObjectProxy):
  def __str__(self):
    m = self.__wrapped__
    if "m" in m.groupdict():
      return m["m"]
    return m[0]

def target(tgt, fn, data):
  print(list(tgt.finditer(data)))
  return tgt.subn

def process(m):
  v = dict()
  coes = dict((cls.__name__, cls) for cls in [int, float, str])
  for (index, value) in enumerate(m.groups()):
    v[index] = value
  for name in m.groupdict().keys():
    index = m.re.groupindex[name]
    value = m[index]
    for coe in coes:
      if name.startswith(coe):
        value = coes[coe](value)
    v[name] = value
    v[index] = value
  return {"v":v,**v,"m":FormattableMatch(m)}

# https://python-forum.io/thread-24481.html
def fstring(f, *arg):
  return eval(f'f{f!r}', None, *arg)

def set_span(m, span, r):
  z = m.start()
  s = m[0]
  if type(span) == str:
    span = m.span(span)
  if type(span) == re.Match:
    span = span.span(0)
  return s[:span[0] - z] + r + s[span[1] - z:]

def run(cmd, m):
  r = fstring(cmd, process(m))
  if "m" in m.groupdict():
    r = set_span(m, "m", r)
  return r

predefs = {
  "$ratio": (
    # {ratio,1,2}
    """{ratio,(?P<m>(?P<intN>-?[0-9]+),(?P<intD>[0-9]+))}""",
    # {ratio,1,2,0.5}
    """{m},{intN / intD}"""
  ),
  "$unratio": (
    # {ratio,1,2}
    """{ratio,(?P<intN>-?[0-9]+),(?P<intD>[0-9]+)}""",
    # 0.5
    """{intN / intD}"""
  ),
}

if __name__ == '__main__':
  argv = sys.argv[1:]
  steps = []
  while len(argv) and argv[0].startswith("$"):
    steps.append(predefs[argv.pop(0)])
  if len(argv) >= 2:
    steps.append((argv.pop(0), argv.pop(0)))
  if len(argv):
    data = "\n".join(argv)
  else:
    data = sys.stdin.read()
    if len(data) and data[-1] == "\n":
      data = data[:-1]
  for (tgt, cmd) in steps:
    data = re.sub(tgt, lambda m: run(cmd, m), data)
  print(data)