#!/usr/bin/env python3
"""mutate_regex.py <src> <dst> -- write a copy of the q63 scanner carrying the
PRE-FIX population regex, for the non-vacuity cell in CHECK-q150.

The mutation is one line: the current rule matches the basename at any depth
(`(?:^|/)verify_[^/]*\\.py$`), the pre-Q150 rule required a slash
(`/verify_.*\\.py$`). If this helper cannot find the line it exits 2 rather
than writing a copy that changes nothing -- a mutant that did not mutate is
the vacuous-cell defect wearing the mutant's clothes.

Deliberately not sed: the pattern contains `|`, `(`, `)` and `/`, so every
delimiter choice is a quoting hazard, and a silently failed substitution here
would make the cell pass by not running.
"""
import sys

src, dst = sys.argv[1], sys.argv[2]
NEW = 'VERIFY_RE = re.compile(r"(?:^|/)verify_[^/]*\\.py$")'
OLD = 'VERIFY_RE = re.compile(r"/verify_.*\\.py$")'

text = open(src, encoding="utf-8").read()
if NEW not in text:
    sys.exit("mutate_regex: no post-fix VERIFY_RE line in %s -- cannot mutate" % src)
out = text.replace(NEW, OLD, 1)
if OLD not in out:
    sys.exit("mutate_regex: substitution did not land")
open(dst, "w", encoding="utf-8").write(out)
print("mutant: %s -> %s (pre-fix regex restored)" % (NEW, OLD))