#!/usr/bin/env python3
"""
backdate.py -- mechanically back-date a WinTesla-era engine header (BT411/BT412
engine/MUNGA*/X.h) to its 1995 form (source410/MUNGA/X.HPP).

Transforms (the mechanical part -- ALWAYS eyeball the result and write the
.NOTES.md sidecar; content drift is NOT detected here):
  #pragma once                ->  #if !defined(X_HPP) / #define X_HPP ... #endif
  #include "y.h"              ->  guarded  #if !defined(Y_HPP) #include <y.hpp> #endif
  (system includes like <string.h> are left alone)

Usage:  py -3 backdate.py <donor.h> <OUTPUT.HPP>
"""
import os
import re
import sys

def main():
    donor, out = sys.argv[1], sys.argv[2]
    name = os.path.splitext(os.path.basename(out))[0].upper()
    guard = "%s_HPP" % name
    body = open(donor, "r", errors="replace").read().splitlines()
    res = []
    warned = set()
    for line in body:
        s = line.strip()
        if s == "#pragma once":
            continue
        # local include, possibly with a relative path -- keep the basename
        m = re.match(r'#include\s+"(?:[.\\/A-Za-z0-9_]*[\\/])?([A-Za-z0-9_]+)\.h(?:pp)?"', s)
        if m:
            inc = m.group(1).lower()
            g = inc.upper() + "_HPP"
            res.append("#\tif !defined(%s)" % g)
            res.append("#\t\tinclude <%s.hpp>" % inc)
            res.append("#\tendif")
            continue
        # post-1994 C++ the 4.52 compiler rejects: de-modernize
        line = re.sub(r"\bstd::", "", line)
        line = re.sub(r"\btrue\b", "True", line)
        line = re.sub(r"\bfalse\b", "False", line)
        line = re.sub(r"\bbool\b", "Logical", line)
        for bad in ("<ostream>",):
            if bad in line:
                line = None
                break
        if line is None:
            continue
        for marker in ("namespace", "static_cast", "reinterpret_cast", "const_cast"):
            if marker in s and marker not in warned:
                warned.add(marker)
                print("WARNING: post-1994 construct '%s' present -- fix by hand" % marker)
        res.append(line)
    # strip leading blank lines
    while res and not res[0].strip():
        res.pop(0)
    with open(out, "w", newline="\r\n") as f:
        f.write("#if !defined(%s)\n#\tdefine %s\n\n" % (guard, guard))
        f.write("\n".join(res))
        f.write("\n\n#endif\n")
    print("wrote %s (%d lines from %s)" % (out, len(res) + 5, donor))

if __name__ == "__main__":
    main()