#!/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
    text = open(donor, "r", errors="replace").read()
    # WinTesla wrapped the 1995 static objects in accessor functions (its
    # static-init-order fix); unwrap them back to plain 1995 definitions.
    text = re.sub(
        r"Derivation\s*\*\s*(\w+)::GetClassDerivations\(\)\s*"
        r"\{\s*static\s+Derivation\s+\w+\s*\(([^;]*?)\);\s*return\s*&\w+;\s*\}",
        r"Derivation\n\t\1::ClassDerivations(\2);",
        text, flags=re.S)
    text = re.sub(
        r"(?:Receiver::)?MessageHandlerSet\s*&?\s*(\w+)::GetMessageHandlers\(\)\s*"
        r"\{\s*static\s+(?:\w+::)?MessageHandlerSet\s+\w+\s*\(([^;]*?)\);\s*return\s*\w+;\s*\}",
        r"\1::MessageHandlerSet\n\t\1::MessageHandlers(\2);",
        text, flags=re.S)
    text = re.sub(
        r"(?:\w+::)?AttributeIndexSet\s*&?\s*(\w+)::GetAttributeIndex\(\)\s*"
        r"\{\s*static\s+(?:\w+::)?AttributeIndexSet\s+\w+\s*\(([^;]*?)\);\s*return\s*\w+;\s*\}",
        r"\1::AttributeIndexSet\n\t\1::AttributeIndex(\2);",
        text, flags=re.S)
    text = re.sub(
        r"MemoryBlock\s*\*\s*(\w+)::GetAllocatedMemory\(\)\s*"
        r"\{\s*static\s+MemoryBlock\s+\w+\s*\(([^;]*?)\);\s*return\s*&\w+;\s*\}",
        r"MemoryBlock\n\t\1::AllocatedMemory(\2);",
        text, flags=re.S)
    body = text.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"\b(\w+)::GetClassDerivations\(\)", r"\1::ClassDerivations", line)
        line = re.sub(r"\b(\w+)::GetMessageHandlers\(\)", r"\1::MessageHandlers", line)
        line = re.sub(r"\b(\w+)::GetAttributeIndex\(\)", r"\1::AttributeIndex", line)
        line = re.sub(r"\b(\w+)::GetAllocatedMemory\(\)", r"\1::AllocatedMemory", line)
        # header-side: 2007 accessor DECLARATIONS -> 1995 static objects
        line = re.sub(r"static\s+Derivation\s*\*\s*GetClassDerivations\(\);",
                      "static Derivation ClassDerivations;", line)
        line = re.sub(r"static\s+(?:\w+::)?MessageHandlerSet\s*&?\s*GetMessageHandlers\(\);",
                      "static MessageHandlerSet MessageHandlers;", line)
        line = re.sub(r"static\s+(?:\w+::)?AttributeIndexSet\s*&?\s*GetAttributeIndex\(\);",
                      "static AttributeIndexSet AttributeIndex;", line)
        line = line.replace("Shutdown(int remainingApps);", "Shutdown(int remainingApps = 0);")
        line = re.sub(r"\*?\s*(?<![:\w])GetClassDerivations\(\)", "ClassDerivations", line)
        line = re.sub(r"(?<![:\w])GetMessageHandlers\(\)", "MessageHandlers", line)
        line = re.sub(r"(?<![:\w])GetAttributeIndex\(\)", "AttributeIndex", line)
        line = line.replace("PostQuitMessage(AbortExitCodeID);", 'Fail("Exiting");')
        for bad in ("atlbase.h", "windows.h", "winsock", "windows.hpp", "<cstdlib>", "<cstring>", "<cstdio>"):
            if bad in line and "#include" in line:
                line = ""
                break
        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)
    out_text = "\n".join(res)
    # cleanups after the accessor unwrap: a deref of the former pointer
    # accessor, and doubled class prefixes from the static rename
    out_text = re.sub(r"\*\s*(\w+)::ClassDerivations\b", r"\1::ClassDerivations", out_text)
    out_text = re.sub(r"\b(\w+)::\1::", r"\1::", out_text)
    is_header = out.upper().endswith((".HPP", ".H", ".THP"))
    with open(out, "w", newline="\r\n") as f:
        if is_header:
            f.write("#if !defined(%s)\n#\tdefine %s\n\n" % (guard, guard))
        f.write(out_text)
        if is_header:
            f.write("\n\n#endif\n")
        else:
            f.write("\n")
    print("wrote %s (%d lines from %s)" % (out, len(res) + 5, donor))

if __name__ == "__main__":
    main()