"""Append a hand fix to the patch file so it survives a re-decompile.

Keeping every fix in one reviewed file, rather than editing generated source,
is what makes prepare-game.ps1 reproducible: the tree is thrown away and rebuilt
on every run, so a fix that is not recorded simply disappears.

    python add_patch.py <patch-file> <java-file-path> <before-file> <after-file>

The before/after files hold the exact text to replace and must match the
decompiled output byte for byte.
"""

import io
import os
import sys


def main():
    patch_file, java_path, before_file, after_file = sys.argv[1:5]
    with io.open(before_file, encoding='utf-8') as handle:
        before = handle.read().rstrip('\n')
    with io.open(after_file, encoding='utf-8') as handle:
        after = handle.read().rstrip('\n')

    if not before or not after:
        print('ERROR: before/after must not be empty')
        return 1
    if before == after:
        print('ERROR: before and after are identical')
        return 1

    existing = ''
    if os.path.isfile(patch_file):
        with io.open(patch_file, encoding='utf-8') as handle:
            existing = handle.read()

    header = '=== FILE %s\n' % java_path
    if header + '--- BEFORE\n' + before + '\n--- AFTER\n' in existing:
        print('patch already present')
        return 0

    with io.open(patch_file, 'a', encoding='utf-8') as handle:
        if existing and not existing.endswith('\n'):
            handle.write('\n')
        handle.write('\n' + header)
        handle.write('--- BEFORE\n' + before + '\n')
        handle.write('--- AFTER\n' + after + '\n')
    print('appended patch for %s' % java_path)
    return 0


if __name__ == '__main__':
    raise SystemExit(main())