#!/usr/bin/env python3
"""Set keys in the [ddraw] section of a cnc-ddraw ddraw.ini.

Usage: patch-ddraw-ini.py [--check] DDRAW_INI KEY=VALUE [KEY=VALUE ...]

Only the global [ddraw] section is touched; the hundreds of per-game preset
sections further down the file are left alone. CRLF line endings are preserved,
because cnc-ddraw writes the file back out as a Windows INI.

Exit status: 0 if the file already matches (or was updated), 1 under --check if
it does not match.
"""
import re
import sys


def main(argv):
    check = False
    if argv and argv[0] == '--check':
        check, argv = True, argv[1:]
    if len(argv) < 2:
        sys.exit(__doc__)

    path, assignments = argv[0], argv[1:]
    wanted = {}
    for a in assignments:
        if '=' not in a:
            sys.exit('not a KEY=VALUE pair: %s' % a)
        k, v = a.split('=', 1)
        wanted[k.strip().lower()] = v

    with open(path, 'rb') as fh:
        raw = fh.read().decode('utf-8', 'surrogateescape')

    newline = '\r\n' if '\r\n' in raw else '\n'
    lines = raw.split(newline)

    out, in_ddraw, pending, changes = [], False, dict(wanted), []
    for line in lines:
        stripped = line.strip()
        if stripped.startswith('['):
            # leaving [ddraw]: append any keys the section never had
            if in_ddraw and pending:
                for k, v in pending.items():
                    out.append('%s=%s' % (k, v))
                    changes.append('added %s=%s' % (k, v))
                pending = {}
            in_ddraw = stripped.lower() == '[ddraw]'
        elif in_ddraw:
            m = re.match(r'^(\s*)([A-Za-z_][A-Za-z0-9_]*)(\s*)=(.*)$', line)
            if m and m.group(2).lower() in pending:
                key = m.group(2).lower()
                want = pending.pop(key)
                if m.group(4) != want:
                    changes.append('%s=%s -> %s=%s' % (m.group(2), m.group(4), m.group(2), want))
                    line = '%s=%s' % (m.group(2), want)
        out.append(line)

    if in_ddraw and pending:
        for k, v in pending.items():
            out.append('%s=%s' % (k, v))
            changes.append('added %s=%s' % (k, v))

    if not changes:
        print('already set: %s' % ', '.join('%s=%s' % kv for kv in wanted.items()))
        return 0

    if check:
        for c in changes:
            print('would change: %s' % c)
        return 1

    with open(path, 'wb') as fh:
        fh.write(newline.join(out).encode('utf-8', 'surrogateescape'))
    for c in changes:
        print(c)
    return 0


if __name__ == '__main__':
    sys.exit(main(sys.argv[1:]))