#!/usr/bin/python3
'''Scan an existing directory tree and record installed directories.

During build a number of directories under /var are created in the state
partition. We want to make sure that those are always there so create a record
of them using systemd's tempfiles config format so they are recreated during
boot if they go missing for any reason.
'''

import optparse
import os
import stat
import sys
import pwd
import grp

def main():
    keep = set()
    parser = optparse.OptionParser(description=__doc__)
    parser.add_option('--root', help='Remove root prefix from output')
    parser.add_option('--output', help='Write output to the given file')
    parser.add_option('--ignore', action='append', default=[],
                      help='Ignore one or more paths (use multiple times)')
    parser.add_option('--allow-user', action='append', default=[],
                      help='Allow entries owned by this user only (use multiple times for multiple users)')
    parser.add_option('--allow-group', action='append', default=[],
                      help='Allow entries owned by this group only (use multiple times for multiple groups)')
    opts, args = parser.parse_args()

    allowed_users = set(opts.allow_user)
    allowed_groups = set(opts.allow_group)

    if opts.root:
        opts.root = os.path.abspath(opts.root)

    for path in args:
        path = os.path.abspath(path)
        if opts.root:
            assert path.startswith(opts.root)

        for dirpath, dirnames, filenames in os.walk(path):
            if any(f.startswith('.keep') for f in filenames):
                keep.add(dirpath)

    # Add all parent directories too
    for path in frozenset(keep):
        split = []
        for pathbit in path.split('/'):
            split.append(pathbit)
            joined = '/'.join(split)
            if not joined:
                continue
            if opts.root and not joined.startswith(opts.root):
                continue
            if opts.root == joined:
                continue
            keep.add(joined)

    config = []
    for path in sorted(keep):
        if opts.root:
            assert path.startswith(opts.root)
            stripped = path[len(opts.root):]
            assert len(stripped) > 1
        else:
            stripped = path

        if stripped in opts.ignore:
            continue

        info = os.stat(path)
        assert stat.S_ISDIR(info.st_mode)
        mode = stat.S_IMODE(info.st_mode)

        try:
            owner = pwd.getpwuid(info.st_uid).pw_name
            if allowed_users and owner not in allowed_users:
                continue
        except KeyError:
            owner = str(info.st_uid)
        try:
            group = grp.getgrgid(info.st_gid).gr_name
            if allowed_groups and group not in allowed_groups:
                continue
        except KeyError:
            group = str(info.st_gid)

        config.append('d %-22s %04o %-10s %-10s - -'
                % (stripped, mode, owner, group))

    if opts.output:
        fd = open(opts.output, 'w')
        fd.write('\n'.join(config)+'\n')
        fd.close()
    else:
        print('\n'.join(config))

if __name__ == '__main__':
    main()