#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Copyright (c) 2017, NORDUnet A/S.
# See LICENSE for licensing information.
#
# Initialise a new CT log.
#

import sys
import os
import argparse
import errno
from time import time
from base64 import b64encode
from certtools import build_merkle_tree, write_file, generate_tree_head_signature
from mergetools import get_sth, perm, get_logorder, hexencode, parse_args

# TODO: Add a `--init-secondary' option too?

def main():
    """
    Initialise a log, either from scratch or by promoting a secondary
    merge node (--promote-secondary).

    Refuse to do anything if there's an sth file present.

    When initialising from scratch, do
    - touch logorder
    - write -1 to fetched
    - write 0 to minsize
    - create perm database if it doesn't exist

    When promoting a secondary (--promote-secondary), do
    - read logorder, let n = length of logorder
    - write n-1 to fetched
    - write n to minsize
    - create perm database if it doesn't exist
    """
    parser = argparse.ArgumentParser(description="")
    parser.add_argument('--promote-secondary', action='store_true')
    parser.add_argument('--config', help="System configuration",
                        required=True)
    parser.add_argument('--localconfig', help="Local configuration",
                        required=True)

    args, config, localconfig = parse_args(parser=parser)

    paths = localconfig["paths"]
    own_key = (localconfig["nodename"],
               "%s/%s-private.pem" % (paths["privatekeys"],
                                      localconfig["nodename"]))
    mergedb = paths["db"]
    sthfile = mergedb + "/sth"
    logorderfile = mergedb + "/logorder"
    currentsizefile = mergedb + "/fetched"
    minsizefile = mergedb + "/minsize"

    # Make sure that we can find our keyfile.
    if not file_exists(own_key[1]):
        print >>sys.stderr, "Unable to open keyfile: %s" % own_key[1]
        return 1

    # Don't do anything if there's already an sth file.
    if file_exists(sthfile):
        print >>sys.stderr, "This log already has an STH file: %s" % sthfile
        print >>sys.stderr, "I refuse to destroy this log."
        return 2

    # Read or touch logorder.
    if args.promote_secondary:
        logorder = get_logorder(logorderfile)
        size = len(logorder)
        last_hash = logorder[size-1]
    else:
        if file_exists(logorderfile):
            print >>sys.stderr, "This log already has logorder file: %s" % logorderfile
            print >>sys.stderr, "I refuse to destroy this log."
            return 3
        open(logorderfile, "a").close()
        size = 0
        last_hash = ''

    # Write fetched.
    currentsize = {"index": size - 1, "hash": hexencode(last_hash)}
    write_file(currentsizefile, currentsize)

    # Write minsize.
    minsize = {"size": size}
    write_file(minsizefile, minsize)

    # Create a chains database.
    perm(localconfig["dbbackend"], mergedb + "/chains")

    return 0

def file_exists(path):
    try:
        os.stat(path)
    except OSError, e:
        if e.errno == errno.ENOENT:
            return False
        raise
    return True

if __name__ == '__main__':
    sys.exit(main())