# $Id: asn1.py 23 2006-11-08 15:45:33Z dugsong $
# -*- coding: utf-8 -*-
"""Abstract Syntax Notation #1."""
from __future__ import absolute_import
from __future__ import print_function

import struct
import time

from . import dpkt
from .compat import compat_ord

# Type class
CLASSMASK = 0xc0
UNIVERSAL = 0x00
APPLICATION = 0x40
CONTEXT = 0x80
PRIVATE = 0xc0

# Constructed (vs. primitive)
CONSTRUCTED = 0x20

# Universal-class tags
TAGMASK = 0x1f
INTEGER = 2
BIT_STRING = 3  # arbitrary bit string
OCTET_STRING = 4  # arbitrary octet string
NULL = 5
OID = 6  # object identifier
SEQUENCE = 16  # ordered collection of types
SET = 17  # unordered collection of types
PRINT_STRING = 19  # printable string
T61_STRING = 20  # T.61 (8-bit) character string
IA5_STRING = 22  # ASCII
UTC_TIME = 23


def utctime(buf):
    """Convert ASN.1 UTCTime string to UTC float.

    TODO: Long description here.

    Args:
        buf: A buffer with format "yymnddhhmm"

    Returns:
        A floating point number, indicates seconds since the Epoch.
    """
    yy = int(buf[:2])
    mn = int(buf[2:4])
    dd = int(buf[4:6])
    hh = int(buf[6:8])
    mm = int(buf[8:10])
    try:
        ss = int(buf[10:12])
        buf = buf[12:]
    except TypeError:
        ss = 0
        buf = buf[10:]
    if buf[0] == '+':
        hh -= int(buf[1:3])
        mm -= int(buf[3:5])
    elif buf[0] == '-':
        hh += int(buf[1:3])
        mm += int(buf[3:5])
    return time.mktime((2000 + yy, mn, dd, hh, mm, ss, 0, 0, 0))


def decode(buf):
    """Sleazy ASN.1 decoder.

    TODO: Long description here.

    Args:
        buf: A buffer with Sleazy ASN.1 data.

    Returns:
        A list of (id, value) tuples from ASN.1 BER/DER encoded buffer.

    Raises:
        UnpackError: An error occurred the ASN.1 length exceed.
    """
    msg = []
    while buf:
        t = compat_ord(buf[0])
        constructed = t & CONSTRUCTED
        tag = t & TAGMASK
        l_ = compat_ord(buf[1])
        c = 0
        if constructed and l_ == 128:
            # XXX - constructed, indefinite length
            msg.append((t, decode(buf[2:])))
        elif l_ >= 128:
            c = l_ & 127
            if c == 1:
                l_ = compat_ord(buf[2])
            elif c == 2:
                l_ = struct.unpack('>H', buf[2:4])[0]
            elif c == 3:
                l_ = struct.unpack('>I', buf[1:5])[0] & 0xfff
                c = 2
            elif c == 4:
                l_ = struct.unpack('>I', buf[2:6])[0]
            else:
                # XXX - can be up to 127 bytes, but...
                raise dpkt.UnpackError('excessive long-form ASN.1 length %d' % l_)

        # Skip type, length
        buf = buf[2 + c:]

        # Parse content
        if constructed:
            msg.append((t, decode(buf)))
        elif tag == INTEGER:
            if l_ == 0:
                n = 0
            elif l_ == 1:
                n = compat_ord(buf[0])
            elif l_ == 2:
                n = struct.unpack('>H', buf[:2])[0]
            elif l_ == 3:
                n = struct.unpack('>I', buf[:4])[0] >> 8
            elif l_ == 4:
                n = struct.unpack('>I', buf[:4])[0]
            else:
                raise dpkt.UnpackError('excessive integer length > %d bytes' % l_)
            msg.append((t, n))
        elif tag == UTC_TIME:
            msg.append((t, utctime(buf[:l_])))
        else:
            msg.append((t, buf[:l_]))

        # Skip content
        buf = buf[l_:]
    return msg


def test_asn1():
    s = (b'0\x82\x02Q\x02\x01\x0bc\x82\x02J\x04xcn=Douglas J Song 1, ou=Information Technology Division,'
         b' ou=Faculty and Staff, ou=People, o=University of Michigan, c=US\n\x01\x00\n\x01\x03\x02\x01'
         b'\x00\x02\x01\x00\x01\x01\x00\x87\x0bobjectclass0\x82\x01\xb0\x04\rmemberOfGroup\x04\x03acl'
         b'\x04\x02cn\x04\x05title\x04\rpostalAddress\x04\x0ftelephoneNumber\x04\x04mail\x04\x06member'
         b'\x04\thomePhone\x04\x11homePostalAddress\x04\x0bobjectClass\x04\x0bdescription\x04\x18'
         b'facsimileTelephoneNumber\x04\x05pager\x04\x03uid\x04\x0cuserPassword\x04\x08joinable\x04\x10'
         b'associatedDomain\x04\x05owner\x04\x0erfc822ErrorsTo\x04\x08ErrorsTo\x04\x10rfc822RequestsTo\x04\n'
         b'RequestsTo\x04\tmoderator\x04\nlabeledURL\x04\nonVacation\x04\x0fvacationMessage\x04\x05drink\x04\x0e'
         b'lastModifiedBy\x04\x10lastModifiedTime\x04\rmodifiersname\x04\x0fmodifytimestamp\x04\x0ccreatorsname'
         b'\x04\x0fcreatetimestamp')
    assert (decode(s) == [(48, [(2, 11), (99, [(4, b'cn=Douglas J Song 1, ou=Information Technology Division, ou=Faculty and Staff, ou=People, o=University of Michigan, c=US'), (10, b'\x00'), (10, b'\x03'), (2, 0), (2, 0), (1, b'\x00'), (135, b'objectclass'), (48, [(4, b'memberOfGroup'), (4, b'acl'), (4, b'cn'), (4, b'title'), (4, b'postalAddress'), (4, b'telephoneNumber'), (4, b'mail'), (4, b'member'), (4, b'homePhone'), (4, b'homePostalAddress'), (4, b'objectClass'), (4, b'description'), (4, b'facsimileTelephoneNumber'), (4, b'pager'), (4, b'uid'), (4, b'userPassword'), (4, b'joinable'), (4, b'associatedDomain'), (4, b'owner'), (4, b'rfc822ErrorsTo'), (4, b'ErrorsTo'), (4, b'rfc822RequestsTo'), (4, b'RequestsTo'), (4, b'moderator'), (4, b'labeledURL'), (4, b'onVacation'), (4, b'vacationMessage'), (4, b'drink'), (4, b'lastModifiedBy'), (4, b'lastModifiedTime'), (4, b'modifiersname'), (4, b'modifytimestamp'), (4, b'creatorsname'), (4, b'createtimestamp')])])])])


if __name__ == '__main__':
    test_asn1()
    print('Tests Successful...')
