"""
<Module Name>
  constants.py

<Author>
  Santiago Torres-Arias <santiago@nyu.edu>

<Started>
  Nov 15, 2017

<Copyright>
  See LICENSE for licensing information.

<Purpose>
  aggregates all the constant definitions and lookup structures for signature
  handling
"""
import logging

import securesystemslib.gpg.rsa as rsa
import securesystemslib.gpg.dsa as dsa
import securesystemslib.gpg.eddsa as eddsa

import securesystemslib.process as process

log = logging.getLogger(__name__)

# By default, we assume and test that gpg2 exists. Otherwise, we assume gpg
# exists.
GPG_COMMAND = "gpg2"
GPG_VERSION_COMMAND = GPG_COMMAND + " --version"
FULLY_SUPPORTED_MIN_VERSION = "2.1.0"

HAVE_GPG = True
NO_GPG_MSG = "GPG support requires a GPG command, {} version {} or newer is" \
  " fully supported.".format(GPG_COMMAND, FULLY_SUPPORTED_MIN_VERSION)

try:
  proc = process.run(GPG_VERSION_COMMAND, stdout=process.PIPE,
    stderr=process.PIPE)

except OSError: # pragma: no cover
  GPG_COMMAND = "gpg"
  GPG_VERSION_COMMAND = GPG_COMMAND + " --version"

  try:
    proc = process.run(GPG_VERSION_COMMAND, stdout=process.PIPE,
      stderr=process.PIPE)

  except OSError:
    HAVE_GPG = False

GPG_SIGN_COMMAND = GPG_COMMAND + \
                   " --detach-sign --digest-algo SHA256 {keyarg} {homearg}"
GPG_EXPORT_PUBKEY_COMMAND = GPG_COMMAND + " {homearg} --export {keyid}"

# See RFC4880 section 4.3. Packet Tags for a list of all packet types The
# relevant packets defined below are described in sections 5.2 (signature),
# 5.5.1.1 (primary pubkey) and 5.5.1.2 (pub subkey), 5.12 (user id) and 5.13
# (user attribute)
PACKET_TYPE_SIGNATURE = 0x02
PACKET_TYPE_PRIMARY_KEY = 0x06
PACKET_TYPE_USER_ID = 0x0D
PACKET_TYPE_USER_ATTR = 0x11
PACKET_TYPE_SUB_KEY = 0x0E


# See sections 5.2.3 (signature) and 5.5.2 (public key) of RFC4880
SUPPORTED_SIGNATURE_PACKET_VERSIONS = {0x04}
SUPPORTED_PUBKEY_PACKET_VERSIONS = {0x04}

# See section 9.1. (public-key algorithms) of RFC4880 (-bis8)
SUPPORTED_SIGNATURE_ALGORITHMS = {
    0x01: {
      "type":"rsa",
      "method": "pgp+rsa-pkcsv1.5",
      "handler": rsa
    },
    0x11: {
      "type": "dsa",
      "method": "pgp+dsa-fips-180-2",
      "handler": dsa
    },
    0x16: {
      "type": "eddsa",
      "method": "pgp+eddsa-ed25519",
      "handler": eddsa
    }
}

SIGNATURE_HANDLERS = {
    "rsa": rsa,
    "dsa": dsa,
    "eddsa": eddsa
}

# The constants for hash algorithms are taken from section 9.4 of RFC4880.
SHA1 = 0x02
SHA256 = 0x08
SHA512 = 0x0A

# See section 5.2.1 of RFC4880
SIGNATURE_TYPE_BINARY = 0x00
SIGNATURE_TYPE_SUB_KEY_BINDING = 0x18
SIGNATURE_TYPE_CERTIFICATES = {0x10, 0x11, 0x12, 0x13}

# See section 5.2.3.4 (Signature Creation Time) of RFC4880
SIG_CREATION_SUBPACKET = 0x02
# See section 5.2.3.5. (Issuer) of RFC4880
PARTIAL_KEYID_SUBPACKET = 0x10
# See section 5.2.3.6 (Key Expiration Time) of RFC4880
KEY_EXPIRATION_SUBPACKET = 0x09
# See section 5.2.3.19 (Primary User ID) of RFC4880
PRIMARY_USERID_SUBPACKET = 0x19
# See section 5.2.3.28. (Issuer Fingerprint) of rfc4880bis-06
FULL_KEYID_SUBPACKET = 0x21