"""
Low-level protocol-related functions.
"""
# pylint: disable=too-many-boolean-expressions,too-many-return-statements
# pylint: disable=too-many-locals,too-many-statements

import base64
import hashlib
import random
import socket
import sys
import time
from binascii import hexlify
from struct import Struct, pack, unpack

import defaults
import helper_db
import highlevelcrypto
import state
from addresses import (
    encodeVarint, decodeVarint, decodeAddress, varintDecodeError)
from bmconfigparser import BMConfigParser
from debug import logger
from fallback import RIPEMD160Hash
from version import softwareVersion

# Service flags
#: This is a normal network node
NODE_NETWORK = 1
#: This node supports SSL/TLS in the current connect (python < 2.7.9
#: only supports an SSL client, so in that case it would only have this
#: on when the connection is a client).
NODE_SSL = 2
# (Proposal) This node may do PoW on behalf of some its peers
# (PoW offloading/delegating), but it doesn't have to. Clients may have
# to meet additional requirements (e.g. TLS authentication)
# NODE_POW = 4
#: Node supports dandelion
NODE_DANDELION = 8

# Bitfield flags
BITFIELD_DOESACK = 1

# Error types
STATUS_WARNING = 0
STATUS_ERROR = 1
STATUS_FATAL = 2

# Object types
OBJECT_GETPUBKEY = 0
OBJECT_PUBKEY = 1
OBJECT_MSG = 2
OBJECT_BROADCAST = 3
OBJECT_ONIONPEER = 0x746f72
OBJECT_I2P = 0x493250
OBJECT_ADDR = 0x61646472

eightBytesOfRandomDataUsedToDetectConnectionsToSelf = pack(
    '>Q', random.randrange(1, 18446744073709551615))

# Compiled struct for packing/unpacking headers
# New code should use CreatePacket instead of Header.pack
Header = Struct('!L12sL4s')

VersionPacket = Struct('>LqQ20s4s36sH')

# Bitfield


def getBitfield(address):
    """Get a bitfield from an address"""
    # bitfield of features supported by me (see the wiki).
    bitfield = 0
    # send ack
    if not BMConfigParser().safeGetBoolean(address, 'dontsendack'):
        bitfield |= BITFIELD_DOESACK
    return pack('>I', bitfield)


def checkBitfield(bitfieldBinary, flags):
    """Check if a bitfield matches the given flags"""
    bitfield, = unpack('>I', bitfieldBinary)
    return (bitfield & flags) == flags


def isBitSetWithinBitfield(fourByteString, n):
    """Check if a particular bit is set in a bitfeld"""
    # Uses MSB 0 bit numbering across 4 bytes of data
    n = 31 - n
    x, = unpack('>L', fourByteString)
    return x & 2**n != 0


# ip addresses


def encodeHost(host):
    """Encode a given host to be used in low-level socket operations"""
    if host.find('.onion') > -1:
        return '\xfd\x87\xd8\x7e\xeb\x43' + base64.b32decode(
            host.split(".")[0], True)
    elif host.find(':') == -1:
        return '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xFF\xFF' + \
            socket.inet_aton(host)
    return socket.inet_pton(socket.AF_INET6, host)


def networkType(host):
    """Determine if a host is IPv4, IPv6 or an onion address"""
    if host.find('.onion') > -1:
        return 'onion'
    elif host.find(':') == -1:
        return 'IPv4'
    return 'IPv6'


def network_group(host):
    """Canonical identifier of network group
       simplified, borrowed from
       GetGroup() in src/netaddresses.cpp in bitcoin core"""
    if not isinstance(host, str):
        return None
    network_type = networkType(host)
    try:
        raw_host = encodeHost(host)
    except socket.error:
        return host
    if network_type == 'IPv4':
        decoded_host = checkIPv4Address(raw_host[12:], True)
        if decoded_host:
            # /16 subnet
            return raw_host[12:14]
    elif network_type == 'IPv6':
        decoded_host = checkIPv6Address(raw_host, True)
        if decoded_host:
            # /32 subnet
            return raw_host[0:12]
    else:
        # just host, e.g. for tor
        return host
    # global network type group for local, private, unroutable
    return network_type


def checkIPAddress(host, private=False):
    """
    Returns hostStandardFormat if it is a valid IP address,
    otherwise returns False
    """
    if host[0:12] == '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xFF\xFF':
        hostStandardFormat = socket.inet_ntop(socket.AF_INET, host[12:])
        return checkIPv4Address(host[12:], hostStandardFormat, private)
    elif host[0:6] == '\xfd\x87\xd8\x7e\xeb\x43':
        # Onion, based on BMD/bitcoind
        hostStandardFormat = base64.b32encode(host[6:]).lower() + ".onion"
        if private:
            return False
        return hostStandardFormat
    else:
        try:
            hostStandardFormat = socket.inet_ntop(socket.AF_INET6, host)
        except ValueError:
            return False
        if hostStandardFormat == "":
            # This can happen on Windows systems which are
            # not 64-bit compatible so let us drop the IPv6 address.
            return False
        return checkIPv6Address(host, hostStandardFormat, private)


def checkIPv4Address(host, hostStandardFormat, private=False):
    """
    Returns hostStandardFormat if it is an IPv4 address,
    otherwise returns False
    """
    if host[0] == '\x7F':  # 127/8
        if not private:
            logger.debug(
                'Ignoring IP address in loopback range: %s',
                hostStandardFormat)
        return hostStandardFormat if private else False
    if host[0] == '\x0A':  # 10/8
        if not private:
            logger.debug(
                'Ignoring IP address in private range: %s', hostStandardFormat)
        return hostStandardFormat if private else False
    if host[0:2] == '\xC0\xA8':  # 192.168/16
        if not private:
            logger.debug(
                'Ignoring IP address in private range: %s', hostStandardFormat)
        return hostStandardFormat if private else False
    if host[0:2] >= '\xAC\x10' and host[0:2] < '\xAC\x20':  # 172.16/12
        if not private:
            logger.debug(
                'Ignoring IP address in private range: %s', hostStandardFormat)
        return hostStandardFormat if private else False
    return False if private else hostStandardFormat


def checkIPv6Address(host, hostStandardFormat, private=False):
    """
    Returns hostStandardFormat if it is an IPv6 address,
    otherwise returns False
    """
    if host == ('\x00' * 15) + '\x01':
        if not private:
            logger.debug('Ignoring loopback address: %s', hostStandardFormat)
        return False
    if host[0] == '\xFE' and (ord(host[1]) & 0xc0) == 0x80:
        if not private:
            logger.debug('Ignoring local address: %s', hostStandardFormat)
        return hostStandardFormat if private else False
    if (ord(host[0]) & 0xfe) == 0xfc:
        if not private:
            logger.debug(
                'Ignoring unique local address: %s', hostStandardFormat)
        return hostStandardFormat if private else False
    return False if private else hostStandardFormat


def haveSSL(server=False):
    """
    Predicate to check if ECDSA server support is required and available

    python < 2.7.9's ssl library does not support ECDSA server due to
    missing initialisation of available curves, but client works ok
    """
    if not server:
        return True
    elif sys.version_info >= (2, 7, 9):
        return True
    return False


def checkSocksIP(host):
    """Predicate to check if we're using a SOCKS proxy"""
    sockshostname = BMConfigParser().safeGet(
        'bitmessagesettings', 'sockshostname')
    try:
        if not state.socksIP:
            state.socksIP = socket.gethostbyname(sockshostname)
    except NameError:  # uninitialised
        state.socksIP = socket.gethostbyname(sockshostname)
    except (TypeError, socket.gaierror):  # None, resolving failure
        state.socksIP = sockshostname
    return state.socksIP == host


def isProofOfWorkSufficient(
        data, nonceTrialsPerByte=0, payloadLengthExtraBytes=0, recvTime=0):
    """
    Validate an object's Proof of Work using method described
    `here <https://bitmessage.org/wiki/Proof_of_work>`_

    Arguments:
        int nonceTrialsPerByte (default: from `.defaults`)
        int payloadLengthExtraBytes (default: from `.defaults`)
        float recvTime (optional) UNIX epoch time when object was
          received from the network (default: current system time)
    Returns:
        True if PoW valid and sufficient, False in all other cases
    """
    if nonceTrialsPerByte < defaults.networkDefaultProofOfWorkNonceTrialsPerByte:
        nonceTrialsPerByte = defaults.networkDefaultProofOfWorkNonceTrialsPerByte
    if payloadLengthExtraBytes < defaults.networkDefaultPayloadLengthExtraBytes:
        payloadLengthExtraBytes = defaults.networkDefaultPayloadLengthExtraBytes
    endOfLifeTime, = unpack('>Q', data[8:16])
    TTL = endOfLifeTime - (int(recvTime) if recvTime else int(time.time()))
    if TTL < 300:
        TTL = 300
    POW, = unpack('>Q', hashlib.sha512(hashlib.sha512(
        data[:8] + hashlib.sha512(data[8:]).digest()
    ).digest()).digest()[0:8])
    return POW <= 2 ** 64 / (
        nonceTrialsPerByte * (
            len(data) + payloadLengthExtraBytes +
            ((TTL * (len(data) + payloadLengthExtraBytes)) / (2 ** 16))))


# Packet creation


def CreatePacket(command, payload=''):
    """Construct and return a packet"""
    payload_length = len(payload)
    checksum = hashlib.sha512(payload).digest()[0:4]

    b = bytearray(Header.size + payload_length)
    Header.pack_into(b, 0, 0xE9BEB4D9, command, payload_length, checksum)
    b[Header.size:] = payload
    return bytes(b)


def assembleVersionMessage(
    remoteHost, remotePort, participatingStreams, server=False, nodeid=None
):
    """
    Construct the payload of a version message,
    return the resulting bytes of running `CreatePacket` on it
    """
    payload = ''
    payload += pack('>L', 3)  # protocol version.
    # bitflags of the services I offer.
    payload += pack(
        '>q',
        NODE_NETWORK |
        (NODE_SSL if haveSSL(server) else 0) |
        (NODE_DANDELION if state.dandelion else 0)
    )
    payload += pack('>q', int(time.time()))

    # boolservices of remote connection; ignored by the remote host.
    payload += pack('>q', 1)
    if checkSocksIP(remoteHost) and server:
        # prevent leaking of tor outbound IP
        payload += encodeHost('127.0.0.1')
        payload += pack('>H', 8444)
    else:
        # use first 16 bytes if host data is longer
        # for example in case of onion v3 service
        try:
            payload += encodeHost(remoteHost)[:16]
        except socket.error:
            payload += encodeHost('127.0.0.1')
        payload += pack('>H', remotePort)  # remote IPv6 and port

    # bitflags of the services I offer.
    payload += pack(
        '>q',
        NODE_NETWORK |
        (NODE_SSL if haveSSL(server) else 0) |
        (NODE_DANDELION if state.dandelion else 0)
    )
    # = 127.0.0.1. This will be ignored by the remote host.
    # The actual remote connected IP will be used.
    payload += '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xFF\xFF' + pack(
        '>L', 2130706433)
    # we have a separate extPort and incoming over clearnet
    # or outgoing through clearnet
    extport = BMConfigParser().safeGetInt('bitmessagesettings', 'extport')
    if (
        extport and ((server and not checkSocksIP(remoteHost)) or (
            BMConfigParser().get('bitmessagesettings', 'socksproxytype')
            == 'none' and not server))
    ):
        payload += pack('>H', extport)
    elif checkSocksIP(remoteHost) and server:  # incoming connection over Tor
        payload += pack(
            '>H', BMConfigParser().getint('bitmessagesettings', 'onionport'))
    else:  # no extport and not incoming over Tor
        payload += pack(
            '>H', BMConfigParser().getint('bitmessagesettings', 'port'))

    if nodeid is not None:
        payload += nodeid[0:8]
    else:
        payload += eightBytesOfRandomDataUsedToDetectConnectionsToSelf
    userAgent = '/PyBitmessage:' + softwareVersion + '/'
    payload += encodeVarint(len(userAgent))
    payload += userAgent

    # Streams
    payload += encodeVarint(len(participatingStreams))
    count = 0
    for stream in sorted(participatingStreams):
        payload += encodeVarint(stream)
        count += 1
        # protocol limit, see specification
        if count >= 160000:
            break

    return CreatePacket('version', payload)


def assembleErrorMessage(fatal=0, banTime=0, inventoryVector='', errorText=''):
    """
    Construct the payload of an error message,
    return the resulting bytes of running `CreatePacket` on it
    """
    payload = encodeVarint(fatal)
    payload += encodeVarint(banTime)
    payload += encodeVarint(len(inventoryVector))
    payload += inventoryVector
    payload += encodeVarint(len(errorText))
    payload += errorText
    return CreatePacket('error', payload)


# Packet decoding


def decryptAndCheckPubkeyPayload(data, address):
    """
    Version 4 pubkeys are encrypted. This function is run when we
    already have the address to which we want to try to send a message.
    The 'data' may come either off of the wire or we might have had it
    already in our inventory when we tried to send a msg to this
    particular address.
    """
    try:
        addressVersion, streamNumber, ripe = decodeAddress(address)[1:]

        readPosition = 20  # bypass the nonce, time, and object type
        embeddedAddressVersion, varintLength = decodeVarint(
            data[readPosition:readPosition + 10])
        readPosition += varintLength
        embeddedStreamNumber, varintLength = decodeVarint(
            data[readPosition:readPosition + 10])
        readPosition += varintLength
        # We'll store the address version and stream number
        # (and some more) in the pubkeys table.
        storedData = data[20:readPosition]

        if addressVersion != embeddedAddressVersion:
            logger.info(
                'Pubkey decryption was UNsuccessful'
                ' due to address version mismatch.')
            return 'failed'
        if streamNumber != embeddedStreamNumber:
            logger.info(
                'Pubkey decryption was UNsuccessful'
                ' due to stream number mismatch.')
            return 'failed'

        tag = data[readPosition:readPosition + 32]
        readPosition += 32
        # the time through the tag. More data is appended onto
        # signedData below after the decryption.
        signedData = data[8:readPosition]
        encryptedData = data[readPosition:]

        # Let us try to decrypt the pubkey
        toAddress, cryptorObject = state.neededPubkeys[tag]
        if toAddress != address:
            logger.critical(
                'decryptAndCheckPubkeyPayload failed due to toAddress'
                ' mismatch. This is very peculiar.'
                ' toAddress: %s, address %s',
                toAddress, address
            )
            # the only way I can think that this could happen
            # is if someone encodes their address data two different ways.
            # That sort of address-malleability should have been caught
            # by the UI or API and an error given to the user.
            return 'failed'
        try:
            decryptedData = cryptorObject.decrypt(encryptedData)
        except:
            # Someone must have encrypted some data with a different key
            # but tagged it with a tag for which we are watching.
            logger.info('Pubkey decryption was unsuccessful.')
            return 'failed'

        readPosition = 0
        # bitfieldBehaviors = decryptedData[readPosition:readPosition + 4]
        readPosition += 4
        publicSigningKey = '\x04' + decryptedData[readPosition:readPosition + 64]
        readPosition += 64
        publicEncryptionKey = '\x04' + decryptedData[readPosition:readPosition + 64]
        readPosition += 64
        specifiedNonceTrialsPerByteLength = decodeVarint(
            decryptedData[readPosition:readPosition + 10])[1]
        readPosition += specifiedNonceTrialsPerByteLength
        specifiedPayloadLengthExtraBytesLength = decodeVarint(
            decryptedData[readPosition:readPosition + 10])[1]
        readPosition += specifiedPayloadLengthExtraBytesLength
        storedData += decryptedData[:readPosition]
        signedData += decryptedData[:readPosition]
        signatureLength, signatureLengthLength = decodeVarint(
            decryptedData[readPosition:readPosition + 10])
        readPosition += signatureLengthLength
        signature = decryptedData[readPosition:readPosition + signatureLength]

        if not highlevelcrypto.verify(
                signedData, signature, hexlify(publicSigningKey)):
            logger.info(
                'ECDSA verify failed (within decryptAndCheckPubkeyPayload)')
            return 'failed'

        logger.info(
            'ECDSA verify passed (within decryptAndCheckPubkeyPayload)')

        sha = hashlib.new('sha512')
        sha.update(publicSigningKey + publicEncryptionKey)
        embeddedRipe = RIPEMD160Hash(sha.digest()).digest()

        if embeddedRipe != ripe:
            # Although this pubkey object had the tag were were looking for
            # and was encrypted with the correct encryption key,
            # it doesn't contain the correct pubkeys. Someone is
            # either being malicious or using buggy software.
            logger.info(
                'Pubkey decryption was UNsuccessful due to RIPE mismatch.')
            return 'failed'

        # Everything checked out. Insert it into the pubkeys table.

        logger.info(
            'within decryptAndCheckPubkeyPayload, '
            'addressVersion: %s, streamNumber: %s\nripe %s\n'
            'publicSigningKey in hex: %s\npublicEncryptionKey in hex: %s',
            addressVersion, streamNumber, hexlify(ripe),
            hexlify(publicSigningKey), hexlify(publicEncryptionKey)
        )

        helper_db.put_pubkey(address, addressVersion, storedData, True)
        return 'successful'
    except varintDecodeError:
        logger.info(
            'Pubkey decryption was UNsuccessful due to a malformed varint.')
        return 'failed'
    except Exception:
        logger.critical(
            'Pubkey decryption was UNsuccessful because of'
            ' an unhandled exception! This is definitely a bug!',
            exc_info=True
        )
        return 'failed'