#!/usr/bin/env python2.7

import re

from django.core.exceptions import ValidationError
from django.utils.translation import ugettext_lazy as _

from pyi2phosts.postkey.models import i2phost


def validate_hostname(data):
    """
    Here we do hostname validation as described in
    http://www.i2p2.i2p/naming.html and some additional checks
    described in http://zzz.i2p/topics/739
    """
    # convert hostname to lowercase and strip leading and trailing whitespaces
    data = data.lower().strip()
    # do lenght check here for avoiding django.db.utils.DatabaseError exceptions
    # when trying to add too long hostname with py-i2phosts-injector
    if len(data) > 67:
        raise ValidationError(_('Too long hostname (should be 67 chars max)'))
    # Must end with '.i2p'.
    if re.match(r'.*\.i2p$', data) == None:
        raise ValidationError(_('Hostname doesn\'t ends with .i2p'))
    # Base 32 hostnames (*.b32.i2p) are not allowed
    if re.match(r'.*\.b32\.i2p$', data):
        raise ValidationError(_('Base32 hostnames are not allowed'))
    # prevent common errors
    if re.match(r'\.i2p$', data):
        raise ValidationError(_('Incomplete hostname'))
    if re.match(r'^http:/', data):
        raise ValidationError(_('Do not paste full URL, just domain'))
    # Must not contain '..'
    if re.search(r'\.\.', data):
        raise ValidationError(_('".." in hostname'))
    # Allow only 4ld domains and below
    if data.count('.') > 3:
        raise ValidationError(_('Subdomains deeper than 4LD are not allowed'))
    # Must contain only [a-z] [0-9] '.' and '-'
    h = re.match(r'([a-z0-9.-]+)\.i2p$', data)
    if h == None:
        raise ValidationError(_('Illegal characters in hostname'))
    else:
        namepart = h.groups()[0]
    # Must not start with '.' or '-'
    if re.match(r'^\.|-', namepart):
        raise ValidationError(_('Hostname must not starts with "." or "-"'))
    # Must not contain '.-' or '-.' (as of 0.6.1.33)
    if re.search(r'(\.-)|(-\.)', namepart):
        raise ValidationError(_('Hostname contain ".-" or "-."'))
    # Must not contain '--' except in 'xn--' for IDN
    if re.search(r'(?<!^xn)--', namepart) and re.search(r'(?<!\.xn)--', namepart):
        raise ValidationError(_('Hostname contain "--" and it\'s not an IDN'))
    # Certain hostnames reserved for project use are not allowed
    if re.search(r'(^|\.)(proxy|router|console|b32|b64)$', namepart):
        raise ValidationError(_('Trying to use reserved hostname'))
    # Block various localhost.* in addition
    if re.match(r'^localhost($|\..*$)', namepart):
        raise ValidationError(_('localhost.* not allowed'))
    return data


def validate_b64hash(data, check_uniq=True):
    """
    Base64 hash validation
    """
    # strip leading and trailing whitespaces
    data = data.strip()
    length = len(data)
    # check for b32 address misuse
    if re.match(r'.*\.b32\.i2p$', data):
        raise ValidationError(_('You should paste base64 hash, not a base32!'))
    # fail if contains .i2p= (full foo.i2p=key)
    if re.search(r'\.i2p=', data):
        raise ValidationError(_('Do not paste full hosts.txt entry! Only base64 hash is needed'))
    # check for pasting router hash
    if length == 44:
        raise ValidationError(_('Do not paste router hash! Go to i2ptunnel page and \
                find a destination hash'))
    # Minimum key length 516 bytes
    if length < 516:
        raise ValidationError(_('Specified base64 hash is less than 516 bytes'))
    # Maximum key length 616 bytes
    if length > 616:
        raise ValidationError(_('Specified base64 hash is bigger than 616 bytes'))
    # keys with cert may ends with anything, so check is relaxed
    if length > 516 and re.match(r'[a-zA-Z0-9\-~=]+$', data) == None:
        raise ValidationError(_('Invalid characters in base64 hash'))
    # base64-validity test
    if length > 516:
        # we need temporary variable here to avoid modifying main "data"
        test_data = data
        # add pad-characters needed for proper decoding cos i2p does not
        for i in range(4):
            quanta, leftover = divmod(len(test_data), 4)
            if leftover:
                test_data += '='
            else:
                break
        # if more than 2 pad chars were added, raise an error
        if i > 2:
            raise ValidationError(_('Corrupted base64 hash'))
    # base64-i2p
    if length == 516 and re.match(r'[a-zA-Z0-9\-~]+AA$', data) == None:
        raise ValidationError(_('Invalid base64 hash'))
    # check ECDSA validity
    if length == 524 and re.match(r'[a-zA-Z0-9\-~]+AEAA[Ec]AAA==$', data) == None:
                raise ValidationError(_('Invalid base64 ECDSA or EdDSA hash'))
    if check_uniq == True:
        # Avoid adding non-unique hashes
        qs = i2phost.objects.filter(b64hash=data)
        if qs.exists():
            raise ValidationError(_('Some host already have the same Base64 hash'))
    return data


def validate_i2purl(data):
    """ Basic I2P URL validator """
    # convert to lowercase and strip leading and trailing whitespaces
    data = data.lower().strip()
    # check for http://, .i2p in domain and GET validity
    if re.match(r'^http://(?:.+?\.i2p)(?:/?|[/?]\S+)$', data) == None:
        raise ValidationError(_('Bad I2P url'))