#!/usr/bin/env python
#
# This file is part of pyasn1 software.
#
# Copyright (c) 2005-2017, Ilya Etingof <etingof@gmail.com>
# License: http://snmplabs.com/pyasn1/license.html
#
from pyasn1 import debug
from pyasn1 import error
from pyasn1.codec.ber import eoo
from pyasn1.compat.integer import from_bytes
from pyasn1.compat.octets import oct2int, octs2ints, ints2octs, null
from pyasn1.type import base
from pyasn1.type import char
from pyasn1.type import tag
from pyasn1.type import tagmap
from pyasn1.type import univ
from pyasn1.type import useful

__all__ = ['decode']

noValue = base.noValue


class AbstractDecoder(object):
    protoComponent = None

    def valueDecoder(self, substrate, asn1Spec,
                     tagSet=None, length=None, state=None,
                     decodeFun=None, substrateFun=None,
                     **options):
        raise error.PyAsn1Error('Decoder not implemented for %s' % (tagSet,))

    def indefLenValueDecoder(self, substrate, asn1Spec,
                             tagSet=None, length=None, state=None,
                             decodeFun=None, substrateFun=None,
                             **options):
        raise error.PyAsn1Error('Indefinite length mode decoder not implemented for %s' % (tagSet,))


class AbstractSimpleDecoder(AbstractDecoder):
    @staticmethod
    def substrateCollector(asn1Object, substrate, length):
        return substrate[:length], substrate[length:]

    def _createComponent(self, asn1Spec, tagSet, value, **options):
        if options.get('native'):
            return value
        elif asn1Spec is None:
            return self.protoComponent.clone(value, tagSet=tagSet)
        elif value is noValue:
            return asn1Spec
        else:
            return asn1Spec.clone(value)


class ExplicitTagDecoder(AbstractSimpleDecoder):
    protoComponent = univ.Any('')

    def valueDecoder(self, substrate, asn1Spec,
                     tagSet=None, length=None, state=None,
                     decodeFun=None, substrateFun=None,
                     **options):
        if substrateFun:
            return substrateFun(
                self._createComponent(asn1Spec, tagSet, '', **options),
                substrate, length
            )

        head, tail = substrate[:length], substrate[length:]

        value, _ = decodeFun(head, asn1Spec, tagSet, length, **options)

        return value, tail

    def indefLenValueDecoder(self, substrate, asn1Spec,
                             tagSet=None, length=None, state=None,
                             decodeFun=None, substrateFun=None,
                             **options):
        if substrateFun:
            return substrateFun(
                self._createComponent(asn1Spec, tagSet, '', **options),
                substrate, length
            )

        value, substrate = decodeFun(substrate, asn1Spec, tagSet, length, **options)

        eooMarker, substrate = decodeFun(substrate, allowEoo=True, **options)

        if eooMarker is eoo.endOfOctets:
            return value, substrate
        else:
            raise error.PyAsn1Error('Missing end-of-octets terminator')


explicitTagDecoder = ExplicitTagDecoder()


class IntegerDecoder(AbstractSimpleDecoder):
    protoComponent = univ.Integer(0)

    def valueDecoder(self, substrate, asn1Spec,
                     tagSet=None, length=None, state=None,
                     decodeFun=None, substrateFun=None,
                     **options):

        if tagSet[0].tagFormat != tag.tagFormatSimple:
            raise error.PyAsn1Error('Simple tag format expected')

        head, tail = substrate[:length], substrate[length:]

        if not head:
            return self._createComponent(asn1Spec, tagSet, 0, **options), tail

        value = from_bytes(head, signed=True)

        return self._createComponent(asn1Spec, tagSet, value, **options), tail


class BooleanDecoder(IntegerDecoder):
    protoComponent = univ.Boolean(0)

    def _createComponent(self, asn1Spec, tagSet, value, **options):
        return IntegerDecoder._createComponent(self, asn1Spec, tagSet, value and 1 or 0, **options)


class BitStringDecoder(AbstractSimpleDecoder):
    protoComponent = univ.BitString(())
    supportConstructedForm = True

    def valueDecoder(self, substrate, asn1Spec,
                     tagSet=None, length=None, state=None,
                     decodeFun=None, substrateFun=None,
                     **options):
        head, tail = substrate[:length], substrate[length:]

        if substrateFun:
            return substrateFun(self._createComponent(asn1Spec, tagSet, noValue, **options),
                                substrate, length)

        if not head:
            raise error.PyAsn1Error('Empty BIT STRING substrate')

        if tagSet[0].tagFormat == tag.tagFormatSimple:  # XXX what tag to check?

            trailingBits = oct2int(head[0])
            if trailingBits > 7:
                raise error.PyAsn1Error(
                    'Trailing bits overflow %s' % trailingBits
                )

            value = self.protoComponent.fromOctetString(head[1:], internalFormat=True, padding=trailingBits)

            return self._createComponent(asn1Spec, tagSet, value, **options), tail

        if not self.supportConstructedForm:
            raise error.PyAsn1Error('Constructed encoding form prohibited at %s' % self.__class__.__name__)

        # All inner fragments are of the same type, treat them as octet string
        substrateFun = self.substrateCollector

        bitString = self.protoComponent.fromOctetString(null, internalFormat=True)

        while head:
            component, head = decodeFun(head, self.protoComponent,
                                        substrateFun=substrateFun, **options)

            trailingBits = oct2int(component[0])
            if trailingBits > 7:
                raise error.PyAsn1Error(
                    'Trailing bits overflow %s' % trailingBits
                )

            bitString = self.protoComponent.fromOctetString(
                component[1:], internalFormat=True,
                prepend=bitString, padding=trailingBits
            )

        return self._createComponent(asn1Spec, tagSet, bitString, **options), tail

    def indefLenValueDecoder(self, substrate, asn1Spec,
                             tagSet=None, length=None, state=None,
                             decodeFun=None, substrateFun=None,
                             **options):

        if substrateFun:
            return substrateFun(self._createComponent(asn1Spec, tagSet, noValue, **options), substrate, length)

        # All inner fragments are of the same type, treat them as octet string
        substrateFun = self.substrateCollector

        bitString = self.protoComponent.fromOctetString(null, internalFormat=True)

        while substrate:
            component, substrate = decodeFun(substrate, self.protoComponent,
                                             substrateFun=substrateFun,
                                             allowEoo=True, **options)
            if component is eoo.endOfOctets:
                break

            trailingBits = oct2int(component[0])
            if trailingBits > 7:
                raise error.PyAsn1Error(
                    'Trailing bits overflow %s' % trailingBits
                )

            bitString = self.protoComponent.fromOctetString(
                component[1:], internalFormat=True,
                prepend=bitString, padding=trailingBits
            )

        else:
            raise error.SubstrateUnderrunError('No EOO seen before substrate ends')

        return self._createComponent(asn1Spec, tagSet, bitString, **options), substrate


class OctetStringDecoder(AbstractSimpleDecoder):
    protoComponent = univ.OctetString('')
    supportConstructedForm = True

    def valueDecoder(self, substrate, asn1Spec,
                     tagSet=None, length=None, state=None,
                     decodeFun=None, substrateFun=None,
                     **options):
        head, tail = substrate[:length], substrate[length:]

        if substrateFun:
            return substrateFun(self._createComponent(asn1Spec, tagSet, noValue, **options),
                                substrate, length)

        if tagSet[0].tagFormat == tag.tagFormatSimple:  # XXX what tag to check?
            return self._createComponent(asn1Spec, tagSet, head, **options), tail

        if not self.supportConstructedForm:
            raise error.PyAsn1Error('Constructed encoding form prohibited at %s' % self.__class__.__name__)

        # All inner fragments are of the same type, treat them as octet string
        substrateFun = self.substrateCollector

        header = null

        while head:
            component, head = decodeFun(head, self.protoComponent,
                                        substrateFun=substrateFun,
                                        **options)
            header += component

        return self._createComponent(asn1Spec, tagSet, header, **options), tail

    def indefLenValueDecoder(self, substrate, asn1Spec,
                             tagSet=None, length=None, state=None,
                             decodeFun=None, substrateFun=None,
                             **options):
        if substrateFun and substrateFun is not self.substrateCollector:
            asn1Object = self._createComponent(asn1Spec, tagSet, noValue, **options)
            return substrateFun(asn1Object, substrate, length)

        # All inner fragments are of the same type, treat them as octet string
        substrateFun = self.substrateCollector

        header = null

        while substrate:
            component, substrate = decodeFun(substrate,
                                             self.protoComponent,
                                             substrateFun=substrateFun,
                                             allowEoo=True, **options)
            if component is eoo.endOfOctets:
                break
            header += component
        else:
            raise error.SubstrateUnderrunError(
                'No EOO seen before substrate ends'
            )

        return self._createComponent(asn1Spec, tagSet, header, **options), substrate


class NullDecoder(AbstractSimpleDecoder):
    protoComponent = univ.Null('')

    def valueDecoder(self, substrate, asn1Spec,
                     tagSet=None, length=None, state=None,
                     decodeFun=None, substrateFun=None,
                     **options):

        if tagSet[0].tagFormat != tag.tagFormatSimple:
            raise error.PyAsn1Error('Simple tag format expected')

        head, tail = substrate[:length], substrate[length:]

        component = self._createComponent(asn1Spec, tagSet, '', **options)

        if head:
            raise error.PyAsn1Error('Unexpected %d-octet substrate for Null' % length)

        return component, tail


class ObjectIdentifierDecoder(AbstractSimpleDecoder):
    protoComponent = univ.ObjectIdentifier(())

    def valueDecoder(self, substrate, asn1Spec,
                     tagSet=None, length=None, state=None,
                     decodeFun=None, substrateFun=None,
                     **options):
        if tagSet[0].tagFormat != tag.tagFormatSimple:
            raise error.PyAsn1Error('Simple tag format expected')

        head, tail = substrate[:length], substrate[length:]
        if not head:
            raise error.PyAsn1Error('Empty substrate')

        head = octs2ints(head)

        oid = ()
        index = 0
        substrateLen = len(head)
        while index < substrateLen:
            subId = head[index]
            index += 1
            if subId < 128:
                oid += (subId,)
            elif subId > 128:
                # Construct subid from a number of octets
                nextSubId = subId
                subId = 0
                while nextSubId >= 128:
                    subId = (subId << 7) + (nextSubId & 0x7F)
                    if index >= substrateLen:
                        raise error.SubstrateUnderrunError(
                            'Short substrate for sub-OID past %s' % (oid,)
                        )
                    nextSubId = head[index]
                    index += 1
                oid += ((subId << 7) + nextSubId,)
            elif subId == 128:
                # ASN.1 spec forbids leading zeros (0x80) in OID
                # encoding, tolerating it opens a vulnerability. See
                # http://www.cosic.esat.kuleuven.be/publications/article-1432.pdf
                # page 7
                raise error.PyAsn1Error('Invalid octet 0x80 in OID encoding')

        # Decode two leading arcs
        if 0 <= oid[0] <= 39:
            oid = (0,) + oid
        elif 40 <= oid[0] <= 79:
            oid = (1, oid[0] - 40) + oid[1:]
        elif oid[0] >= 80:
            oid = (2, oid[0] - 80) + oid[1:]
        else:
            raise error.PyAsn1Error('Malformed first OID octet: %s' % head[0])

        return self._createComponent(asn1Spec, tagSet, oid, **options), tail


class RealDecoder(AbstractSimpleDecoder):
    protoComponent = univ.Real()

    def valueDecoder(self, substrate, asn1Spec,
                     tagSet=None, length=None, state=None,
                     decodeFun=None, substrateFun=None,
                     **options):
        if tagSet[0].tagFormat != tag.tagFormatSimple:
            raise error.PyAsn1Error('Simple tag format expected')

        head, tail = substrate[:length], substrate[length:]

        if not head:
            return self._createComponent(asn1Spec, tagSet, 0.0, **options), tail

        fo = oct2int(head[0])
        head = head[1:]
        if fo & 0x80:  # binary encoding
            if not head:
                raise error.PyAsn1Error("Incomplete floating-point value")
            n = (fo & 0x03) + 1
            if n == 4:
                n = oct2int(head[0])
                head = head[1:]
            eo, head = head[:n], head[n:]
            if not eo or not head:
                raise error.PyAsn1Error('Real exponent screwed')
            e = oct2int(eo[0]) & 0x80 and -1 or 0
            while eo:  # exponent
                e <<= 8
                e |= oct2int(eo[0])
                eo = eo[1:]
            b = fo >> 4 & 0x03  # base bits
            if b > 2:
                raise error.PyAsn1Error('Illegal Real base')
            if b == 1:  # encbase = 8
                e *= 3
            elif b == 2:  # encbase = 16
                e *= 4
            p = 0
            while head:  # value
                p <<= 8
                p |= oct2int(head[0])
                head = head[1:]
            if fo & 0x40:  # sign bit
                p = -p
            sf = fo >> 2 & 0x03  # scale bits
            p *= 2 ** sf
            value = (p, 2, e)
        elif fo & 0x40:  # infinite value
            value = fo & 0x01 and '-inf' or 'inf'
        elif fo & 0xc0 == 0:  # character encoding
            if not head:
                raise error.PyAsn1Error("Incomplete floating-point value")
            try:
                if fo & 0x3 == 0x1:  # NR1
                    value = (int(head), 10, 0)
                elif fo & 0x3 == 0x2:  # NR2
                    value = float(head)
                elif fo & 0x3 == 0x3:  # NR3
                    value = float(head)
                else:
                    raise error.SubstrateUnderrunError(
                        'Unknown NR (tag %s)' % fo
                    )
            except ValueError:
                raise error.SubstrateUnderrunError(
                    'Bad character Real syntax'
                )
        else:
            raise error.SubstrateUnderrunError(
                'Unknown encoding (tag %s)' % fo
            )
        return self._createComponent(asn1Spec, tagSet, value, **options), tail


class AbstractConstructedDecoder(AbstractDecoder):
    protoComponent = None


class UniversalConstructedTypeDecoder(AbstractConstructedDecoder):
    protoRecordComponent = None
    protoSequenceComponent = None

    def _getComponentTagMap(self, asn1Object, idx):
        raise NotImplementedError()

    def _getComponentPositionByType(self, asn1Object, tagSet, idx):
        raise NotImplementedError()

    def _decodeComponents(self, substrate, tagSet=None, decodeFun=None, **options):
        components = []
        componentTypes = set()
        while substrate:
            component, substrate = decodeFun(substrate, **options)
            if component is eoo.endOfOctets:
                break
            components.append(component)
            componentTypes.add(component.tagSet)

        # Now we have to guess is it SEQUENCE/SET or SEQUENCE OF/SET OF
        # The heuristics is:
        # * 1+ components of different types -> likely SEQUENCE/SET
        # * otherwise -> likely SEQUENCE OF/SET OF
        if len(componentTypes) > 1:
            protoComponent = self.protoRecordComponent
        else:
            protoComponent = self.protoSequenceComponent

        asn1Object = protoComponent.clone(
            # construct tagSet from base tag from prototype ASN.1 object
            # and additional tags recovered from the substrate
            tagSet=tag.TagSet(protoComponent.tagSet.baseTag, *tagSet.superTags)
        )

        for idx, component in enumerate(components):
            asn1Object.setComponentByPosition(
                idx, component,
                verifyConstraints=False,
                matchTags=False, matchConstraints=False
            )

        return asn1Object, substrate

    def valueDecoder(self, substrate, asn1Spec,
                     tagSet=None, length=None, state=None,
                     decodeFun=None, substrateFun=None,
                     **options):
        if tagSet[0].tagFormat != tag.tagFormatConstructed:
            raise error.PyAsn1Error('Constructed tag format expected')

        head, tail = substrate[:length], substrate[length:]

        if substrateFun is not None:
            if asn1Spec is not None:
                asn1Object = asn1Spec.clone()
            elif self.protoComponent is not None:
                asn1Object = self.protoComponent.clone(tagSet=tagSet)
            else:
                asn1Object = self.protoRecordComponent, self.protoSequenceComponent

            return substrateFun(asn1Object, substrate, length)

        if asn1Spec is None:
            asn1Object, trailing = self._decodeComponents(
                head, tagSet=tagSet, decodeFun=decodeFun, **options
            )
            if trailing:
                raise error.PyAsn1Error('Unused trailing %d octets encountered' % len(trailing))
            return asn1Object, tail

        asn1Object = asn1Spec.clone()

        if asn1Spec.typeId in (univ.Sequence.typeId, univ.Set.typeId):

            namedTypes = asn1Spec.componentType

            isSetType = asn1Spec.typeId == univ.Set.typeId
            isDeterministic = not isSetType and not namedTypes.hasOptionalOrDefault

            seenIndices = set()
            idx = 0
            while head:
                if not namedTypes:
                    componentType = None
                elif isSetType:
                    componentType = namedTypes.tagMapUnique
                else:
                    try:
                        if isDeterministic:
                            componentType = namedTypes[idx].asn1Object
                        elif namedTypes[idx].isOptional or namedTypes[idx].isDefaulted:
                            componentType = namedTypes.getTagMapNearPosition(idx)
                        else:
                            componentType = namedTypes[idx].asn1Object
                    except IndexError:
                        raise error.PyAsn1Error(
                            'Excessive components decoded at %r' % (asn1Spec,)
                        )

                component, head = decodeFun(head, componentType, **options)

                if not isDeterministic and namedTypes:
                    if isSetType:
                        idx = namedTypes.getPositionByType(component.effectiveTagSet)
                    elif namedTypes[idx].isOptional or namedTypes[idx].isDefaulted:
                        idx = namedTypes.getPositionNearType(component.effectiveTagSet, idx)

                asn1Object.setComponentByPosition(
                    idx, component,
                    verifyConstraints=False,
                    matchTags=False, matchConstraints=False
                )

                seenIndices.add(idx)
                idx += 1

            if namedTypes:
                if not namedTypes.requiredComponents.issubset(seenIndices):
                    raise error.PyAsn1Error('ASN.1 object %s has uninitialized components' % asn1Object.__class__.__name__)

                if  namedTypes.hasOpenTypes:

                    openTypes = options.get('openTypes', {})

                    if openTypes or options.get('decodeOpenTypes', False):

                        for idx, namedType in enumerate(namedTypes.namedTypes):
                            if not namedType.openType:
                                continue

                            if namedType.isOptional and not asn1Object.getComponentByPosition(idx).isValue:
                                continue

                            governingValue = asn1Object.getComponentByName(
                                namedType.openType.name
                            )

                            try:
                                openType = openTypes[governingValue]

                            except KeyError:

                                try:
                                    openType = namedType.openType[governingValue]

                                except KeyError:
                                    continue

                            component, rest = decodeFun(
                                asn1Object.getComponentByPosition(idx).asOctets(),
                                asn1Spec=openType
                            )

                            asn1Object.setComponentByPosition(idx, component)

            else:
                asn1Object.verifySizeSpec()

        else:
            asn1Object = asn1Spec.clone()

            componentType = asn1Spec.componentType

            idx = 0

            while head:
                component, head = decodeFun(head, componentType, **options)
                asn1Object.setComponentByPosition(
                    idx, component,
                    verifyConstraints=False,
                    matchTags=False, matchConstraints=False
                )
                idx += 1

        return asn1Object, tail

    def indefLenValueDecoder(self, substrate, asn1Spec,
                             tagSet=None, length=None, state=None,
                             decodeFun=None, substrateFun=None,
                             **options):
        if tagSet[0].tagFormat != tag.tagFormatConstructed:
            raise error.PyAsn1Error('Constructed tag format expected')

        if substrateFun is not None:
            if asn1Spec is not None:
                asn1Object = asn1Spec.clone()
            elif self.protoComponent is not None:
                asn1Object = self.protoComponent.clone(tagSet=tagSet)
            else:
                asn1Object = self.protoRecordComponent, self.protoSequenceComponent

            return substrateFun(asn1Object, substrate, length)

        if asn1Spec is None:
            return self._decodeComponents(
                substrate, tagSet=tagSet, decodeFun=decodeFun, allowEoo=True, **options
            )

        asn1Object = asn1Spec.clone()

        if asn1Spec.typeId in (univ.Sequence.typeId, univ.Set.typeId):

            namedTypes = asn1Object.componentType

            isSetType = asn1Object.typeId == univ.Set.typeId
            isDeterministic = not isSetType and not namedTypes.hasOptionalOrDefault

            seenIndices = set()
            idx = 0
            while substrate:
                if len(namedTypes) <= idx:
                    asn1Spec = None
                elif isSetType:
                    asn1Spec = namedTypes.tagMapUnique
                else:
                    try:
                        if isDeterministic:
                            asn1Spec = namedTypes[idx].asn1Object
                        elif namedTypes[idx].isOptional or namedTypes[idx].isDefaulted:
                            asn1Spec = namedTypes.getTagMapNearPosition(idx)
                        else:
                            asn1Spec = namedTypes[idx].asn1Object
                    except IndexError:
                        raise error.PyAsn1Error(
                            'Excessive components decoded at %r' % (asn1Object,)
                        )

                component, substrate = decodeFun(substrate, asn1Spec, allowEoo=True, **options)
                if component is eoo.endOfOctets:
                    break

                if not isDeterministic and namedTypes:
                    if isSetType:
                        idx = namedTypes.getPositionByType(component.effectiveTagSet)
                    elif namedTypes[idx].isOptional or namedTypes[idx].isDefaulted:
                        idx = namedTypes.getPositionNearType(component.effectiveTagSet, idx)

                asn1Object.setComponentByPosition(
                    idx, component,
                    verifyConstraints=False,
                    matchTags=False, matchConstraints=False
                )

                seenIndices.add(idx)
                idx += 1

            else:
                raise error.SubstrateUnderrunError(
                    'No EOO seen before substrate ends'
                )

            if namedTypes:
                if not namedTypes.requiredComponents.issubset(seenIndices):
                    raise error.PyAsn1Error('ASN.1 object %s has uninitialized components' % asn1Object.__class__.__name__)

                if  namedTypes.hasOpenTypes:

                    openTypes = options.get('openTypes', None)

                    if openTypes or options.get('decodeOpenTypes', False):

                        for idx, namedType in enumerate(namedTypes.namedTypes):
                            if not namedType.openType:
                                continue

                            if namedType.isOptional and not asn1Object.getComponentByPosition(idx).isValue:
                                continue

                            governingValue = asn1Object.getComponentByName(
                                namedType.openType.name
                            )

                            try:
                                openType = openTypes[governingValue]

                            except KeyError:

                                try:
                                    openType = namedType.openType[governingValue]

                                except KeyError:
                                    continue

                            component, rest = decodeFun(
                                asn1Object.getComponentByPosition(idx).asOctets(),
                                asn1Spec=openType, allowEoo=True
                            )

                            if component is not eoo.endOfOctets:
                                asn1Object.setComponentByPosition(idx, component)

                else:
                    asn1Object.verifySizeSpec()

        else:
            asn1Object = asn1Spec.clone()

            componentType = asn1Spec.componentType

            idx = 0

            while substrate:
                component, substrate = decodeFun(substrate, componentType, allowEoo=True, **options)

                if component is eoo.endOfOctets:
                    break

                asn1Object.setComponentByPosition(
                    idx, component,
                    verifyConstraints=False,
                    matchTags=False, matchConstraints=False
                )
                idx += 1
            else:
                raise error.SubstrateUnderrunError(
                    'No EOO seen before substrate ends'
                )

        return asn1Object, substrate


class SequenceOrSequenceOfDecoder(UniversalConstructedTypeDecoder):
    protoRecordComponent = univ.Sequence()
    protoSequenceComponent = univ.SequenceOf()


class SequenceDecoder(SequenceOrSequenceOfDecoder):
    protoComponent = univ.Sequence()


class SequenceOfDecoder(SequenceOrSequenceOfDecoder):
    protoComponent = univ.SequenceOf()


class SetOrSetOfDecoder(UniversalConstructedTypeDecoder):
    protoRecordComponent = univ.Set()
    protoSequenceComponent = univ.SetOf()


class SetDecoder(SetOrSetOfDecoder):
    protoComponent = univ.Set()



class SetOfDecoder(SetOrSetOfDecoder):
    protoComponent = univ.SetOf()


class ChoiceDecoder(AbstractConstructedDecoder):
    protoComponent = univ.Choice()

    def valueDecoder(self, substrate, asn1Spec,
                     tagSet=None, length=None, state=None,
                     decodeFun=None, substrateFun=None,
                     **options):
        head, tail = substrate[:length], substrate[length:]

        if asn1Spec is None:
            asn1Object = self.protoComponent.clone(tagSet=tagSet)
        else:
            asn1Object = asn1Spec.clone()

        if substrateFun:
            return substrateFun(asn1Object, substrate, length)

        if asn1Object.tagSet == tagSet:  # explicitly tagged Choice
            component, head = decodeFun(
                head, asn1Object.componentTagMap, **options
            )

        else:
            component, head = decodeFun(
                head, asn1Object.componentTagMap,
                tagSet, length, state, **options
            )

        effectiveTagSet = component.effectiveTagSet

        asn1Object.setComponentByType(
            effectiveTagSet, component,
            verifyConstraints=False,
            matchTags=False, matchConstraints=False,
            innerFlag=False
        )

        return asn1Object, tail

    def indefLenValueDecoder(self, substrate, asn1Spec,
                             tagSet=None, length=None, state=None,
                             decodeFun=None, substrateFun=None,
                             **options):
        if asn1Spec is None:
            asn1Object = self.protoComponent.clone(tagSet=tagSet)
        else:
            asn1Object = asn1Spec.clone()

        if substrateFun:
            return substrateFun(asn1Object, substrate, length)

        if asn1Object.tagSet == tagSet:  # explicitly tagged Choice
            component, substrate = decodeFun(
                substrate, asn1Object.componentType.tagMapUnique, **options
            )
            # eat up EOO marker
            eooMarker, substrate = decodeFun(
                substrate, allowEoo=True, **options
            )
            if eooMarker is not eoo.endOfOctets:
                raise error.PyAsn1Error('No EOO seen before substrate ends')

        else:
            component, substrate = decodeFun(
                substrate, asn1Object.componentType.tagMapUnique,
                tagSet, length, state, **options
            )

        effectiveTagSet = component.effectiveTagSet

        asn1Object.setComponentByType(
            effectiveTagSet, component,
            verifyConstraints=False,
            matchTags=False, matchConstraints=False,
            innerFlag=False
        )

        return asn1Object, substrate


class AnyDecoder(AbstractSimpleDecoder):
    protoComponent = univ.Any()

    def valueDecoder(self, substrate, asn1Spec,
                     tagSet=None, length=None, state=None,
                     decodeFun=None, substrateFun=None,
                     **options):
        if asn1Spec is None or asn1Spec is not None and tagSet != asn1Spec.tagSet:
            fullSubstrate = options['fullSubstrate']

            # untagged Any container, recover inner header substrate
            length += len(fullSubstrate) - len(substrate)
            substrate = fullSubstrate

        if substrateFun:
            return substrateFun(self._createComponent(asn1Spec, tagSet, noValue, **options),
                                substrate, length)

        head, tail = substrate[:length], substrate[length:]

        return self._createComponent(asn1Spec, tagSet, head, **options), tail

    def indefLenValueDecoder(self, substrate, asn1Spec,
                             tagSet=None, length=None, state=None,
                             decodeFun=None, substrateFun=None,
                             **options):
        if asn1Spec is not None and tagSet == asn1Spec.tagSet:
            # tagged Any type -- consume header substrate
            header = null
        else:
            fullSubstrate = options['fullSubstrate']

            # untagged Any, recover header substrate
            header = fullSubstrate[:-len(substrate)]

        # Any components do not inherit initial tag
        asn1Spec = self.protoComponent

        if substrateFun and substrateFun is not self.substrateCollector:
            asn1Object = self._createComponent(asn1Spec, tagSet, noValue, **options)
            return substrateFun(asn1Object, header + substrate, length + len(header))

        # All inner fragments are of the same type, treat them as octet string
        substrateFun = self.substrateCollector

        while substrate:
            component, substrate = decodeFun(substrate, asn1Spec,
                                             substrateFun=substrateFun,
                                             allowEoo=True, **options)
            if component is eoo.endOfOctets:
                break
            header += component
        else:
            raise error.SubstrateUnderrunError(
                'No EOO seen before substrate ends'
            )
        if substrateFun:
            return header, substrate
        else:
            return self._createComponent(asn1Spec, tagSet, header, **options), substrate


# character string types
class UTF8StringDecoder(OctetStringDecoder):
    protoComponent = char.UTF8String()


class NumericStringDecoder(OctetStringDecoder):
    protoComponent = char.NumericString()


class PrintableStringDecoder(OctetStringDecoder):
    protoComponent = char.PrintableString()


class TeletexStringDecoder(OctetStringDecoder):
    protoComponent = char.TeletexString()


class VideotexStringDecoder(OctetStringDecoder):
    protoComponent = char.VideotexString()


class IA5StringDecoder(OctetStringDecoder):
    protoComponent = char.IA5String()


class GraphicStringDecoder(OctetStringDecoder):
    protoComponent = char.GraphicString()


class VisibleStringDecoder(OctetStringDecoder):
    protoComponent = char.VisibleString()


class GeneralStringDecoder(OctetStringDecoder):
    protoComponent = char.GeneralString()


class UniversalStringDecoder(OctetStringDecoder):
    protoComponent = char.UniversalString()


class BMPStringDecoder(OctetStringDecoder):
    protoComponent = char.BMPString()


# "useful" types
class ObjectDescriptorDecoder(OctetStringDecoder):
    protoComponent = useful.ObjectDescriptor()


class GeneralizedTimeDecoder(OctetStringDecoder):
    protoComponent = useful.GeneralizedTime()


class UTCTimeDecoder(OctetStringDecoder):
    protoComponent = useful.UTCTime()


tagMap = {
    univ.Integer.tagSet: IntegerDecoder(),
    univ.Boolean.tagSet: BooleanDecoder(),
    univ.BitString.tagSet: BitStringDecoder(),
    univ.OctetString.tagSet: OctetStringDecoder(),
    univ.Null.tagSet: NullDecoder(),
    univ.ObjectIdentifier.tagSet: ObjectIdentifierDecoder(),
    univ.Enumerated.tagSet: IntegerDecoder(),
    univ.Real.tagSet: RealDecoder(),
    univ.Sequence.tagSet: SequenceOrSequenceOfDecoder(),  # conflicts with SequenceOf
    univ.Set.tagSet: SetOrSetOfDecoder(),  # conflicts with SetOf
    univ.Choice.tagSet: ChoiceDecoder(),  # conflicts with Any
    # character string types
    char.UTF8String.tagSet: UTF8StringDecoder(),
    char.NumericString.tagSet: NumericStringDecoder(),
    char.PrintableString.tagSet: PrintableStringDecoder(),
    char.TeletexString.tagSet: TeletexStringDecoder(),
    char.VideotexString.tagSet: VideotexStringDecoder(),
    char.IA5String.tagSet: IA5StringDecoder(),
    char.GraphicString.tagSet: GraphicStringDecoder(),
    char.VisibleString.tagSet: VisibleStringDecoder(),
    char.GeneralString.tagSet: GeneralStringDecoder(),
    char.UniversalString.tagSet: UniversalStringDecoder(),
    char.BMPString.tagSet: BMPStringDecoder(),
    # useful types
    useful.ObjectDescriptor.tagSet: ObjectDescriptorDecoder(),
    useful.GeneralizedTime.tagSet: GeneralizedTimeDecoder(),
    useful.UTCTime.tagSet: UTCTimeDecoder()
}

# Type-to-codec map for ambiguous ASN.1 types
typeMap = {
    univ.Set.typeId: SetDecoder(),
    univ.SetOf.typeId: SetOfDecoder(),
    univ.Sequence.typeId: SequenceDecoder(),
    univ.SequenceOf.typeId: SequenceOfDecoder(),
    univ.Choice.typeId: ChoiceDecoder(),
    univ.Any.typeId: AnyDecoder()
}

# Put in non-ambiguous types for faster codec lookup
for typeDecoder in tagMap.values():
    if typeDecoder.protoComponent is not None:
        typeId = typeDecoder.protoComponent.__class__.typeId
        if typeId is not None and typeId not in typeMap:
            typeMap[typeId] = typeDecoder


(stDecodeTag,
 stDecodeLength,
 stGetValueDecoder,
 stGetValueDecoderByAsn1Spec,
 stGetValueDecoderByTag,
 stTryAsExplicitTag,
 stDecodeValue,
 stDumpRawValue,
 stErrorCondition,
 stStop) = [x for x in range(10)]


class Decoder(object):
    defaultErrorState = stErrorCondition
    #    defaultErrorState = stDumpRawValue
    defaultRawDecoder = AnyDecoder()
    supportIndefLength = True

    # noinspection PyDefaultArgument
    def __init__(self, tagMap, typeMap={}):
        self.__tagMap = tagMap
        self.__typeMap = typeMap
        # Tag & TagSet objects caches
        self.__tagCache = {}
        self.__tagSetCache = {}
        self.__eooSentinel = ints2octs((0, 0))

    def __call__(self, substrate, asn1Spec=None,
                 tagSet=None, length=None, state=stDecodeTag,
                 decodeFun=None, substrateFun=None,
                 **options):

        if debug.logger & debug.flagDecoder:
            logger = debug.logger
        else:
            logger = None

        if logger:
            logger('decoder called at scope %s with state %d, working with up to %d octets of substrate: %s' % (debug.scope, state, len(substrate), debug.hexdump(substrate)))

        allowEoo = options.pop('allowEoo', False)

        # Look for end-of-octets sentinel
        if allowEoo and self.supportIndefLength:
            if substrate[:2] == self.__eooSentinel:
                if logger:
                    logger('end-of-octets sentinel found')
                return eoo.endOfOctets, substrate[2:]

        value = noValue

        tagMap = self.__tagMap
        typeMap = self.__typeMap
        tagCache = self.__tagCache
        tagSetCache = self.__tagSetCache

        fullSubstrate = substrate

        while state is not stStop:
            if state is stDecodeTag:
                if not substrate:
                    raise error.SubstrateUnderrunError(
                        'Short octet stream on tag decoding'
                    )
                # Decode tag
                isShortTag = True
                firstOctet = substrate[0]
                substrate = substrate[1:]
                try:
                    lastTag = tagCache[firstOctet]
                except KeyError:
                    integerTag = oct2int(firstOctet)
                    tagClass = integerTag & 0xC0
                    tagFormat = integerTag & 0x20
                    tagId = integerTag & 0x1F
                    if tagId == 0x1F:
                        isShortTag = False
                        lengthOctetIdx = 0
                        tagId = 0
                        try:
                            while True:
                                integerTag = oct2int(substrate[lengthOctetIdx])
                                lengthOctetIdx += 1
                                tagId <<= 7
                                tagId |= (integerTag & 0x7F)
                                if not integerTag & 0x80:
                                    break
                            substrate = substrate[lengthOctetIdx:]
                        except IndexError:
                            raise error.SubstrateUnderrunError(
                                'Short octet stream on long tag decoding'
                            )
                    lastTag = tag.Tag(
                        tagClass=tagClass, tagFormat=tagFormat, tagId=tagId
                    )
                    if isShortTag:
                        # cache short tags
                        tagCache[firstOctet] = lastTag
                if tagSet is None:
                    if isShortTag:
                        try:
                            tagSet = tagSetCache[firstOctet]
                        except KeyError:
                            # base tag not recovered
                            tagSet = tag.TagSet((), lastTag)
                            tagSetCache[firstOctet] = tagSet
                    else:
                        tagSet = tag.TagSet((), lastTag)
                else:
                    tagSet = lastTag + tagSet
                state = stDecodeLength
                if logger:
                    logger('tag decoded into %s, decoding length' % tagSet)
            if state is stDecodeLength:
                # Decode length
                if not substrate:
                    raise error.SubstrateUnderrunError(
                        'Short octet stream on length decoding'
                    )
                firstOctet = oct2int(substrate[0])
                if firstOctet < 128:
                    size = 1
                    length = firstOctet
                elif firstOctet > 128:
                    size = firstOctet & 0x7F
                    # encoded in size bytes
                    encodedLength = octs2ints(substrate[1:size + 1])
                    # missing check on maximum size, which shouldn't be a
                    # problem, we can handle more than is possible
                    if len(encodedLength) != size:
                        raise error.SubstrateUnderrunError(
                            '%s<%s at %s' % (size, len(encodedLength), tagSet)
                        )
                    length = 0
                    for lengthOctet in encodedLength:
                        length <<= 8
                        length |= lengthOctet
                    size += 1
                else:
                    size = 1
                    length = -1

                substrate = substrate[size:]
                if length == -1:
                    if not self.supportIndefLength:
                        raise error.PyAsn1Error('Indefinite length encoding not supported by this codec')
                else:
                    if len(substrate) < length:
                        raise error.SubstrateUnderrunError('%d-octet short' % (length - len(substrate)))
                state = stGetValueDecoder
                if logger:
                    logger('value length decoded into %d, payload substrate is: %s' % (length, debug.hexdump(length == -1 and substrate or substrate[:length])))
            if state is stGetValueDecoder:
                if asn1Spec is None:
                    state = stGetValueDecoderByTag
                else:
                    state = stGetValueDecoderByAsn1Spec
            #
            # There're two ways of creating subtypes in ASN.1 what influences
            # decoder operation. These methods are:
            # 1) Either base types used in or no IMPLICIT tagging has been
            #    applied on subtyping.
            # 2) Subtype syntax drops base type information (by means of
            #    IMPLICIT tagging.
            # The first case allows for complete tag recovery from substrate
            # while the second one requires original ASN.1 type spec for
            # decoding.
            #
            # In either case a set of tags (tagSet) is coming from substrate
            # in an incremental, tag-by-tag fashion (this is the case of
            # EXPLICIT tag which is most basic). Outermost tag comes first
            # from the wire.
            #
            if state is stGetValueDecoderByTag:
                try:
                    concreteDecoder = tagMap[tagSet]
                except KeyError:
                    concreteDecoder = None
                if concreteDecoder:
                    state = stDecodeValue
                else:
                    try:
                        concreteDecoder = tagMap[tagSet[:1]]
                    except KeyError:
                        concreteDecoder = None
                    if concreteDecoder:
                        state = stDecodeValue
                    else:
                        state = stTryAsExplicitTag
                if logger:
                    logger('codec %s chosen by a built-in type, decoding %s' % (concreteDecoder and concreteDecoder.__class__.__name__ or "<none>", state is stDecodeValue and 'value' or 'as explicit tag'))
                    debug.scope.push(concreteDecoder is None and '?' or concreteDecoder.protoComponent.__class__.__name__)
            if state is stGetValueDecoderByAsn1Spec:
                if asn1Spec.__class__ is tagmap.TagMap:
                    try:
                        chosenSpec = asn1Spec[tagSet]
                    except KeyError:
                        chosenSpec = None
                    if logger:
                        logger('candidate ASN.1 spec is a map of:')
                        for firstOctet, v in asn1Spec.presentTypes.items():
                            logger('  %s -> %s' % (firstOctet, v.__class__.__name__))
                        if asn1Spec.skipTypes:
                            logger('but neither of: ')
                            for firstOctet, v in asn1Spec.skipTypes.items():
                                logger('  %s -> %s' % (firstOctet, v.__class__.__name__))
                        logger('new candidate ASN.1 spec is %s, chosen by %s' % (chosenSpec is None and '<none>' or chosenSpec.prettyPrintType(), tagSet))
                elif tagSet == asn1Spec.tagSet or tagSet in asn1Spec.tagMap:
                    chosenSpec = asn1Spec
                    if logger:
                        logger('candidate ASN.1 spec is %s' % asn1Spec.__class__.__name__)
                else:
                    chosenSpec = None

                if chosenSpec is not None:
                    try:
                        # ambiguous type or just faster codec lookup
                        concreteDecoder = typeMap[chosenSpec.typeId]
                        if logger:
                            logger('value decoder chosen for an ambiguous type by type ID %s' % (chosenSpec.typeId,))
                    except KeyError:
                        # use base type for codec lookup to recover untagged types
                        baseTagSet = tag.TagSet(chosenSpec.tagSet.baseTag,  chosenSpec.tagSet.baseTag)
                        try:
                            # base type or tagged subtype
                            concreteDecoder = tagMap[baseTagSet]
                            if logger:
                                logger('value decoder chosen by base %s' % (baseTagSet,))
                        except KeyError:
                            concreteDecoder = None
                    if concreteDecoder:
                        asn1Spec = chosenSpec
                        state = stDecodeValue
                    else:
                        state = stTryAsExplicitTag
                else:
                    concreteDecoder = None
                    state = stTryAsExplicitTag
                if logger:
                    logger('codec %s chosen by ASN.1 spec, decoding %s' % (state is stDecodeValue and concreteDecoder.__class__.__name__ or "<none>", state is stDecodeValue and 'value' or 'as explicit tag'))
                    debug.scope.push(chosenSpec is None and '?' or chosenSpec.__class__.__name__)
            if state is stDecodeValue:
                if not options.get('recursiveFlag', True) and not substrateFun:  # deprecate this
                    substrateFun = lambda a, b, c: (a, b[:c])

                options.update(fullSubstrate=fullSubstrate)

                if length == -1:  # indef length
                    value, substrate = concreteDecoder.indefLenValueDecoder(
                        substrate, asn1Spec,
                        tagSet, length, stGetValueDecoder,
                        self, substrateFun,
                        **options
                    )
                else:
                    value, substrate = concreteDecoder.valueDecoder(
                        substrate, asn1Spec,
                        tagSet, length, stGetValueDecoder,
                        self, substrateFun,
                        **options
                    )

                if logger:
                    logger('codec %s yields type %s, value:\n%s\n...remaining substrate is: %s' % (concreteDecoder.__class__.__name__, value.__class__.__name__, isinstance(value, base.Asn1Item) and value.prettyPrint() or value, substrate and debug.hexdump(substrate) or '<none>'))

                state = stStop
                break
            if state is stTryAsExplicitTag:
                if tagSet and tagSet[0].tagFormat == tag.tagFormatConstructed and tagSet[0].tagClass != tag.tagClassUniversal:
                    # Assume explicit tagging
                    concreteDecoder = explicitTagDecoder
                    state = stDecodeValue
                else:
                    concreteDecoder = None
                    state = self.defaultErrorState
                if logger:
                    logger('codec %s chosen, decoding %s' % (concreteDecoder and concreteDecoder.__class__.__name__ or "<none>", state is stDecodeValue and 'value' or 'as failure'))
            if state is stDumpRawValue:
                concreteDecoder = self.defaultRawDecoder
                if logger:
                    logger('codec %s chosen, decoding value' % concreteDecoder.__class__.__name__)
                state = stDecodeValue
            if state is stErrorCondition:
                raise error.PyAsn1Error(
                    '%s not in asn1Spec: %r' % (tagSet, asn1Spec)
                )
        if logger:
            debug.scope.pop()
            logger('decoder left scope %s, call completed' % debug.scope)
        return value, substrate


#: Turns BER octet stream into an ASN.1 object.
#:
#: Takes BER octet-stream and decode it into an ASN.1 object
#: (e.g. :py:class:`~pyasn1.type.base.PyAsn1Item` derivative) which
#: may be a scalar or an arbitrary nested structure.
#:
#: Parameters
#: ----------
#: substrate: :py:class:`bytes` (Python 3) or :py:class:`str` (Python 2)
#:     BER octet-stream
#:
#: Keyword Args
#: ------------
#: asn1Spec: any pyasn1 type object e.g. :py:class:`~pyasn1.type.base.PyAsn1Item` derivative
#:     A pyasn1 type object to act as a template guiding the decoder. Depending on the ASN.1 structure
#:     being decoded, *asn1Spec* may or may not be required. Most common reason for
#:     it to require is that ASN.1 structure is encoded in *IMPLICIT* tagging mode.
#:
#: Returns
#: -------
#: : :py:class:`tuple`
#:     A tuple of pyasn1 object recovered from BER substrate (:py:class:`~pyasn1.type.base.PyAsn1Item` derivative)
#:     and the unprocessed trailing portion of the *substrate* (may be empty)
#:
#: Raises
#: ------
#: :py:class:`~pyasn1.error.PyAsn1Error`
#:     On decoding errors
#:
#: Examples
#: --------
#: Decode BER serialisation without ASN.1 schema
#:
#: .. code-block:: pycon
#:
#:    >>> s, _ = decode(b'0\t\x02\x01\x01\x02\x01\x02\x02\x01\x03')
#:    >>> str(s)
#:    SequenceOf:
#:     1 2 3
#:
#: Decode BER serialisation with ASN.1 schema
#:
#: .. code-block:: pycon
#:
#:    >>> seq = SequenceOf(componentType=Integer())
#:    >>> s, _ = decode(b'0\t\x02\x01\x01\x02\x01\x02\x02\x01\x03', asn1Spec=seq)
#:    >>> str(s)
#:    SequenceOf:
#:     1 2 3
#:
decode = Decoder(tagMap, typeMap)

# XXX
# non-recursive decoding; return position rather than substrate
