#
# This file is part of pysnmp software.
#
# Copyright (c) 2005-2020, Ilya Etingof <etingof@gmail.com>
# License: https://www.pysnmp.com/pysnmp/license.html
#
import sys
from pysnmp.proto import rfc1902, rfc1905, rfc3411, errind, error
from pysnmp.proto.api import v2c  # backend is always SMIv2 compliant
from pysnmp.proto.proxy import rfc2576
import pysnmp.smi.error
from pysnmp import debug


# 3.2
class CommandResponderBase:
    acmID = 3  # default MIB access control method to use
    pduTypes = ()

    smiToSnmpErrorMap = {
        pysnmp.smi.error.TooBigError: "tooBig",
        pysnmp.smi.error.NoSuchNameError: "noSuchName",
        pysnmp.smi.error.BadValueError: "badValue",
        pysnmp.smi.error.ReadOnlyError: "readOnly",
        pysnmp.smi.error.GenError: "genErr",
        pysnmp.smi.error.NoAccessError: "noAccess",
        pysnmp.smi.error.WrongTypeError: "wrongType",
        pysnmp.smi.error.WrongLengthError: "wrongLength",
        pysnmp.smi.error.WrongEncodingError: "wrongEncoding",
        pysnmp.smi.error.WrongValueError: "wrongValue",
        pysnmp.smi.error.NoCreationError: "noCreation",
        pysnmp.smi.error.InconsistentValueError: "inconsistentValue",
        pysnmp.smi.error.ResourceUnavailableError: "resourceUnavailable",
        pysnmp.smi.error.CommitFailedError: "commitFailed",
        pysnmp.smi.error.UndoFailedError: "undoFailed",
        pysnmp.smi.error.AuthorizationError: "authorizationError",
        pysnmp.smi.error.NotWritableError: "notWritable",
        pysnmp.smi.error.InconsistentNameError: "inconsistentName",
    }

    def __init__(self, snmpEngine, snmpContext):
        snmpEngine.msgAndPduDsp.registerContextEngineId(
            snmpContext.contextEngineId, self.pduTypes, self.processPdu
        )
        self.snmpContext = snmpContext
        self.__pendingReqs = {}

    def handleMgmtOperation(self, snmpEngine, stateReference, contextName, PDU, acInfo):
        pass

    def close(self, snmpEngine):
        snmpEngine.msgAndPduDsp.unregisterContextEngineId(
            self.snmpContext.contextEngineId, self.pduTypes
        )
        self.snmpContext = self.__pendingReqs = None

    def sendVarBinds(
        self, snmpEngine, stateReference, errorStatus, errorIndex, varBinds
    ):
        (
            messageProcessingModel,
            securityModel,
            securityName,
            securityLevel,
            contextEngineId,
            contextName,
            pduVersion,
            PDU,
            origPdu,
            maxSizeResponseScopedPDU,
            statusInformation,
        ) = self.__pendingReqs[stateReference]

        v2c.apiPDU.setErrorStatus(PDU, errorStatus)
        v2c.apiPDU.setErrorIndex(PDU, errorIndex)
        v2c.apiPDU.setVarBinds(PDU, varBinds)

        debug.logger & debug.flagApp and debug.logger(
            "sendVarBinds: stateReference {}, errorStatus {}, errorIndex {}, varBinds {}".format(
                stateReference, errorStatus, errorIndex, varBinds
            )
        )

        self.sendPdu(snmpEngine, stateReference, PDU)

    # backward compatibility
    sendRsp = sendVarBinds

    def sendPdu(self, snmpEngine, stateReference, PDU):
        (
            messageProcessingModel,
            securityModel,
            securityName,
            securityLevel,
            contextEngineId,
            contextName,
            pduVersion,
            _,
            origPdu,
            maxSizeResponseScopedPDU,
            statusInformation,
        ) = self.__pendingReqs[stateReference]

        # Agent-side API complies with SMIv2
        if messageProcessingModel == 0:
            PDU = rfc2576.v2ToV1(PDU, origPdu)

        # 3.2.6
        try:
            snmpEngine.msgAndPduDsp.returnResponsePdu(
                snmpEngine,
                messageProcessingModel,
                securityModel,
                securityName,
                securityLevel,
                contextEngineId,
                contextName,
                pduVersion,
                PDU,
                maxSizeResponseScopedPDU,
                stateReference,
                statusInformation,
            )

        except error.StatusInformation:
            debug.logger & debug.flagApp and debug.logger(
                f"sendPdu: stateReference {stateReference}, statusInformation {sys.exc_info()[1]}"
            )
            (
                snmpSilentDrops,
            ) = snmpEngine.msgAndPduDsp.mibInstrumController.mibBuilder.importSymbols(
                "__SNMPv2-MIB", "snmpSilentDrops"
            )
            snmpSilentDrops.syntax += 1

    _getRequestType = rfc1905.GetRequestPDU.tagSet
    _getNextRequestType = rfc1905.GetNextRequestPDU.tagSet
    _setRequestType = rfc1905.SetRequestPDU.tagSet
    _counter64Type = rfc1902.Counter64.tagSet

    def releaseStateInformation(self, stateReference):
        if stateReference in self.__pendingReqs:
            del self.__pendingReqs[stateReference]

    def processPdu(
        self,
        snmpEngine,
        messageProcessingModel,
        securityModel,
        securityName,
        securityLevel,
        contextEngineId,
        contextName,
        pduVersion,
        PDU,
        maxSizeResponseScopedPDU,
        stateReference,
    ):
        # Agent-side API complies with SMIv2
        if messageProcessingModel == 0:
            origPdu = PDU
            PDU = rfc2576.v1ToV2(PDU)
        else:
            origPdu = None

        # 3.2.1
        if (
            PDU.tagSet not in rfc3411.readClassPDUs
            and PDU.tagSet not in rfc3411.writeClassPDUs
        ):
            raise error.ProtocolError("Unexpected PDU class %s" % PDU.tagSet)

        # 3.2.2 --> no-op

        # 3.2.4
        rspPDU = v2c.apiPDU.getResponse(PDU)

        statusInformation = {}

        self.__pendingReqs[stateReference] = (
            messageProcessingModel,
            securityModel,
            securityName,
            securityLevel,
            contextEngineId,
            contextName,
            pduVersion,
            rspPDU,
            origPdu,
            maxSizeResponseScopedPDU,
            statusInformation,
        )

        # 3.2.5
        varBinds = v2c.apiPDU.getVarBinds(PDU)

        debug.logger & debug.flagApp and debug.logger(
            f"processPdu: stateReference {stateReference}, varBinds {varBinds}"
        )

        try:
            self.handleMgmtOperation(
                snmpEngine,
                stateReference,
                contextName,
                PDU,
                (self.__verifyAccess, snmpEngine),
            )

            return

        # SNMPv2 SMI exceptions
        except pysnmp.smi.error.SmiError:
            errorIndication = sys.exc_info()[1]

            debug.logger & debug.flagApp and debug.logger(
                f"processPdu: stateReference {stateReference}, errorIndication {errorIndication}"
            )
            if "oid" in errorIndication:
                # Request REPORT generation
                statusInformation["oid"] = errorIndication["oid"]
                statusInformation["val"] = errorIndication["val"]

            errorStatus = self.smiToSnmpErrorMap.get(
                errorIndication.__class__, "genErr"
            )

            try:
                errorIndex = errorIndication["idx"] + 1

            except KeyError:
                errorIndex = 1

            if len(varBinds) > errorIndex:
                errorIndex = 1

            # rfc1905: 4.2.1.3
            if errorStatus == "tooBig":
                errorIndex = 0
                varBinds = []

            # Report error
            self.sendVarBinds(
                snmpEngine, stateReference, errorStatus, errorIndex, varBinds
            )

        except pysnmp.error.PySnmpError:
            debug.logger & debug.flagApp and debug.logger(
                "processPdu: stateReference %s, error "
                "%s" % (stateReference, sys.exc_info()[1])
            )

        self.releaseStateInformation(stateReference)

    def __verifyAccess(self, name, syntax, idx, viewType, acCtx):
        snmpEngine = acCtx
        execCtx = snmpEngine.observer.getExecutionContext(
            "rfc3412.receiveMessage:request"
        )
        (securityModel, securityName, securityLevel, contextName, pduType) = (
            execCtx["securityModel"],
            execCtx["securityName"],
            execCtx["securityLevel"],
            execCtx["contextName"],
            execCtx["pdu"].getTagSet(),
        )
        try:
            snmpEngine.accessControlModel[self.acmID].isAccessAllowed(
                snmpEngine,
                securityModel,
                securityName,
                securityLevel,
                viewType,
                contextName,
                name,
            )
        # Map ACM errors onto SMI ones
        except error.StatusInformation:
            statusInformation = sys.exc_info()[1]
            debug.logger & debug.flagApp and debug.logger(
                f"__verifyAccess: name {name}, statusInformation {statusInformation}"
            )
            errorIndication = statusInformation["errorIndication"]
            # 3.2.5...
            if (
                errorIndication == errind.noSuchView
                or errorIndication == errind.noAccessEntry
                or errorIndication == errind.noGroupName
            ):
                raise pysnmp.smi.error.AuthorizationError(name=name, idx=idx)
            elif errorIndication == errind.otherError:
                raise pysnmp.smi.error.GenError(name=name, idx=idx)
            elif errorIndication == errind.noSuchContext:
                (
                    snmpUnknownContexts,
                ) = snmpEngine.msgAndPduDsp.mibInstrumController.mibBuilder.importSymbols(
                    "__SNMP-TARGET-MIB", "snmpUnknownContexts"
                )
                snmpUnknownContexts.syntax += 1
                # Request REPORT generation
                raise pysnmp.smi.error.GenError(
                    name=name,
                    idx=idx,
                    oid=snmpUnknownContexts.name,
                    val=snmpUnknownContexts.syntax,
                )
            elif errorIndication == errind.notInView:
                return 1
            else:
                raise error.ProtocolError("Unknown ACM error %s" % errorIndication)
        else:
            # rfc2576: 4.1.2.1
            if (
                securityModel == 1
                and syntax is not None
                and self._counter64Type == syntax.getTagSet()
                and self._getNextRequestType == pduType
            ):
                # This will cause MibTree to skip this OID-value
                raise pysnmp.smi.error.NoAccessError(name=name, idx=idx)


class GetCommandResponder(CommandResponderBase):
    pduTypes = (rfc1905.GetRequestPDU.tagSet,)

    # rfc1905: 4.2.1
    def handleMgmtOperation(self, snmpEngine, stateReference, contextName, PDU, acInfo):
        (acFun, acCtx) = acInfo
        # rfc1905: 4.2.1.1
        mgmtFun = self.snmpContext.getMibInstrum(contextName).readVars
        self.sendVarBinds(
            snmpEngine,
            stateReference,
            0,
            0,
            mgmtFun(v2c.apiPDU.getVarBinds(PDU), (acFun, acCtx)),
        )
        self.releaseStateInformation(stateReference)


class NextCommandResponder(CommandResponderBase):
    pduTypes = (rfc1905.GetNextRequestPDU.tagSet,)

    # rfc1905: 4.2.2
    def handleMgmtOperation(self, snmpEngine, stateReference, contextName, PDU, acInfo):
        (acFun, acCtx) = acInfo
        # rfc1905: 4.2.2.1
        mgmtFun = self.snmpContext.getMibInstrum(contextName).readNextVars
        varBinds = v2c.apiPDU.getVarBinds(PDU)
        while True:
            rspVarBinds = mgmtFun(varBinds, (acFun, acCtx))
            try:
                self.sendVarBinds(snmpEngine, stateReference, 0, 0, rspVarBinds)
            except error.StatusInformation:
                idx = sys.exc_info()[1]["idx"]
                varBinds[idx] = (rspVarBinds[idx][0], varBinds[idx][1])
            else:
                break
        self.releaseStateInformation(stateReference)


class BulkCommandResponder(CommandResponderBase):
    pduTypes = (rfc1905.GetBulkRequestPDU.tagSet,)
    maxVarBinds = 64

    # rfc1905: 4.2.3
    def handleMgmtOperation(self, snmpEngine, stateReference, contextName, PDU, acInfo):
        (acFun, acCtx) = acInfo
        nonRepeaters = v2c.apiBulkPDU.getNonRepeaters(PDU)
        if nonRepeaters < 0:
            nonRepeaters = 0
        maxRepetitions = v2c.apiBulkPDU.getMaxRepetitions(PDU)
        if maxRepetitions < 0:
            maxRepetitions = 0

        reqVarBinds = v2c.apiPDU.getVarBinds(PDU)

        N = min(int(nonRepeaters), len(reqVarBinds))
        M = int(maxRepetitions)
        R = max(len(reqVarBinds) - N, 0)

        if R:
            M = min(M, self.maxVarBinds // R)

        debug.logger & debug.flagApp and debug.logger(
            "handleMgmtOperation: N %d, M %d, R %d" % (N, M, R)
        )

        mgmtFun = self.snmpContext.getMibInstrum(contextName).readNextVars

        if N:
            rspVarBinds = mgmtFun(reqVarBinds[:N], (acFun, acCtx))
        else:
            rspVarBinds = []

        varBinds = reqVarBinds[-R:]
        while M and R:
            rspVarBinds.extend(mgmtFun(varBinds, (acFun, acCtx)))
            varBinds = rspVarBinds[-R:]
            M -= 1

        if len(rspVarBinds):
            self.sendVarBinds(snmpEngine, stateReference, 0, 0, rspVarBinds)
            self.releaseStateInformation(stateReference)
        else:
            raise pysnmp.smi.error.SmiError()


class SetCommandResponder(CommandResponderBase):
    pduTypes = (rfc1905.SetRequestPDU.tagSet,)

    # rfc1905: 4.2.5
    def handleMgmtOperation(self, snmpEngine, stateReference, contextName, PDU, acInfo):
        (acFun, acCtx) = acInfo
        mgmtFun = self.snmpContext.getMibInstrum(contextName).writeVars
        # rfc1905: 4.2.5.1-13
        try:
            self.sendVarBinds(
                snmpEngine,
                stateReference,
                0,
                0,
                mgmtFun(v2c.apiPDU.getVarBinds(PDU), (acFun, acCtx)),
            )
            self.releaseStateInformation(stateReference)
        except (
            pysnmp.smi.error.NoSuchObjectError,
            pysnmp.smi.error.NoSuchInstanceError,
        ):
            e = pysnmp.smi.error.NotWritableError()
            e.update(sys.exc_info()[1])
            raise e