// Copyright (C) 2014-2016 Internet Systems Consortium, Inc. ("ISC")
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

#include <config.h>
#include <dhcp/iface_mgr.h>
#include <dhcpsrv/cfg_subnets4.h>
#include <dhcpsrv/dhcpsrv_log.h>
#include <dhcpsrv/subnet_id.h>
#include <dhcpsrv/addr_utilities.h>
#include <asiolink/io_address.h>
#include <stats/stats_mgr.h>

using namespace isc::asiolink;

namespace isc {
namespace dhcp {

void
CfgSubnets4::add(const Subnet4Ptr& subnet) {
    /// @todo: Check that this new subnet does not cross boundaries of any
    /// other already defined subnet.
    if (isDuplicate(*subnet)) {
        isc_throw(isc::dhcp::DuplicateSubnetID, "ID of the new IPv4 subnet '"
                  << subnet->getID() << "' is already in use");
    }
    LOG_DEBUG(dhcpsrv_logger, DHCPSRV_DBG_TRACE, DHCPSRV_CFGMGR_ADD_SUBNET4)
              .arg(subnet->toText());
    subnets_.push_back(subnet);
}

Subnet4Ptr
CfgSubnets4::selectSubnet4o6(const SubnetSelector& selector) const {

    for (Subnet4Collection::const_iterator subnet = subnets_.begin();
         subnet != subnets_.end(); ++subnet) {
        Cfg4o6& cfg4o6 = (*subnet)->get4o6();

        // Is this an 4o6 subnet at all?
        if (!cfg4o6.enabled()) {
            continue; // No? Let's try the next one.
        }

        // First match criteria: check if we have a prefix/len defined.
        std::pair<asiolink::IOAddress, uint8_t> pref = cfg4o6.getSubnet4o6();
        if (!pref.first.isV6Zero()) {

            // Let's check if the IPv6 address is in range
            IOAddress first = firstAddrInPrefix(pref.first, pref.second);
            IOAddress last = lastAddrInPrefix(pref.first, pref.second);
            if ((first <= selector.remote_address_) &&
                (selector.remote_address_ <= last)) {
                return (*subnet);
            }
        }

        // Second match criteria: check if the interface-id matches
        if (cfg4o6.getInterfaceId() && selector.interface_id_ &&
            cfg4o6.getInterfaceId()->equals(selector.interface_id_)) {
            return (*subnet);
        }

        // Third match criteria: check if the interface name matches
        if (!cfg4o6.getIface4o6().empty() && !selector.iface_name_.empty()
            && cfg4o6.getIface4o6() == selector.iface_name_) {
            return (*subnet);
        }
    }

    // Ok, wasn't able to find any matching subnet.
    return (Subnet4Ptr());
}

Subnet4Ptr
CfgSubnets4::selectSubnet(const SubnetSelector& selector) const {

    // First use RAI link select sub-option or subnet select option
    if (!selector.option_select_.isV4Zero()) {
        return (selectSubnet(selector.option_select_,
                             selector.client_classes_));
    }

    // If relayed message has been received, try to match the giaddr with the
    // relay address specified for a subnet. It is also possible that the relay
    // address will not match with any of the relay addresses accross all
    // subnets, but we need to verify that for all subnets before we can try
    // to use the giaddr to match with the subnet prefix.
    if (!selector.giaddr_.isV4Zero()) {
        for (Subnet4Collection::const_iterator subnet = subnets_.begin();
             subnet != subnets_.end(); ++subnet) {

            // Check if the giaddr is equal to the one defined for the subnet.
            if (selector.giaddr_ != (*subnet)->getRelayInfo().addr_) {
                continue;
            }

            // If a subnet meets the client class criteria return it.
            if ((*subnet)->clientSupported(selector.client_classes_)) {
                return (*subnet);
            }
        }
    }

    // If we got to this point it means that we were not able to match the
    // giaddr with any of the addresses specified for subnets. Let's determine
    // what address from the client's packet to use to match with the
    // subnets' prefixes.

    IOAddress address = IOAddress::IPV4_ZERO_ADDRESS();
    // If there is a giaddr, use it for subnet selection.
    if (!selector.giaddr_.isV4Zero()) {
        address = selector.giaddr_;

    // If it is a Renew or Rebind, use the ciaddr.
    } else if (!selector.ciaddr_.isV4Zero() &&
               !selector.local_address_.isV4Bcast()) {
        address = selector.ciaddr_;

    // If ciaddr is not specified, use the source address.
    } else if (!selector.remote_address_.isV4Zero() &&
               !selector.local_address_.isV4Bcast()) {
        address = selector.remote_address_;

    // If local interface name is known, use the local address on this
    // interface.
    } else if (!selector.iface_name_.empty()) {
        IfacePtr iface = IfaceMgr::instance().getIface(selector.iface_name_);
        // This should never happen in the real life. Hence we throw an
        // exception.
        if (iface == NULL) {
            isc_throw(isc::BadValue, "interface " << selector.iface_name_
                      << " doesn't exist and therefore it is impossible"
                      " to find a suitable subnet for its IPv4 address");
        }

        // Attempt to select subnet based on the interface name.
        Subnet4Ptr subnet = selectSubnet(selector.iface_name_,
                                         selector.client_classes_);

        // If it matches - great. If not, we'll try to use a different
        // selection criteria below.
        if (subnet) {
            return (subnet);
        } else {
            // Let's try to get an address from the local interface and
            // try to match it to defined subnet.
            iface->getAddress4(address);
        }
    }

    // Unable to find a suitable address to use for subnet selection.
    if (address.isV4Zero()) {
        return (Subnet4Ptr());
    }

    // We have identified an address in the client's packet that can be
    // used for subnet selection. Match this packet with the subnets.
    return (selectSubnet(address, selector.client_classes_));
}

Subnet4Ptr
CfgSubnets4::selectSubnet(const std::string& iface,
                 const ClientClasses& client_classes) const {
    for (Subnet4Collection::const_iterator subnet = subnets_.begin();
         subnet != subnets_.end(); ++subnet) {

        // If there's no interface specified for this subnet, proceed to
        // the next subnet.
        if ((*subnet)->getIface().empty()) {
            continue;
        }

        // If it's specified, but does not match, proceed to the next
        // subnet.
        if ((*subnet)->getIface() != iface) {
            continue;
        }

        // If a subnet meets the client class criteria return it.
        if ((*subnet)->clientSupported(client_classes)) {
            LOG_DEBUG(dhcpsrv_logger, DHCPSRV_DBG_TRACE,
                      DHCPSRV_CFGMGR_SUBNET4_IFACE)
                .arg((*subnet)->toText())
                .arg(iface);
            return (*subnet);
        }
    }

    // Failed to find a subnet.
    return (Subnet4Ptr());
}

Subnet4Ptr
CfgSubnets4::selectSubnet(const IOAddress& address,
                 const ClientClasses& client_classes) const {
    for (Subnet4Collection::const_iterator subnet = subnets_.begin();
         subnet != subnets_.end(); ++subnet) {

        // Address is in range for the subnet prefix, so return it.
        if (!(*subnet)->inRange(address)) {
            continue;
        }

        // If a subnet meets the client class criteria return it.
        if ((*subnet)->clientSupported(client_classes)) {
            LOG_DEBUG(dhcpsrv_logger, DHCPSRV_DBG_TRACE, DHCPSRV_CFGMGR_SUBNET4_ADDR)
                .arg((*subnet)->toText())
                .arg(address.toText());
            return (*subnet);
        }
    }

    // Failed to find a subnet.
    return (Subnet4Ptr());
}

bool
CfgSubnets4::isDuplicate(const Subnet4& subnet) const {
    for (Subnet4Collection::const_iterator subnet_it = subnets_.begin();
         subnet_it != subnets_.end(); ++subnet_it) {
        if ((*subnet_it)->getID() == subnet.getID()) {
            return (true);
        }
    }
    return (false);
}

void
CfgSubnets4::removeStatistics() {
    using namespace isc::stats;

    // For each v4 subnet currently configured, remove the statistic.
    /// @todo: May move this to CfgSubnets4 class if there will be more
    /// statistics here.
    for (Subnet4Collection::const_iterator subnet4 = subnets_.begin();
         subnet4 != subnets_.end(); ++subnet4) {

        StatsMgr::instance().del(StatsMgr::generateName("subnet",
                                                        (*subnet4)->getID(),
                                                        "total-addresses"));

        StatsMgr::instance().del(StatsMgr::generateName("subnet",
                                                        (*subnet4)->getID(),
                                                        "assigned-addresses"));
    }
}

void
CfgSubnets4::updateStatistics() {
    using namespace isc::stats;

    /// @todo: May move this to CfgSubnets4 class if there will be more
    /// statistics here.
    for (Subnet4Collection::const_iterator subnet = subnets_.begin();
         subnet != subnets_.end(); ++subnet) {

        StatsMgr::instance().setValue(
            StatsMgr::generateName("subnet", (*subnet)->getID(), "total-addresses"),
            static_cast<int64_t>((*subnet)->getPoolCapacity(Lease::TYPE_V4)));
    }
}

} // end of namespace isc::dhcp
} // end of namespace isc