/*
 * Copyright 2017-present Open Networking Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.onosproject.net.pi.impl;

import com.google.common.collect.Sets;
import org.onosproject.net.Device;
import org.onosproject.net.group.Group;
import org.onosproject.net.group.GroupBucket;
import org.onosproject.net.group.GroupDescription;
import org.onosproject.net.pi.model.PiActionProfileId;
import org.onosproject.net.pi.model.PiActionProfileModel;
import org.onosproject.net.pi.model.PiPipeconf;
import org.onosproject.net.pi.model.PiPipelineInterpreter;
import org.onosproject.net.pi.runtime.PiAction;
import org.onosproject.net.pi.runtime.PiActionProfileGroup;
import org.onosproject.net.pi.runtime.PiActionProfileGroupId;
import org.onosproject.net.pi.runtime.PiActionProfileMember;
import org.onosproject.net.pi.runtime.PiActionProfileMemberId;
import org.onosproject.net.pi.runtime.PiGroupKey;
import org.onosproject.net.pi.runtime.PiTableAction;
import org.onosproject.net.pi.service.PiTranslationException;

import java.nio.ByteBuffer;
import java.util.Set;

import static java.lang.String.format;
import static org.onosproject.net.pi.impl.PiFlowRuleTranslatorImpl.translateTreatment;
import static org.onosproject.net.pi.impl.PiUtils.getInterpreterOrNull;
import static org.onosproject.net.pi.runtime.PiTableAction.Type.ACTION;

/**
 * Implementation of group translation logic.
 */
final class PiGroupTranslatorImpl {

    private static final Set<GroupDescription.Type> SUPPORTED_GROUP_TYPES =
            Sets.immutableEnumSet(
                    GroupDescription.Type.SELECT,
                    GroupDescription.Type.INDIRECT);

    private PiGroupTranslatorImpl() {
        // Hides constructor.
    }

    /**
     * Returns a PI action profile group equivalent to the given group, for the
     * given pipeconf and device.
     *
     * @param group    group
     * @param pipeconf pipeconf
     * @param device   device
     * @return PI action profile group
     * @throws PiTranslationException if the group cannot be translated
     */
    static PiActionProfileGroup translate(Group group, PiPipeconf pipeconf, Device device)
            throws PiTranslationException {

        if (!SUPPORTED_GROUP_TYPES.contains(group.type())) {
            throw new PiTranslationException(format(
                    "group type %s not supported", group.type()));
        }

        // Get action profile from group key.
        // TODO: define proper field in group class.
        if (!(group.appCookie() instanceof PiGroupKey)) {
            throw new PiTranslationException(
                    "group app cookie is not PI (class should be PiGroupKey)");
        }
        final PiGroupKey groupKey = (PiGroupKey) group.appCookie();
        final PiActionProfileId actionProfileId = groupKey.actionProfileId();

        // Check validity of action profile against pipeconf.
        final PiActionProfileModel actionProfileModel = pipeconf.pipelineModel()
                .actionProfiles(actionProfileId)
                .orElseThrow(() -> new PiTranslationException(format(
                        "no such action profile '%s'", actionProfileId)));
        if (!actionProfileModel.hasSelector()) {
            throw new PiTranslationException(format(
                    "action profile '%s' does not support dynamic selection",
                    actionProfileId));
        }

        // Check group validity.
        if (actionProfileModel.maxGroupSize() > 0
                && group.buckets().buckets().size() > actionProfileModel.maxGroupSize()) {
            throw new PiTranslationException(format(
                    "too many buckets, max group size for action profile '%s' is %d",
                    actionProfileId, actionProfileModel.maxGroupSize()));
        }

        final PiActionProfileGroup.Builder piActionGroupBuilder = PiActionProfileGroup.builder()
                .withId(PiActionProfileGroupId.of(group.id().id()))
                .withActionProfileId(groupKey.actionProfileId())
                // We set the maximum group size as specified in the model,
                // however this might be highly inefficient for some HW targets
                // which pre-allocate resources for the whole group.
                .withMaxSize(actionProfileModel.maxGroupSize());

        // Translate group buckets to PI group members
        final PiPipelineInterpreter interpreter = getInterpreterOrNull(device, pipeconf);
        short bucketIdx = 0;
        for (GroupBucket bucket : group.buckets().buckets()) {
            /*
            FIXME: the way member IDs are computed can cause collisions!
            Problem: In P4Runtime action profile members, i.e. action buckets,
            are associated to a numeric ID chosen at member insertion time. This
            ID must be unique for the whole action profile (i.e. the group table
            in OpenFlow). In ONOS, GroupBucket doesn't specify any ID.

            Solutions:
            - Change GroupBucket API to force application wanting to perform
            group operations to specify a member id.
            - Maintain state to dynamically allocate/deallocate member IDs, e.g.
            in a dedicated service, or in a P4Runtime Group Provider.

            Hack: Statically derive member ID by combining groupId and position
            of the bucket in the list.
             */
            final ByteBuffer bb = ByteBuffer.allocate(4)
                    .putShort((short) (group.id().id() & 0xffff))
                    .putShort(bucketIdx);
            bb.rewind();
            final int memberId = bb.getInt();
            bucketIdx++;

            final PiTableAction tableAction = translateTreatment(
                    bucket.treatment(), interpreter,
                    groupKey.tableId(), pipeconf.pipelineModel());
            if (tableAction == null) {
                throw new PiTranslationException(
                        "bucket treatment translator returned null");
            }

            if (tableAction.type() != ACTION) {
                throw new PiTranslationException(format(
                        "action of type '%s' cannot be used in action profile members",
                        tableAction.type()));
            }

            final PiActionProfileMember member = PiActionProfileMember.builder()
                    .forActionProfile(groupKey.actionProfileId())
                    .withId(PiActionProfileMemberId.of(memberId))
                    .withAction((PiAction) tableAction)
                    .build();

            piActionGroupBuilder.addMember(member, bucket.weight());
        }

        return piActionGroupBuilder.build();
    }
}