/*
 * 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.Maps;
import com.google.common.collect.Sets;
import org.onlab.util.ImmutableByteSequence;
import org.onosproject.net.Device;
import org.onosproject.net.flow.FlowRule;
import org.onosproject.net.flow.TrafficSelector;
import org.onosproject.net.flow.TrafficTreatment;
import org.onosproject.net.flow.criteria.Criterion;
import org.onosproject.net.flow.criteria.PiCriterion;
import org.onosproject.net.flow.instructions.Instruction;
import org.onosproject.net.flow.instructions.PiInstruction;
import org.onosproject.net.pi.model.PiActionModel;
import org.onosproject.net.pi.model.PiActionParamModel;
import org.onosproject.net.pi.model.PiMatchFieldId;
import org.onosproject.net.pi.model.PiMatchFieldModel;
import org.onosproject.net.pi.model.PiPipeconf;
import org.onosproject.net.pi.model.PiPipelineInterpreter;
import org.onosproject.net.pi.model.PiPipelineModel;
import org.onosproject.net.pi.model.PiTableId;
import org.onosproject.net.pi.model.PiTableModel;
import org.onosproject.net.pi.runtime.PiAction;
import org.onosproject.net.pi.runtime.PiActionParam;
import org.onosproject.net.pi.runtime.PiExactFieldMatch;
import org.onosproject.net.pi.runtime.PiFieldMatch;
import org.onosproject.net.pi.runtime.PiLpmFieldMatch;
import org.onosproject.net.pi.runtime.PiMatchKey;
import org.onosproject.net.pi.runtime.PiRangeFieldMatch;
import org.onosproject.net.pi.runtime.PiTableAction;
import org.onosproject.net.pi.runtime.PiTableEntry;
import org.onosproject.net.pi.runtime.PiTernaryFieldMatch;
import org.onosproject.net.pi.service.PiTranslationException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Collection;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.StringJoiner;

import static java.lang.String.format;
import static org.onlab.util.ImmutableByteSequence.ByteSequenceTrimException;
import static org.onlab.util.ImmutableByteSequence.fit;
import static org.onosproject.net.flow.criteria.Criterion.Type.PROTOCOL_INDEPENDENT;
import static org.onosproject.net.pi.impl.CriterionTranslatorHelper.translateCriterion;
import static org.onosproject.net.pi.impl.PiUtils.getInterpreterOrNull;
import static org.onosproject.net.pi.impl.PiUtils.translateTableId;

/**
 * Implementation of flow rule translation logic.
 */
final class PiFlowRuleTranslatorImpl {

    public static final int MAX_PI_PRIORITY = (int) Math.pow(2, 24);
    private static final Logger log = LoggerFactory.getLogger(PiFlowRuleTranslatorImpl.class);

    private PiFlowRuleTranslatorImpl() {
        // Hide constructor.
    }

    /**
     * Returns a PI table entry equivalent to the given flow rule, for the given pipeconf and device.
     *
     * @param rule     flow rule
     * @param pipeconf pipeconf
     * @param device   device
     * @return PI table entry
     * @throws PiTranslationException if the flow rule cannot be translated
     */
    static PiTableEntry translate(FlowRule rule, PiPipeconf pipeconf, Device device)
            throws PiTranslationException {

        PiPipelineModel pipelineModel = pipeconf.pipelineModel();

        // Retrieve interpreter, if any.
        final PiPipelineInterpreter interpreter = getInterpreterOrNull(device, pipeconf);
        // Get table model.
        final PiTableId piTableId = translateTableId(rule.table(), interpreter);
        final PiTableModel tableModel = getTableModel(piTableId, pipelineModel);
        // Translate selector.
        final Collection<PiFieldMatch> fieldMatches = translateFieldMatches(interpreter, rule.selector(), tableModel);
        // Translate treatment.
        final PiTableAction piTableAction = translateTreatment(rule.treatment(), interpreter, piTableId, pipelineModel);

        // Build PI entry.
        final PiTableEntry.Builder tableEntryBuilder = PiTableEntry.builder();

        // In the P4 world 0 is the highest priority, in ONOS the lowest one.
        // FIXME: move priority conversion to the driver, where different constraints might apply
        // e.g. less bits for encoding priority in TCAM-based implementations.
        final int newPriority;
        if (rule.priority() > MAX_PI_PRIORITY) {
            log.warn("Flow rule priority too big, setting translated priority to max value {}: {}",
                     MAX_PI_PRIORITY, rule);
            newPriority = 0;
        } else {
            newPriority = MAX_PI_PRIORITY - rule.priority();
        }

        tableEntryBuilder
                .forTable(piTableId)
                .withPriority(newPriority)
                .withMatchKey(PiMatchKey.builder()
                                      .addFieldMatches(fieldMatches)
                                      .build())
                .withAction(piTableAction);

        if (!rule.isPermanent()) {
            if (tableModel.supportsAging()) {
                tableEntryBuilder.withTimeout((double) rule.timeout());
            } else {
                log.warn("Flow rule is temporary, but table '{}' doesn't support " +
                                 "aging, translating to permanent.", tableModel.id());
            }

        }

        return tableEntryBuilder.build();
    }


    /**
     * Returns a PI action equivalent to the given treatment, optionally using the given interpreter. This method also
     * checks that the produced PI table action is suitable for the given table ID and pipeline model. If suitable, the
     * returned action instance will have parameters well-sized, according to the table model.
     *
     * @param treatment     traffic treatment
     * @param interpreter   interpreter
     * @param tableId       PI table ID
     * @param pipelineModel pipeline model
     * @return PI table action
     * @throws PiTranslationException if the treatment cannot be translated or if the PI action is not suitable for the
     *                                given pipeline model
     */
    static PiTableAction translateTreatment(TrafficTreatment treatment, PiPipelineInterpreter interpreter,
                                            PiTableId tableId, PiPipelineModel pipelineModel)
            throws PiTranslationException {
        PiTableModel tableModel = getTableModel(tableId, pipelineModel);
        return typeCheckAction(buildAction(treatment, interpreter, tableId), tableModel);
    }

    private static PiTableModel getTableModel(PiTableId piTableId, PiPipelineModel pipelineModel)
            throws PiTranslationException {
        return pipelineModel.table(piTableId)
                .orElseThrow(() -> new PiTranslationException(format(
                        "Not such a table in pipeline model: %s", piTableId)));
    }

    /**
     * Builds a PI action out of the given treatment, optionally using the given interpreter.
     */
    private static PiTableAction buildAction(TrafficTreatment treatment, PiPipelineInterpreter interpreter,
                                             PiTableId tableId)
            throws PiTranslationException {

        PiTableAction piTableAction = null;

        // If treatment has only one instruction of type PiInstruction, use that.
        for (Instruction inst : treatment.allInstructions()) {
            if (inst.type() == Instruction.Type.PROTOCOL_INDEPENDENT) {
                if (treatment.allInstructions().size() == 1) {
                    piTableAction = ((PiInstruction) inst).action();
                } else {
                    throw new PiTranslationException(format(
                            "Unable to translate treatment, found multiple instructions " +
                                    "of which one is protocol-independent: %s", treatment));
                }
            }
        }

        if (piTableAction == null && interpreter != null) {
            // No PiInstruction, use interpreter to build action.
            try {
                piTableAction = interpreter.mapTreatment(treatment, tableId);
            } catch (PiPipelineInterpreter.PiInterpreterException e) {
                throw new PiTranslationException(
                        "Interpreter was unable to translate treatment. " + e.getMessage());
            }
        }

        if (piTableAction == null) {
            // No PiInstruction, no interpreter. It's time to give up.
            throw new PiTranslationException(
                    "Unable to translate treatment, neither an interpreter or a "
                            + "protocol-independent instruction were provided.");
        }

        return piTableAction;
    }

    private static PiTableAction typeCheckAction(PiTableAction piTableAction, PiTableModel table)
            throws PiTranslationException {
        switch (piTableAction.type()) {
            case ACTION:
                return checkPiAction((PiAction) piTableAction, table);
            default:
                // FIXME: should we check? how?
                return piTableAction;

        }
    }

    private static PiTableAction checkPiAction(PiAction piAction, PiTableModel table)
            throws PiTranslationException {
        // Table supports this action?
        PiActionModel actionModel = table.action(piAction.id()).orElseThrow(
                () -> new PiTranslationException(format("Not such action '%s' for table '%s'",
                                                        piAction.id(), table.id())));

        // Is the number of runtime parameters correct?
        if (actionModel.params().size() != piAction.parameters().size()) {
            throw new PiTranslationException(format(
                    "Wrong number of runtime parameters for action '%s', expected %d but found %d",
                    actionModel.id(), actionModel.params().size(), piAction.parameters().size()));
        }

        // Forge a new action instance with well-sized parameters.
        // The same comment as in typeCheckFieldMatch() about duplicating field match instances applies here.
        PiAction.Builder newActionBuilder = PiAction.builder().withId(piAction.id());
        for (PiActionParam param : piAction.parameters()) {
            PiActionParamModel paramModel = actionModel.param(param.id())
                    .orElseThrow(() -> new PiTranslationException(format(
                            "Not such parameter '%s' for action '%s'", param.id(), actionModel)));
            try {
                newActionBuilder.withParameter(new PiActionParam(param.id(),
                                                                 fit(param.value(), paramModel.bitWidth())));
            } catch (ByteSequenceTrimException e) {
                throw new PiTranslationException(format(
                        "Size mismatch for parameter '%s' of action '%s': %s",
                        param.id(), piAction.id(), e.getMessage()));
            }
        }

        return newActionBuilder.build();
    }

    /**
     * Builds a collection of PI field matches out of the given selector, optionally using the given interpreter. The
     * field matches returned are guaranteed to be compatible for the given table model.
     */
    private static Collection<PiFieldMatch> translateFieldMatches(PiPipelineInterpreter interpreter,
                                                                  TrafficSelector selector, PiTableModel tableModel)
            throws PiTranslationException {

        Map<PiMatchFieldId, PiFieldMatch> fieldMatches = Maps.newHashMap();

        // If present, find a PiCriterion and get its field matches as a map. Otherwise, use an empty map.
        Map<PiMatchFieldId, PiFieldMatch> piCriterionFields = selector.criteria().stream()
                .filter(c -> c.type().equals(PROTOCOL_INDEPENDENT))
                .map(c -> (PiCriterion) c)
                .findFirst()
                .map(PiCriterion::fieldMatches)
                .map(c -> {
                    Map<PiMatchFieldId, PiFieldMatch> fieldMap = Maps.newHashMap();
                    c.forEach(fieldMatch -> fieldMap.put(fieldMatch.fieldId(), fieldMatch));
                    return fieldMap;
                })
                .orElse(Maps.newHashMap());

        Set<Criterion> translatedCriteria = Sets.newHashSet();
        Set<Criterion> ignoredCriteria = Sets.newHashSet();
        Set<PiMatchFieldId> usedPiCriterionFields = Sets.newHashSet();
        Set<PiMatchFieldId> ignoredPiCriterionFields = Sets.newHashSet();

        for (PiMatchFieldModel fieldModel : tableModel.matchFields()) {

            PiMatchFieldId fieldId = fieldModel.id();

            int bitWidth = fieldModel.bitWidth();
            int fieldByteWidth = (int) Math.ceil((double) bitWidth / 8);

            Optional<Criterion.Type> criterionType =
                    interpreter == null
                            ? Optional.empty()
                            : interpreter.mapPiMatchFieldId(fieldId);

            Criterion criterion = criterionType.map(selector::getCriterion).orElse(null);

            if (!piCriterionFields.containsKey(fieldId) && criterion == null) {
                // Neither a field in PiCriterion is available nor a Criterion mapping is possible.
                // Can ignore if the match is ternary or LPM.
                switch (fieldModel.matchType()) {
                    case TERNARY:
                        // Wildcard the whole field.
                        fieldMatches.put(fieldId, new PiTernaryFieldMatch(
                                fieldId,
                                ImmutableByteSequence.ofZeros(fieldByteWidth),
                                ImmutableByteSequence.ofZeros(fieldByteWidth)));
                        break;
                    case LPM:
                        // LPM with prefix 0
                        fieldMatches.put(fieldId, new PiLpmFieldMatch(fieldId,
                                                                      ImmutableByteSequence.ofZeros(fieldByteWidth),
                                                                      0));
                        break;
                    // FIXME: Can we handle the case of RANGE or VALID match?
                    default:
                        throw new PiTranslationException(format(
                                "No value found for required match field '%s'", fieldId));
                }
                // Next field.
                continue;
            }

            PiFieldMatch fieldMatch = null;

            if (criterion != null) {
                // Criterion mapping is possible for this field id.
                try {
                    fieldMatch = translateCriterion(criterion, fieldId, fieldModel.matchType(), bitWidth);
                    translatedCriteria.add(criterion);
                } catch (PiTranslationException ex) {
                    // Ignore exception if the same field was found in PiCriterion.
                    if (piCriterionFields.containsKey(fieldId)) {
                        ignoredCriteria.add(criterion);
                    } else {
                        throw ex;
                    }
                }
            }

            if (piCriterionFields.containsKey(fieldId)) {
                // Field was found in PiCriterion.
                if (fieldMatch != null) {
                    // Field was already translated from other criterion.
                    // Throw exception only if we are trying to match on different values of the same field...
                    if (!fieldMatch.equals(piCriterionFields.get(fieldId))) {
                        throw new PiTranslationException(format(
                                "Duplicate match field '%s': instance translated from criterion '%s' is different to " +
                                        "what found in PiCriterion.", fieldId, criterion.type()));
                    }
                    ignoredPiCriterionFields.add(fieldId);
                } else {
                    fieldMatch = piCriterionFields.get(fieldId);
                    fieldMatch = typeCheckFieldMatch(fieldMatch, fieldModel);
                    usedPiCriterionFields.add(fieldId);
                }
            }

            fieldMatches.put(fieldId, fieldMatch);
        }

        // Check if all criteria have been translated.
        StringJoiner skippedCriteriaJoiner = new StringJoiner(", ");
        selector.criteria().stream()
                .filter(c -> !c.type().equals(PROTOCOL_INDEPENDENT))
                .filter(c -> !translatedCriteria.contains(c) && !ignoredCriteria.contains(c))
                .forEach(c -> skippedCriteriaJoiner.add(c.type().name()));
        if (skippedCriteriaJoiner.length() > 0) {
            throw new PiTranslationException(format(
                    "The following criteria cannot be translated for table '%s': %s",
                    tableModel.id(), skippedCriteriaJoiner.toString()));
        }

        // Check if all fields found in PiCriterion have been used.
        StringJoiner skippedPiFieldsJoiner = new StringJoiner(", ");
        piCriterionFields.keySet().stream()
                .filter(k -> !usedPiCriterionFields.contains(k) && !ignoredPiCriterionFields.contains(k))
                .forEach(k -> skippedPiFieldsJoiner.add(k.id()));
        if (skippedPiFieldsJoiner.length() > 0) {
            throw new PiTranslationException(format(
                    "The following PiCriterion field matches are not supported in table '%s': %s",
                    tableModel.id(), skippedPiFieldsJoiner.toString()));
        }

        return fieldMatches.values();
    }

    private static PiFieldMatch typeCheckFieldMatch(PiFieldMatch fieldMatch, PiMatchFieldModel fieldModel)
            throws PiTranslationException {

        // Check parameter type and size
        if (!fieldModel.matchType().equals(fieldMatch.type())) {
            throw new PiTranslationException(format(
                    "Wrong match type for field '%s', expected %s, but found %s",
                    fieldMatch.fieldId(), fieldModel.matchType().name(), fieldMatch.type().name()));
        }

        int modelBitWidth = fieldModel.bitWidth();

        /*
        Here we try to be robust against wrong size fields with the goal of having PiCriterion independent of the
        pipeline model. We duplicate the field match, fitting the byte sequences to the bit-width specified in the
        model. This operation is expensive when performed for each field match of each flow rule, but should be
        mitigated by the translation cache provided by PiFlowRuleTranslationServiceImpl.
        */

        try {
            switch (fieldModel.matchType()) {
                case EXACT:
                    return new PiExactFieldMatch(fieldMatch.fieldId(),
                                                 fit(((PiExactFieldMatch) fieldMatch).value(), modelBitWidth));
                case TERNARY:
                    return new PiTernaryFieldMatch(fieldMatch.fieldId(),
                                                   fit(((PiTernaryFieldMatch) fieldMatch).value(), modelBitWidth),
                                                   fit(((PiTernaryFieldMatch) fieldMatch).mask(), modelBitWidth));
                case LPM:
                    PiLpmFieldMatch lpmfield = (PiLpmFieldMatch) fieldMatch;
                    if (lpmfield.prefixLength() > modelBitWidth) {
                        throw new PiTranslationException(format(
                                "Invalid prefix length for LPM field '%s', found %d but field has bit-width %d",
                                fieldMatch.fieldId(), lpmfield.prefixLength(), modelBitWidth));
                    }
                    return new PiLpmFieldMatch(fieldMatch.fieldId(),
                                               fit(lpmfield.value(), modelBitWidth),
                                               lpmfield.prefixLength());
                case RANGE:
                    return new PiRangeFieldMatch(fieldMatch.fieldId(),
                                                 fit(((PiRangeFieldMatch) fieldMatch).lowValue(), modelBitWidth),
                                                 fit(((PiRangeFieldMatch) fieldMatch).highValue(), modelBitWidth));
                case VALID:
                    return fieldMatch;
                default:
                    // Should never be here.
                    throw new RuntimeException(
                            "Unrecognized match type " + fieldModel.matchType().name());
            }
        } catch (ByteSequenceTrimException e) {
            throw new PiTranslationException(format(
                    "Size mismatch for field %s: %s", fieldMatch.fieldId(), e.getMessage()));
        }
    }
}