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/*
 Copyright 2013 Red Hat, Inc. and/or its affiliates.

 This file is part of lightblue.

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program.  If not, see .
 */
package com.redhat.lightblue.assoc.ep;

import java.util.Map;
import java.util.HashMap;
import java.util.List;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.Arrays;

import java.util.stream.Collectors;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.JsonNodeFactory;

import com.redhat.lightblue.assoc.BindQuery;

import com.redhat.lightblue.eval.QueryEvaluator;

import com.redhat.lightblue.query.QueryExpression;
import com.redhat.lightblue.query.NaryLogicalExpression;
import com.redhat.lightblue.query.NaryLogicalOperator;

import com.redhat.lightblue.util.Tuples;

/**
 * This class contains the different variations of search and assembly
 * algorithmss as static methods
 */
public final class Searches {

    private static final Logger LOGGER = LoggerFactory.getLogger(Searches.class);

    private Searches() {
    }

    /**
     * Given a parent document and an association query, returns a query for
     * each slot that will be used to retrieve the child documents that will be
     * attached to that slot
     */
    public static Map writeChildQueriesFromParentDoc(AssociationQuery aq,
                                                                                 ResultDocument parentDocument) {
        Map binders = parentDocument.getBindersForChild(aq);
        LOGGER.debug("writeChildQueriesForParentDoc: aq={} binders={}", aq, binders);
        Map queries = new HashMap<>();
        for (Map.Entry entry : binders.entrySet()) {
            if (aq.getQuery() != null) {
                queries.put(entry.getKey(), entry.getValue().iterate(aq.getQuery()));
            } else {
                queries.put(entry.getKey(), null);
            }
        }
        LOGGER.debug("Queries:{}", queries);
        return queries;
    }

    /**
     * Writes queries form a join tuple
     */
    public static List writeQueriesForJoinTuple(JoinTuple tuple, ExecutionBlock childBlock) {
        LOGGER.debug("writeQueriesForJoinTuples tuple:{}, child:{}", tuple, childBlock);
        Tuples btuples = new Tuples<>();
        if (tuple.getParentDocument() != null) {
            AssociationQuery aq = childBlock.getAssociationQueryForEdge(tuple.getParentDocument().getBlock());
            BindQuery parentb = tuple.getParentDocument().getBindersForSlot(tuple.getParentDocumentSlot(), aq);
            List l = new ArrayList<>(1);
            l.add(parentb);
            btuples.add(l);
        }
        if (tuple.getChildTuple() != null) {
            // Add the child binders to the b-tuples
            for (ResultDocument childDoc : tuple.getChildTuple()) {
                AssociationQuery aq = childBlock.getAssociationQueryForEdge(childDoc.getBlock());
                List binders = childDoc.getBindersForParent(aq);
                btuples.add(binders);
            }
        }
        List queries = new ArrayList<>();
        for (ExecutionBlock sourceBlock : tuple.getBlocks()) {
            AssociationQuery aq = childBlock.getAssociationQueryForEdge(sourceBlock);
            if (aq.getQuery() != null) {
                queries.add(aq.getQuery());
            }
        }
        QueryExpression query = and(queries);
        ArrayList ret = new ArrayList<>();
        if (query != null) {
            for (Iterator> itr = btuples.tuples(); itr.hasNext();) {
                List binders = itr.next();
                BindQuery allBinders = BindQuery.combine(binders);
                ret.add(allBinders.iterate(query));
            }
        }
        LOGGER.debug("queries={}", ret);
        return ret;
    }

    /**
     * Associates child documents obtained from 'aq' to all the slots in the
     * parent document
     */
    public static void associateDocs(ResultDocument parentDoc,
                                     List childDocs,
                                     AssociationQuery aq) {
        List slots = parentDoc.getSlots().get(aq.getReference());
        for (ChildSlot slot : slots) {
            associateDocs(parentDoc, slot, childDocs, aq);
        }
    }

    /**
     * Associate child documents with their parents. The association query is
     * for the association from the child to the parent, so caller must flip it
     * before sending it in if necessary. The caller also make sure parentDocs
     * is a unique stream.
     *
     * @param parentDoc The parent document
     * @param parentSlot The slot in parent docuemnt to which the results will
     * be attached
     * @param childDocs The child documents
     * @param aq The association query from parent to child. This may not be the
     * same association query between the blocks. If the child block is before
     * the parent block, a new aq must be constructed for the association from
     * the parent to the child
     */
    public static void associateDocs(ResultDocument parentDoc,
                                     ChildSlot parentSlot,
                                     List childDocs,
                                     AssociationQuery aq) {
        if (!childDocs.isEmpty()) {
            LOGGER.debug("Associating docs");
            ExecutionBlock childBlock = childDocs.get(0).getBlock();
            ArrayNode destNode = (ArrayNode) parentDoc.getDoc().get(parentSlot.getSlotFieldName());
            BindQuery binders = parentDoc.getBindersForSlot(parentSlot, aq);
            // No binders means all child docs will be added to the parent            
            if (binders.getBindings().isEmpty()) {
                if (destNode == null) {
                    destNode = JsonNodeFactory.instance.arrayNode();
                    parentDoc.getDoc().modify(parentSlot.getSlotFieldName(), destNode, true);
                }
                for (ResultDocument d : childDocs) {
                    destNode.add(d.getDoc().getRoot());
                }
            } else {
                QueryExpression boundQuery = binders.iterate(aq.getQuery());
                LOGGER.debug("Association query:{}", boundQuery);
                QueryEvaluator qeval = QueryEvaluator.getInstance(boundQuery, childBlock.getMetadata());
                for (ResultDocument childDoc : childDocs) {
                    if (qeval.evaluate(childDoc.getDoc()).getResult()) {
                        if (destNode == null) {
                            destNode = JsonNodeFactory.instance.arrayNode();
                            parentDoc.getDoc().modify(parentSlot.getSlotFieldName(), destNode, true);
                        }
                        destNode.add(childDoc.getDoc().getRoot());
                    }
                }
            }
        }
    }

    /**
     * Combines queries with AND. Queries can be null, but at least one of them
     * must be non-null
     */
    public static QueryExpression and(QueryExpression... q) {
        return combine(NaryLogicalOperator._and, Arrays.asList(q));
    }

    public static QueryExpression and(List list) {
        return combine(NaryLogicalOperator._and, list);
    }

    public static QueryExpression combine(NaryLogicalOperator op, List list) {
        List l = list.stream().filter(q -> q != null).collect(Collectors.toList());
        if (l.size() == 0) {
            return null;
        } else if (l.size() == 1) {
            return l.get(0);
        } else {
            return new NaryLogicalExpression(op, l);
        }
    }

}