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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.mediator;

import java.io.Serializable;

import java.util.Map;
import java.util.HashMap;
import java.util.Set;
import java.util.HashSet;

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

import com.redhat.lightblue.crud.MetadataResolver;
import com.redhat.lightblue.crud.CrudConstants;

import com.redhat.lightblue.metadata.AbstractGetMetadata;
import com.redhat.lightblue.metadata.EntityMetadata;
import com.redhat.lightblue.metadata.MetadataStatus;
import com.redhat.lightblue.metadata.CompositeMetadata;
import com.redhat.lightblue.metadata.Metadata;
import com.redhat.lightblue.metadata.FieldTreeNode;
import com.redhat.lightblue.metadata.Field;
import com.redhat.lightblue.metadata.ResolvedReferenceField;
import com.redhat.lightblue.metadata.EntityAccess;
import com.redhat.lightblue.metadata.FieldAccess;
import com.redhat.lightblue.metadata.FieldCursor;

import com.redhat.lightblue.query.QueryExpression;
import com.redhat.lightblue.query.Projection;

import com.redhat.lightblue.util.Path;
import com.redhat.lightblue.util.Error;

/**
 * This implementation combines the implementations for GetMetadata interface
 * used by CompositeMetadata, and MetadataResolver interface used by the CRUD
 * subsystem to access metadata by name.
 */
public class DefaultMetadataResolver implements MetadataResolver, Serializable {

    private static final long serialVersionUID = 1l;

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

    private final Map metadataMap = new HashMap<>();
    private final Metadata md;

    private CompositeMetadata cmd;
    private Set roles;

    private final class Gmd extends AbstractGetMetadata {
        public Gmd(Projection projection,
                   QueryExpression query) {
            super(projection, query);
        }

        @Override
        protected EntityMetadata retrieveMetadata(Path injectionPath,
                                                  String entityName,
                                                  String entityVersion) {
            return DefaultMetadataResolver.this.getMetadata(entityName, entityVersion);
        }
    }

    /**
     * Constructs the metadata resolver with the given metadata implementation
     */
    public DefaultMetadataResolver(Metadata metadata) {
        this.md = metadata;
    }

    /**
     * This method builds the composite metadata for the given top level entity
     * name and entity version, for the given query and projections
     */
    public void initialize(String entityName,
                           String entityVersion,
                           final QueryExpression query,
                           final Projection projection) {
        if (cmd != null) {
            throw new IllegalStateException("Metadata resolver was already initialized");
        }

        LOGGER.debug("Initializing with {}:{}", entityName, entityVersion);
        EntityMetadata emd = getMetadata(entityName, entityVersion);
        cmd = CompositeMetadata.buildCompositeMetadata(emd, new Gmd(projection, query));
        LOGGER.debug("Composite metadata:{}", cmd);

        LOGGER.debug("Collecting metadata roles");
        roles = new HashSet<>();
        addMetadataRoles(roles, cmd);
        FieldCursor c = cmd.getFieldCursor();
        while (c.next()) {
            FieldTreeNode node = c.getCurrentNode();
            addFieldRoles(roles, node);
            if (node instanceof ResolvedReferenceField) {
                addMetadataRoles(roles, ((ResolvedReferenceField) node).getReferencedMetadata());
            }
        }
        LOGGER.debug("Metadata roles:{}", roles);
    }

    /**
     * Returns the top level entity name
     */
    public String getTopLevelEntityName() {
        return cmd.getName();
    }

    /**
     * Returns the top level entity version
     */
    public String getTopLevelEntityVersion() {
        return cmd.getVersion().getValue();
    }

    /**
     * Returns the top level entity metadata
     */
    public CompositeMetadata getTopLevelEntityMetadata() {
        return cmd;
    }

    /**
     * Returns the version of the entity metadata relevant in the current
     * operation
     */
    @Override
    public EntityMetadata getEntityMetadata(String entityName) {
        return metadataMap.get(entityName);
    }

    /**
     * Returns the composite metadata for this operation
     */
    public CompositeMetadata getCompositeMetadata() {
        return cmd;
    }

    /**
     * Return all roles referenced in metadata
     */
    public Set getMetadataRoles() {
        return roles;
    }

    private void addMetadataRoles(Set roles, EntityMetadata em) {
        EntityAccess a = em.getAccess();
        a.getFind().addRolesTo(roles);
        a.getUpdate().addRolesTo(roles);
        a.getInsert().addRolesTo(roles);
        a.getDelete().addRolesTo(roles);
    }

    private void addFieldRoles(Set roles, FieldTreeNode node) {
        if (node instanceof Field) {
            Field field = (Field) node;
            FieldAccess a = field.getAccess();
            a.getFind().addRolesTo(roles);
            a.getInsert().addRolesTo(roles);
            a.getUpdate().addRolesTo(roles);
        }
    }

    private EntityMetadata getMetadata(String entityName,
                                       String version) {
        EntityMetadata emd = metadataMap.get(entityName);
        if (emd != null) {
            if (!emd.getVersion().getValue().equals(version)) {
                throw Error.get(CrudConstants.ERR_METADATA_APPEARS_TWICE, entityName + ":" + version
                        + " and " + emd.getVersion().getValue());
            }
        } else {
            LOGGER.debug("Retrieving entity metadata {}:{}", entityName, version);
            emd = md.getEntityMetadata(entityName, version);
            if (emd == null || emd.getEntitySchema() == null) {
                throw Error.get(CrudConstants.ERR_UNKNOWN_ENTITY, entityName + ":" + version);
            }
            if (emd.getEntitySchema().getStatus() == MetadataStatus.DISABLED) {
                throw Error.get(CrudConstants.ERR_DISABLED_METADATA, entityName + ":" + version);
            }
            metadataMap.put(entityName, emd);
        }
        return emd;
    }
}