data-object-junction.js

/**
 * MOST Web Framework
 * A JavaScript Web Framework
 * http://themost.io
 * Created by Kyriakos Barbounakis<k.barbounakis@gmail.com> on 2014-10-13.
 *
 * Copyright (c) 2014, Kyriakos Barbounakis k.barbounakis@gmail.com
 Anthi Oikonomou anthioikonomou@gmail.com
 All rights reserved.
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are met:
 * Redistributions of source code must retain the above copyright notice, this
 list of conditions and the following disclaimer.
 * Redistributions in binary form must reproduce the above copyright notice,
 this list of conditions and the following disclaimer in the documentation
 and/or other materials provided with the distribution.
 * Neither the name of MOST Web Framework nor the names of its
 contributors may be used to endorse or promote products derived from
 this software without specific prior written permission.
 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * @ignore
 */
var util = require('util'),
    _ = require('lodash'),
    async = require('async'),
    qry = require('most-query'),
    types = require('./types'),
    DataQueryable = require('./data-queryable').DataQueryable;

/**
 * @classdesc Represents a many-to-many association between two data models.
 * <p>
 *     This association may be defined in a field of a data model as follows:
 * </p>
 * <pre class="prettyprint"><code>
 {
     "name": "Group", "id": 91, "title": "User Group", "inherits":"Account", "hidden": false, "sealed": false, "abstract": false, "version": "1.1",
     "fields": [
        ...
        {
			"name": "members",
            "title": "Group Members",
            "description": "Contains the collection of group members (users or groups).",
            "type": "Account",
			"mapping": {
				"associationAdapter": "GroupMembers", "parentModel": "Group",
				"parentField": "id", "childModel": "User", "childField": "id",
				"associationType": "junction", "cascade": "delete",
				"select": [
					"id",
					"name",
					"alternateName"
				]
			}
		}
        ...
     ]
     }
 </code></pre>
 <p>
 where model [Group] has a many-to-many association with model [User] in order to define the groups where a user belongs.
 This association will produce a database table with name of the specified association adapter name. If this name is missing
 then it will produce a table with a default name which comes of the concatenation of the model and the associated model.
 </p>
 <p>
 An instance of DataObjectJunction class overrides DataQueryable methods for filtering associated objects:
 </p>
 <pre class="prettyprint"><code>
 //check if a user belongs to Administrators group by querying user groups
 var groups = context.model('Group');
 groups.where('name').equal('Administrators')
 .first().then(function(result) {
        var group = groups.convert(result);
        group.property('members').where('name').equal('alexis.rees@example.com').count().then(function(result) {
            done(null, result);
        });
    }).catch(function(err) {
        done(err);
    });
 </code></pre>
 <p>
 Connects two objects (by inserting an association between parent and child object):
 </p>
 <pre class="prettyprint"><code>
 //add a user (by name) in Administrators group
 var groups = context.model('Group');
 groups.where('name').equal('Administrators')
 .first().then(function(result) {
        var group = groups.convert(result);
        group.property('members').insert({ name: 'alexis.rees@example.com' }).then(function() {
            done();
        });
    }).catch(function(err) {
        done(err);
    });
 </code></pre>
 <p>
 Disconnects two objects (by removing an existing association):
 </p>
 <pre class="prettyprint"><code>
 //remove a user (by name) from Administrators group
 var groups = context.model('Group');
 groups.where('name').equal('Administrators')
 .first().then(function(result) {
        var group = groups.convert(result);
        group.property('members').remove({ name: 'alexis.rees@example.com' }).then(function() {
            done();
        });
    }).catch(function(err) {
        done(err);
    });
 </code></pre>
 * @class
 * @constructor
 * @augments DataQueryable
 * @param {DataObject} obj An object which represents the parent data object
 * @param {String|*} association A string that represents the name of the field which holds association mapping or the association mapping itself.
 * @property {DataModel} baseModel - The model associated with this data object junction
 * @property {DataObject} parent - Gets or sets the parent data object associated with this instance of DataObjectJunction class.
 * @property {DataAssociationMapping} mapping - Gets or sets the mapping definition of this data object association.
 */
function DataObjectJunction(obj, association) {
    /**
     * @type {DataObject}
     * @private
     */
    var parent_ = obj,
        DataModel = require('./data-model').DataModel;

    /**
     * Gets or sets the parent data object
     * @type DataObject
     */
    Object.defineProperty(this, 'parent', { get: function () {
        return parent_;
    }, set: function (value) {
        parent_ = value;
    }, configurable: false, enumerable: false});
    var self = this;
    if (typeof association === 'string') {
        //infer mapping from field name
        //set relation mapping
        if (self.parent!=null) {
            var model = self.parent.getModel();
            if (model!=null)
                self.mapping = model.inferMapping(association);
        }
    }
    else if (typeof association === 'object' && association !=null) {
        //get the specified mapping
        if (association instanceof types.DataAssociationMapping)
            self.mapping = association;
        else
            self.mapping = _.assign(new types.DataAssociationMapping(), association);
    }
    //get related model
    var relatedModel = this.parent.context.model(self.mapping.childModel);
    //call super class constructor
    DataObjectJunction.super_.call(this, relatedModel);
    //modify query (add join model)
    var adapter = relatedModel.viewAdapter;
    var left = {}, right = {};
    this.query.select(relatedModel.attributes.filter(function(x) {
        return !x.many;
    }).map(function(x) {
        return qry.fields.select(x.name).from(adapter);
    }));
    left[adapter] = [ relatedModel.primaryKey ];
    right[this.mapping.associationAdapter] = [qry.fields.select(DataObjectJunction.STR_VALUE_FIELD).from(this.mapping.associationAdapter).$name];
    var field1 = qry.fields.select(DataObjectJunction.STR_OBJECT_FIELD).from(this.mapping.associationAdapter).$name;
    this.query.join(this.mapping.associationAdapter, []).with([left, right]).where(field1).equal(obj[this.mapping.parentField]).prepare();
    var baseModel;
    Object.defineProperty(this, 'baseModel', {
        get: function() {
            if (baseModel)
                return baseModel;
            //get parent context
            var context = self.parent.context, conf = context.getConfiguration();
            //search in cache (configuration.current.cache)
            if (conf.models[self.mapping.associationAdapter]) {
                baseModel = new DataModel(conf.models[self.mapping.associationAdapter]);
                baseModel.context = self.parent.context;
                return baseModel;
            }
            //get parent and child field in order to get junction field types
            var parentModel = self.parent.getModel();
            var parentField = parentModel.field(self.mapping.parentField);
            var childModel = self.parent.context.model(self.mapping.childModel);
            var childField = childModel.field(self.mapping.childField);
            var adapter = self.mapping.associationAdapter;
            baseModel = self.parent.context.model(adapter);
            if (_.isNil(baseModel)) {
                conf.models[self.mapping.associationAdapter] = { name:adapter, title: adapter, source:adapter, type:"hidden", hidden:true, sealed:false, view:adapter, version:'1.0', fields:[
                    { name: "id", type:"Counter", primary: true },
                    { name: "parentId", indexed: true, nullable:false, type: (parentField.type=='Counter') ? 'Integer' : parentField.type },
                    { name: "valueId", indexed: true, nullable:false, type: (childField.type=='Counter') ? 'Integer' : childField.type } ],
                    "constraints": [
                        {
                            "description": "The relation between two objects must be unique.",
                            "type":"unique",
                            "fields": [ "parentId", "valueId" ]
                        }
                    ], "privileges":[
                        { "mask":15, "type":"global" }
                    ]};
                //initialize base model
                baseModel = new DataModel(conf.models[self.mapping.associationAdapter]);
                baseModel.context = self.parent.context;
            }
            return baseModel;
        },configurable:false, enumerable:false
    });

    /**
     * Gets an instance of DataModel class which represents the data adapter of this association
     * @returns {DataModel}
     */
    this.getBaseModel = function() {
        return this.baseModel;
    };

    this.getChildField = function() {
        return _.find(this.getBaseModel().attributes, function(x) {
           return x.name === DataObjectJunction.STR_VALUE_FIELD;
        });
    };

    this.getParentField = function() {
        return _.find(this.getBaseModel().attributes, function(x) {
            return x.name === DataObjectJunction.STR_OBJECT_FIELD;
        });
    };


}
DataObjectJunction.STR_OBJECT_FIELD = 'parentId';
DataObjectJunction.STR_VALUE_FIELD = 'valueId';

util.inherits(DataObjectJunction, DataQueryable);

/**
 * Migrates the underlying data association adapter.
 * @param callback - A callback function where the first argument will contain the Error object if an error occured, or null otherwise.
 */
DataObjectJunction.prototype.migrate = function(callback) {
    var model = this.getBaseModel();
    model.migrate(function(err) {
        if (err) {
            return callback(err);
        }
        //migrate related model
        var childModel = self.parent.context.model(self.mapping.childModel);
        return childModel.migrate(callback);
    });
};
/**
 * Overrides DataQueryable.execute() method
 * @param callback - A callback function where the first argument will contain the Error object if an error occured, or null otherwise.
 * @ignore
 */
DataObjectJunction.prototype.execute = function(callback) {
    var self = this;
    self.migrate(function(err) {
        if (err) { callback(err); return; }
        DataObjectJunction.super_.prototype.execute.call(self, callback);
    });
};

function insert_(obj, callback) {
    var self = this, arr = [];
    if (_.isArray(obj))
        arr = obj;
    else {
        arr.push(obj);
    }
    self.migrate(function(err) {
        if (err)
            callback(err);
        else {
            async.eachSeries(arr, function(item, cb) {
                var child = item;
                if (typeof item !== 'object') {
                    child = {};
                    child[self.mapping.childField] = item;
                }
                //validate if child identifier exists
                if (child.hasOwnProperty(self.mapping.childField)) {
                    insertSingleObject_.call(self, child, function(err) {
                        cb(err);
                    });
                }
                else {
                    /**
                     * Get related model. The related model is the model of any child object of this junction.
                     * @type {DataModel}
                     */
                    var relatedModel = self.parent.context.model(self.mapping.childModel);
                    //find object by querying child object
                    relatedModel.find(child).select(self.mapping.childField).first(function (err, result) {
                        if (err) {
                            cb(err);
                        }
                        else {
                            /**
                             * Validates related object, inserts this object if does not exists
                             * and finally defines the relation between child and parent objects
                             */
                            if (!result) {
                                //ensure silent mode
                                if (self.getBaseModel().$silent) { relatedModel.silent(); }
                                //insert related item if does not exists
                                relatedModel.save(child, function(err) {
                                    if (err) {
                                        cb(err);
                                    }
                                    else {
                                        //insert relation between child and parent
                                        insertSingleObject_.call(self, child, function(err) { cb(err); });
                                    }
                                });
                            }
                            else {
                                //set primary key
                                child[self.mapping.childField] = result[self.mapping.childField];
                                //insert relation between child and parent
                                insertSingleObject_.call(self, child, function(err) { cb(err); });
                            }
                        }
                    });
                }

            }, callback);
        }
    });
}

/**
 * Inserts an association between parent object and the given object or array of objects.
 * @param {*|Array} obj - An object or an array of objects to be related with parent object
 * @param {Function=} callback - A callback function where the first argument will contain the Error object if an error occured, or null otherwise.
 * @returns {Promise<T>|*} - If callback parameter is missing then returns a Promise object.
 * @example
 //add a user (by name) in Administrators group
 var groups = context.model('Group');
 groups.where('name').equal('Administrators')
 .first().then(function(result) {
        var group = groups.convert(result);
        group.property('members').insert({ name: 'alexis.rees@example.com' }).then(function() {
            done();
        });
    }).catch(function(err) {
        done(err);
    });
 */
DataObjectJunction.prototype.insert = function(obj, callback) {
    var self = this;
    if (typeof callback !== 'function') {
        var Q = require('q'), deferred = Q.defer();
        insert_.call(self, obj, function(err) {
            if (err) { return deferred.reject(err); }
            deferred.resolve(null);
        });
        return deferred.promise;
    }
    else {
        return insert_.call(self, obj, callback);
    }
};

function clear_(callback) {
    var self = this;
    self.migrate(function(err) {
        if (err) { return callback(); }
        //get parent id
        var parentId = self.parent[self.mapping.parentField];
        //get relation model
        var relationModel = self.getBaseModel();
        //validate relation existence
        relationModel.where(DataObjectJunction.STR_OBJECT_FIELD).equal(parentId).all(function(err, result) {
            if (err) { return callback(); }
            if (result.length==0) { return callback();  }
            relationModel.remove(result, callback);
        });
    });
}

/**
 * Removes all associations
 * @param {Function=} callback
 * @returns {Promise|*}
 * @deprecated This method is deprecated. Use DataObjectJunction.removeAll() instead.
 */
DataObjectJunction.prototype.clear = function(callback) {
    return this.removeAll(callback);
};

/**
 * Removes all associations
 * @param {Function=} callback
 * @returns {Promise|*}
 */
DataObjectJunction.prototype.removeAll = function(callback) {
    var self = this;
    if (typeof callback !== 'function') {
        var Q = require('q'), deferred = Q.defer();
        clear_.call(self, function(err) {
            if (err) { return deferred.reject(err); }
            deferred.resolve();
        });
        return deferred.promise;
    }
    else {
        return clear_.call(self, callback);
    }
};

/**
 * Inserts a new relation between a parent and a child object.
 * @param {*} obj An object or an identifier that represents the child object
 * @param {Function} callback
 * @private
 */
function insertSingleObject_(obj, callback) {
    var self = this;
    //get parent and child
    var child = obj;
    if (typeof obj !== 'object') {
        child = {};
        child[self.mapping.childField] = obj;
    }
    var parentId = self.parent[self.mapping.parentField], childId = child[self.mapping.childField];
    //get relation model
    var relationModel = self.getBaseModel();
    //validate relation existence
    relationModel.where(DataObjectJunction.STR_OBJECT_FIELD).equal(parentId).and(DataObjectJunction.STR_VALUE_FIELD).equal(childId).first(function(err, result) {
        if (err) {
            //on error exit with error
            return callback(err);
        }
        else {
            if (result) {
                //if relation already exists, do nothing
                return callback(null);
            }
            else {
                //otherwise create new item
                var newItem = { };
                newItem[DataObjectJunction.STR_OBJECT_FIELD] = parentId;
                newItem[DataObjectJunction.STR_VALUE_FIELD] = childId;
                //and insert it
                relationModel.insert(newItem, callback);
            }
        }
    });

};
/**
 * Migrates current junction data storage
 * @param {Function} callback
 */
DataObjectJunction.prototype.migrate = function(callback)
{
    var self = this;
    //get migration model
    var migrationModel = self.parent.context.model("Migration");
    //get related model
    var relationModel = self.getBaseModel();
    migrationModel.find({ appliesTo:relationModel.source, version: relationModel.version }).first(function(err, result) {
        if (err) {
            callback(err);
        }
        else {
            if (!result) {
                //migrate junction table
                relationModel.migrate(function(err) {
                    if (err) {
                        callback(err);
                    }
                    else
                        callback(null);
                })
            }
            else
                callback(null);
        }
    });
};

function remove_(obj, callback) {
    var self = this;
    var arr = [];
    if (_.isArray(obj))
        arr = obj;
    else {
        arr.push(obj);
    }
    self.migrate(function(err) {
        if (err)
            callback(err);
        else
        {
            async.eachSeries(arr, function(item, cb) {
                var child = item;
                if (typeof item !== 'object') {
                    child = {};
                    child[self.mapping.childField] = item;
                }
                //get related model
                var relatedModel = self.parent.context.model(self.mapping.childModel);
                //find object by querying child object
                relatedModel.find(child).select([self.mapping.childField]).first(function (err, result) {
                    if (err) {
                        cb(null);
                    }
                    else {
                        if (!result) {
                            //child was not found (do nothing or throw exception)
                            cb(null);
                        }
                        else {
                            child[self.mapping.childField] = result[self.mapping.childField];
                            removeSingleObject_.call(self, child, function(err) {
                                cb(err);
                            });
                        }
                    }
                });
            }, callback);
        }
    });
}

/**
 * Removes the association between parent object and the given object or array of objects.
 * @param {*|Array} obj - An object or an array of objects to be disconnected from parent object
 * @param {Function=} callback - A callback function where the first argument will contain the Error object if an error occured, or null otherwise.
 * @returns {Promise<T>|*} - If callback parameter is missing then returns a Promise object.
 * @example
 //remove a user (by name) from Administrators group
 var groups = context.model('Group');
 groups.where('name').equal('Administrators')
 .first().then(function(result) {
        var group = groups.convert(result);
        group.property('members').remove({ name: 'alexis.rees@example.com' }).then(function() {
            done();
        });
    }).catch(function(err) {
        done(err);
    });
 */
DataObjectJunction.prototype.remove = function(obj, callback) {
    var self = this;
    if (typeof callback !== 'function') {
        var Q = require('q'), deferred = Q.defer();
        remove_.call(self, obj, function(err) {
            if (err) { return deferred.reject(err); }
            deferred.resolve(null);
        });
        return deferred.promise;
    }
    else {
        return remove_.call(self, obj, callback);
    }
};

/**
 * Removes a relation between a parent and a child object.
 * @param {*} obj An object or an identifier that represents the child object
 * @param {Function} callback
 * @private
 */
 function removeSingleObject_(obj, callback) {
    var self = this;
    //get parent and child
    var child = obj;
    if (typeof obj !== 'object') {
        child = {};
        child[self.mapping.childField] = obj;
    }
    var parentId = self.parent[self.mapping.parentField], childId = child[self.mapping.childField];
    //get relation model
    var relationModel = self.getBaseModel();
    relationModel.where(DataObjectJunction.STR_OBJECT_FIELD).equal(parentId).and(DataObjectJunction.STR_VALUE_FIELD).equal(childId).first(function(err, result) {
        if (err) {
            callback(err);
        }
        else {
            if (!result) {
                callback(null);
            }
            else {
                //otherwise remove item
                relationModel.remove(result, callback);
            }
        }
    });
};

if (typeof exports !== 'undefined')
{
    module.exports = {
        DataObjectJunction:DataObjectJunction
    };
}