import DataModel from '../export';
import { extend2 } from '../utils';
import { rowDiffsetIterator } from './row-diffset-iterator';
import { isArrEqual } from '../utils/helper';
/**
* Union operation can be termed as vertical stacking of all rows from both the DataModel instances, provided that both
* of the {@link DataModel} instances should have same column names.
*
* @example
* //@preamble_start
* Promise.all([loadData('/static/cars.json'), loadData('/static/cars-schema.json')]).then(function (params) {
* const data = params[0];
* const schema = params[1];
* const DataModel = muze.DataModel;
* const dm = new DataModel(data, schema);
* //@preamble_end
* // DataModel instance is created from https://www.charts.com/static/cars.json data,
* // https://www.charts.com/static/cars-schema.json schema and assigned to variable dm. DataModel is extracted from
* // muze namespace and assigned to the variable DataModel.
*
* // Creates two small DataModel instance from the original DataModel instance, one only for european cars,
* // another for cars from USA. Used the chain operation here for conciseness.
* const usaMakerDM = dm.select(fields => fields.Origin.value === 'USA');
* const euroMakerDM = dm.select(fields => fields.Origin.value === 'Europe');
*
* const union = DataModel.Operators.union;
* const outputDM = union(usaMakerDM, euroMakerDM);
* //@preamble_start
* printDM(outputDM);
* });
* //@preamble_end
*
* @text
* This is the functional version of `union` operator. `union` can also be used as
* {@link /muze/api/datamodel/union | chained operator}.
*
* @public
* @segment Operators
*
* @param {DataModel} topDM One of the two operands of union. Instance of DataModel.
* @param {DataModel} bottomDM Another operands of union. Instance of DataModel.
*
* @return {DataModel} New DataModel instance with the result of the operation.
*/
export function union (dm1, dm2) {
const hashTable = {};
const schema = [];
const schemaNameArr = [];
const data = [];
const dm1FieldStore = dm1.getFieldspace();
const dm2FieldStore = dm2.getFieldspace();
const dm1FieldStoreFieldObj = dm1FieldStore.fieldsObj();
const dm2FieldStoreFieldObj = dm2FieldStore.fieldsObj();
const name = `${dm1FieldStore.name} union ${dm2FieldStore.name}`;
// For union the columns should match otherwise return a clone of the dm1
if (!isArrEqual(dm1._colIdentifier.split(',').sort(), dm2._colIdentifier.split(',').sort())) {
return null;
}
// Prepare the schema
(dm1._colIdentifier.split(',')).forEach((fieldName) => {
const field = dm1FieldStoreFieldObj[fieldName];
schema.push(extend2({}, field.schema));
schemaNameArr.push(field.schema.name);
});
/**
* The helper function to create the data.
*
* @param {dm} dm - The dm instance for which the data is inserted.
* @param {Object} fieldsObj - The fieldStore object format.
*/
function prepareDataHelper (dm, fieldsObj) {
rowDiffsetIterator(dm._rowDiffset, (i) => {
const tuple = {};
let hashData = '';
schemaNameArr.forEach((schemaName) => {
const value = fieldsObj[schemaName].data[i];
hashData += `-${value}`;
tuple[schemaName] = value;
});
if (!hashTable[hashData]) {
data.push(tuple);
hashTable[hashData] = true;
}
});
}
// Prepare the data
prepareDataHelper(dm1, dm1FieldStoreFieldObj);
prepareDataHelper(dm2, dm2FieldStoreFieldObj);
return new DataModel(data, schema, { name });
}