/**

* @license Apache-2.0

*

* Copyright (c) 2018 The Stdlib Authors.

*

* 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.

*/

'use strict';

// MODULES //

var isCollection = require( '@stdlib/assert/is-collection' );

var returnValues = require( '@stdlib/array/base/group-values' );

var returnIndices = require( '@stdlib/array/base/group-indices' );

var returnPairs = require( '@stdlib/array/base/group-entries' );

var format = require( '@stdlib/string/format' );

var validate = require( './validate.js' );

// MAIN //

/**

* Groups values as arrays associated with distinct keys.

*

* @param {Collection} collection - collection to group

* @param {Options} [options] - function options

* @param {string} [options.returns="values"] - if `values`, values are returned; if `indices`, indices are returned; if `*`, both indices and values are returned

* @param {Collection} groups - collection defining which group an element in the input collection belongs to

* @throws {TypeError} first argument must be a collection

* @throws {TypeError} options argument must be an object

* @throws {TypeError} last argument must be a collection

* @throws {TypeError} must provide valid options

* @throws {RangeError} first and last arguments must be the same length

* @returns {Object} group results

*

* @example

* var arr = [ 'beep', 'boop', 'foo', 'bar' ];

* var groups = [ 'b', 'b', 'f', 'b' ];

*

* var out = group( arr, groups );

* // returns { 'b': [ 'beep', 'boop', 'bar' ], 'f': [ 'foo' ] }

*

* @example

* var arr = [ 'beep', 'boop', 'foo', 'bar' ];

* var groups = [ 'b', 'b', 'f', 'b' ];

*

* var opts = {

* 'returns': 'indices'

* };

*

* var out = group( arr, opts, groups );

* // returns { 'b': [ 0, 1, 3 ], 'f': [ 2 ] }

*

* @example

* var arr = [ 'beep', 'boop', 'foo', 'bar' ];

* var groups = [ 'b', 'b', 'f', 'b' ];

*

* var opts = {

* 'returns': '*'

* };

*

* var out = group( arr, opts, groups );

* // returns { 'b': [ [ 0, 'beep' ], [ 1, 'boop' ], [ 3, 'bar' ] ], 'f': [ [ 2, 'foo' ] ] }

*/

function group( collection, options, groups ) {

var opts;

var err;

var g;

if ( !isCollection( collection ) ) {

throw new TypeError( format( 'invalid argument. First argument must be a collection. Value: `%s`.', collection ) );

}

opts = {

'returns': 'values'

};

if ( arguments.length === 2 ) {

g = options;

} else {

err = validate( opts, options );

if ( err ) {

throw err;

}

g = groups;

}

if ( !isCollection( g ) ) {

throw new TypeError( format( 'invalid argument. Last argument must be a collection. Value: `%s`.', g ) );

}

if ( collection.length !== g.length ) {

throw new RangeError( 'invalid arguments. First and last arguments must be the same length.' );

}

if ( opts.returns === 'values' ) {

return returnValues( collection, g );

}

if ( opts.returns === 'indices' ) {

return returnIndices( collection, g );

}

return returnPairs( collection, g );

}

// EXPORTS //

module.exports = group;