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* @license Apache-2.0
*
* Copyright (c) 2025 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 copy = require( '@stdlib/array/base/copy-indexed' );
var ndarray = require( '@stdlib/ndarray/base/ctor' );
var getShape = require( '@stdlib/ndarray/base/shape' );
var getStrides = require( '@stdlib/ndarray/base/strides' );
var getOffset = require( '@stdlib/ndarray/base/offset' );
var getOrder = require( '@stdlib/ndarray/base/order' );
var getDType = require( '@stdlib/ndarray/base/dtype' );
var getData = require( '@stdlib/ndarray/base/data-buffer' );
var normalizeIndices = require( '@stdlib/ndarray/base/normalize-indices' );
var format = require( '@stdlib/string/format' );
var join = require( '@stdlib/array/base/join' );
// MAIN //
/**
* Broadcasts an input ndarray to a target shape keeping the specified dimensions unchanged.
*
* @param {ndarray} arr - input array
* @param {NonNegativeIntegerArray} shape - desired shape
* @param {IntegerArray} [dims] - list of dimensions to exclude
* @throws {Error} input array cannot have more dimensions than the desired shape
* @throws {Error} input array and desired shape must be broadcast compatible
* @throws {RangeError} dimension indices must not exceed desired shape bounds
* @throws {Error} must provide unique dimension indices
* @returns {ndarray} broadcasted array
*
* @example
* var array = require( '@stdlib/ndarray/array' );
*
* var x = array( [ [ 1, 2, 3 ] ] );
* // returns <ndarray>
*
* var shx = x.shape;
* // returns [ 1, 3 ]
*
* var y = broadcastArrayExceptDimensions( x, [ 2, 2, 3 ], [ -2 ] );
* // returns <ndarray>
*
* var shy = y.shape;
* // returns [ 2, 1, 3 ]
*
* var v = y.get( 0, 0, 0 );
* // returns 1
*
* v = y.get( 0, 0, 1 );
* // returns 2
*
* v = y.get( 0, 0, 2 );
* // returns 3
*
* v = y.get( 1, 0, 0 );
* // returns 1
*
* v = y.get( 1, 0, 1 );
* // returns 2
*
* v = y.get( 1, 0, 2 );
* // returns 3
*/
function broadcastArrayExceptDimensions( arr, shape, dims ) {
var strides;
var dim;
var sh;
var st;
var dl;
var di;
var N;
var M;
var d;
var i;
var j;
N = shape.length;
sh = getShape( arr, false );
M = sh.length;
if ( N < M ) {
throw new Error( 'invalid argument. Cannot broadcast an array to a shape having fewer dimensions. Arrays can only be broadcasted to shapes having the same or more dimensions.' );
}
// Initialize a strides array...
strides = [];
for ( i = 0; i < N; i++ ) {
strides.push( 0 );
}
// Determine the output array strides...
st = getStrides( arr, false );
if ( !dims ) {
dims = [ -1 ];
}
// Verify that we've been provided a list of unique dimension indices...
dl = dims.length;
dims = normalizeIndices( dims, N - 1 );
if ( dims === null ) {
throw new RangeError( format( 'invalid argument. Third argument contains an out-of-bounds dimension index. Value: [%s].', join( dims, ',' ) ) );
}
dims.sort();
if ( dims.length !== dl ) {
throw new Error( format( 'invalid argument. Third argument must contain a list of unique dimension indices. Value: [%s].', join( dims, ',' ) ) );
}
di = dims.length - 1;
for ( i = N-1; i >= 0; i-- ) {
j = M - N + i;
if ( di >= 0 && dims[ di ] === i ) {
if ( j >= 0 ) {
shape[ i ] = sh[ j ];
strides[ i ] = st[ j ];
}
di -= 1;
continue;
}
if ( j < 0 ) {
// Prepended singleton dimension; stride is zero...
continue;
}
d = sh[ j ];
dim = shape[ i ];
if ( dim !== 0 && dim < d ) {
throw new Error( format( 'invalid argument. Input array cannot be broadcast to the specified shape, as the specified shape has a dimension whose size is less than the size of the corresponding dimension in the input array. Array shape: (%s). Desired shape: (%s). Dimension: %u.', copy( sh ).join( ', ' ), copy( shape ).join( ', ' ), i ) );
}
if ( d === dim ) {
strides[ i ] = st[ j ];
} else if ( d === 1 ) {
// In order to broadcast dimensions, we set the stride for that dimension to zero...
strides[ i ] = 0;
} else {
// At this point, we know that `dim > d` and that `d` does not equal `1` (e.g., `dim=3` and `d=2`); in which case, the shapes are considered incompatible (even for desired shapes which are multiples of array dimensions, as might be desired when "tiling" an array; e.g., `dim=4` and `d=2`)...
throw new Error( format( 'invalid argument. Input array and the specified shape are broadcast incompatible. Array shape: (%s). Desired shape: (%s). Dimension: %u.', copy( sh ).join( ', ' ), copy( shape ).join( ', ' ), i ) );
}
}
return ndarray( getDType( arr ), getData( arr ), copy( shape ), strides, getOffset( arr ), getOrder( arr ) ); // eslint-disable-line max-len
}
// EXPORTS //
module.exports = broadcastArrayExceptDimensions;
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