132 lines
3.5 KiB
JavaScript
132 lines
3.5 KiB
JavaScript
/**
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* @license Apache-2.0
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*
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* Copyright (c) 2020 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var isString = require( '@stdlib/assert/is-string' ).isPrimitive;
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var isInteger = require( '@stdlib/assert/is-integer' ).isPrimitive;
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var codePointAt = require( './../../code-point-at' );
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var hasUTF16SurrogatePairAt = require( '@stdlib/assert/has-utf16-surrogate-pair-at' );
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var grapheme = require( './../../tools/grapheme-cluster-break' );
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var format = require( './../../format' );
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// VARIABLES //
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var breakType = grapheme.breakType;
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var breakProperty = grapheme.breakProperty;
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var emojiProperty = grapheme.emojiProperty;
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// MAIN //
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/**
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* Returns the next extended grapheme cluster break in a string after a specified position.
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*
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* @param {string} str - input string
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* @param {integer} [fromIndex=0] - position
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* @throws {TypeError} first argument must be a string
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* @throws {TypeError} second argument must be an integer
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* @returns {NonNegativeInteger} next grapheme break position
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*
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* @example
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* var out = nextGraphemeClusterBreak( 'last man standing', 4 );
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* // returns 5
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*
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* @example
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* var out = nextGraphemeClusterBreak( 'presidential election', 8 );
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* // returns 9
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*
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* @example
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* var out = nextGraphemeClusterBreak( 'अनुच्छेद', 1 );
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* // returns 3
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*
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* @example
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* var out = nextGraphemeClusterBreak( '🌷' );
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* // returns -1
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*/
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function nextGraphemeClusterBreak( str, fromIndex ) {
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var breaks;
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var emoji;
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var len;
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var idx;
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var cp;
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var i;
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if ( !isString( str ) ) {
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throw new TypeError( format( 'invalid argument. First argument must be a string. Value: `%s`.', str ) );
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}
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if ( arguments.length > 1 ) {
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if ( !isInteger( fromIndex ) ) {
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throw new TypeError( format( 'invalid argument. Second argument must be an integer. Value: `%s`.', fromIndex ) );
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}
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idx = fromIndex;
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} else {
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idx = 0;
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}
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len = str.length;
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if ( idx < 0 ) {
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idx += len;
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if ( idx < 0 ) {
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idx = 0;
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}
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}
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if ( len === 0 || idx >= len ) {
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return -1;
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}
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// Initialize caches for storing grapheme break and emoji properties:
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breaks = [];
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emoji = [];
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// Get the code point for the starting index:
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cp = codePointAt( str, idx );
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// Get the corresponding grapheme break and emoji properties:
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breaks.push( breakProperty( cp ) );
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emoji.push( emojiProperty( cp ) );
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// Begin searching for the next grapheme cluster break...
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for ( i = idx+1; i < len; i++ ) {
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// If the current character is part of a surrogate pair, move along...
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if ( hasUTF16SurrogatePairAt( str, i-1 ) ) {
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continue;
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}
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// Get the next code point:
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cp = codePointAt( str, i );
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// Get the corresponding grapheme break and emoji properties:
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breaks.push( breakProperty( cp ) );
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emoji.push( emojiProperty( cp ) );
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// Determine if we've encountered a grapheme cluster break...
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if ( breakType( breaks, emoji ) > 0 ) {
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// We've found a break!
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return i;
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}
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}
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// Unable to find a grapheme cluster break:
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return -1;
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}
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// EXPORTS //
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module.exports = nextGraphemeClusterBreak;
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