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import { isValidElement, cloneElement } from 'react';
/**
* Prevent widows by replacing spaces between the last `wordsToKeep` words in the text with non-breaking spaces
* @param {string|@i18n-calypso/TranslateResult} text the text to work on
* @param {number} wordsToKeep the number of words to keep together
* @returns {string} the widow-prevented string
*/
export function preventWidows( text, wordsToKeep = 2 ) {
return preventWidowsInPart(
'string' === typeof text ? text.trim() : text,
Math.max( 1, wordsToKeep - 1 )
).part;
}
const reverseSpaceRegex = /\s+(\S*)$/;
/**
* The helper function to preventWidows that calls itself recursively searching for spaces to substitute with
* non-breaking spaces.
* @param {string|@i18n-calypso/TranslateResult} part The section of the content to search, a string or a component
* or an array of strings and components
* @param {number} spacesToSubstitute The number of spaces to substitute with non-breaking spaces. This is one less than the preventWidows wordsToKeep
* @returns object Contains two keys `part` the possibly modified `part` parameter passed in, and `substituted` the number of spaces substituted.
*/
function preventWidowsInPart( part, spacesToSubstitute ) {
let substituted = 0;
if ( 'string' === typeof part && part.length > 0 ) {
let text = part;
let retVal = '';
// If the part is a string, work from the right looking for spaces
// TODO Work out if we can tell that this is a RTL language, and if it's appropriate to join words in this way
while ( substituted < spacesToSubstitute && reverseSpaceRegex.test( text ) ) {
const match = reverseSpaceRegex.exec( text );
retVal = '\xA0' + match[ 1 ] + retVal;
text = text.replace( reverseSpaceRegex, '' );
substituted++;
}
retVal = text + retVal;
// Return the modified string and the number of spaces substituted
return { part: retVal, substituted };
}
/* If we're called with an array construct a copy of the array by calling
* ourself on each element until we have substituted enough spaces. Then
* concatentate the rest of the array
*/
if ( Array.isArray( part ) && part.length > 0 ) {
let elements = [];
let idx = part.length - 1;
while ( substituted < spacesToSubstitute && idx >= 0 ) {
const result = preventWidowsInPart( part[ idx ], spacesToSubstitute - substituted );
elements.unshift( result.part );
substituted += result.substituted;
idx--;
}
elements = part.slice( 0, idx + 1 ).concat( elements );
return { part: elements, substituted };
}
/* If we're called with a component, and it has children
* then call ourself with the value of the children prop
* (an array that will be handled above)
*
* Then return a cloned component with the possibly modified
* children, along with the tally of substituted spaces.
*/
if ( isValidElement( part ) && part.props.children ) {
const result = preventWidowsInPart( part.props.children, spacesToSubstitute );
if ( result.substituted > 0 ) {
// pass children as spread arguments to prevent missing array key warnings
const partArray = Array.isArray( result.part ) ? result.part : [ result.part ];
return {
part: cloneElement( part, part.props, ...partArray ),
substituted: result.substituted,
};
}
return { part, substituted };
}
// For anything else e.g. an element without children, there's nothing to do.
return { part, substituted };
}
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