// '{{GENDER:$2}}' -> ''
if ( message.match( /{{GENDER:\$2}}/ ) ) {
	return message.replace( /{{GENDER:\$2}}/, '' );
}

// '{{GENDER:$2|foo}}' -> 'foo'
if ( message.match( /{{GENDER:\$2\|[^|]+}}/ ) ) {
	return message.replace( /{{GENDER:\$2\|([^|]+)}}/, '$1' );
}

// '{{GENDER:$2|bar|baz}}' -> '{{GENDER:$2|bar|baz|bar}}'
if ( message.match( /{{GENDER:\$2\|[^|]+\|[^|]+}}/ ) ) {
	message = message.replace( /{{GENDER:\$2\|([^|]+)\|([^|]+)}}/, '{{GENDER:$$2|$1|$2|$1}}' );
}

// '{{GENDER:$2|foo|bar|baz}}' -> 'foo' or 'bar' or 'baz'
return message.replace(
	/{{GENDER:\$2\|([^|]+)\|([^|]+)\|([^|]+)}}/,
	function ( match, form1, form2, form3, offset, string ) {
		switch ( gender ) {
			case 'male':
				return form1;
			case 'female':
				return form2;
			default:
				return form3;
		}
	}
);

"$1 {{GENDER:$2|changed}} visibility of {{PLURAL:$5|a revision|$5 revisions}} on page $3: $4"
= "$1 {{GENDER:$2|changed}} visibility of {{PLURAL:1|a revision|1 revisions}} on page $3: $4"
   OR
= "$1 {{GENDER:$2|changed}} visibility of {{PLURAL:3|a revision|3 revisions}} on page $3: $4"

"{{PLURAL:1|a revision|1 revisions}}" or "{{PLURAL:3|a revision|3 revisions}}"

"logentry-delete-revision" -> "غيّر{{GENDER:$2||ت}} $1 إمكانية مشاهدة {{PLURAL:$5||مراجعة واحدة|مراجعتين|$5 مراجعات|$5 مراجعة}} في صفحة $3: $4"

var message = "$1 deleted page $3"; // logentry-delete-delete for English after GENDER processing
var groups = message.split( /(\$\d+)/ );
// groups = [ "", "$1", " deleted page ", "$3", "" ]
// handle messages starting and ending with variables, don't create extra text nodes (TODO is this needed?)
if ( groups[0] === '' ) {
	groups.shift();
}
if ( groups[ groups.length - 1 ] === '' ) {
	groups.pop();
}
// groups = [ "$1", " deleted page ", "$3" ]
// TODO do we care about leading and trailing whitespace in the array elements?
if ( groups.indexOf( '$1' ) !== -1 ) {
	// userLink variable is what we want to have for $1
	groups[ groups.indexOf( '$1' ) ] = userLink;
}
if ( groups.indexOf( '$3' ) !== -1 ) {
	// targetPage variable is what we want to have for $3
	groups[ groups.indexOf( '$3' ) ] = targetPage;
}
// And so on for any other parameters, message-specific
return groups;
// returns array of string or (jQuery or VNode) objects to pass to jQuery.append() or a custom render function

class GenderLookup {
	// Cache is for a specific wiki, at least for now - it would be pretty complicated to support a single cache for multiple wikis that are being processed in parallel, especially with dealing with users who may not have set their gender on all sites
	// Cache assumes gender doesn't change for any user during the viewing, including between refreshes - it is unlikely that a user, who has made a log entry that is being shown, changes their gender preference in the time between the initial fetching of their gender and any subsequent refresh, and it makes things a whole lot easier
	this.cache = mw.Map; // key is username, value is gender "male", "female", or "unknown"

	this.api = mw.ForeignApi; // api to use for this wiki

	saveResults: function ( apiResult ) {
		// Convert raw api result to the format that mw.Map.set will accept
		toSet = {};
		apiResult.query.users.forEach( u => toSet[ u.name ] = u.gender )
		this.cache.set( toSet );
	}

	loadGenders: function ( usernames ) : Promise {
		// Like SiteBase.actuallyGetWatchlist() except simpler recursion, load the first 50 and
		// then call saveResults(), either resolve immediately or call recursively with the next,
		// Promise doesn't include the actual genders, this is called after we analyze all of the
		// log entries to figure out which genders we needed to fetch 
	}


	getGender: function ( username ) : string {
		// Fallback to "unknown" in case we missed a lookup
		return this.cache.get( username, 'unknown' );
	}

}

// Handle {{GENDER}} tags that don't actually depend on the gender given
// 1. For translations where there is no form specified, replace with empty string: '{{GENDER:$2}}' -> ''
message = message.replace( /{{GENDER:\$\d}}/g, '' );
// 2. For translations where there is only one form specified, use that: '{{GENDER:$2|foo}}' -> 'foo'
message = message.replace( /{{GENDER:\$\d\|([^|]+)}}/g, '$1' );
// 3. For translations that only specify 2 forms, add the 3rd form using male for unknown: '{{GENDER:$2|bar|baz}}' -> '{{GENDER:$2|bar|baz|bar}}'
message = message.replace( /{{GENDER:\$(\d)\|([^|]+)\|([^|]+)}}/g, '{{GENDER:$$$1|$2|$3|$2}}' );

// Starting from the pre-processed message above, substitute all gender variables, which should each have a value of "male", "female", or "unknown" (code should enforce this)
// Then:
message = message.replace(
	/{{GENDER:(male|female|unknown)\|([^|]+)\|([^|]+)\|([^|]+)}}/g,
	function ( match, gender, form1, form2, form3, offset, string ) {
		switch ( gender ) {
			case 'male':
				return form1;
			case 'female':
				return form2;
			case 'unknown':
				return form3;
		}
	}
);

// Where paramName is '$2', '$5' or similar, and paramValue is the result to replace it with, and message is the source string
// Need to replace all matches, string.replaceAll is not always available, so use a regex
var regex = new RegExp( mw.util.escapeRegExp( paramName ), 'g' );
return message.replace( regex, paramValue );

// Where message is a string like '{{PLURAL:10|one edit|12=a dozen edits|10 edits}}' from {{PLURAL:$5|one edit|12=a dozen edits|$5 edits}}
message = message.replace(
	/{{PLURAL:(\d+)\|([^}]+)}}/g,
	function ( match, num, formsStr, offset, string ) {
		// We know that `num` should be a numerical string, because we just substituted it. Convert to a number for mw.language
		num = parseInt( num, 10 );

		// Split up form to either explicit (use a specific message if the number is exactly the one specified) or normal (use a specific message based on the plural rules for the language)
		var forms = formsStr.split( '|' );
		var explicitForms = {};
		var normalForms = [];
		forms.forEach(
			function ( form ) {
				if ( /^\d+=/.test( form ) ) {
					// Explicit plural forms like 12=a dozen
					var explicitFormNumber = parseInt( form.split( /=/ )[ 0 ], 10 );
					explicitForms[ explicitFormNumber ] = form.slice( form.indexOf( '=' ) + 1 );
				} else {
					normalForms.push( form );
				}
			}
		);

		return mw.language.convertPlural( num, normalForms, explicitForms );
	}
);

{
	"action": "query",
	"meta": "siteinfo|allmessages",
	"siprop": "namespaces",
	"ammessages": "blanknamespace",
	"format": "json",
	"formatversion": "2"
}

1) Visit w/load.php?modules=ext.globalwatchlist.specialglobalwatchlist on patchdemo or wherever the new code is, and copy
2) Visit https://meta.wikimedia.org/w/load.php?modules=ext.globalwatchlist.specialglobalwatchlist, identify the current version (ext.globalwatchlist.specialglobalwatchlist@12789 -> 12789) and in the new code change the implemented version
3) delete from current module registry: `delete mw.loader.moduleRegistry['ext.globalwatchlist.specialglobalwatchlist']`
4) delete from current store: `delete mw.loader.store.items['ext.globalwatchlist.specialglobalwatchlist@12789']`
5) run the implement script from 1) with the changed version from 2) in the console
6) save the changed version `mw.loader.store.add( 'ext.globalwatchlist.specialglobalwatchlist' )`