reactive_settings.js

// language=Handlebars
const RAW_CLASS_TEMPLATE = `
class SettingsClass extends {{baseClassName}} {
    namespace = {{toStringLiteral namespace}}

    //// Private Methods ////
    static _register() {
        {{#each settings as | setting |}}
            game.settings.register(
                this.namespace,
                {{toStringLiteral setting.keyName}},
                {
                    ...{{toObjectLiteral 16 setting.config}},
                    callback: function(value) {
                        {{setting.fieldName}} = value;
                    }
                },
            );
        {{/each}}
    }

    //// Property Logic ////
    {{#each settings as | setting |}}
        // Logic for {{setting.keyName}}/{{setting.fieldName}}
        _{{setting.fieldName}} = null;

        get {{setting.fieldName}}() {
            {{toThisProperty setting.fieldName}};
        }

        set {{setting.fieldName}}(value) {
            {{toThisProperty setting.fieldName}} = value;
            game.settings.set(this.namespace, {{toStringLiteral setting.keyName}}, value);
        }


    {{/each}}
}

return SettingsClass
`

// Constants
const Handlebars = Handlebars.create();
const CLASS_TEMPLATE = Handlebars.compile(RAW_CLASS_TEMPLATE, {noEscape: true})


// Helpers
Handlebars.registerHelper('toStringLiteral', function (value) {
    return '"' + value + '"';
})

Handlebars.registerHelper('toThisProperty', function (value) {
    return 'this._' + value;
})

Handlebars.registerHelper('toObjectLiteral', function (count, value) {
    const lead = '\n' + ' '.repeat(count)
    return JSON
      .stringify(value, null, '    ')
      .replaceAll('\n', lead);
})


// API
function createSettingsClass(settings) {
    return Function(CLASS_TEMPLATE(settings))()
}