scramjet/src/shared/rewriters/css.ts

// This CSS rewriter uses code from Meteor
// You can find the original source code at https://github.com/MeteorProxy/Meteor

import { encodeUrl } from "./url";

export function rewriteCss(css: string, origin?: URL) {
    const regex =
    /(@import\s+(?!url\())?\s*url\(\s*(['"]?)([^'")]+)\2\s*\)|@import\s+(['"])([^'"]+)\4/g

    return css.replace(
        regex,
        (
            match,
            importStatement,
            urlQuote,
            urlContent,
            importQuote,
            importContent
        ) => {
            const url = urlContent || importContent
            const encodedUrl = encodeUrl(url.trim(), origin)

            if (importStatement) {
                return `@import url(${urlQuote}${encodedUrl}${urlQuote})`
            }

            if (importQuote) {
                return `@import ${importQuote}${encodedUrl}${importQuote}`
            }

            return `url(${urlQuote}${encodedUrl}${urlQuote})`
        }
    )

}