otion/server/index.mjs

Atomic CSS-in-JS with a featherweight runtime

const STYLE_ELEMENT_ID = "__otion";

/**
 * Creates an injector which collects style rules during server-side rendering.
 */

function VirtualInjector({
  nonce,
  target: ruleTexts = []
} = {}) {
  return {
    nonce,
    ruleTexts,

    insert(rule, index) {
      ruleTexts.splice(index, 0, rule);
      return index;
    }

  };
}

/**
 * Transforms an injector's data into `<style>` tag properties. Useful as a base to build custom server-side renderers upon.
 *
 * @param injector Server-side style rule injector.
 *
 * @returns Properties of a `<style>` tag as an object.
 */

function getStyleProps(injector) {
  return {
    id: STYLE_ELEMENT_ID,
    nonce: injector.nonce,
    textContent: injector.ruleTexts.join("")
  };
}
/**
 * Transforms an injector's data into a `<style>` tag string.
 *
 * @param injector Server-side style rule injector.
 *
 * @returns A stringified `<style>` tag containing server-renderable CSS.
 */

function getStyleTag(injector) {
  const {
    id,
    nonce,
    textContent
  } = getStyleProps(injector);
  let props = `id="${id}"`;
  if (nonce) props += ` nonce="${nonce}"`;
  return `<style ${props}>${textContent}</style>`;
}
/**
 * Filters out style rules which are not statically referenced by the given HTML code.
 *
 * @param injector Server-side style rule injector.
 * @param html HTML code of the underlying page.
 *
 * @returns A copy of the given injector instance with the unused rules filtered out.
 */

function filterOutUnusedRules(injector, html) {
  const usedIdentNames = new Set();
  const re = /<[^>]+\s+?class\s*?=\s*?(".+?"|'.+?'|[^>\s]+)/gi;
  let matches; // eslint-disable-next-line no-cond-assign

  while ((matches = re.exec(html)) != null) {
    const classAttributeValue = matches[1];
    const unquotedClassAttributeValue = classAttributeValue[0] === '"' || classAttributeValue[0] === "'" ? classAttributeValue.slice(1, -1) : classAttributeValue;
    unquotedClassAttributeValue.trim().split(/\s+/) // Ignore excess white space between class names
    .forEach(className => usedIdentNames.add(className));
  }

  const ruleTextsByIdentName = injector.ruleTexts.map(ruleText => [// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
  /_[0-9a-z]+/.exec(ruleText)[0], ruleText]);
  return { ...injector,
    ruleTexts: ruleTextsByIdentName.filter(([identName, ruleText]) => {
      if (usedIdentNames.has(identName)) return true; // Only a `@keyframes` name can be referenced by other scoped rules

      const isReferencedByAnOtherUsedRule = ruleText[0] === "@" && ruleText[1] === "k" && ruleTextsByIdentName.some(([otherIdentName, otherRuleText]) => usedIdentNames.has(otherIdentName) && otherRuleText.includes(identName));
      if (isReferencedByAnOtherUsedRule) return true;
      return false;
    }).map(([, ruleText]) => ruleText)
  };
}

export { VirtualInjector, filterOutUnusedRules, getStyleProps, getStyleTag };
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