prefixer.js

/**
 * Based on https://github.com/jsstyles/css-vendor, but without having to
 * convert between different cases all the time.
 *
 * @flow
 */

import createStaticPrefixer from 'inline-style-prefixer/static/createPrefixer';
import createDynamicPrefixer from 'inline-style-prefixer/dynamic/createPrefixer';
import ExecutionEnvironment from 'exenv';

import staticData from './prefix-data/static';
import dynamicData from './prefix-data/dynamic';

import {camelCaseToDashCase} from './camel-case-props-to-dash-case';

const prefixAll: (style: Object) => Object = createStaticPrefixer(staticData);
const InlineStylePrefixer = createDynamicPrefixer(dynamicData, prefixAll);

function transformValues(style) {
  return Object.keys(style).reduce((newStyle, key) => {
    let value = style[key];
    if (Array.isArray(value)) {
      value = value.join(';' + key + ':');
    } else if (
      value &&
      typeof value === 'object' &&
      typeof value.toString === 'function'
    ) {
      value = value.toString();
    }

    newStyle[key] = value;
    return newStyle;
  }, {});
}

// Flatten prefixed values that are arrays to strings.
//
// We get prefixed styles back in the form of:
// - `display: "flex"` OR
// - `display: "-webkit-flex"` OR
// - `display: [/* ... */, "-webkit-flex", "flex"]
//
// The last form is problematic for eventual use in the browser and server
// render. More confusingly, we have to do **different** things on the
// browser and server (noted inline below).
//
// https://github.com/FormidableLabs/radium/issues/958
function flattenStyleValues(style) {
  return Object.keys(style).reduce((newStyle, key) => {
    let val = style[key];
    if (Array.isArray(val)) {
      if (ExecutionEnvironment.canUseDOM) {
        // For the **browser**, when faced with multiple values, we just take
        // the **last** one, which is the original passed in value before
        // prefixing. This _should_ work, because `inline-style-prefixer`
        // we're just passing through what would happen without ISP.

        val = val[val.length - 1].toString();
      } else {
        // For the **server**, we just concatenate things together and convert
        // the style object values into a hacked-up string of like `display:
        // "-webkit-flex;display:flex"` that will SSR render correctly to like
        // `"display:-webkit-flex;display:flex"` but would otherwise be
        // totally invalid values.

        // We convert keys to dash-case only for the serialize values and
        // leave the real key camel-cased so it's as expected to React and
        // other parts of the processing chain.
        val = val.join(`;${camelCaseToDashCase(key)}:`);
      }
    }

    newStyle[key] = val;
    return newStyle;
  }, {});
}

let _hasWarnedAboutUserAgent = false;
let _lastUserAgent;
let _cachedPrefixer;

function getPrefixer(
  userAgent: ?string
): {
  +prefix: (style: Object) => Object,
  prefixedKeyframes: string
} {
  const actualUserAgent =
    userAgent || (global && global.navigator && global.navigator.userAgent);

  if (process.env.NODE_ENV !== 'production') {
    if (!actualUserAgent && !_hasWarnedAboutUserAgent) {
      /* eslint-disable no-console */
      console.warn(
        'Radium: userAgent should be supplied for server-side rendering. See ' +
          'https://github.com/FormidableLabs/radium/tree/master/docs/api#radium ' +
          'for more information.'
      );
      /* eslint-enable no-console */
      _hasWarnedAboutUserAgent = true;
    }
  }

  if (
    process.env.NODE_ENV === 'test' ||
    (!_cachedPrefixer || actualUserAgent !== _lastUserAgent)
  ) {
    if (actualUserAgent === 'all') {
      _cachedPrefixer = {
        prefix: prefixAll,
        prefixedKeyframes: 'keyframes'
      };
    } else {
      _cachedPrefixer = new InlineStylePrefixer({userAgent: actualUserAgent});
    }
    _lastUserAgent = actualUserAgent;
  }

  return _cachedPrefixer;
}

export function getPrefixedKeyframes(userAgent?: ?string): string {
  return getPrefixer(userAgent).prefixedKeyframes || 'keyframes';
}

// Returns a new style object with vendor prefixes added to property names and
// values.
export function getPrefixedStyle(style: Object, userAgent?: ?string): Object {
  const styleWithFallbacks = transformValues(style);
  const prefixer = getPrefixer(userAgent);
  const prefixedStyle = prefixer.prefix(styleWithFallbacks);
  const flattenedStyle = flattenStyleValues(prefixedStyle);
  return flattenedStyle;
}