systrace/catapult/third_party/polymer/components/shadycss/src/style-util.js

/**
@license
Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
Code distributed by Google as part of the polymer project is also
subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
*/

'use strict';

import {nativeShadow, nativeCssVariables, cssBuild} from './style-settings.js';
import {parse, stringify, types, StyleNode} from './css-parse.js'; // eslint-disable-line no-unused-vars
import {MEDIA_MATCH} from './common-regex.js';
import {processUnscopedStyle, isUnscopedStyle} from './unscoped-style-handler.js';

/**
 * @param {string|StyleNode} rules
 * @param {function(StyleNode)=} callback
 * @return {string}
 */
export function toCssText (rules, callback) {
  if (!rules) {
    return '';
  }
  if (typeof rules === 'string') {
    rules = parse(rules);
  }
  if (callback) {
    forEachRule(rules, callback);
  }
  return stringify(rules, nativeCssVariables);
}

/**
 * @param {HTMLStyleElement} style
 * @return {StyleNode}
 */
export function rulesForStyle(style) {
  if (!style['__cssRules'] && style.textContent) {
    style['__cssRules'] = parse(style.textContent);
  }
  return style['__cssRules'] || null;
}

// Tests if a rule is a keyframes selector, which looks almost exactly
// like a normal selector but is not (it has nothing to do with scoping
// for example).
/**
 * @param {StyleNode} rule
 * @return {boolean}
 */
export function isKeyframesSelector(rule) {
  return Boolean(rule['parent']) &&
  rule['parent']['type'] === types.KEYFRAMES_RULE;
}

/**
 * @param {StyleNode} node
 * @param {Function=} styleRuleCallback
 * @param {Function=} keyframesRuleCallback
 * @param {boolean=} onlyActiveRules
 */
export function forEachRule(node, styleRuleCallback, keyframesRuleCallback, onlyActiveRules) {
  if (!node) {
    return;
  }
  let skipRules = false;
  let type = node['type'];
  if (onlyActiveRules) {
    if (type === types.MEDIA_RULE) {
      let matchMedia = node['selector'].match(MEDIA_MATCH);
      if (matchMedia) {
        // if rule is a non matching @media rule, skip subrules
        if (!window.matchMedia(matchMedia[1]).matches) {
          skipRules = true;
        }
      }
    }
  }
  if (type === types.STYLE_RULE) {
    styleRuleCallback(node);
  } else if (keyframesRuleCallback &&
    type === types.KEYFRAMES_RULE) {
    keyframesRuleCallback(node);
  } else if (type === types.MIXIN_RULE) {
    skipRules = true;
  }
  let r$ = node['rules'];
  if (r$ && !skipRules) {
    for (let i=0, l=r$.length, r; (i<l) && (r=r$[i]); i++) {
      forEachRule(r, styleRuleCallback, keyframesRuleCallback, onlyActiveRules);
    }
  }
}

// add a string of cssText to the document.
/**
 * @param {string} cssText
 * @param {string} moniker
 * @param {Node} target
 * @param {Node} contextNode
 * @return {HTMLStyleElement}
 */
export function applyCss(cssText, moniker, target, contextNode) {
  let style = createScopeStyle(cssText, moniker);
  applyStyle(style, target, contextNode);
  return style;
}

/**
 * @param {string} cssText
 * @param {string} moniker
 * @return {HTMLStyleElement}
 */
export function createScopeStyle(cssText, moniker) {
  let style = /** @type {HTMLStyleElement} */(document.createElement('style'));
  if (moniker) {
    style.setAttribute('scope', moniker);
  }
  style.textContent = cssText;
  return style;
}

/**
 * Track the position of the last added style for placing placeholders
 * @type {Node}
 */
let lastHeadApplyNode = null;

// insert a comment node as a styling position placeholder.
/**
 * @param {string} moniker
 * @return {!Comment}
 */
export function applyStylePlaceHolder(moniker) {
  let placeHolder = document.createComment(' Shady DOM styles for ' +
    moniker + ' ');
  let after = lastHeadApplyNode ?
    lastHeadApplyNode['nextSibling'] : null;
  let scope = document.head;
  scope.insertBefore(placeHolder, after || scope.firstChild);
  lastHeadApplyNode = placeHolder;
  return placeHolder;
}

/**
 * @param {HTMLStyleElement} style
 * @param {?Node} target
 * @param {?Node} contextNode
 */
export function applyStyle(style, target, contextNode) {
  target = target || document.head;
  let after = (contextNode && contextNode.nextSibling) ||
    target.firstChild;
  target.insertBefore(style, after);
  if (!lastHeadApplyNode) {
    lastHeadApplyNode = style;
  } else {
    // only update lastHeadApplyNode if the new style is inserted after the old lastHeadApplyNode
    let position = style.compareDocumentPosition(lastHeadApplyNode);
    if (position === Node.DOCUMENT_POSITION_PRECEDING) {
      lastHeadApplyNode = style;
    }
  }
}

/**
 * @param {string} buildType
 * @return {boolean}
 */
export function isTargetedBuild(buildType) {
  return nativeShadow ? buildType === 'shadow' : buildType === 'shady';
}

/**
 * Walk from text[start] matching parens and
 * returns position of the outer end paren
 * @param {string} text
 * @param {number} start
 * @return {number}
 */
export function findMatchingParen(text, start) {
  let level = 0;
  for (let i=start, l=text.length; i < l; i++) {
    if (text[i] === '(') {
      level++;
    } else if (text[i] === ')') {
      if (--level === 0) {
        return i;
      }
    }
  }
  return -1;
}

/**
 * @param {string} str
 * @param {function(string, string, string, string)} callback
 */
export function processVariableAndFallback(str, callback) {
  // find 'var('
  let start = str.indexOf('var(');
  if (start === -1) {
    // no var?, everything is prefix
    return callback(str, '', '', '');
  }
  //${prefix}var(${inner})${suffix}
  let end = findMatchingParen(str, start + 3);
  let inner = str.substring(start + 4, end);
  let prefix = str.substring(0, start);
  // suffix may have other variables
  let suffix = processVariableAndFallback(str.substring(end + 1), callback);
  let comma = inner.indexOf(',');
  // value and fallback args should be trimmed to match in property lookup
  if (comma === -1) {
    // variable, no fallback
    return callback(prefix, inner.trim(), '', suffix);
  }
  // var(${value},${fallback})
  let value = inner.substring(0, comma).trim();
  let fallback = inner.substring(comma + 1).trim();
  return callback(prefix, value, fallback, suffix);
}

/**
 * @param {Element} element
 * @param {string} value
 */
export function setElementClassRaw(element, value) {
  // use native setAttribute provided by ShadyDOM when setAttribute is patched
  if (nativeShadow) {
    element.setAttribute('class', value);
  } else {
    window['ShadyDOM']['nativeMethods']['setAttribute'].call(element, 'class', value);
  }
}

export const wrap = window['ShadyDOM'] && window['ShadyDOM']['wrap'] || ((node) => node);

/**
 * @param {Element | {is: string, extends: string}} element
 * @return {{is: string, typeExtension: string}}
 */
export function getIsExtends(element) {
  let localName = element['localName'];
  let is = '', typeExtension = '';
  /*
  NOTE: technically, this can be wrong for certain svg elements
  with `-` in the name like `<font-face>`
  */
  if (localName) {
    if (localName.indexOf('-') > -1) {
      is = localName;
    } else {
      typeExtension = localName;
      is = (element.getAttribute && element.getAttribute('is')) || '';
    }
  } else {
    is = /** @type {?} */(element).is;
    typeExtension = /** @type {?} */(element).extends;
  }
  return {is, typeExtension};
}

/**
 * @param {Element|DocumentFragment} element
 * @return {string}
 */
export function gatherStyleText(element) {
  /** @type {!Array<string>} */
  const styleTextParts = [];
  const styles = /** @type {!NodeList<!HTMLStyleElement>} */(element.querySelectorAll('style'));
  for (let i = 0; i < styles.length; i++) {
    const style = styles[i];
    if (isUnscopedStyle(style)) {
      if (!nativeShadow) {
        processUnscopedStyle(style);
        style.parentNode.removeChild(style);
      }
    } else {
      styleTextParts.push(style.textContent);
      style.parentNode.removeChild(style);
    }
  }
  return styleTextParts.join('').trim();
}

/**
 * Split a selector separated by commas into an array in a smart way
 * @param {string} selector
 * @return {!Array<string>}
 */
export function splitSelectorList(selector) {
  const parts = [];
  let part = '';
  for (let i = 0; i >= 0 && i < selector.length; i++) {
    // A selector with parentheses will be one complete part
    if (selector[i] === '(') {
      // find the matching paren
      const end = findMatchingParen(selector, i);
      // push the paren block into the part
      part += selector.slice(i, end + 1);
      // move the index to after the paren block
      i = end;
    } else if (selector[i] === ',') {
      parts.push(part);
      part = '';
    } else {
      part += selector[i];
    }
  }
  // catch any pieces after the last comma
  if (part) {
    parts.push(part);
  }
  return parts;
}

const CSS_BUILD_ATTR = 'css-build';

/**
 * Return the polymer-css-build "build type" applied to this element
 *
 * @param {!HTMLElement} element
 * @return {string} Can be "", "shady", or "shadow"
 */
export function getCssBuild(element) {
  if (cssBuild !== undefined) {
    return /** @type {string} */(cssBuild);
  }
  if (element.__cssBuild === undefined) {
    // try attribute first, as it is the common case
    const attrValue = element.getAttribute(CSS_BUILD_ATTR);
    if (attrValue) {
      element.__cssBuild = attrValue;
    } else {
      const buildComment = getBuildComment(element);
      if (buildComment !== '') {
        // remove build comment so it is not needlessly copied into every element instance
        removeBuildComment(element);
      }
      element.__cssBuild = buildComment;
    }
  }
  return element.__cssBuild || '';
}

/**
 * Check if the given element, either a <template> or <style>, has been processed
 * by polymer-css-build.
 *
 * If so, then we can make a number of optimizations:
 * - polymer-css-build will decompose mixins into individual CSS Custom Properties,
 * so the ApplyShim can be skipped entirely.
 * - Under native ShadowDOM, the style text can just be copied into each instance
 * without modification
 * - If the build is "shady" and ShadyDOM is in use, the styling does not need
 * scoping beyond the shimming of CSS Custom Properties
 *
 * @param {!HTMLElement} element
 * @return {boolean}
 */
export function elementHasBuiltCss(element) {
  return getCssBuild(element) !== '';
}

/**
 * For templates made with tagged template literals, polymer-css-build will
 * insert a comment of the form `<!--css-build:shadow-->`
 *
 * @param {!HTMLElement} element
 * @return {string}
 */
export function getBuildComment(element) {
  const buildComment = element.localName === 'template' ?
      /** @type {!HTMLTemplateElement} */ (element).content.firstChild :
      element.firstChild;
  if (buildComment instanceof Comment) {
    const commentParts = buildComment.textContent.trim().split(':');
    if (commentParts[0] === CSS_BUILD_ATTR) {
      return commentParts[1];
    }
  }
  return '';
}

/**
 * Check if the css build status is optimal, and do no unneeded work.
 *
 * @param {string=} cssBuild CSS build status
 * @return {boolean} css build is optimal or not
 */
export function isOptimalCssBuild(cssBuild = '') {
  // CSS custom property shim always requires work
  if (cssBuild === '' || !nativeCssVariables) {
    return false;
  }
  return nativeShadow ? cssBuild === 'shadow' : cssBuild === 'shady';
}

/**
 * @param {!HTMLElement} element
 */
function removeBuildComment(element) {
  const buildComment = element.localName === 'template' ?
      /** @type {!HTMLTemplateElement} */ (element).content.firstChild :
      element.firstChild;
  buildComment.parentNode.removeChild(buildComment);
}