'use strict';

/**
 * This code is mostly from the old Etherpad. Please help us to comment this code.
 * This helps other people to understand this code better and helps them to improve it.
 * TL;DR COMMENTS ON THIS FILE ARE HIGHLY APPRECIATED
 */

/**
 * Copyright 2009 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS-IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

const makeCSSManager = (emptyStylesheetTitle, doc) => {
  if (doc === true) {
    doc = 'parent';
  } else if (!doc) {
    doc = 'inner';
  }

  const getSheetByTitle = (title) => {
    let win;
    if (doc === 'parent') {
      win = window.parent.parent;
    } else if (doc === 'inner') {
      win = window;
    } else if (doc === 'outer') {
      win = window.parent;
    } else {
      throw new Error('Unknown dynamic style container');
    }
    const allSheets = win.document.styleSheets;

    for (let i = 0; i < allSheets.length; i++) {
      const s = allSheets[i];
      if (s.title === title) {
        return s;
      }
    }
    return null;
  };

  const browserSheet = getSheetByTitle(emptyStylesheetTitle);

  const browserRules = () => (browserSheet.cssRules || browserSheet.rules);

  const browserDeleteRule = (i) => {
    if (browserSheet.deleteRule) browserSheet.deleteRule(i);
    else browserSheet.removeRule(i);
  };

  const browserInsertRule = (i, selector) => {
    if (browserSheet.insertRule) browserSheet.insertRule(`${selector} {}`, i);
    else browserSheet.addRule(selector, null, i);
  };
  const selectorList = [];

  const indexOfSelector = (selector) => {
    for (let i = 0; i < selectorList.length; i++) {
      if (selectorList[i] === selector) {
        return i;
      }
    }
    return -1;
  };

  const selectorStyle = (selector) => {
    let i = indexOfSelector(selector);
    if (i < 0) {
      // add selector
      browserInsertRule(0, selector);
      selectorList.splice(0, 0, selector);
      i = 0;
    }
    return browserRules().item(i).style;
  };

  const removeSelectorStyle = (selector) => {
    const i = indexOfSelector(selector);
    if (i >= 0) {
      browserDeleteRule(i);
      selectorList.splice(i, 1);
    }
  };

  return {
    selectorStyle,
    removeSelectorStyle,
    info: () => `${selectorList.length}:${browserRules().length}`,
  };
};

exports.makeCSSManager = makeCSSManager;