/**
 * Copyright 2018 Google LLC
 *
 * 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.
 */

import { parse, stringify } from 'postcss';

/**
 * Parse a textual CSS Stylesheet into a Stylesheet instance.
 * Stylesheet is a mutable postcss AST with format similar to CSSOM.
 * @see https://github.com/postcss/postcss/
 * @private
 * @param {String} stylesheet
 * @returns {css.Stylesheet} ast
 */
export function parseStylesheet(stylesheet) {
  return parse(stylesheet);
}

/**
 * Serialize a postcss Stylesheet to a String of CSS.
 * @private
 * @param {css.Stylesheet} ast          A Stylesheet to serialize, such as one returned from `parseStylesheet()`
 * @param {Object} options              Options used by the stringify logic
 * @param {Boolean} [options.compress]  Compress CSS output (removes comments, whitespace, etc)
 */
export function serializeStylesheet(ast, options) {
  let cssStr = '';

  stringify(ast, (result, node, type) => {
    if (!options.compress) {
      cssStr += result;
      return;
    }

    // Simple minification logic
    if (node?.type === 'comment') return;

    if (node?.type === 'decl') {
      const prefix = node.prop + node.raws.between;

      cssStr += result.replace(prefix, prefix.trim());
      return;
    }

    if (type === 'start') {
      if (node.type === 'rule' && node.selectors) {
        cssStr += node.selectors.join(',') + '{';
      } else {
        cssStr += result.replace(/\s\{$/, '{');
      }
      return;
    }

    if (type === 'end' && result === '}' && node?.raws?.semicolon) {
      cssStr = cssStr.slice(0, -1);
    }

    cssStr += result.trim();
  });

  return cssStr;
}

/**
 * Converts a walkStyleRules() iterator to mark nodes with `.$$remove=true` instead of actually removing them.
 * This means they can be removed in a second pass, allowing the first pass to be nondestructive (eg: to preserve mirrored sheets).
 * @private
 * @param {Function} iterator   Invoked on each node in the tree. Return `false` to remove that node.
 * @returns {(rule) => void} nonDestructiveIterator
 */
export function markOnly(predicate) {
  return (rule) => {
    const sel = rule.selectors;
    if (predicate(rule) === false) {
      rule.$$remove = true;
    }
    rule.$$markedSelectors = rule.selectors;
    if (rule._other) {
      rule._other.$$markedSelectors = rule._other.selectors;
    }
    rule.selectors = sel;
  };
}

/**
 * Apply filtered selectors to a rule from a previous markOnly run.
 * @private
 * @param {css.Rule} rule The Rule to apply marked selectors to (if they exist).
 */
export function applyMarkedSelectors(rule) {
  if (rule.$$markedSelectors) {
    rule.selectors = rule.$$markedSelectors;
  }
  if (rule._other) {
    applyMarkedSelectors(rule._other);
  }
}

/**
 * Recursively walk all rules in a stylesheet.
 * @private
 * @param {css.Rule} node       A Stylesheet or Rule to descend into.
 * @param {Function} iterator   Invoked on each node in the tree. Return `false` to remove that node.
 */
export function walkStyleRules(node, iterator) {
  node.nodes = node.nodes.filter((rule) => {
    if (hasNestedRules(rule)) {
      walkStyleRules(rule, iterator);
    }
    rule._other = undefined;
    rule.filterSelectors = filterSelectors;
    return iterator(rule) !== false;
  });
}

/**
 * Recursively walk all rules in two identical stylesheets, filtering nodes into one or the other based on a predicate.
 * @private
 * @param {css.Rule} node       A Stylesheet or Rule to descend into.
 * @param {css.Rule} node2      A second tree identical to `node`
 * @param {Function} iterator   Invoked on each node in the tree. Return `false` to remove that node from the first tree, true to remove it from the second.
 */
export function walkStyleRulesWithReverseMirror(node, node2, iterator) {
  if (node2 === null) return walkStyleRules(node, iterator);

  [node.nodes, node2.nodes] = splitFilter(
    node.nodes,
    node2.nodes,
    (rule, index, rules, rules2) => {
      const rule2 = rules2[index];
      if (hasNestedRules(rule)) {
        walkStyleRulesWithReverseMirror(rule, rule2, iterator);
      }
      rule._other = rule2;
      rule.filterSelectors = filterSelectors;
      return iterator(rule) !== false;
    }
  );
}

// Checks if a node has nested rules, like @media
// @keyframes are an exception since they are evaluated as a whole
function hasNestedRules(rule) {
  return (
    rule.nodes &&
    rule.nodes.length &&
    rule.nodes.some((n) => n.type === 'rule' || n.type === 'atrule') &&
    rule.name !== 'keyframes'
  );
}

// Like [].filter(), but applies the opposite filtering result to a second copy of the Array without a second pass.
// This is just a quicker version of generating the compliment of the set returned from a filter operation.
function splitFilter(a, b, predicate) {
  const aOut = [];
  const bOut = [];
  for (let index = 0; index < a.length; index++) {
    if (predicate(a[index], index, a, b)) {
      aOut.push(a[index]);
    } else {
      bOut.push(a[index]);
    }
  }
  return [aOut, bOut];
}

// can be invoked on a style rule to subset its selectors (with reverse mirroring)
function filterSelectors(predicate) {
  if (this._other) {
    const [a, b] = splitFilter(
      this.selectors,
      this._other.selectors,
      predicate
    );
    this.selectors = a;
    this._other.selectors = b;
  } else {
    this.selectors = this.selectors.filter(predicate);
  }
}
