/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {DefaultTreeDocument, DefaultTreeElement, parseFragment} from 'parse5';

/**
 * Parses a HTML fragment and traverses all AST nodes in order find elements that
 * include the specified attribute.
 */
export function findElementsWithAttribute(html: string, attributeName: string) {
  const document = parseFragment(html, {sourceCodeLocationInfo: true}) as DefaultTreeDocument;
  const elements: DefaultTreeElement[] = [];

  const visitNodes = nodes => {
    nodes.forEach(node => {
      if (node.childNodes) {
        visitNodes(node.childNodes);
      }

      if (node.attrs && node.attrs.some(attr => attr.name === attributeName.toLowerCase())) {
        elements.push(node);
      }
    });
  };

  visitNodes(document.childNodes);

  return elements;
}

/**
 * Finds elements with explicit tag names that also contain the specified attribute. Returns the
 * attribute start offset based on the specified HTML.
 */
export function findAttributeOnElementWithTag(html: string, name: string, tagNames: string[]) {
  return findElementsWithAttribute(html, name)
      .filter(element => tagNames.includes(element.tagName))
      .map(element => getStartOffsetOfAttribute(element, name));
}

/**
 * Finds elements that contain the given attribute and contain at least one of the other
 * specified attributes. Returns the primary attribute's start offset based on the specified HTML.
 */
export function findAttributeOnElementWithAttrs(html: string, name: string, attrs: string[]) {
  return findElementsWithAttribute(html, name)
      .filter(element => attrs.some(attr => hasElementAttribute(element, attr)))
      .map(element => getStartOffsetOfAttribute(element, name));
}

/** Shorthand function that checks if the specified element contains the given attribute. */
function hasElementAttribute(element: DefaultTreeElement, attributeName: string): boolean {
  return element.attrs && element.attrs.some(attr => attr.name === attributeName.toLowerCase());
}


/** Gets the start offset of the given attribute from a Parse5 element. */
export function getStartOffsetOfAttribute(element: any, attributeName: string): number {
  return element.sourceCodeLocation.attrs[attributeName.toLowerCase()].startOffset;
}