0591-tag-validator.js

/**
 * Tag Validator
 * Time Complexity: O(N)
 * Space Complexity: O(N)
 */
var isValid = function (snippetContent) {
  const tagRepository = [];
  let currentReadPosition = 0;
  const contentLength = snippetContent.length;

  while (currentReadPosition < contentLength) {
    const isOutsideAnyTag =
      currentReadPosition > 0 && tagRepository.length === 0;
    if (isOutsideAnyTag) {
      return false;
    }

    const cdataStartSequence = "<![CDATA[";
    if (snippetContent.startsWith(cdataStartSequence, currentReadPosition)) {
      if (tagRepository.length === 0) {
        return false;
      }
      const cdataContentStartIndex =
        currentReadPosition + cdataStartSequence.length;
      const cdataEndSequenceIndex = snippetContent.indexOf(
        "]]>",
        cdataContentStartIndex,
      );
      if (cdataEndSequenceIndex === -1) {
        return false;
      }
      currentReadPosition = cdataEndSequenceIndex + 3;
      continue;
    }

    const closingTagStartSequence = "</";
    if (
      snippetContent.startsWith(closingTagStartSequence, currentReadPosition)
    ) {
      const tagNameIdentifierStart =
        currentReadPosition + closingTagStartSequence.length;
      const tagNameIdentifierEnd = snippetContent.indexOf(
        ">",
        tagNameIdentifierStart,
      );
      if (tagNameIdentifierEnd === -1) {
        return false;
      }
      const extractedTagString = snippetContent.slice(
        tagNameIdentifierStart,
        tagNameIdentifierEnd,
      );
      if (!/^[A-Z]{1,9}$/.test(extractedTagString)) {
        return false;
      }
      if (
        tagRepository.length === 0 ||
        tagRepository.pop() !== extractedTagString
      ) {
        return false;
      }
      currentReadPosition = tagNameIdentifierEnd + 1;
      continue;
    }

    const openingTagCharacter = "<";
    if (snippetContent[currentReadPosition] === openingTagCharacter) {
      const tagContentStart = currentReadPosition + 1;
      const tagContentEnd = snippetContent.indexOf(">", tagContentStart);
      if (tagContentEnd === -1) {
        return false;
      }
      const tagTextContent = snippetContent.slice(
        tagContentStart,
        tagContentEnd,
      );
      if (!/^[A-Z]{1,9}$/.test(tagTextContent)) {
        return false;
      }
      tagRepository.push(tagTextContent);
      currentReadPosition = tagContentEnd + 1;
      continue;
    }

    if (tagRepository.length === 0) {
      return false;
    }
    currentReadPosition++;
  }

  return tagRepository.length === 0;
};