'use strict';

const util = require('./util');

const defaultOptions = {
  allowBooleanAttributes: false, //A tag can have attributes without any value
  localeRange: 'a-zA-Z',
};

const props = ['allowBooleanAttributes', 'localeRange'];

//const tagsPattern = new RegExp("<\\/?([\\w:\\-_\.]+)\\s*\/?>","g");
exports.validate = function (xmlData, options) {
  options = util.buildOptions(options, defaultOptions, props);

  //xmlData = xmlData.replace(/(\r\n|\n|\r)/gm,"");//make it single line
  //xmlData = xmlData.replace(/(^\s*<\?xml.*?\?>)/g,"");//Remove XML starting tag
  //xmlData = xmlData.replace(/(<!DOCTYPE[\s\w\"\.\/\-\:]+(\[.*\])*\s*>)/g,"");//Remove DOCTYPE
  const localRangeRegex = new RegExp(`[${options.localeRange}]`);

  if (localRangeRegex.test("<#$'\"\\\/:0")) {
    return getErrorObject('InvalidOptions', 'Invalid localeRange', 1);
  }

  const tags = [];
  let tagFound = false;

  //indicates that the root tag has been closed (aka. depth 0 has been reached)
  let reachedRoot = false;

  if (xmlData[0] === '\ufeff') {
    // check for byte order mark (BOM)
    xmlData = xmlData.substr(1);
  }
  const regxAttrName = new RegExp(`^[${options.localeRange}_][${options.localeRange}0-9\\-\\.:]*$`);
  const regxTagName = new RegExp(`^([${options.localeRange}_])[${options.localeRange}0-9\\.\\-_:]*$`);
  for (let i = 0; i < xmlData.length; i++) {
    if (xmlData[i] === '<') {
      //starting of tag
      //read until you reach to '>' avoiding any '>' in attribute value

      i++;
      if (xmlData[i] === '?') {
        i = readPI(xmlData, ++i);
        if (i.err) {
          return i;
        }
      } else if (xmlData[i] === '!') {
        i = readCommentAndCDATA(xmlData, i);
        continue;
      } else {
        let closingTag = false;
        if (xmlData[i] === '/') {
          //closing tag
          closingTag = true;
          i++;
        }
        //read tagname
        let tagName = '';
        for (
          ;
          i < xmlData.length &&
          xmlData[i] !== '>' &&
          xmlData[i] !== ' ' &&
          xmlData[i] !== '\t' &&
          xmlData[i] !== '\n' &&
          xmlData[i] !== '\r';
          i++
        ) {
          tagName += xmlData[i];
        }
        tagName = tagName.trim();
        //console.log(tagName);

        if (tagName[tagName.length - 1] === '/') {
          //self closing tag without attributes
          tagName = tagName.substring(0, tagName.length - 1);
          //continue;
          i--;
        }
        if (!validateTagName(tagName, regxTagName)) {
          let msg;
          if(tagName.trim().length === 0) {
            msg = "There is an unnecessary space between tag name and backward slash '</ ..'.";
          }else{
            msg = `Tag '${tagName}' is an invalid name.`;
          }
          return getErrorObject('InvalidTag', msg, getLineNumberForPosition(xmlData, i));
        }

        const result = readAttributeStr(xmlData, i);
        if (result === false) {
          return getErrorObject('InvalidAttr', `Attributes for '${tagName}' have open quote.`, getLineNumberForPosition(xmlData, i));
        }
        let attrStr = result.value;
        i = result.index;

        if (attrStr[attrStr.length - 1] === '/') {
          //self closing tag
          attrStr = attrStr.substring(0, attrStr.length - 1);
          const isValid = validateAttributeString(attrStr, options, regxAttrName);
          if (isValid === true) {
            tagFound = true;
            //continue; //text may presents after self closing tag
          } else {
            //the result from the nested function returns the position of the error within the attribute
            //in order to get the 'true' error line, we need to calculate the position where the attribute begins (i - attrStr.length) and then add the position within the attribute
            //this gives us the absolute index in the entire xml, which we can use to find the line at last
            return getErrorObject(isValid.err.code, isValid.err.msg, getLineNumberForPosition(xmlData, i - attrStr.length + isValid.err.line));
          }
        } else if (closingTag) {
          if (!result.tagClosed) {
            return getErrorObject('InvalidTag', `Closing tag '${tagName}' doesn't have proper closing.`, getLineNumberForPosition(xmlData, i));
          } else if (attrStr.trim().length > 0) {
            return getErrorObject('InvalidTag', `Closing tag '${tagName}' can't have attributes or invalid starting.`, getLineNumberForPosition(xmlData, i));
          } else {
            const otg = tags.pop();
            if (tagName !== otg) {
              return getErrorObject('InvalidTag', `Closing tag '${otg}' is expected inplace of '${tagName}'.`, getLineNumberForPosition(xmlData, i));
            }

            //when there are no more tags, we reached the root level.
            if(tags.length == 0)
            {
              reachedRoot = true;
            }
          }
        } else {
          const isValid = validateAttributeString(attrStr, options, regxAttrName);
          if (isValid !== true) {
            //the result from the nested function returns the position of the error within the attribute
            //in order to get the 'true' error line, we need to calculate the position where the attribute begins (i - attrStr.length) and then add the position within the attribute
            //this gives us the absolute index in the entire xml, which we can use to find the line at last
            return getErrorObject(isValid.err.code, isValid.err.msg, getLineNumberForPosition(xmlData, i - attrStr.length + isValid.err.line));
          }

          //if the root level has been reached before ...
          if(reachedRoot === true) {
              return getErrorObject('InvalidXml', 'Multiple possible root nodes found.', getLineNumberForPosition(xmlData, i));
          } else {
              tags.push(tagName);
          }
          tagFound = true;
        }

        //skip tag text value
        //It may include comments and CDATA value
        for (i++; i < xmlData.length; i++) {
          if (xmlData[i] === '<') {
            if (xmlData[i + 1] === '!') {
              //comment or CADATA
              i++;
              i = readCommentAndCDATA(xmlData, i);
              continue;
            } else {
              break;
            }
          }
        } //end of reading tag text value
        if (xmlData[i] === '<') {
          i--;
        }
      }
    } else {
      if (xmlData[i] === ' ' || xmlData[i] === '\t' || xmlData[i] === '\n' || xmlData[i] === '\r') {
        continue;
      }
      return getErrorObject('InvalidChar', `char '${xmlData[i]}' is not expected.`, getLineNumberForPosition(xmlData, i));
    }
  }

  if (!tagFound) {
    return getErrorObject('InvalidXml', 'Start tag expected.', 1);
  } else if (tags.length > 0) {
    return getErrorObject('InvalidXml', `Invalid '${JSON.stringify(tags, null, 4).replace(/\r?\n/g, '')}' found.`, 1);
  }

  return true;
};

/**
 * Read Processing insstructions and skip
 * @param {*} xmlData
 * @param {*} i
 */
function readPI(xmlData, i) {
  var start = i;
  for (; i < xmlData.length; i++) {
    if (xmlData[i] == '?' || xmlData[i] == ' ') {
      //tagname
      var tagname = xmlData.substr(start, i - start);
      if (i > 5 && tagname === 'xml') {
        return getErrorObject('InvalidXml', 'XML declaration allowed only at the start of the document.', getLineNumberForPosition(xmlData, i));
      } else if (xmlData[i] == '?' && xmlData[i + 1] == '>') {
        //check if valid attribut string
        i++;
        break;
      } else {
        continue;
      }
    }
  }
  return i;
}

function readCommentAndCDATA(xmlData, i) {
  if (xmlData.length > i + 5 && xmlData[i + 1] === '-' && xmlData[i + 2] === '-') {
    //comment
    for (i += 3; i < xmlData.length; i++) {
      if (xmlData[i] === '-' && xmlData[i + 1] === '-' && xmlData[i + 2] === '>') {
        i += 2;
        break;
      }
    }
  } else if (
    xmlData.length > i + 8 &&
    xmlData[i + 1] === 'D' &&
    xmlData[i + 2] === 'O' &&
    xmlData[i + 3] === 'C' &&
    xmlData[i + 4] === 'T' &&
    xmlData[i + 5] === 'Y' &&
    xmlData[i + 6] === 'P' &&
    xmlData[i + 7] === 'E'
  ) {
    let angleBracketsCount = 1;
    for (i += 8; i < xmlData.length; i++) {
      if (xmlData[i] === '<') {
        angleBracketsCount++;
      } else if (xmlData[i] === '>') {
        angleBracketsCount--;
        if (angleBracketsCount === 0) {
          break;
        }
      }
    }
  } else if (
    xmlData.length > i + 9 &&
    xmlData[i + 1] === '[' &&
    xmlData[i + 2] === 'C' &&
    xmlData[i + 3] === 'D' &&
    xmlData[i + 4] === 'A' &&
    xmlData[i + 5] === 'T' &&
    xmlData[i + 6] === 'A' &&
    xmlData[i + 7] === '['
  ) {
    for (i += 8; i < xmlData.length; i++) {
      if (xmlData[i] === ']' && xmlData[i + 1] === ']' && xmlData[i + 2] === '>') {
        i += 2;
        break;
      }
    }
  }

  return i;
}

var doubleQuote = '"';
var singleQuote = "'";

/**
 * Keep reading xmlData until '<' is found outside the attribute value.
 * @param {string} xmlData
 * @param {number} i
 */
function readAttributeStr(xmlData, i) {
  let attrStr = '';
  let startChar = '';
  let tagClosed = false;
  for (; i < xmlData.length; i++) {
    if (xmlData[i] === doubleQuote || xmlData[i] === singleQuote) {
      if (startChar === '') {
        startChar = xmlData[i];
      } else if (startChar !== xmlData[i]) {
        //if vaue is enclosed with double quote then single quotes are allowed inside the value and vice versa
        continue;
      } else {
        startChar = '';
      }
    } else if (xmlData[i] === '>') {
      if (startChar === '') {
        tagClosed = true;
        break;
      }
    }
    attrStr += xmlData[i];
  }
  if (startChar !== '') {
    return false;
  }

  return { value: attrStr, index: i, tagClosed: tagClosed };
}

/**
 * Select all the attributes whether valid or invalid.
 */
const validAttrStrRegxp = new RegExp('(\\s*)([^\\s=]+)(\\s*=)?(\\s*([\'"])(([\\s\\S])*?)\\5)?', 'g');

//attr, ="sd", a="amit's", a="sd"b="saf", ab  cd=""

function validateAttributeString(attrStr, options, regxAttrName) {
  //console.log("start:"+attrStr+":end");

  //if(attrStr.trim().length === 0) return true; //empty string

  const matches = util.getAllMatches(attrStr, validAttrStrRegxp);
  const attrNames = {};

  for (let i = 0; i < matches.length; i++) {
    if (matches[i][1].length === 0) {
      //nospace before attribute name: a="sd"b="saf"
      return getErrorObject('InvalidAttr', `Attribute '${matches[i][2]}' has no space in starting.`, getPositionFromMatch(attrStr, matches[i][0]))
    } else if (matches[i][3] === undefined && !options.allowBooleanAttributes) {
      //independent attribute: ab
      return getErrorObject('InvalidAttr', `boolean attribute '${matches[i][2]}' is not allowed.`, getPositionFromMatch(attrStr, matches[i][0]));
    }
    /* else if(matches[i][6] === undefined){//attribute without value: ab=
                    return { err: { code:"InvalidAttr",msg:"attribute " + matches[i][2] + " has no value assigned."}};
                } */
    const attrName = matches[i][2];
    if (!validateAttrName(attrName, regxAttrName)) {
      return getErrorObject('InvalidAttr', `Attribute '${attrName}' is an invalid name.`, getPositionFromMatch(attrStr, matches[i][0]));
    }
    if (!attrNames.hasOwnProperty(attrName)) {
      //check for duplicate attribute.
      attrNames[attrName] = 1;
    } else {
      return getErrorObject('InvalidAttr', `Attribute '${attrName}' is repeated.`, getPositionFromMatch(attrStr, matches[i][0]));
    }
  }

  return true;
}

function getErrorObject(code, message, lineNumber) {
  return {
    err: {
      code: code,
      msg: message,
      line: lineNumber,
    },
  };
}

function validateAttrName(attrName, regxAttrName) {
  // const validAttrRegxp = new RegExp(regxAttrName);
  return util.doesMatch(attrName, regxAttrName);
}

//const startsWithXML = new RegExp("^[Xx][Mm][Ll]");
//  startsWith = /^([a-zA-Z]|_)[\w.\-_:]*/;

function validateTagName(tagname, regxTagName) {
  /*if(util.doesMatch(tagname,startsWithXML)) return false;
    else*/
  //return !tagname.toLowerCase().startsWith("xml") || !util.doesNotMatch(tagname, regxTagName);
  return !util.doesNotMatch(tagname, regxTagName);
}

//this function returns the line number for the character at the given index
function getLineNumberForPosition(xmlData, index) {
  var lines = xmlData.substring(0, index).split(/\r?\n/);
  return lines.length;
}

//this function returns the position of the last character of match within attrStr
function getPositionFromMatch(attrStr, match) {
  return attrStr.indexOf(match) + match.length;
}