text: const _ = require('underscore-plus')
  const {Range} = require('atom')
  
  const TOC_END = '<!-- TOC END -->'
  const TOC_START_REGEXP = /<!-- TOC START (.*)?-->/i
  const TOC_END_REGEXP = new RegExp(`${_.escapeRegExp(TOC_END)}`, 'i')
  
  // TOC generation
  // -------------------------
  function linkFor (text) {
    return text
      .toLowerCase()
      .trim()
      .replace(/(&nbsp;|<([^>]+)>)/gi, '') // this strips all <tags> from the title and just leaves the text in place.
      .replace(
        /[^a-z0-9\- _\u00AA\u00B5\u00BA\u00C0-\u00D6\u00D8-\u00F6\u00F8-\u02C1\u02C6-\u02D1\u02E0-\u02E4\u02EC\u02EE\u0370-\u0374\u0376\u0377\u037A-\u037D\u037F\u0386\u0388-\u038A\u038C\u038E-\u03A1\u03A3-\u03F5\u03F7-\u0481\u048A-\u052F\u0531-\u0556\u0559\u0561-\u0587\u05D0-\u05EA\u05F0-\u05F2\u0620-\u064A\u066E\u066F\u0671-\u06D3\u06D5\u06E5\u06E6\u06EE\u06EF\u06FA-\u06FC\u06FF\u0710\u0712-\u072F\u074D-\u07A5\u07B1\u07CA-\u07EA\u07F4\u07F5\u07FA\u0800-\u0815\u081A\u0824\u0828\u0840-\u0858\u08A0-\u08B4\u0904-\u0939\u093D\u0950\u0958-\u0961\u0971-\u0980\u0985-\u098C\u098F\u0990\u0993-\u09A8\u09AA-\u09B0\u09B2\u09B6-\u09B9\u09BD\u09CE\u09DC\u09DD\u09DF-\u09E1\u09F0\u09F1\u0A05-\u0A0A\u0A0F\u0A10\u0A13-\u0A28\u0A2A-\u0A30\u0A32\u0A33\u0A35\u0A36\u0A38\u0A39\u0A59-\u0A5C\u0A5E\u0A72-\u0A74\u0A85-\u0A8D\u0A8F-\u0A91\u0A93-\u0AA8\u0AAA-\u0AB0\u0AB2\u0AB3\u0AB5-\u0AB9\u0ABD\u0AD0\u0AE0\u0AE1\u0AF9\u0B05-\u0B0C\u0B0F\u0B10\u0B13-\u0B28\u0B2A-\u0B30\u0B32\u0B33\u0B35-\u0B39\u0B3D\u0B5C\u0B5D\u0B5F-\u0B61\u0B71\u0B83\u0B85-\u0B8A\u0B8E-\u0B90\u0B92-\u0B95\u0B99\u0B9A\u0B9C\u0B9E\u0B9F\u0BA3\u0BA4\u0BA8-\u0BAA\u0BAE-\u0BB9\u0BD0\u0C05-\u0C0C\u0C0E-\u0C10\u0C12-\u0C28\u0C2A-\u0C39\u0C3D\u0C58-\u0C5A\u0C60\u0C61\u0C85-\u0C8C\u0C8E-\u0C90\u0C92-\u0CA8\u0CAA-\u0CB3\u0CB5-\u0CB9\u0CBD\u0CDE\u0CE0\u0CE1\u0CF1\u0CF2\u0D05-\u0D0C\u0D0E-\u0D10\u0D12-\u0D3A\u0D3D\u0D4E\u0D5F-\u0D61\u0D7A-\u0D7F\u0D85-\u0D96\u0D9A-\u0DB1\u0DB3-\u0DBB\u0DBD\u0DC0-\u0DC6\u0E01-\u0E30\u0E32\u0E33\u0E40-\u0E46\u0E81\u0E82\u0E84\u0E87\u0E88\u0E8A\u0E8D\u0E94-\u0E97\u0E99-\u0E9F\u0EA1-\u0EA3\u0EA5\u0EA7\u0EAA\u0EAB\u0EAD-\u0EB0\u0EB2\u0EB3\u0EBD\u0EC0-\u0EC4\u0EC6\u0EDC-\u0EDF\u0F00\u0F40-\u0F47\u0F49-\u0F6C\u0F88-\u0F8C\u1000-\u102A\u103F\u1050-\u1055\u105A-\u105D\u1061\u1065\u1066\u106E-\u1070\u1075-\u1081\u108E\u10A0-\u10C5\u10C7\u10CD\u10D0-\u10FA\u10FC-\u1248\u124A-\u124D\u1250-\u1256\u1258\u125A-\u125D\u1260-\u1288\u128A-\u128D\u1290-\u12B0\u12B2-\u12B5\u12B8-\u12BE\u12C0\u12C2-\u12C5\u12C8-\u12D6\u12D8-\u1310\u1312-\u1315\u1318-\u135A\u1380-\u138F\u13A0-\u13F5\u13F8-\u13FD\u1401-\u166C\u166F-\u167F\u1681-\u169A\u16A0-\u16EA\u16F1-\u16F8\u1700-\u170C\u170E-\u1711\u1720-\u1731\u1740-\u1751\u1760-\u176C\u176E-\u1770\u1780-\u17B3\u17D7\u17DC\u1820-\u1877\u1880-\u18A8\u18AA\u18B0-\u18F5\u1900-\u191E\u1950-\u196D\u1970-\u1974\u1980-\u19AB\u19B0-\u19C9\u1A00-\u1A16\u1A20-\u1A54\u1AA7\u1B05-\u1B33\u1B45-\u1B4B\u1B83-\u1BA0\u1BAE\u1BAF\u1BBA-\u1BE5\u1C00-\u1C23\u1C4D-\u1C4F\u1C5A-\u1C7D\u1CE9-\u1CEC\u1CEE-\u1CF1\u1CF5\u1CF6\u1D00-\u1DBF\u1E00-\u1F15\u1F18-\u1F1D\u1F20-\u1F45\u1F48-\u1F4D\u1F50-\u1F57\u1F59\u1F5B\u1F5D\u1F5F-\u1F7D\u1F80-\u1FB4\u1FB6-\u1FBC\u1FBE\u1FC2-\u1FC4\u1FC6-\u1FCC\u1FD0-\u1FD3\u1FD6-\u1FDB\u1FE0-\u1FEC\u1FF2-\u1FF4\u1FF6-\u1FFC\u2071\u207F\u2090-\u209C\u2102\u2107\u210A-\u2113\u2115\u2119-\u211D\u2124\u2126\u2128\u212A-\u212D\u212F-\u2139\u213C-\u213F\u2145-\u2149\u214E\u2183\u2184\u2C00-\u2C2E\u2C30-\u2C5E\u2C60-\u2CE4\u2CEB-\u2CEE\u2CF2\u2CF3\u2D00-\u2D25\u2D27\u2D2D\u2D30-\u2D67\u2D6F\u2D80-\u2D96\u2DA0-\u2DA6\u2DA8-\u2DAE\u2DB0-\u2DB6\u2DB8-\u2DBE\u2DC0-\u2DC6\u2DC8-\u2DCE\u2DD0-\u2DD6\u2DD8-\u2DDE\u2E2F\u3005\u3006\u3031-\u3035\u303B\u303C\u3041-\u3096\u309D-\u309F\u30A1-\u30FA\u30FC-\u30FF\u3105-\u312D\u3131-\u318E\u31A0-\u31BA\u31F0-\u31FF\u3400-\u4DB5\u4E00-\u9FD5\uA000-\uA48C\uA4D0-\uA4FD\uA500-\uA60C\uA610-\uA61F\uA62A\uA62B\uA640-\uA66E\uA67F-\uA69D\uA6A0-\uA6E5\uA717-\uA71F\uA722-\uA788\uA78B-\uA7AD\uA7B0-\uA7B7\uA7F7-\uA801\uA803-\uA805\uA807-\uA80A\uA80C-\uA822\uA840-\uA873\uA882-\uA8B3\uA8F2-\uA8F7\uA8FB\uA8FD\uA90A-\uA925\uA930-\uA946\uA960-\uA97C\uA984-\uA9B2\uA9CF\uA9E0-\uA9E4\uA9E6-\uA9EF\uA9FA-\uA9FE\uAA00-\uAA28\uAA40-\uAA42\uAA44-\uAA4B\uAA60-\uAA76\uAA7A\uAA7E-\uAAAF\uAAB1\uAAB5\uAAB6\uAAB9-\uAABD\uAAC0\uAAC2\uAADB-\uAADD\uAAE0-\uAAEA\uAAF2-\uAAF4\uAB01-\uAB06\uAB09-\uAB0E\uAB11-\uAB16\uAB20-\uAB26\uAB28-\uAB2E\uAB30-\uAB5A\uAB5C-\uAB65\uAB70-\uABE2\uAC00-\uD7A3\uD7B0-\uD7C6\uD7CB-\uD7FB\uF900-\uFA6D\uFA70-\uFAD9\uFB00-\uFB06\uFB13-\uFB17\uFB1D\uFB1F-\uFB28\uFB2A-\uFB36\uFB38-\uFB3C\uFB3E\uFB40\uFB41\uFB43\uFB44\uFB46-\uFBB1\uFBD3-\uFD3D\uFD50-\uFD8F\uFD92-\uFDC7\uFDF0-\uFDFB\uFE70-\uFE74\uFE76-\uFEFC\uFF21-\uFF3A\uFF41-\uFF5A\uFF66-\uFFBE\uFFC2-\uFFC7\uFFCA-\uFFCF\uFFD2-\uFFD7\uFFDA-\uFFDC]/g,
        ''
      )
      .replace(/\s/g, '-') // Replace remaining spaces to hyphen
  }
  
  function titleFor (text) {
    return text
      .replace(/!\[.*?\]\(.*?\)/g, '') // Remove img link
      .replace(/\[(.*?)\]\(.*?\)/g, '$1') // extract link txt
      .replace(/<a .*?>(.*?)<\/a>/g, '$1') // extract link txt from a tag
      .trim()
  }
  
  // Set title and link
  function injectTitleAndLink (headers) {
    const countByLink = {}
  
    for (const header of headers) {
      let linkSuffix
      const title = titleFor(header.subject)
      const link = linkFor(title)
  
      if (!(link in countByLink)) {
        countByLink[link] = 0
        linkSuffix = ''
      } else {
        countByLink[link] += 1
        linkSuffix = '-' + countByLink[link]
      }
      header.title = title
      header.link = link + linkSuffix
    }
  }
  
  function buildTocText (editor, headers, options) {
    injectTitleAndLink(headers)
  
    const listChar = options.asterisk ? '*' : '-'
    return headers
      .filter(header => options.min <= header.level && header.level <= options.max)
      .map(header => {
        const indent = editor.buildIndentString(header.level - options.min)
        if (options.link) {
          return `${indent}${listChar} [${header.title}](#${header.link})`
        } else {
          return `${indent}${listChar} [${header.title}]`
        }
      })
      .join('\n')
  }
  
  // Extract markdown headers from editor
  // -------------------------
  function isMarkdownHeader (editor, bufferPosition) {
    const {scopes} = editor.scopeDescriptorForBufferPosition(bufferPosition)
    const scope = scopes[1]
    return (scope != null) && ( scope.startsWith('markup.heading') || scope.startsWith('heading.markup.md') )
  }
  
  const MARKDOWN_HEADER_REGEXP = /^(#+)\s*(.*$)$/g
  function scanHeaders (editor) {
    const headers = []
    editor.scan(MARKDOWN_HEADER_REGEXP, ({match, range}) => {
      if (!isMarkdownHeader(editor, range.start)) {
        return
      }
      const level = match[1].length
      const subject = match[2]
      headers.push({level, subject})
    })
    return headers
  }
  
  // Misc
  // -------------------------
  function deserializeTocOptions (text) {
    const options = {}
    for (const param of text.trim().split(/\s+/)) {
      let [key, value] = param.split(':')
      switch (key) {
        case 'min':
        case 'max': // integer
          const number = Number(value)
          if (number >= 1) options[key] = number
          break
        case 'asterisk':
          if (['true', 'false'].includes(value)) {
            options[key] = value === 'true'
          }
          break
        case 'link':
        case 'update': // boolean
          if (['true', 'false'].includes(value)) {
            options[key] = value === 'true'
          }
          break
      }
    }
    return options
  }
  
  function serializeTocOptions (tocOptions) {
    return JSON.stringify(tocOptions)
      .replace(/[{"}]/g, '')
      .replace(/,/g, ' ')
  }
  
  function getDefaultTocOptions () {
    return {
      min: atom.config.get('markdown-toc-auto.min'),
      max: atom.config.get('markdown-toc-auto.max'),
      link: atom.config.get('markdown-toc-auto.link'),
      asterisk: atom.config.get('markdown-toc-auto.asterisk'),
      update: atom.config.get('markdown-toc-auto.update')
    }
  }
  
  // Public
  // -------------------------
  function insertToc (editor, range, options = {}) {
    range = Range.fromObject(range)
    options = Object.assign(getDefaultTocOptions(), options)
  
    let toc = ''
    toc += `<!-- TOC START ${serializeTocOptions(options)} -->\n`
    toc += buildTocText(editor, scanHeaders(editor), options) + '\n'
    toc += TOC_END + (range.isEmpty() ? '\n\n' : '')
  
    const bufferPositionByCursor = new Map()
    // Save original cursor position for the cusor which point will change.
    for (const cursor of editor.getCursors()) {
      const point = cursor.getBufferPosition()
      if (range.containsPoint(point)) {
        bufferPositionByCursor.set(cursor, point)
      }
    }
  
    editor.setTextInBufferRange(range, toc)
    editor.buffer.groupLastChanges()
  
    // Restore oiginal cursor position
    for (const cursor of editor.getCursors()) {
      const point = bufferPositionByCursor.get(cursor)
      if (point) {
        cursor.setBufferPosition(point)
      }
    }
  }
  
  function insertTocAtPoint (editor, point) {
    insertToc(editor, [point, point])
  }
  
  function updateToc (editor) {
    const range = findTocRange(editor)
    if (range) {
      const tocStartRowText = editor.lineTextForBufferRow(range.start.row)
      const match = tocStartRowText.match(TOC_START_REGEXP)
      if (match) {
        const options = deserializeTocOptions(match[1])
        if (options.update) {
          insertToc(editor, range, options)
        }
      }
    }
  }
  
  function findTocRange (editor) {
    const tocRange = []
    const scanRange = new Range([0, 0], editor.getEofBufferPosition())
    editor.scanInBufferRange(TOC_START_REGEXP, scanRange, ({range}) => tocRange.push(range))
  
    if (tocRange.length === 0) {
      return
    }
  
    scanRange.start = tocRange[0].end
    editor.scanInBufferRange(TOC_END_REGEXP, scanRange, ({range}) => tocRange.push(range))
    if (tocRange.length === 2) {
      return new Range(tocRange[0].start, tocRange[1].end)
    }
  }
  
  module.exports = {
    updateToc,
    linkFor,
    titleFor,
    insertTocAtPoint,
    deserializeTocOptions,
    serializeTocOptions
  }
  