'use strict'

var ccount = require('ccount')
var decode = require('parse-entities')
var decimal = require('is-decimal')
var alphabetical = require('is-alphabetical')
var whitespace = require('is-whitespace-character')
var locate = require('../locate/url')

module.exports = url
url.locator = locate
url.notInLink = true

var exclamationMark = 33 // '!'
var ampersand = 38 // '&'
var rightParenthesis = 41 // ')'
var asterisk = 42 // '*'
var comma = 44 // ','
var dash = 45 // '-'
var dot = 46 // '.'
var colon = 58 // ':'
var semicolon = 59 // ';'
var questionMark = 63 // '?'
var lessThan = 60 // '<'
var underscore = 95 // '_'
var tilde = 126 // '~'

var leftParenthesisCharacter = '('
var rightParenthesisCharacter = ')'

function url(eat, value, silent) {
  var self = this
  var gfm = self.options.gfm
  var tokenizers = self.inlineTokenizers
  var length = value.length
  var previousDot = -1
  var protocolless = false
  var dots
  var lastTwoPartsStart
  var start
  var index
  var pathStart
  var path
  var code
  var end
  var leftCount
  var rightCount
  var content
  var children
  var url
  var exit

  if (!gfm) {
    return
  }

  // `WWW.` doesn’t work.
  if (value.slice(0, 4) === 'www.') {
    protocolless = true
    index = 4
  } else if (value.slice(0, 7).toLowerCase() === 'http://') {
    index = 7
  } else if (value.slice(0, 8).toLowerCase() === 'https://') {
    index = 8
  } else {
    return
  }

  // Act as if the starting boundary is a dot.
  previousDot = index - 1

  // Parse a valid domain.
  start = index
  dots = []

  while (index < length) {
    code = value.charCodeAt(index)

    if (code === dot) {
      // Dots may not appear after each other.
      if (previousDot === index - 1) {
        break
      }

      dots.push(index)
      previousDot = index
      index++
      continue
    }

    if (
      decimal(code) ||
      alphabetical(code) ||
      code === dash ||
      code === underscore
    ) {
      index++
      continue
    }

    break
  }

  // Ignore a final dot:
  if (code === dot) {
    dots.pop()
    index--
  }

  // If there are not dots, exit.
  if (dots[0] === undefined) {
    return
  }

  // If there is an underscore in the last two domain parts, exit:
  // `www.example.c_m` and `www.ex_ample.com` are not OK, but
  // `www.sub_domain.example.com` is.
  lastTwoPartsStart = dots.length < 2 ? start : dots[dots.length - 2] + 1

  if (value.slice(lastTwoPartsStart, index).indexOf('_') !== -1) {
    return
  }

  /* istanbul ignore if - never used (yet) */
  if (silent) {
    return true
  }

  end = index
  pathStart = index

  // Parse a path.
  while (index < length) {
    code = value.charCodeAt(index)

    if (whitespace(code) || code === lessThan) {
      break
    }

    index++

    if (
      code === exclamationMark ||
      code === asterisk ||
      code === comma ||
      code === dot ||
      code === colon ||
      code === questionMark ||
      code === underscore ||
      code === tilde
    ) {
      // Empty
    } else {
      end = index
    }
  }

  index = end

  // If the path ends in a closing paren, and the count of closing parens is
  // higher than the opening count, then remove the supefluous closing parens.
  if (value.charCodeAt(index - 1) === rightParenthesis) {
    path = value.slice(pathStart, index)
    leftCount = ccount(path, leftParenthesisCharacter)
    rightCount = ccount(path, rightParenthesisCharacter)

    while (rightCount > leftCount) {
      index = pathStart + path.lastIndexOf(rightParenthesisCharacter)
      path = value.slice(pathStart, index)
      rightCount--
    }
  }

  if (value.charCodeAt(index - 1) === semicolon) {
    // GitHub doesn’t document this, but final semicolons aren’t paret of the
    // URL either.
    index--

    // // If the path ends in what looks like an entity, it’s not part of the path.
    if (alphabetical(value.charCodeAt(index - 1))) {
      end = index - 2

      while (alphabetical(value.charCodeAt(end))) {
        end--
      }

      if (value.charCodeAt(end) === ampersand) {
        index = end
      }
    }
  }

  content = value.slice(0, index)
  url = decode(content, {nonTerminated: false})

  if (protocolless) {
    url = 'http://' + url
  }

  exit = self.enterLink()

  // Temporarily remove all tokenizers except text in url.
  self.inlineTokenizers = {text: tokenizers.text}
  children = self.tokenizeInline(content, eat.now())
  self.inlineTokenizers = tokenizers

  exit()

  return eat(content)({type: 'link', title: null, url: url, children: children})
}