const commonUselessAnswerParts = [
  'A helyes válasz az ',
  'A helyes válasz a ',
  'A helyes válaszok: ',
  'A helyes válaszok:',
  'A helyes válasz: ',
  'A helyes válasz:',
  'The correct answer is:',
  '\''
]
const commonUselessStringParts = [',', '\\.', ':', '!']
const lengthDiffMultiplier = 10 /* Percent minus for length difference */
const minMatchAmmount = 60 /* Minimum ammount to consider that two questions match during answering */

const assert = (val) => {
  if (!val) { throw new Error('Assertion failed') }
}

class StringUtils {
  RemoveStuff (value, removableStrings) {
    removableStrings.forEach((x) => {
      var regex = new RegExp(x, 'g')
      value = value.replace(regex, '')
    })
    return value
  }

  SimplifyQuery (q) {
    assert(q)

    var result = q.replace(/\n/g, ' ').replace(/\s/g, ' ')
    return this.RemoveUnnecesarySpaces(result)
  }

  ShortenString (toShorten, ammount) {
    assert(toShorten)

    var result = ''
    var i = 0
    while (i < toShorten.length && i < ammount) {
      result += toShorten[i]
      i++
    }
    return result
  }

  ReplaceCharsWithSpace (val, char) {
    assert(val)
    assert(char)

    var toremove = this.NormalizeSpaces(val)

    var regex = new RegExp(char, 'g')
    toremove = toremove.replace(regex, ' ')

    return this.RemoveUnnecesarySpaces(toremove)
  }

  // removes whitespace from begining and and, and replaces multiple spaces with one space
  RemoveUnnecesarySpaces (toremove) {
    assert(toremove)

    toremove = this.NormalizeSpaces(toremove)
    while (toremove.includes('  ')) {
      toremove = toremove.replace(/ {2}/g, ' ')
    }
    return toremove.trim()
  }

  // simplifies a string for easier comparison
  SimplifyStringForComparison (value) {
    assert(value)

    value = this.RemoveUnnecesarySpaces(value).toLowerCase()
    return this.RemoveStuff(value, commonUselessStringParts)
  }

  RemoveSpecialChars (value) {
    assert(value)

    return this.RemoveStuff(value, ['&'])
  }

  // if the value is empty, or whitespace
  EmptyOrWhiteSpace (value) {
    // replaces /n-s with "". then replaces spaces with "". if it equals "", then its empty, or only consists of white space
    if (value === undefined) { return true }
    return (value.replace(/\n/g, '').replace(/ /g, '').replace(/\s/g, ' ') === '')
  }

  // damn nonbreaking space
  NormalizeSpaces (input) {
    assert(input)

    return input.replace(/\s/g, ' ')
  }

  CompareString (s1, s2) {
    if (!s1 || !s2) {
      return 0
    }

    s1 = this.SimplifyStringForComparison(s1).split(' ')
    s2 = this.SimplifyStringForComparison(s2).split(' ')
    var match = 0
    for (var i = 0; i < s1.length; i++) {
      if (s2.includes(s1[i])) { match++ }
    }
    var percent = Math.round(((match / s1.length) * 100).toFixed(2)) // matched words percent
    var lengthDifference = Math.abs(s2.length - s1.length)
    percent -= lengthDifference * lengthDiffMultiplier
    if (percent < 0) { percent = 0 }
    return percent
  }

  AnswerPreProcessor (value) {
    assert(value)

    return this.RemoveStuff(
      value, commonUselessAnswerParts)
  }

  // 'a. pécsi sör' -> 'pécsi sör'
  RemoveAnswerLetters (value) {
    assert(value)

    let s = value.split('. ')
    if (s[0].length < 2 && s.length > 1) {
      s.shift()
      return s.join(' ')
    } else {
      return value
    }
  }

  SimplifyQA (value, mods) {
    if (!value) { return }

    const reducer = (res, fn) => {
      return fn(res)
    }

    return mods.reduce(reducer, value)
  }

  SimplifyAnswer (value) {
    return this.SimplifyQA(
      value,
      [
        this.RemoveSpecialChars.bind(this),
        this.RemoveUnnecesarySpaces.bind(this),
        this.AnswerPreProcessor.bind(this),
        this.RemoveAnswerLetters.bind(this)
      ])
  }

  SimplifyQuestion (value) {
    return this.SimplifyQA(
      value,
      [
        this.RemoveSpecialChars.bind(this),
        this.RemoveUnnecesarySpaces.bind(this)
      ])
  }

  SimplifyStack (stack) {
    return this.SimplifyQuery(stack)
  }
}

const SUtils = new StringUtils()

class Question {
  constructor (q, a, i) {
    this.Q = SUtils.SimplifyQuestion(q)
    this.A = SUtils.SimplifyAnswer(a)
    this.I = i
  }

  toString () {
    var r = '?' + this.Q + '\n!' + this.A
    if (this.I) { r += '\n>' + this.I }
    return r
  }

  HasQuestion () {
    return this.Q !== undefined
  }

  HasAnswer () {
    return this.A !== undefined
  }

  HasImage () {
    return this.I !== undefined && (typeof this.I === 'string' || Array.isArray(this.I))
  }

  IsComplete () {
    return this.HasQuestion() && this.HasAnswer()
  }

  Compare (q2, i) {
    assert(q2)

    if (typeof q2 === 'string') {
      var qmatchpercent = SUtils.CompareString(this.Q, q2)

      if (i === undefined || i.length === 0) { return qmatchpercent } else {
        if (this.HasImage()) {
          const imatchpercent = this.HasImage() ? SUtils.CompareString(this.I.join(' '), i.join(' '))
            : 0
          return (qmatchpercent + imatchpercent) / 2
        } else {
          qmatchpercent -= 30
          if (qmatchpercent < 0) { return 0 } else { return qmatchpercent }
        }
      }
    } else {
      const qmatchpercent = SUtils.CompareString(this.Q, q2.Q)
      const amatchpercent = SUtils.CompareString(this.A, q2.A)
      if (this.I !== undefined) {
        const imatchpercent = this.I === undefined ? SUtils.CompareString(this.I.join(' '), q2.I.join(
          ' ')) : 0
        return (qmatchpercent + amatchpercent + imatchpercent) / 3
      } else {
        return (qmatchpercent + amatchpercent) / 2
      }
    }
  }
}

class Subject {
  constructor (n) {
    assert(n)

    this.Name = n
    this.Questions = []
    this.active = false
  }

  setIndex (i) {
    this.index = i
  }

  getIndex () {
    return this.index || -1
  }

  get length () {
    return this.Questions.length
  }

  markActive () {
    this.active = true
  }

  getIfActive () {
    return this.active
  }

  AddQuestion (q) {
    assert(q)

    this.Questions.push(q)
  }

  getSubjNameWithoutYear () {
    let t = this.Name.split(' - ')
    if (t[0].match(/^[0-9]{4}\/[0-9]{2}\/[0-9]{1}$/i)) {
      return t[1] || ''
    } else {
      return ''
    }
  }

  getYear () {
    let t = this.Name.split(' - ')[0]
    if (t.match(/^[0-9]{4}\/[0-9]{2}\/[0-9]{1}$/i)) {
      return t
    } else {
      return ''
    }
  }

  Search (q, img) {
    assert(q)

    var r = []
    for (let i = 0; i < this.length; i++) {
      let percent = this.Questions[i].Compare(q, img)
      if (percent > minMatchAmmount) {
        r.push({
          q: this.Questions[i],
          match: percent
        })
      }
    }

    for (let i = 0; i < r.length; i++) {
      for (var j = i; j < r.length; j++) {
        if (r[i].match < r[j].match) {
          var tmp = r[i]
          r[i] = r[j]
          r[j] = tmp
        }
      }
    }

    return r
  }

  toString () {
    var r = []
    for (var i = 0; i < this.Questions.length; i++) { r.push(this.Questions[i].toString()) }
    return '+' + this.Name + '\n' + r.join('\n')
  }
}

class QuestionDB {
  constructor (getVal, setVal) {
    this.Subjects = []
    this.getVal = getVal
    this.setVal = setVal
  }

  get length () {
    return this.Subjects.length
  }

  get activeIndexes () {
    var r = []
    for (var i = 0; i < this.length; i++) {
      if (this.getVal('Is' + i + 'Active')) {
        r.push(i)
      }
    }
    return r
  }

  GetIfActive (ind) {
    return this.getVal('Is' + ind + 'Active')
  }

  ChangeActive (i, value) {
    this.setVal('Is' + i + 'Active', !!value)
  }

  AddQuestion (subj, q) {
    assert(subj)

    var i = 0
    while (i < this.Subjects.length && this.Subjects[i].Name !== subj) { i++ }
    if (i < this.Subjects.length) { this.Subjects[i].AddQuestion(q) } else {
      const n = new Subject(subj)
      n.AddQuestion(q)
      this.Subjects.push(n)
    }
  }

  Search (q, img) {
    assert(q)

    var r = []
    for (let i = 0; i < this.length; i++) {
      if (this.GetIfActive(i)) { r = r.concat(this.Subjects[i].Search(q, img)) }
    }

    for (let i = 0; i < r.length; i++) {
      for (var j = i; j < r.length; j++) {
        if (r[i].match < r[j].match) {
          var tmp = r[i]
          r[i] = r[j]
          r[j] = tmp
        }
      }
    }

    return r
  }

  AddSubject (subj) {
    assert(subj)

    var i = 0
    while (i < this.length && subj.Name !== this.Subjects[i].Name) { i++ }

    if (i < this.length) {
      this.Subjects.concat(subj.Questions)
    } else {
      this.Subjects.push(subj)
    }
  }

  toString () {
    var r = []
    for (var i = 0; i < this.Subjects.length; i++) { r.push(this.Subjects[i].toString()) }
    return r.join('\n\n')
  }
}

module.exports.StringUtils = StringUtils
module.exports.Question = Question
module.exports.Subject = Subject
module.exports.QuestionDB = QuestionDB