const { calculateTokenCharactersRange } = require('../helpers')

const {
  TOKEN_TEXT,
  TOKEN_COMMENT_START
} = require('../constants/token-types')
const {
  OPEN_TAG_START_CONTEXT,
  CLOSE_TAG_CONTEXT,
  DOCTYPE_START_CONTEXT,
  COMMENT_CONTENT_CONTEXT
} = require('../constants/tokenizer-contexts')

const COMMENT_START = '<!--'

function generateTextToken (state) {
  const range = calculateTokenCharactersRange(state, { keepBuffer: false })

  return {
    type: TOKEN_TEXT,
    content: state.accumulatedContent,
    startPosition: range.startPosition,
    endPosition: range.endPosition
  }
}

function openingCornerBraceWithText (state, tokens) {
  if (state.accumulatedContent.length !== 0) {
    tokens.push(generateTextToken(state))
  }

  state.accumulatedContent = state.decisionBuffer
  state.decisionBuffer = ''
  state.currentContext = OPEN_TAG_START_CONTEXT
  state.caretPosition++
}

function openingCornerBraceWithSlash (state, tokens) {
  if (state.accumulatedContent.length !== 0) {
    tokens.push(generateTextToken(state))
  }

  state.accumulatedContent = state.decisionBuffer
  state.decisionBuffer = ''
  state.currentContext = CLOSE_TAG_CONTEXT
  state.caretPosition++
}

function doctypeStart (state, tokens) {
  if (state.accumulatedContent.length !== 0) {
    tokens.push(generateTextToken(state))
  }

  state.accumulatedContent = state.decisionBuffer
  state.decisionBuffer = ''
  state.currentContext = DOCTYPE_START_CONTEXT
  state.caretPosition++
}

function commentStart (state, tokens) {
  if (state.accumulatedContent.length !== 0) {
    tokens.push(generateTextToken(state))
  }

  const commentStartRange = {
    startPosition: state.caretPosition - (COMMENT_START.length - 1),
    endPosition: state.caretPosition
  }

  tokens.push({
    type: TOKEN_COMMENT_START,
    content: state.decisionBuffer,
    startPosition: commentStartRange.startPosition,
    endPosition: commentStartRange.endPosition
  })

  state.accumulatedContent = ''
  state.decisionBuffer = ''
  state.currentContext = COMMENT_CONTENT_CONTEXT
  state.caretPosition++
}

function handleContentEnd (state, tokens) {
  const textContent = state.accumulatedContent + state.decisionBuffer

  if (textContent.length !== 0) {
    const range = calculateTokenCharactersRange(state, { keepBuffer: false })

    tokens.push({
      type: TOKEN_TEXT,
      content: textContent,
      startPosition: range.startPosition,
      endPosition: range.endPosition
    })
  }
}

function isIncompleteDoctype (chars) {
  const charsUpperCase = chars.toUpperCase()

  return (
    charsUpperCase === '<!'
    || charsUpperCase === '<!D'
    || charsUpperCase === '<!DO'
    || charsUpperCase === '<!DOC'
    || charsUpperCase === '<!DOCT'
    || charsUpperCase === '<!DOCTY'
    || charsUpperCase === '<!DOCTYP'
  )
}

const OPEN_TAG_START_PATTERN = /^<\w/

function parseSyntax (chars, state, tokens) {
  if (OPEN_TAG_START_PATTERN.test(chars)) {
    return openingCornerBraceWithText(state, tokens)
  }

  if (chars === '</') {
    return openingCornerBraceWithSlash(state, tokens)
  }

  if (
    chars === '<'
    || chars === '<!'
    || chars === '<!-'
  ) {
    state.caretPosition++

    return
  }

  if (chars === COMMENT_START) {
    return commentStart(state, tokens)
  }

  if (isIncompleteDoctype(chars)) {
    state.caretPosition++

    return
  }

  if (chars.toUpperCase() === '<!DOCTYPE') {
    return doctypeStart(state, tokens)
  }

  state.accumulatedContent += state.decisionBuffer
  state.decisionBuffer = ''
  state.caretPosition++
}

module.exports = {
  parseSyntax,
  handleContentEnd
}