module.exports =
class TokenIterator {
  constructor (languageMode) {
    this.languageMode = languageMode
  }

  reset (line) {
    this.line = line
    this.index = null
    this.startColumn = 0
    this.endColumn = 0
    this.scopes = this.line.openScopes.map(id => this.languageMode.grammar.scopeForId(id))
    this.scopeStarts = this.scopes.slice()
    this.scopeEnds = []
    return this
  }

  next () {
    const {tags} = this.line

    if (this.index != null) {
      this.startColumn = this.endColumn
      this.scopeEnds.length = 0
      this.scopeStarts.length = 0
      this.index++
    } else {
      this.index = 0
    }

    while (this.index < tags.length) {
      const tag = tags[this.index]
      if (tag < 0) {
        const scope = this.languageMode.grammar.scopeForId(tag)
        if ((tag % 2) === 0) {
          if (this.scopeStarts[this.scopeStarts.length - 1] === scope) {
            this.scopeStarts.pop()
          } else {
            this.scopeEnds.push(scope)
          }
          this.scopes.pop()
        } else {
          this.scopeStarts.push(scope)
          this.scopes.push(scope)
        }
        this.index++
      } else {
        this.endColumn += tag
        this.text = this.line.text.substring(this.startColumn, this.endColumn)
        return true
      }
    }

    return false
  }

  getScopes () {
    return this.scopes
  }

  getScopeStarts () {
    return this.scopeStarts
  }

  getScopeEnds () {
    return this.scopeEnds
  }

  getText () {
    return this.text
  }

  getBufferStart () {
    return this.startColumn
  }

  getBufferEnd () {
    return this.endColumn
  }
}