class Prism::LexCompat::Heredoc::DedentingHeredoc

def <<(token)
  case token.event
  when :on_embexpr_beg, :on_heredoc_beg
    @embexpr_balance += 1
    @dedent = 0 if @dedent_next && @ended_on_newline
  when :on_embexpr_end, :on_heredoc_end
    @embexpr_balance -= 1
  when :on_tstring_content
    if embexpr_balance == 0
      line = token.value
      if dedent_next && !(line.strip.empty? && line.end_with?("\n"))
        leading = line[/\A(\s*)\n?/, 1]
        next_dedent = 0
        leading.each_char do |char|
          if char == "\t"
            next_dedent = next_dedent - (next_dedent % TAB_WIDTH) + TAB_WIDTH
          else
            next_dedent += 1
          end
        end
        @dedent = [dedent, next_dedent].compact.min
        @dedent_next = true
        @ended_on_newline = line.end_with?("\n")
        tokens << token
        return
      end
    end
  end
  @dedent_next = token.event == :on_tstring_content && embexpr_balance == 0
  @ended_on_newline = false
  tokens << token
end

def initialize
  @tokens = []
  @dedent_next = true
  @dedent = nil
  @embexpr_balance = 0
  @ended_on_newline = false
end

def to_a
  # If every line in the heredoc is blank, we still need to split up the
  # string content token into multiple tokens.
  if dedent.nil?
    results = []
    embexpr_balance = 0
    tokens.each do |token|
      case token.event
      when :on_embexpr_beg, :on_heredoc_beg
        embexpr_balance += 1
        results << token
      when :on_embexpr_end, :on_heredoc_end
        embexpr_balance -= 1
        results << token
      when :on_tstring_content
        if embexpr_balance == 0
          lineno = token[0][0]
          column = token[0][1]
          token.value.split(/(?<=\n)/).each_with_index do |value, index|
            column = 0 if index > 0
            results << Token.new([[lineno, column], :on_tstring_content, value, token.state])
            lineno += 1
          end
        else
          results << token
        end
      else
        results << token
      end
    end
    return results
  end
  # If the minimum common whitespace is 0, then we need to concatenate
  # string nodes together that are immediately adjacent.
  if dedent == 0
    results = []
    embexpr_balance = 0
    index = 0
    max_index = tokens.length
    while index < max_index
      token = tokens[index]
      results << token
      index += 1
      case token.event
      when :on_embexpr_beg, :on_heredoc_beg
        embexpr_balance += 1
      when :on_embexpr_end, :on_heredoc_end
        embexpr_balance -= 1
      when :on_tstring_content
        if embexpr_balance == 0
          while index < max_index && tokens[index].event == :on_tstring_content
            token.value << tokens[index].value
            index += 1
          end
        end
      end
    end
    return results
  end
  # Otherwise, we're going to run through each token in the list and
  # insert on_ignored_sp tokens for the amount of dedent that we need to
  # perform. We also need to remove the dedent from the beginning of
  # each line of plain string content tokens.
  results = []
  dedent_next = true
  embexpr_balance = 0
  tokens.each do |token|
    # Notice that the structure of this conditional largely matches the
    # whitespace calculation we performed above. This is because
    # checking if the subsequent token needs to be dedented is common to
    # both the dedent calculation and the ignored_sp insertion.
    case token.event
    when :on_embexpr_beg
      embexpr_balance += 1
      results << token
    when :on_embexpr_end
      embexpr_balance -= 1
      results << token
    when :on_tstring_content
      if embexpr_balance == 0
        # Here we're going to split the string on newlines, but maintain
        # the newlines in the resulting array. We'll do that with a look
        # behind assertion.
        splits = token.value.split(/(?<=\n)/)
        index = 0
        while index < splits.length
          line = splits[index]
          lineno = token[0][0] + index
          column = token[0][1]
          # Blank lines do not count toward common leading whitespace
          # calculation and do not need to be dedented.
          if dedent_next || index > 0
            column = 0
          end
          # If the dedent is 0 and we're not supposed to dedent the next
          # line or this line doesn't start with whitespace, then we
          # should concatenate the rest of the string to match ripper.
          if dedent == 0 && (!dedent_next || !line.start_with?(/\s/))
            line = splits[index..].join
            index = splits.length
          end
          # If we are supposed to dedent this line or if this is not the
          # first line of the string and this line isn't entirely blank,
          # then we need to insert an on_ignored_sp token and remove the
          # dedent from the beginning of the line.
          if (dedent > 0) && (dedent_next || index > 0)
            deleting = 0
            deleted_chars = []
            # Gather up all of the characters that we're going to
            # delete, stopping when you hit a character that would put
            # you over the dedent amount.
            line.each_char.with_index do |char, i|
              case char
              when "\r"
                if line[i + 1] == "\n"
                  break
                end
              when "\n"
                break
              when "\t"
                deleting = deleting - (deleting % TAB_WIDTH) + TAB_WIDTH
              else
                deleting += 1
              end
              break if deleting > dedent
              deleted_chars << char
            end
            # If we have something to delete, then delete it from the
            # string and insert an on_ignored_sp token.
            if deleted_chars.any?
              ignored = deleted_chars.join
              line.delete_prefix!(ignored)
              results << Token.new([[lineno, 0], :on_ignored_sp, ignored, token[3]])
              column = ignored.length
            end
          end
          results << Token.new([[lineno, column], token[1], line, token[3]]) unless line.empty?
          index += 1
        end
      else
        results << token
      end
    else
      results << token
    end
    dedent_next =
      ((token.event == :on_tstring_content) || (token.event == :on_heredoc_end)) &&
      embexpr_balance == 0
  end
  results
end