class RuboCop::Cop::Style::Semicolon

def autocorrect(range)
  return unless range
  ->(corrector) { corrector.remove(range) }
end

def check_for_line_terminator_or_opener
  each_semicolon { |line, column| convention_on(line, column, true) }
end

def convention_on(line, column, autocorrect)
  range = source_range(@processed_source.buffer, line, column)
  # Don't attempt to autocorrect if semicolon is separating statements
  # on the same line
  add_offense(autocorrect ? range : nil, location: range)
end

def each_semicolon
  tokens_for_lines.each do |line, tokens|
    yield line, tokens.last.column if tokens.last.semicolon?
    yield line, tokens.first.column if tokens.first.semicolon?
  end
end

def investigate(processed_source)
  return if processed_source.blank?
  @processed_source = processed_source
  check_for_line_terminator_or_opener
end

def on_begin(node)
  return if cop_config['AllowAsExpressionSeparator']
  exprs = node.children
  return if exprs.size < 2
  # create a map matching lines to the number of expressions on them
  exprs_lines = exprs.map { |e| e.source_range.line }
  lines = exprs_lines.group_by { |i| i }
  # every line with more than 1 expression on it is an offense
  lines.each do |line, expr_on_line|
    next unless expr_on_line.size > 1
    # TODO: Find the correct position of the semicolon. We don't know
    # if the first semicolon on the line is a separator of
    # expressions. It's just a guess.
    column = @processed_source[line - 1].index(';')
    convention_on(line, column, false)
  end
end

def tokens_for_lines
  @processed_source.tokens.group_by(&:line)
end