module SyntaxTree::Reflection::Type

def parse(comment)
  comment = comment.gsub(/\n/, " ")
  unless comment.start_with?("[")
    raise "Comment does not start with a bracket: #{comment.inspect}"
  end
  count = 1
  found =
    comment.chars[1..]
      .find
      .with_index(1) do |char, index|
        count += { "[" => 1, "]" => -1 }.fetch(char, 0)
        break index if count == 0
      end
  # If we weren't able to find the end of the balanced brackets, then
  # the comment is malformed.
  if found.nil?
    raise "Comment does not have balanced brackets: #{comment.inspect}"
  end
  parse_type(comment[1...found].strip)
end

def parse_type(value)
  case value
  when "Integer"
    Integer
  when "String"
    String
  when "Symbol"
    Symbol
  when "boolean"
    UnionType.new([TrueClass, FalseClass])
  when "nil"
    NilClass
  when ":\"::\""
    :"::"
  when ":call"
    :call
  when ":nil"
    :nil
  when /\AArray\[(.+)\]\z/
    ArrayType.new(parse_type($1.strip))
  when /\A\[(.+)\]\z/
    TupleType.new($1.strip.split(/\s*,\s*/).map { parse_type(_1) })
  else
    if value.include?("|")
      UnionType.new(value.split(/\s*\|\s*/).map { parse_type(_1) })
    else
      CONSTANTS.fetch(value.to_sym)
    end
  end
end