module FakeFS::Globber

def drop_root(path_parts)
  # we need to remove parts from root dir at least for windows and jruby
  return path_parts if path_parts.nil? || path_parts.empty?
  root = RealFile.expand_path('/').split(File::SEPARATOR).first
  path_parts.shift if path_parts.first == root
  path_parts
end

def each_char_with_levels(string, level_start, level_end)
  level = 0
  string.each_char do |chr|
    yield chr, level
    case chr
    when level_start
      level += 1
    when level_end
      level -= 1
    end
  end
end

def expand(pattern)
  pattern = pattern.to_s
  return [pattern] if pattern[0] != '{' || pattern[-1] != '}'
  part = +''
  result = []
  each_char_with_levels pattern, '{', '}' do |chr, level|
    case level
    when 0
      case chr
      when '{'
        # noop
      else
        part << chr
      end
    when 1
      case chr
      when ','
        result << part
        part = +''
      when '}'
        # noop
      else
        part << chr
      end
    else
      part << chr
    end
  end
  result << part
  result
end

def path_components(pattern)
  pattern = pattern.to_s
  part = +''
  result = []
  each_char_with_levels pattern, '{', '}' do |chr, level|
    if level == 0 && chr == File::SEPARATOR
      result << part
      part = +''
    else
      part << chr
    end
  end
  result << part
  drop_root(result).reject(&:empty?)
end

def regexp(pattern, find_flags = 0, gave_char_class = false)
  pattern = pattern.to_s
  # Escape .+?*()$ characters unless already escaped.
  regex_body =
    pattern
    .gsub(/(?<!\\)\./, '\.')
    .gsub(/(?<!\\)\+/) { '\+' }
    .gsub(/(?<!\\)\?/, '.')
    .gsub(/(?<!\\)\*/, '.*')
    .gsub(/(?<!\\)\(/, '\(')
    .gsub(/(?<!\\)\)/, '\)')
    .gsub(/(?<!\\)\$/, '\$')
  # Unless we're expecting character class contructs in regexes, escape all brackets
  # since if we're expecting them, the string should already be properly escaped.
  unless gave_char_class
    regex_body = regex_body.gsub(/(?<!\\)([\[\]])/, '\\\\\1')
  end
  # This matches nested braces and attempts to do something correct most of the time
  # There are known issues (i.e. {,*,*/*}) that cannot be resolved with out a total
  # refactoring
  loop do
    break unless regex_body.gsub!(/(?<re>\{(?:(?>[^{}]+)|\g<re>)*\})/) do
      "(#{Regexp.last_match[1][1..-2].gsub(',', '|')})"
    end
  end
  # if we are matching dot files/directories, add that to the regex
  if find_flags == File::FNM_DOTMATCH
    regex_body = "(\.)?" + regex_body
  end
  regex_body = regex_body.gsub(/\A\./, '(?!\.).')
  /\A#{regex_body}\Z/
end