defmodule HttpCookie.URL do
  @moduledoc false

  # 5.1.2.  Canonicalized Host Names
  #
  # A canonicalized host name is the string generated by the following
  # algorithm:
  #
  # 1.  Convert the host name to a sequence of individual domain name
  #     labels.
  #
  # 2.  Convert each label that is not a Non-Reserved LDH (NR-LDH) label,
  #     to an A-label (see Section 2.3.2.1 of [RFC5890] for the former
  #     and latter), or to a "punycode label" (a label resulting from the
  #     "ToASCII" conversion in Section 4 of [RFC3490]), as appropriate
  #     (see Section 6.3 of this specification).
  #
  # 3.  Concatenate the resulting labels, separated by a %x2E (".")
  #     character.
  def canonicalize_domain(domain) do
    domain
    |> :idna.to_ascii()
    |> to_string()
    |> String.downcase()
  end

  def normalize_path(path) when path in [nil, ""], do: "/"
  def normalize_path(path), do: path

  # 5.1.4.  Paths and Path-Match
  #
  # The user agent MUST use an algorithm equivalent to the following
  # algorithm to compute the default-path of a cookie:
  #
  #   1.  Let uri-path be the path portion of the request-uri if such a
  #       portion exists (and empty otherwise).  For example, if the
  #       request-uri contains just a path (and optional query string),
  #       then the uri-path is that path (without the %x3F ("?") character
  #       or query string), and if the request-uri contains a full
  #       absoluteURI, the uri-path is the path component of that URI.
  #
  #   2.  If the uri-path is empty or if the first character of the uri-
  #       path is not a %x2F ("/") character, output %x2F ("/") and skip
  #       the remaining steps.
  #
  #   3.  If the uri-path contains no more than one %x2F ("/") character,
  #       output %x2F ("/") and skip the remaining step.
  #
  #   4.  Output the characters of the uri-path from the first character up
  #       to, but not including, the right-most %x2F ("/").
  def default_path(request_url) do
    request_path = normalize_path(request_url.path)

    cond do
      request_path == "/" -> "/"
      request_path =~ ~r|^[^/]| -> "/"
      request_path =~ ~r|^/[^/]*$| -> "/"
      true -> String.split(request_path, ~r|/[^/]*$|) |> hd()
    end
  end

  # 5.1.4.  Paths and Path-Match
  # [...]
  # A request-path path-matches a given cookie-path if at least one of
  # the following conditions holds:
  #
  # o  The cookie-path and the request-path are identical.
  def path_match?(path, path), do: true

  # (continued)
  # o  The cookie-path is a prefix of the request-path, and the last
  #    character of the cookie-path is %x2F ("/").
  #
  # o  The cookie-path is a prefix of the request-path, and the first
  #    character of the request-path that is not included in the cookie-
  #    path is a %x2F ("/") character.
  def path_match?(request_path, cookie_path) do
    cond do
      String.starts_with?(request_path, cookie_path) and String.ends_with?(cookie_path, "/") ->
        true

      request_path =~ ~r|^#{Regex.escape(cookie_path)}/| ->
        true

      true ->
        false
    end
  end

  # 5.1.3.  Domain Matching
  #
  # A string domain-matches a given domain string if at least one of the
  # following conditions hold:
  #
  # o  The domain string and the string are identical.  (Note that both
  #    the domain string and the string will have been canonicalized to
  #    lower case at this point.)
  def domain_match?(domain, domain), do: true

  # (continued)
  # o  All of the following conditions hold:
  #
  #    *  The domain string is a suffix of the string.
  #
  #    *  The last character of the string that is not included in the
  #       domain string is a %x2E (".") character.
  #
  #    *  The string is a host name (i.e., not an IP address).
  def domain_match?(request_domain, cookie_domain) do
    request_domain =~ ~r/\.#{Regex.escape(cookie_domain)}$/ and !ip_address?(request_domain)
  end

  # NOTE: A "public suffix" is a domain that is controlled by a
  # public registry, such as "com", "co.uk", and "pvt.k12.wy.us".
  # This step is essential for preventing attacker.com from
  # disrupting the integrity of example.com by setting a cookie
  # with a Domain attribute of "com".  Unfortunately, the set of
  # public suffixes (also known as "registry controlled domains")
  # changes over time.  If feasible, user agents SHOULD use an
  # up-to-date public suffix list, such as the one maintained by
  # the Mozilla project at <http://publicsuffix.org/>.
  def public_suffix?(""), do: false

  if Code.ensure_loaded?(PublicSuffix) do
    def public_suffix?(domain) do
      domain == PublicSuffix.public_suffix(domain)
    end
  else
    def public_suffix?(_domain) do
      # work around for typing violation that's reported
      # because the function only returns false when the
      # dependency is missing - but it should not be called in that
      # case anyway because the option velidation should fail before that
      if :rand.uniform(10) <= 10 do
        raise "Missing :public_suffix dependency"
      else
        true
      end
    end
  end

  def ip_address?(str) do
    charlist = String.to_charlist(str)

    case :inet.parse_address(charlist) do
      {:ok, _ip} -> true
      _ -> false
    end
  end
end